They look like starfishes, but they aren’t: the brittle stars

Some month ago, we talked about starfishes and we said that there are some animals, which are also echinoderms, with which they can be easily confused. Well, in this post we will talk about these animals: the brittle stars. We are going to explain their features to distinguish them from starfishes and we are going to expose some Mediterranean species. 

THE BRITTLE STARS

The brittle stars or ophiuroids are a class of echinoderms with more than 2,000 living species, which live in all types of seafloor.

Brittle star (Picture: Jose Manuel Cubero, Biodiversidad Virtual).

What features do you have to pay attention to differentiate a brittle star from a starfish? Brittle stars have five arms, which are thin and sharply originate from the central disk. This feature is key to not confuse them with starfishes. Another characteristic you have to observe to differentiate brittle stars from starfishes is in the bottom (oral side) of the animal: the ambulacral grooves are closed and covered by plates. Furthermore, tube feet don’t have suckers because they are more involved in locomotion than in feeding. In fact, their arms are constituted by articulated ossicles (called vertebrae) that allow their displacement.

Having the arms so thin, where are their organs? The mouth is in the lower part of the body and is surrounded by plates acting as jaws. They have no anus, so products that are not digested are expelled through the mouth. All organs are located in the central disc. They use bursae to breathe, which are bags in which water enters and leaves. In addition, the reproductive organs are connected to these bags, so that they expel gametes with water (although some species incubate their offspring). Most species have separate males and females.

Anatomy of a brittle star (Picture: Animal Diversity Web).

Where can you observe brittle stars? Brittle stars normally live in rocky seafloor with low or without light, usually hidden in cracks, where they feed on suspension particles, but some of them are carnivorous and one species can catch fishes by using their arms as a cage.

SOME EXAMPLES FROM THE MEDITERRANEAN SEA

In the Mediterranean Sea, we can find about 34 brittle star species. Six of them are endemic and other 2 species are exotic. Here, we will explain 5 of them.

SMOOTH BRITTLE STAR (Ophioderma longicauda)

It is the largest species. It comprises a pentagon-shaped central disc (about 3 cm of diameter) with arms, which are a bit bony and are 15 cm long. It has a brown colour on the dorsal side and is lighter in the ventral side and arms. They can be find till 50-70 meters deep under rocks, in holes and cracks; but the young individuals can hide between seaweed. They feed on worms and bivalves, mainly during the night.

Smooth brittle star (Ophioderma longicauda) (Picture: Fernando Herranz, Educa Madrid).

COMMON BRITTLE STAR (Ophiothrix fragilis)

Common brittle stars have the whole body covered with long spines, which can take a variable colour (usually brown and grey tonalities). They can measure up to 12 cm. It is the most abundant in both hard and soft bottoms, up to 100 meters deep. It feeds on particles with the ambulacral system. Did you know that they can live about 10 years? A curiosity: if you take one of these brittle stars and let it fall to the bottom, it sinks with open arms, allowing you to distinguish it from the following species.

Common brittle star (Ophiothrix fragilis) (Picture: Animal Base).

BLACK BRITTLE STAR (Ophiocomina nigra)

Although it is similar to the previous species, it can be distinguished from the common brittle star by the fact that in this species the spines are only in the arms, are shorter and are laterally arranged. It also has a brown to black colour, while arms are lighter than the disk (measuring up to 2.5 cm in diameter). It lives in shallow, rocky and sandy areas. To differentiate it from the common brittle star, if you catch one of them and you let the brittle star to drop, the ophiurid sinks with arms folded upwards.

Black brittle star (Ophiocomina nigra) (Picture: Segrest Farms)

AMPHIURA CHIAJEI

It is a small brittle star, with his body normally buried in the mud, so that only shows the arms abroad, which are very long and are used to collect debris. Its color is orange red. It is usually found between 10 and 200 meters deep.

Amphiura chiajei (Picture: Anders Salesjö Photography).

ASTROSPARTUS MEDITERRANEUS

This brittle star can not be confused with any other: it has its entire body covered with granules and has a considerable size. It is of uniform grey colour. They live in deep rocky substrates, sedimentary continental shelf and over gorgonian between 50 and 200 meters deep.

Astrospartus mediterraneus (Picture: Ranenere).

REFERENCES

• Ballesteros E & Llobet T (2015). Fauna i flora de la mar Mediterrània. Ed. Brau
• Club de Buceo de Biología: Ophiocomina nigra
• Club de Buceo de Biología: Ophioderma longicauda
• Club de Buceo de Biología: Ophiothrix fragilis
• Coll M, Piroddi C, Steenbeek J, Kaschner K, Ben Rais Lasram F, et al. (2010) The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats. PLoS ONE 5(8): e11842. doi:10.1371/journal.pone.0011842
• Hichman, Roberts,Larson, l’Anson & Eisenhour (2006). Principios integrales de Zoología. Ed. McGraw Hill (13 ed).
• Martin P (1999). Claves para la clasificación de la fauna marina. Ed. Omega
• Riedl R (1986). Fauna y flora del Mar Mediterráneo. Ed. Omega
• Vàzquez, J & Maluquer-Margalef, J (coord.) (2014). Guia pràctica per conèixer la natura de Catalunya. IPCENA. Lleida. 576 p.
• Foto de portada: Animal Base

Warning: Blowfish is already in the Mediterranean!

Since some time ago, newspapers are talking and warning about the arrival of the blowfish in the Mediterranean. This post expects to describe these famous animals and explain which the danger is for humans. 

HOW IS  THE BLOWFISH OF THE MEDITERRANEAN?

Blowfishes are a group present in the Mediterranean because they have accessed through the Suez Canal, so blowfishes are an exotic species. The species in the Mediterranean is the silver-cheeked toadfish (Lagocephalus sceleratus). Quickly, they established in the Eastern Mediterranean, but recently they have been found in the Adriatic sea (east of Italy). In this article published in the Mediterranean Marine Science, you may find a map with the concrete places (we cannot publish here for copyright). The silver-cheeked toadfish is native to tropical waters of the Pacific and Indian oceans, including Red Sea, where lives in muddy and sandy sea bottoms close to coral reefs between 10 and 180 m deep. They feed on a wide variety of animals and plants thanks to its powerful beak.

Their colouration is greenish with dark spots above, silver band from mouth to caudal fin and white belly. They can be distinguished from other blowfishes of similar colouration for their symmetric tail. The spines of the fins, moreover, are all soft. Their body is not covered by scales, but some small spines in the belly and in the dorsal part of the body. With two big teeth in each jaw, they constitute some kind of beak. When they feel in danger, they absorb water in a lateral cavity in the stomach to swell the body. The biggest animals can measure more than one metre long, but in average, they measure 40 cm.

Lagocephalus sceleratus (Picture: Il Giornale dei Marinai).

WHICH IS THE DANGER?

Like other fish with a powerful jaws and big enough, the blowfish can produce a deep injury. Some species of blowfish can be specially aggressive. Most of the accidents are produced when manipulating alive animals.

However, this fish is poisonous and, in fact, it has caused some human deaths due to the presence of the toxin tetrodotoxin, which is 1,200 times more poisonous than cyanide. This toxin can paralyse the muscles, so it stops breathing and produce death by suffocation. It is known that with 0.009 mg for each kg of body weight is lethal. To give an example, a person with 70 kg who ingest 0.63 mg of the toxin may die (yes, in mg!). Most curious is the fact that the toxin is not produced by theirselves, but bacteria that ingest through food.

REFERENCES

• Bergbauer, Myers & Kirschner (2009). Guía de animales marinos peligrosos. Ed. Omega
• FishBase: Lagocephalus sceleratus
• IUCN: Lagocephalus sceleratus
• Nader M., Indary S., Boustany L., 2012. FAO EastMed The Puffer Fish Lagocephalus sceleratus (Gmelin, 1789) in the Eastern Mediterranean. GCP/INT/041/EC – GRE – ITA/TD-10

How is the life of a marine turtle?

I have talked about marine turtles in some past posts. In concrete, about the loggerhead sea turtle (Caretta caretta). In the following weeks, I am going to talk more about this amazing marine animals. In particular, this week I will explain how is the life of a marine turtle, especially about the loggerhead sea turtle, and in the next one, I am talking about which are the threats that endanger these animals and about what we can do to save them. 

INTRODUCTION

Loggerhead sea turtle is one of the seven sea turtles on Earth. It has a worldwide distribution, being the most abundant species in the Mediterranean, and it can be identified by the presence of a carapace that measures between 80 and 100 cm long with 5 lateral scutes, so that the first of them is in contact with the nuchal scute. It is endangered according to IUCN (International Union for the Conservation of Nature). The loggerhead sea turtle feeds on jelly plankton like jellyfishes during the oceanic stage, but feeds on fishes and squids in the neritic stage. Additionally, they can consume salt water due to the presence of salt glands placed in the cranium. Like other sea turtles, it cannot hide its head and fins inside the carapace.

Identification key for a loggerhead sea turtle (Caretta caretta) (Picture from MarineBio).

HOW IS THE LIFE OF A MARINE TURTLE?

In marine turtles, the reproductive cycles are circadian, it is that it happens regularly over the time. The periodicity depends on each species, but in the case of the loggerhead sea turtle usually is biannual, so it takes place every two years (but sometimes every three years). Anyway, this cycle is not strict because it is dependant on some factors like food availability or illnesses.

The gregarious behaviour of many species is explained for the ability to recognise the individuals of the same species. In order to recognise each other, most of the species use smell, but they can use sight and sound. During the mating, when the female accept the male, the male bites the female in the neck and in the anterior fins. The male put itself on the female and catches her with the nails of the anterior fins (in the case of the loggerhead, it has two nails per fin). Mating takes place in the sea and usually in the first hours of the day. Moreover, a female can be impregnated by several males.

Mating of a loggerhead sea turtle (Caretta caretta) (Picture: OceanWide Images).

The moment when the marine turtles lay the eggs depend on the moon phases, tides, temperature and wind, but it usually happens during summer in sandy beaches. Females return to the beaches where they were born, coming from feeding grounds. They navigate using marine currents, temperature changes, magnetic signals and the sound and smell of the beach.

Depending on the features of the beach, this will be more or less suitable for each marine turtle species. The loggerhead prefers open and shallow beaches and bays, continental or insular, with a slope between 5-10º and with a calm swell. Moreover, these beaches have to be protected by bushes in the terrestrial part and by coral or rockery reefs in the marine part. They usually lay on the first terrace of the beach, in zones without plants and in the first attempt. All the sea turtles have in common the fact that the lay is done beyond the highest tide.

When the female finds the place, with the anterior fins do a cavity where to place its body (called bed) and next, with the posterior fins, dig out the nest and place the eggs. During the period from which the female leave the water and dig out the nest, the animal is very sensitive to bother and can stop doing the nest and come back to water. 

Sea turtles do several lays per year. In the case of loggerheads, they usually do between 2 and 4 lays per year, with 100 eggs that weights 40 grammes (this is 4 kilos per lay). Despite of this, we have to have in consideration that the number of eggs produced for a female is limited by the capacity of storage of the female, which is related with the size. Between each lay in the same reproductive cycle, the mating is not necessary because they can store sperm.

Turtle laying the eggs in a beach (Picture: Brandon Cole).

Eggs are incubated during 50-60 days under the sand of the beach (in the loggerhead). The hatching is synchronized and when the small turtles reach the surface in few minutes are oriented thanks to the beach slope, the sound of the waves and the light of the moon on the sea.

Loggerhead sea turtle baby (Caretta caretta) (Picture: Rewilding Europe).

During the first days of life, turtles present a high buoyancy. In the first weeks, small turtles remain in marine currents and gyres, where food is abundant, so they have a pelagic life. If they are male, the most probable is that they will never touch the land. 

When they are born, the carapace is soft  and, for this reason, the number of individuals that will survive is just a 10% of which leave the egg due to the predators, like crabs, sharks and seagulls. During the first year only survives 10-30% of the animals. Year after year, the mortality rate decreases for the increase of size and the hardening of the carapace. A study has found that just 10 out of every 10.000 eggs will become adults and just one will die for age.

Adult of a loggerhead sea turtle (Caretta caretta) (Picture: Deviant Art).

Sea turtles do long-distance migrations, specially in the young stage. When they abandon the beach where they were born, during the next 10 years, they will be travelling long distances. The migrations are between feeding and reproductive grounds.

Then, the cycle restarts with the newborns.

REFERENCES

• Cardona L, Álvarez de Quevedo I, Borrell A, Aguilar A (2012). Massive Consumption of Gelatinous Plankton by Mediterranean Apex Predators. PLoS ONE 7(3): e31329. doi:10.1371/journal.pone.0031329
• Consejería de Medio Ambiente de la Junta de Andalucía (2014). Varamientos de Especies Marinas Amenazadas. Guías prácticas voluntariado ambiental.
• CRAM: Caretta caretta
• Dodd, C. Kenneth, Jr. 1988. Synopsis of the biological data on the Loggerhead Sea Turtle Caretta caretta (Linnaeus 1758). U.S. Fish Wildl. Serv., Biol. Rep. 88(14). 110 pp.
• IUCN: Caretta caretta 
• Márquez, R (1996). Las tortugas marinas y nuestro tiempo. México: IEPSA
• Smith, T & Smith R (2007). Ecología. Pearson Educación (6 ed.)

Trotting the sea: seahorses

Little by little, we have been disclosing the wonders that hide seas and oceans of the world: cetaceans, sharks, jellyfishes, starfishes, marine turtles, nudibranchs, pyrosomids, ctenophora, coral, among others. Today we will know a little bit more about some animals with a curious shape: seahorses. 

INTRODUCTION

Seahorses, together with pipefishes and the leafy, ruby and weedy seadragons, constitute the Syngnathidae family. They are small fishes with a long body, which present a unique feature: females lay the eggs inside a pectoral cavity of male, where are fecundated, and then they are released. Watch this video of a male seahorse realising the small seahorses:

These animals live in coastal waters of tropical and subtropical seas, what include Mediterranean sea, mainly in algae and Posidonia. In the Mediterranean, we can find three genus of Syngnathidae:  Hippocampus, Syngnathus y Nerophis; but here we will focus on the first one, which corresponds to seahorses.

SEAHORSES

Seahorses, which use the tail like a tiller and to hold on to objects, maintain their vertical position thanks to an organ that allow their buoyancy called swim bladder (present in all fishes) and the tail. All seahorse species are included in the genus Hippocampus, with about 50 species. They feed on small invertebrates, mainly crustaceans present in the plankton. When the prey is close, its mouth acts as a hoover.

In the Mediterranean, we find two species of seahorse: the short snouted seahorse (Hippocampus hippocampus) and the seahorse (Hippocampus guttulatus).

SHORT SNOUTED SEAHORSE (Hippocampus hippocampus)

The short snouted seahorse, with a brown grey colouration, present a short snout and they lack appendixes in the head and back. They can measure 15 cm. They live in sandy and detritus sea-floors till 10 m deep. When a female wants to introduce the egg mass inside the male, they do not hold on each other. Males release the little seahorses after 4 weeks. Their conservation status is unknown.

Short snouted seahorse (Hippocampus hippocampus) (Picture: Alex Mustard, Arkive).

SEAHORSE (Hippocampus guttulatus)

This seahorse, different from the other one, presents long snout and abundant appendixes in the head and trunk. They can also measure 15 cm long. They usually live in seagrasses, but is quite difficult to see them. In this case, the male and the female hold on to each other when she wants to introduce the egg mass in the male. Its conservation status is also unknown.

Seahorse (Hippocampus guttulatus) (Foto: Florian Graner, Arkive).

REFERENCES

• Ballesteros y Llobet (2015). Fauna i Flora de la mar Mediterrània. Ed. Brau
• Club de Inmersión de Biología: Hippocampus hippocampus
• Club de Inmersión de Biología: Hippocampus guttulatus 
• IUCN: Hippocampus guttulatus 
• IUCN: Hippocampus hippocampus
• Martin (1999). Claves para la clasificación de la fauna marina. Ed. Omega
• Riedl (1986). Fauna y Flora del Mar Mediterráneo. Ed. Omega

Starfishes

Summer is the perfect season of the year to go and enjoy the sea and you probably are one of these people who practise snorkel or who dive. In this case, I want to explain which are the main features of starfishes, with which animals can be confused and some examples of the Mediterranean sea. 

INTRODUCTION

Starfishes (Asteroidea) are included in the phylum of Echinoderms, together with sea urchins (Echinoidea), sea cucumbers (Holothuroidea), crinoids (Crinoidea) and brittle stars or ophiuroids (Ophiuroidea).

Echinoderms: (A) Asteroidea, (B) Ophiuroidea, (C) Holothuroidea, (D) Crinoidea y (E) Echinoidea. (Pictures: Fresno.pntic)

Echinoderms are all marine animals, which present the following main features:

• Body with pentamerous radial symmetry in the adult phase, but with bilateral symmetry in the larval phase (there is just one symmetry axis).
• They are all mobile, except some sessile species (affixed on the sea-floor) of crinoids.
• Endoskeleton consisting of ossicles.
• Water vascular system: system projected from the body wall with some expansions similar to tentacles called podium, which can be spread out due to de liquid pressure. Normally, they present an opening called madreporite.

It is important to remember that they are marine animals and, if you want to observe them, you must not extract them from the water because they begin to die in just 10 seconds. 

STARFISHES

There is about 1,500 species of starfishes, which are all included in the Asteroidea class. Starfishes live in sandy, muddy, rocky and coral reefs seafloors, depending on the species. They can measure from some centimetres to one metre.

Externally, starfishes have a central disc from which the arms are originated. From the mouth, which is placed in the lower part (or oral part), and throughout the arms there is the ambulacral ridge, from which the podiums are originated. The upper part (or aboral part) is usually coarse and with spines. In the base of this spines there is structures called pedicellarie, which function is to remove the particles that remove debris from the body surface and in some cases are used to capture small fishes. Gas exchange takes place through papulae, which are thin-walled bulges on the aboral surface of the disc and arms. Anus and madreporite are placed in the aboral surface.

External anatomy of a starfish (Picture: JKL Bahweting Middle School).

An important feature of echinoderms is the water vascular system. In the case of starfishes, it plays an important role in locomotion, in food capture, in excretion and in breathing.

Many starfishes are carnivorous and feed on molluscs, crustaceans, worms, echinoderms and other invertebrates, sometime on small fishes too. Some starfishes can feed on small particles of plankton or other organic particles.

WATCH OUT! Starfishes can be confused with ophiuroids, but ophiuroids have thinner and more mobile arms than starfishes, in addition to the absence of anus and the fact that they do not use podium to get around, so they move the arms. 

SOME EXAMPLES OF THE MEDITERRANEAN SEA

ASTROPECTEN

This group includes 6 Mediterranean species, which live in sandy and muddy seafloors and with 5 arms covered by scales and spikes. The most common is the red comb-star (Astropecten aranciacus), which present two lines of big and sharp spines, and with a red – orange colouration.

Red comb-star (Astropecten aranciacus) (Picture: NaturaMediterráneo).

BLUE SPINY STARFISH (Coscinasterias tenuispina)

This starfish measures between 7 and 10 cm and usually present between 7 and 9 arms of different sizes, which are covered by small spines. It is bluish white and brown. The most common reproduction system of this species is fission, and for this reason a large section of the coast can be occupied by the same genetic individual. The blue spiny starfish usually lives under the stones.

Blue spiny starfish (Coscinasterias tenuispina) (Picture: Animales Marinos).

SPINY-STARFISH (Marthasterias glacialis)

The spiny-starfish, which can measure 80 cm of diameter, always presents 5 arms, which are covered by hard spikes. Its colouration is greenish or brownish, with light spots when they live deeper. It can live in rocky or sandy seafloors, until 180 metres deep.

Spiny-starfish (Marthasterias glacialis) (Picture: Tato Grasso, Creative Commons).

RED STARFISH (Echinaster sepositus)

Red starfish, which can measure 30 cm, has a red to orange body, with 5 long and cylindrical arms, covered by small spines. It can be found utill 1000 metres deep, always in rocky bottoms.

Red starfish (Echinaster sepositus) (Picture: Tato Grasso, Creative Commons).

HACELIA (Hacelia attenuata)

This starfish, with also 5 cylindrical arms, has a red to orange body. It can be confused with the red starfish, but this has the papulae in longitudinal lines, while in Echinaster their distribution is irregular.

Hacelia (Hacelia attenuata) (Picture: European Marine Life).

STARLET (Asterina gibbosa)

The arms of this little star (from 2 to 4 cm) are not many differentiated from the central disc. It can present different colours, from greenish grey to red. It can be observed on rocks, sand or behind sea-grass.

Starlet (Asterina gibbosa) (Picture: Glaucus).

REFERENCES

• Club d’Immersió de Biologia: Estrelles de mar
• Corbera & Muñoz-Ramos (1991). Els invertebrats litorals dels Països Catalans. Ed. Pòrtic
• Hickman, Roberts, Larson, l’Anson & Eisenhhour (2006). Principios integrales de Zoología. Ed. McGraw Hill (13 ed)
• Martin (1999). Claves para la clasificación de la fauna marina. Ed. Omega
• Riedl (1986). Fauna y Flora del Mar Mediterráneo. Ed. Omega
• Foto de portada: Coscinasterias tenuispina (Foto: F Cardigos ImagDOP)

Fishes with bad spines

This week, after the amazing success of the last post, I will change the direction of the article and I will focus on the fishes with bad spines, it is, fishes with venomous spines, but focusing on the Mediterranean species. 

INTRODUCTION

Despite seas and oceans of the planet are inhabited by a high number of potentially dangerous animals for humans, understanding its danger for bites, electric discharges or for its consumption; the truth is that in only few cases these animals attack deliberately; so, accidents are that: accidents produced by ignorance or carelessness. We have to have into consideration that we are not a prey of this fishes, so: which is the sense that this animals attack us deliberately?

These fishes with bad spines are catalogued as actively venomous animals, it is, they have a venomous apparatus with glands that produce poison and a mechanism that permits the introduction inside another animal, like spines or teeth. This poison are used to defend themselves or/and to capture their preys.

PREVENTION IS BETTER THAN CURE

These are some tips to prevent possible injuries when you go to the beach or when you are diving. They are useful to avoid venomous fishes and other marine animals:

Prevention at the beach

• To inform about venomous animal of your destination.
• Don’t touch anything that you don’t know.
• Watch your step. There may be sea urchins or fishes…
• Taking a swim at night or in desert beaches suppose more risk.
• Use full-body neoprene in waters with potentially dangerous fauna, like Australia.
• Don’t swim close to the bottom (sand, rocks or reefs).

Prevention while diving

• Control your flotability in order to don’t touch anything.
• Don’t put your hands inside cavities, cracks or holes if you don’t see the interior.
• Leave a exit way for animals.
• Don’t feed fishes.

MEDITERRANEAN FISHES WITH VENOMOUS SPINES

Myliobatiformes

Description. They include whiprays. Their body is flatten and with a circular or rhomboidal shape. They are the only venomous fishes that can produce a deep wound. The venomous spines are place in the upper part of the tail, with different shapes, sizes and positions according to the family. They usually are on the seafloor (benthonic species), often buried with sediment and with the eyes and spiracles on the water, so the most part of the accidents are for involuntary footsteps.

Danger. In whiprays, the needle is placed far from the the base of the tail, what allows for a wide outreach, but only it is a defensive weapon. The needle is hard and with hooks in the edge. It is in its interior where are venomous glands, which acts on heart muscles. In addition to the wound, the symptoms are: nausea, diarrhoea, vomit, sweating, circulatory disruptions and anxiety.

Mediterranean  species. There are two venomous species in the Mediterranean: roughtail stingray (Dasyatis centroura) and common stingray (Dasyatis pastinaca). Roughtail stingray can measure 210 cm, has a rhomboidal shape and in the central part of the back and in the tail it has bony tubercles. They live in coastal waters, where feed on crustaceans, cephalopods and small fishes. On the other hand, common stingray, that also inhabits in coastal waters, doesn’t have bony tubercles in the back, but in the tail.

Roughtail stingray (Dasyatis centroura) (Picture: Okeefes)

Common stingray (Dasyatis pastinaca) (Picture: Ictioterm)

Scorpaenidae

Description. With a robust body, Scorpaenidae fishes have big pectoral fins and a wild and big head. Its colouration is brown reddish and irregular.

Danger. Most of the species live on the rocks or behind corals, so the risk is on step on them. The poison produce a reduction of pressure and lung edema and an increase of pressure on lung arteries, and cramps. The hard spines placed in front of the dorsal fin, the three first of the anal fin and the two first of the ventral fins present poison.

Mediterranean species. In the Mediterranean, there is 3 species with venomous spines: the largescaled scorpionfish (Scorpaena scrofa), the small red scorpionfish (Scorpaena notata) and the brown scorpionfish (Scorpaena porcus). The largescaled scorpionfish is the biggest species in the Mediterranean (till 50 cm) and live in rocky and sandy seafloors. It can be easily identified by long dorsal spines with separated membrane. On the other hand, the small red scorpionfish has a short tentacle above each eye, has not appendixes in the chin, its size is about 20 cm and with a black spot in the dorsal fin. Finally, the brown scorpionfish has large tentacles above the eyes and in the chin.

Largescaled scorpionfish (Scorpaena scrofa) (Picture: Ictioterm)

Small red scorpionfish (Scorpaena notata) (Picture: Dein Freund der Baum, Creative Commons).

Brown scorpionfish (Scorpaena porcus) (Foto de Maestro Pescador)

Trachinidae

Description. These fishes has a long and laterally flatten body. The mouth is wide and orientated upwards.

Danger. All the species live in sandy seafloors, where bury theirselves. The venomous spines are the 5-7 first of the dorsal fin and the spine in the gill operculum. The poison produce an intense pain in the affected zone and cause sweating, nausea and secondary infections.

Mediterranean species. There are two venomous species in the Mediterranean: streaked weever (Trachinus radiatus) and the greater weever (Trachinus draco). The streaked weever can be identified by: a brown yellowish to gray body with dark spots and the first dorsal fin has six spiny spines. Such can be the gravity of the bite that can be lethal. The greater weever has a grey greenish to brown yellowish body; with short, dark and yellow lines and with 5-7 spiny spines in the first dorsal fin.

Streaked weever (Trachinus radiatus) (Picture: SnipView).

Greater weever (Trachinus draco) (Picture: Biopix).

Rabbitfishes

Description. They are typical species of coral reef and in lagoons in Indian and Pacific oceans, but one species can be found in the Eastern Mediterranean, where lives in rocky seafloors with algae. Its body is oval and very laterally flatten, with a small head and mouth.

Danger. Rabbitfishes are shy, so it is difficult to be hurt by their spiny spines, which are all over the body: 13 in the dorsal fin, 7 in the anal fin and 2 more in the ventral fin. Poison causes a hard pain, but it doesn’t persist so much.

Mediterranean species. The marbled spinefoot (Siganus rivulatus) has an olive light body with irregular brown spots. It can be confused with salema porgies (Sarpa salpa). It is an invasive species.

Marbled spinefoot (Siganus rivulatus) (Picture: Stephan Moldzio, Fishbase).

Remember: you don’t have to be afraid of sea and nature. With common sense and respect towards nature you won’t suffer any harm.

REFERENCES

• Ballesteros E & Llobet, T (2015). Fauna i flora de la mar Mediterrània. Ed. Brau
• Bergbauer, Myers & Kirschner (2009). Guía de animales marinos peligrosos. Ed. Omega
• Martin, P (1999). Claves para la clasificación de la fauna marina. Ed. Omega
• Riedl (1986). Fauna y Flora del Mar Mediterráneo. Ed. Omega

Cetaceans have a negative response to summer maritime traffic in Westeran Mediterranean Sea

A team of researchers of several Italian organizations has published on May 2015 its findings about the responses of cetaceans in high sea waters to summer maritime traffic in the Western Mediterranean Sea. This post is a summary of this study. 

INTRODUCTION

Nowadays, cetaceans have to face several threats, like the loss of their habitat, depletion of resources, interaction with fisheries and chemical and acoustic pollution, among others. In the case of ship transport, it can cause long-term changes in distribution, short-term changes in behaviour or direct physical injuries (e. g. collisions).

The Mediterranean Sea is one of the world’s busiest waterways. Moreover, shipping traffic is growing together with the concern of its impacts on fauna. In addition, we have to have in consideration that summer month are the busiest in naval traffic, especially due to the increase on cruise ships and passenger ferries.

The goal of this study was to outcome if the intensity of traffic in high sea waters was statistically different between presence and absence of cetacean sightings.

STUDY AREA AND DATA COLLECTION

Because of most of the Mediterranean cetaceans are mainly pelagic and there is a lack of information in these areas, the research had been conducted along six transects within shipping routes that connects Italy, France and Spain in high sea waters (placed in Ligurian-Provençal basin, the northern and central Tyrrhenian Sea and the Sardinian and Balearic Seas).

Mediterranean Sea basin (Picture from Encylopaedia Britannica)

The transects were surveyed from June to September between 2009 and 2013 using ferries as observation platforms. During this period, more than 95,000 km were surveyed and the presence of eight cetacean species was recorded.

Introductory online course on cetaceans. Now, 40% off, till 30th June. Available only in Spanish. More info here. Click the picture to access to the coupon. 

CETACEANS AND MARITIME TRAFFIC

In locations with cetacean sightings, the number of vessels was 20% lower than the number of vessels in the absence of sightings. In the case of the three most frequently sighted species; fin whale (Balaenoptera physalus), striped dolphin (Stenella coeruleoalba) and sperm whale (Physeter macrocephalus); this difference was, respectively, 18%, 20% and 2%. Concerning other species, in the case of Cuvier’s beaked whale (Ziphius cavirostris) the difference was 29% and in the Risso’s dolphin (Grampus griseus) was 43%. It was found that for bottlenose dolphins (Tursiops truncatus) the difference was insignificant. Finally, for common dolphin (Delphinus delphis) and for pilot whale (Globicephala melas) any conclusion can be given.

Nevertheless, despite the number of ships recorded during cetacean sightings was lower in all areas, the percentage difference range from 11 to 49% among areas.

So, in high sea areas during summer, where cetaceans were seen, there were a significantly lower abundance of ships. Some explanations can be given: animals could tend to avoid more impacted zones with small displacements by seeking areas with fewer vessels, could change their distribution to occupy low traffic areas or could increase diving activity where intense traffic occurs. The intensity of the response of cetaceans to the intensity of traffic has important differences among areas and species. So, there are several factors that affects this percentage difference, like specific ecological needs and local environmental conditions. 

In the case of fin whale, where marine traffic is intense, the presence of fin whales is generally lower, with the exception occurring in the central part of the Ligurian Sea. The explanation could be that this region is ecologically favourable in summer since it is a feeding ground for this species and these whales are present for feeding reasons. Therefore, there is a coexistence between traffic and fin whales.

Fin whale (Balaenoptera physalus) (Picture from Circe)

Another example is striped dolphin. Due to its high mobility, this dolphin can avoid the presence of vessels and this could be the reason why there is a negative response between this species and ship presence.

Striped dolphin (Stenella coeruleoalba) (Picture from Marc Arenas Camps)

About sperm whale and Cuvier’s beaked whale, there were no difference in both species in the Ligurian Sea and the reason probably is that sperm and Cuvier’s beaked whale have their feeding grounds in this basin and, moreover, the slopes and submarine canyons are confined in specific areas. However, differences are observed in other areas.

Sperm whale (Physeter macrocephalus) (Picture: Gabriel Barathieu, Creative Commons).

Cuvier’s beaked whale (Ziphius cavirostris) (Picture: Todd Pusser, Arkive).

Finally, bottlenose dolphin did not show any response to traffic. Probably, because it is a coastal species, it is more used to sharing its typical habitat with maritime traffic.

Bottlenose dolphin (Tursiops truncatus) (Picture: Brandon Cole).

REFERENCES

This post has been based on this paper:

• Campana, I; Crosti, R; Angeletti, D; Carosso, L, David, L; Di-Méglio, N; Moulins, A; Rosso, M; Tepsich, P & Arcangeli, A (2015). Cetacean response to summer maritime traffic in the Western Mediterranean Sea. Marine Environmental Research, 109, 1-8

You can save bluefin tuna!

Bluefin tuna is an endangered predator fish. Last week, we explained that other species like sardines and mackerel are also endangered due to overfishing. This week, we will focus on this species and we will explain its biology and distribution, in addition to the reasons why it is under threat. 

BIOLOGY

Bluefin tuna (Thunnus thynnus) is the biggest species of the Scombridae family and one of the biggest bony fishes. Despite they can achieve a length of 3 meters, they usually range between 0.4 and 2 meters. Moreover, they weight between 140 and 680 kilos, but it is difficult to find an organism that exceed 450 kilos. It is a migratory animal with a high economical value for its red and dusky meat. The body is fusiform and can be distinguished from the rest of tunas by pectoral fins: they are rather short and reach the 11th or 12th dorsal spine.

Bluefin tuna (Thunnus thynnus) (Picture from Club de la Mar).

Back and upper sides are dark blue to black, with a grey or green iridescence. Inferior sides are silvery with grey spots and bands. Anal in is dark and yellow.

Diet of bluefin tuna includes squids, eels and crustaceans, but also schooling fishes like herrings and mackerels.

DISTRIBUTION

Bluefin tuna lives in subtropical and temperate waters of North Pacific, Atlantic, Mediterranean and Black Sea. Despite bluefin tuna can be found along the year in the Mediterranean, they are present mainly in June and July.

Free bluefin tuna (Picture from Animals on Earth).

CONSERVATION STATUS AND PROBLEMS

According to IUCN, bluefin tuna is endangered and its population is in decline. Due to overfishing, being the most important the illegal fishing, it is estimated that Western Atlantic population has decreased in an 87% since 1970. Anyway, other references indicates that this drop has been between 29 to 51%. In 1996, scientist alarmed that worldwide catch quotas must be reduced an 80% to recover populations in 20 years, but in fact they were increased. Nevertheless, it seems like the reduction of captures recently has produced an increase of populations.

Because they achieve maturity in an advanced age, they are specially vulnerable to overexplotation. Despite catch quotas have been established, the measure have not had always success for several reasons: disembark of small fishes (and big) has continued, the lack of regulations in some areas, fishermen ignore restrictions in some countries and the lack of fines when breaking the lows.

Between 2000 and 2004, it had been captured about 32,000 – 35,000 tonnes per year in the Eastern Atlantic and Mediterranean, achieving 50,000-60,000 tonnes in 2006, so the stock status is overexploited. Nowadays, the catch quota is restricted to 13,500 annual tonnes, but 3,000 tones are for Spain.

This tuna is captured with different types of fishing: purse-seine, longline and tramps. The reason of its fishing is to meet demand of Japanese market of sashimi (just one piece of tuna can be sold for 90,000€), what caused its overfishing. In addition, it is a goal species in recreational fishing of United States and Canada.

Bluefin tuna sashimi (Picture from TripAdvisor).

So, fisheries are being reduced and, at the moment, neither European Union nor other countries have acted to save it. In addition, governments have ignored experts.

¿WHAT WILL IT HAPPEN IF WE RUN OUT OF BLUEFIN TUNA?

Bluefin tuna is a predator of jellyfishes. Its reduction, together with the rise of sea temperature, is causing a rising of jellyfishes. Moreover, its disappearance would produce an imbalance of food webs.

If you are worried about the status of bluefin tuna and the oceans, when you go to a fish market, don’t buy it and also when you go to a Japanese restaurant, refuse to eat any dish with tuna. Only reducing the demand, we will be able to stop its fishing. 

REFERENCES

• Schultz, K (2003). Field guide to Saltwater fish. Wiley (1 ed).
• IUCN: Thunnus thynnus. 
• Slow Food: El atún rojo.
• WWF: Atún rojo

Mediterranean Monk Seal: Until when will it survive?

In this post, we will do an approach to Mediterranean Monk Seal (Monachus monachus), a critically endangered species that, in fact, is the most endangered pinniped species in the world. Here, we are going to do a short historical review and we are going to talk about its natural history, its habitat and distribution, its threats and status and, finally, its conservation. 

INTRODUCTION

Mediterranean Monk Seal (Monachus monachus) is one of the three species included in the genus Monachus (Monk Seals). The other two species are Hawaiian Monk Seal (Monachus schauinslandi), which is critically endangered, and Caribbean Monk Seal (Monachus tropicalis), which is extinct.

Mediterranean Monk Seal (Monachus monachus) (Photo: Sá, Wild Wonders of Europe)

Mediterranean Monk Seals were hunted for fur, oil and meat since Prehistory. Romans were responsible of an important decline, but thanks to the empire’ fall the animals were able to recover. More recently, the two world wars, the industrial revolution, the explosion of tourism and industrial fishing have produced the reduction and disappearance of the species in some regions.

MEDITERRANEAN MONK SEAL’S NATURAL HISTORY

When they are born, their length is 94 cm and their weight is 15-20 kg. Until weaning (at about 16-17 weeks), growth takes place fast. The pups’ pelt is soft and downy and the coat is black to dark brown, with a white patch in the belly.

Adult individuals have a length of 2.4 m (from nose to tail) and weigh 250-300 kg. Males are only slightly bigger than females. Juveniles and adults have very short hair. While adult males are black with a white patch in the belly, adult females are brown and grey with a lighter belly colouration. In any case, they can present more patches on the throat (males) and back (females).

Female individual of Mediterranean Monk Seal (Photo: Sá, Wild Wonders of Europe)

Male individual of Mediterranean Monk Seal (Photo: Sá, Wild Wonders of Europe)

Males and females reach sexual maturity between 5 and 6 years. After a gestation lasting 9-11 month, one pup is born (generally in autumn).

They feed on fish and cephalopods.

HABITAT AND DISTRIBUTION

This species’ habitat is inaccessible caves with underwater entrances. The truth is that in ancient times, they inhabit open beaches of sand and rocks. Mediterranean monk seals can be found in warm temperate, subtropical and tropical waters of the Mediterranean Sea and the east Atlantic Ocean.

Mediterranean Monk Seal habitat (Photo: Sá, Wild Wonders of Europe)

Mediterranean Monk Seal on beach (Photo: Hellio & Van Ingen)

In ancient times, the species’ distribution was bigger than now. While now they just are present only in the northeast Mediterranean and in the northeast Atlantic, long ago they were present in all through the Mediterranean Sea, Black Sea, Atlantic coast of Africa and some Atlantic islands.

Distribution map of Mediterranean Monk Seal (Monachus monachus) (Picture: TheAnimalFiles.com)

STATUS AND THREATS

With just 350-450 individuals (maybe 550), the Mediterranean Monk Seal is one of the world’s most endangered marine mammals and is the most endangered pinniped species and it is described as critically endangered by IUCN.

Mediterranean Monk Seal is critically endangered, according to IUCN (Picture: IUCN).

The main threats against the species are:

• Habitat degeneration and loss by development in the coast. The driving causes to this may be hunting, mass tourism, pleasure boats and diving. The result is that the caves occupied now are not adequate for their survival, so the recovery is only possible if they return to sandy beaches.
• Killing them on purpose by fisherman and fish farm operators because they find it a nuisance that destroys their nets and steals their fish. In Greece, deliberate killing accounts for 43% of the deaths of adult and juvenile animals.

Deliberate killing of a Mediterranean Monk Seal (Monachus monachus) (Picture: E. Tounta, MOm).

• Accidental entanglement in fishing gear. It is unknown if this has an important impact nowadays, but in the recent past it was and, in fact, it has played a significant role in the elimination of the species from some parts.
• Decreased food availability due to overfishing. Malnourishment; susceptibility towards pathogens; affected growth, reproduction, juvenile survival and mortality rate and dispersion are the possible effects of this.
• Unusual events: disease (like morbillivirus), toxic algae, rockslides, cave collapses or oil spills.
• Pollution, maybe caused by organochlorine compounds used in pesticides.
• Inbreeding depression, that results in reduced fecundity and pup survival. This factor is not a significant threat in the short term, but it can be a future threat because this causes reduced fertility, increased infant mortality and a distorted sex ratio.

CONSERVATION

Since 1970s, conservation measures have been developed, but the improvements are hardly seen. Conservation measures include:

• Development of marine protected areas (MPA) in Madeira, Greece, Turkey and Cabo Blanco. In fact, what is necessary is a network of MPA.
• Orphaned and hurt animals are rescued.
• Educational programs.
• Scientific investigation to identify its habitat areas.
• International coordination of conservation activities.

On the other hand, ex situ conservation measures (like captive breeding and translocation) are not used because the species is so sensitive to human disturbance that it could be another threat.

REFERENCES

• Fauna Iberica: Foca monje
• IUCN Red List: Monachus monachus 
• MarineBio: Mediterranean Monk Seals
• NOAA Fisheries, Office of Protected Resources: Mediterranean Monk Seal
• The Monachus Guardian (main source)
• Wildscreen Arkive: Mediterranean Monk Seal

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Jellyfishes: what are they and how can we identify them?

Jellyfishes generally are marine animals that, like anemones, gorgonians and corals, like the red coral of the Mediterranean, are part of the cnidarians. In this article, we will see what is a jellyfish and how can we identify the most common ones. Moreover, we will know its danger. If you arrive at the end of the post, you will find a little surprise. 

INTRODUCTION

Cnidarians are one of the most ancient animals that inhabit in the Earth, as they appeared 600 million years ago. They are characterized by the presence of a cells called cnidocytes, which have urticating organelles. It is thought that nowadays there are more than 9,000 species, classified in four classes: Anthozoa, Scyphozoa, Cubozoa and Hydrozoa. Despite they have a simple structure and functionality, they inhabit almost all the aquatic environments, mainly marine. There are two basic forms in the life cycle of a cnidarian: polyp, in which the animal is sedentary, with a tubular body and that reproduces asexually; and medusa, which can freely swim, with a bell-like shape and that reproduces sexually. There are organisms that only are one of this two stages, while others are polyp first and then medusa.

Cnidarian body plan (Picture from College of DuPage BIO1151)

WHAT IS A JELLYFISH?

Like we have seen, jellyfishes are a morphological type of cnidarians and they don’t constitute a taxonomical group by themselves. Despite its shape is a little bit variable, they are much less variable than polyps because all of them live in a similar way. Almost all of them have a free life, but there are some cases in which they are retained in the polyp’s colony, acting as reproductive structures.

Its shape is bell-like, plate-like or umbrella-like, with a thick jellied layer. The external surface (exumbrella) is convex and the internal (subumbrella) is concave. Hydrozoa’s jellyfishes have the mouth in the central, lower part of the umbrella, in the end of a tubular extension called manubrium, while in the Scyphozoa this is very reduced. Tentacles hang from the umbrella and they are full of cnidocytes. Jellyfishes never form colonies, but they can live in shoals. Many people confuse jellyfishes with ctenophora, but with this features you can’t confuse them.

IN WHICH CLASSES ARE THERE JELLYFISHES?

Anthozoa never produce jellyfishes.

Scyphozoa constitute the group of the biggest jellyfishes. The fact that they don’t have velum is what allows to differentiate Scyphozoa’s jellyfishes from Hydrozoa’s jellyfishes. The margins of the mouth form oral arms, which can be very long.

Many hydrozoa produce jellyfishes. These are almost transparent and small. Different from Scyphozoa’s jellyfishes, they present velum in the margin of the umbrella, which is a withdrawal of the tissues. 

General morphology of an Hydrozoa’s jellyfish (Picture obtained from Systematic Biology).

Jellyfishes of the Cubozoa class have cube-like shape, with one or more tentacles in each edge. They are usually very poisonous.

KEYS TO IDENTIFY JELLYFISHES FROM THE MEDITERRANEAN SEA

Despite the main species of the Mediterranean Sea can be easily identified by their looks, here we are exposing a simplified dichotomous keys  in order to recognise the 8 most common species.  

1. Jellyfishes with velum (Hydrozoa’s jellyfish)
   • Pelagic colony in which the individuals are specialized on doing different functions (Subclass Siphonofora)
     • The central part of the colony is a flatten disc with a jellied consistency (Order Anthomedusae): Velella velella
     • Centre without a disc-like shape (Order Siphonophora): Physalia physalis
   • Jellyfish with a little contractile umbrella and a very mobile velum:
     • Entire margin of the umbrella: Olindas phosphorica
     • Margin of the umbrella with vertical lines that are divided into lobes: Solmissus albescens
2. Jellyfishes without velum (Scyphozoa’s jellyfishes)
   • Jellyfishes with just one oral opening:
     • Short tentacles: Aurelia aurita
     • Long tentacles: Pelagia noctiluca
   • Jellyfishes with the mouth plugged by tentacles:
     • Long tentacles: Rhizostoma pulmo
     • Short tentacles: Cothylorhiza tuberculata

JELLYFISHES OF THE MEDITERRANEAN

By-the-wind-sailor (Velella velella)

By-the-wind-sailors (Velella velella) are organisms with a diameter of the disc between 1 and 8 cm. This disc is circular or oval, blue and has an small sail. In the periphery, there is a ring of polyps with a tentacle-like shape. It means that they actually aren’t jellyfishes, but they are colonies with appearance of a jellyfish. This jellyfish is frequently seen in our coasts, whose danger is law, almost non-existent.

By-the-wind-sailor (Velella velella) (Picture: Denis Riek)

Portuguese man of war (Physalia physalis)

The Portuguese man of war (Physalia physalis) present a buoyant part that measure 30 cm long and 10 cm wide, which is purple and transparent. In the submerged part, there are the tentacles, which are thin and long, so long that can measure 20-30 m (yes, metres!). Despite it is a rare species, it is highly dangerous due to neurotoxic, citotoxic and cardiotoxic toxins. Their bites are very painful and in some cases can produce death. Like the previous one, it is a colony of polyps, so it is neither a jellyfish.

Portuguese man of war (Physalia physalis) (Picture from Madrimasd)

Olindias phosphorica

Olindias phosphorica is a jellyfish with a yellow and pink-blue umbrella, that present several channels towards the centre. Gonads are very patent and have a dun and reddish colouration. It has a high danger because its bite is painful, similar to a wasp.

Olindias phosphorica (Picture of Jordi Regàs)

Solmissus albescens

Solmissus albescens is characterised by the presence of 12-16 white tentacles and many quadrangular lobes. The umbrella is transparent and it looks like crystal. Measure between 2,3 – 3 cm of diameter.

Solmissus albescens (Picture of Jordi Regàs).

Common jellyfish (Aurelia aurita)

Common jellyfish (Aurelia aurita) is an animal with an umbrella similar to a plate, with 25 cm of diameter, transparent but spotted in blue. It has 4 oral and long tentacles and other shorter in the margin. The four reproductive organs are purple-violet and has a shape similar to horseshoe. It is frequently seen, with a low danger because its poison is little toxic.

Common jellyfish (Aurelia aurita (Picture of Alexander Vasenin, Creative Commons)

Pink jellyfish (Pelagia noctiluca)

Pink jellyfish (Pelagia noctiluca) is the most frequent jellyfish in the Mediterranean. It can be recognized for the presence of a pink to red umbrella of 5-10 cm, from which hangs 4 oral tentacles and 16 marginal tentacles that can measure 2 m long. The surface of the umbrella has brown spots. Its danger is high because its poison is powerful, although it is not lethal. Curiosity: it is luminescent during the night.

Pink jellyfish (Pelagia noctiluca) (Picture of Jordi Regàs).

Compass jellyfish (Chrysaora hysoscella)

Compass jellyfish (Chrysaora hysoscella) is an animal with flatten umbrella that can achieve 30 cm of diameter, which is reddish white and with 16 brown strips. It has 4 oral and long tentacles and 24 marginal ones. Its danger is high, similar to pink jellyfish, despite is much less frequent than this.

Compass jellyfish (Chrysaora hysoscella) (Picture: Antoni López-Arenas i Cama)

Shiff arms jellyfish (Rhizostoma pulmo)

Shiff arms jellyfishes (Rhizostoma pulmo) are animals with an umbrella that measures between 10 and 40 cm of diameter, bell-like shaped, blue white and with a violet margin. They just have 8 oral, joined, not branched and blue white tentacles. It is frequently seen and its danger is high because it causes irritation and burning.

Shiff arms jellyfish (Rhizostoma pulmo) (Picture of Jordi Regàs)

Cotylorhiza tuberculata

Cothylorhiza tuberculata has a look similar to fried egg. The umbrella is flatten, measures between 20 and 35 cm of diameter, yellowish brown and with an orange protuberance in the middle. They have 8 oral tentacles covered with button-like appendixes in the end that are blue or white. Its danger is low and it is one of the most common.

Cotylorhiza tuberculata (Picture of Jordi Regàs)

BONUS TRACK: CITIZEN SCIENCE

The Institute of Marine Sciences (CSIC) is doing a research about jellyfishes, which is at the same time a citizen science project in the context of Seawatchers. If you want to collaborate, here there is the information.

REFEREES

• Species Guide of the Dive Club of Biology
• Jellyfish alert Project of the Institute of Marine Sciences
• El mar a fondos: Cnidarios
• Rupert Riedl (1986). Fauna y flora del Mar Mediterráneo. Editoral Omega
• Martin (1999). Claves para la clasificación de la fauna marina. Editorial Omega
• Hickman, Roberts, Larson, l’Anson & Eisenhour (2006). Integrated Principles of Zoology. Editorial McGraw Hill (13th ed.)
• Brusca & Brusca (2005). Invertebrates. Editorial McGraw Hill (2nd ed.)

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