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, 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.
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.
Ballesteros y Llobet (2015). Fauna i Flora de la mar Mediterrània. Ed. Brau
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.
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
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.
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 scorpionfishhas 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.
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.
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.
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.
Ballesteros E & Llobet, T (2015). Fauna i flora de la mar Mediterrània. Ed. Brau
Last week, we saw the mechanisms of poikilotherm fishes (or cold-blooded fishes) to fight against high and low temperatures. This week I will talk about endotherm fishes (or warm-blooded fishes).
99% of fishes are cold-blooded, it is that the body temperature is similar to water temperature. Since some weeks ago, it was known that tuna, the group of basking sharks and swordfishes are regionally warm-blooded animals. Now, it is known that, in addition to this regionally warm-blooded specie, opah is totally endotherm.
This warm-blooded fishes, either regionally or totally, have, in general, something in common: they are big predators of fast preys and their bodies are hydrodynamic.
THE CASE OF TUNA AND BASKING SHARKS
Tuna and basking sharks have myoglobin-rich muscles (a blood pigment useful for the diffusion and storage of oxygen inside muscles), called red muscles, which are the responsible of swimming, which increase a lot temperature during this activity. Thanks to these muscles, this animals can constantly swim because they give the necessary energy. But, as they breathe through gills, it is necessary something more to maintain a constant temperature.
This “something” is counter-current circulatory system of the blood. The red muscles are placed close to vertebral column. Longitudinal arteries and veins carry the blood for all the body and are placed en each side of the body under the skin. Longitudinal arteries branch in small arteries that go to red muscles. Blood move away of red muscles through veins that flow into longitudinal veins, and go to heart. It is called a counter-current circulation because arteries carry the blood to red muscles and veins move away blood from there. In fact, main arteries and veins divide into small crossed vessels, what is called a rete mirabile.
This counter-current system allows that heat received in veins from red muscles is transferred into arteries that get in in them, instead of going to the periphery of the body and gills, where this heat would be lost to water. So, it allows to maintain the heat produced in red muscles.
Some species of tuna, like bluefin tuna, and of basking sharks, moreover, can maintain a high temperature in other parts of the body, like stomach and guts, brain and eyes. This organs are irrigated by a rete mirabile.
THE CASE OF SWORDFISH
Swordfishes have two particularities that differ from the prior examples:
They just heat the brain and ocular retina.
They have heater tissues.
Heater tissues consist on an extraocular muscles, that in the past were the responsible of moving the eyes in all directions. Nowadays, they are not contractile, but maintain a lot of mitochondria, which are the responsible to produce heat. This heat is maintained in the head of the animal due to a counter-current circulation, allowing the warming of brain and retina.
THE CASE OF OPAH
A study published in Science this May has revealed that opah (Lampris guttatus) is a totally warm-blooded animal. According to this study, body temperature of opah is 5ºC higher than sea temperature.
Most of this heat is produced in pectoral fin muscles, which are surrounded by a fat layer of 1 cm that acts as a thermal insulation. Despite of this, to maintain a high body temperature, they use their gills (like a radiator), in which there is a counter-current circulation of the blood. So, blood warmed in muscles of pectoral fins goes to gills to get oxygen, but avoid the loose of heat with a counter-current system.
Moreover, they have a secondary circuit that maintain the temperature in the brain and eyes.
Hickman, Roberts, Larson, l’Anson & Eisenhour (2006). Principios integrales de Zoología. McGraw Hill (13 ed).
Hill, Wyse & Anderson (2006). Fisiología animal. Editorial Medica Panamericana (1 ed)
Wegner, N; Snodgrass, O; Dewar, H & Hyde, JR (2015). Whole-body endothermy in a mesopelagic fish, the opah, Lampris guttatus. Science. Vol. 348 no. 6236 pp. 786-789, DOI: 10.1126/science.aaa8902
Oh the occasion of the accident of the Russian fishing boat called Oleg Naydenov close to Grand Canary (Spain), the article of this week is about the effects of petroleum on marine environment. Here, I am going to talk about the origin of the petroleum in the sea, which are the transformations that suffer and the effects on marine fauna and flora.
The accident of the Russian fishing boat called Oleg Naydenov off of Grand Canary, which has finished with its sinking, is causing the appearance of oil in an area of 12 square km. The reason is that it sank with more than 1,400 tonnes of oil, 30 of diesel oil and 65 more of lubricant.
ORIGIN OF HYDROCARBONS IN THE SEA
Despite oil tanker accidents have a huge impact in the media, they represent a small portion of the amount of hydrocarbons that get in the sea. In general terms, these are the main sources of petroleum in the sea:
Industrial discharges and urban dredging: 37%.
Boat’s operations: 33%.
Oil tanker accidents: 12%.
Natural sources: 7%.
Exploration and production of hydrocarbons: 2%.
Although this values can vary depending of the sources, in general they represent quite good the proportions. It has been estimated that, each year, are poured into the sea 3,800 millions of litres of hydrocarbon, equivalent to 1,500 Olympic pools.
HYDROCARBON TRANSFORMATIONS IN THE SEA
When hydrocarbons are spilled into the sea (accidentally or deliberately), their features and shape change. This changes are physical, chemical and biological. This are the mechanisms:
Evaporation: it allows that certain substances of the hydrocarbons go to the atmosphere, reducing about 40% its volume just in the first day. In any case, the surrounding atmosphere will be flammable.
Dispersion: it consists on the fragmentation of the oil patch into small drops. When these drops are small enough, they remain in suspension and they mix with water and favours the biodegradation and sedimentation.
Emulsification: consists on the absorption of water so the hydrocarbon’s volume increases between 3 and 4 times. This hampers the oxidation and biodegradation.
Solution: depending on the product’s composition, the water temperature and its agitation. Only the more volatile components can be dissolved.
Oxidation: the effect of the oxidation can produce a compound that is easier or more difficult to degrade.
Sedimentation: consists on the down vertical displacement of the hydrocarbon’s particles. Depending on its density (with respect to water), the size and the agitation of the sea.
Biodegradation: consists on the elimination of hydrocarbons by living beings, like bacteria and fungus.
PETROLEUM’S EFFECTS ON MARINE ENVIRONMENT
As we have said in the beginning of the post, the main goal of this is to comment which are the effects of petroleum (and other hydrocarbons) on marine fauna and flora. Let’s start!
The effects of petroleum on fauna are wide due to the high diversity of marine organisms. The main effects on the marine biodiversity are:
Direct contamination: petroleum sticks on feathers, fur and scales, what make difficult the thermal isolation, movements and other important functions. As a consequence, this kills fishes, marine mammals and birds.
Modification of gas exchange: the petroleum sheet reduces the content of oxygen in the water, what produce the dead of the plankton and fishes, what produce the dead of the organisms that feed on them.
Alteration of seafloor: when petroleum is placed over the seafloor kills and produce sublethal effects on benthonic flora and fauna.
Intoxication: petroleum poisons marine fauna, soaking into its digestive system and its skin and mucosa. The result is, on the one hand, the dead for suffocation and genetic disruptions on fishes, molluscs, marine mammals, reptiles and birds; and, on the other hand, the intoxification of other organisms like humans when they feed on them.
Increase of the infections: because petroleum produces a reduction of the resistance to infections. This is specially important in birds because when they clean the feathers theirself, they swallow petroleum, so they present sublethal concentrations.
Negative effects on fertility, reproduction and propagation of fauna and flora.
Modification of the behaviour.
Destruction of food sources.
Incorporation of cancerous substances on food webs.
Effects on the availability of light: we cannot forget that the petroleum patch in the sea surface produce an important reduction of light in the water column. This causes a reduction or elimination of photosynthesis, essential process for the maintenance of food webs because the algae growth depends on light, which is consumed by herbivorous (and so on) and produce an oxygen input into the water. Moreover, we have to take in consideration that algae communities are shelter for many larvae and youthful fishes.
Marine communities alteration: at community level, there is a gradient of vulnerability of oil spills. From less to more vulnerability, the communities are: exposed cliffs, exposed rock platforms, fine sand beaches, middle to big sand beaches, exposed tidal planes, big sand beaches, gravel beaches, protected rocky beaches, protected tidal planes, marshlands and mangroves, subtidal seafloors of sand and gravel, mud subtidal seafloors, batial and abyssal seafloors, infralittoral and circalittoral seafloors and reef corals.
Notes of the subject Ecotoxicology and marine pollution of the Master in Oceanography and Marine Environment Management of the University of Barcelona.
EmerCoast Coast. “Training on marine pollution risks. Environmental risks in the littoral and marine environments”.
Course”Marine Pollution” from EuroInnova.
Greenpeace (2012). Environmental impact of petroleum (Brochuere).
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