Sex change is also in animals

Sex change is not only present in humans (known as transexuality), but there are some examples of animals that change sex, that is, they are born male or female, and throughout his life, species change to the opposite sex. Do you want to know some of these species? Remember that you can also read a post in this blog about Homosexuality in animals.

TRANSEXUALITY IN ANIMALS

The animal sex change is a fact not very widespread, but is present especially among fish and some mollusks, jellyfishes, crustaceans, echinoderms and worms.

However, in the case of animals, the term used is not transsexuality. The change of sex in the animal kingdom is a particular type of hermaphroditism: sequential hermaphroditism.

This change of sex is usually genetically programmed and  it is influenced by the environment in which it develops. However, at birth they have already both sexes, so that sex determination is not given by the genes.

There are different types of sequential hermaphroditism:

• Protandry: when an organisms is born male and changes to female, such as the clownfish (Amphip
• Protogyny: when an organisms is born female and changes to male, such as wrasses.
• Bidirectional sex change: when an organism has both full female and male sexual organs, but act as a male or female during different stages of its life, such as the  fish Lythrypnus dalli. 

It is clear that this strategy supposes an important benefit in front of other species: in front of extreme conditions, the organisms have the capacity of assuring the future generations by changing their sex.

THE CLOWNFISH

The clownfish is one of the best known examples of sex change in the animal kingdom. Our friend Nemo, throughout its life will become a female. Clownfishes are all born males, but after a certain age they change sex. They can also change sex in case the female dies, so although Nemo’s mother died, found his mother in his father.

Couple of clownfishes, with the female bigger than the male (Picture: Georggete Douwma, Arkive).

The form of reproduction of these very colourful and known fishes is most curious: in each anemone, cnidarian animals with which they live in symbiosis, lives a harem, consisting of one female (bigger in size than the male), a reproductive male and several non-breeding males.

Cycle of clownfish changing sex (Picture: The fisheries blog).

Si la hembra muere, el macho reproductor se transforma en hembra y el macho no reproductor de mayor tamaño madura sexualmente.

JANTHINIDAE SEA-SNAILS

Janthinidae is a group of sea-snails with a unique feature: they use their mucus to produce a bubble raft to float in the ocean. Some of them can produce a bubble per minute.

Violet sea-snail (Janthina janthina) (Picture: Roboastra).

Well, this family of gastropods is made up of individuals who may change sex. Like the clownfish, organisms are born male and then change to female.

BLUESTREAK CLEANER WRASSE

The bluestreak cleaner wrasse (Labroides dimidiatus) is a fish in which the sex change is triggered by some behavioural patterns.

Bluestreak cleaner wrasse (Labroides dimidiatus) (Picture: Darwin Books Cats).

There is usually a dominant male that keeps a harem of females, but if he dies, the dominant female will assume the position of the male in a few hours, courting other females although the change of sex can be extended for two weeks.

THE COMMON SLIPPER SHELL: WHEN SIZE MATTERS

The common slipper shell (Crepidula fornicata) is a marine snail in which the sex change is produced by the size of the animal. This molluscs are born male but, at a certain size, they become females.

They are very curious snails: they live stacked on the top of other animal, with larger organisms at the bottom. This means that the individual of the base is a female and males are above. Thus, when the female dies, the larger male becomes the female of the group.

Common slipper shell (Crepidula fornicata) (Picture: Dr. Keith Hiscock).

It is an exotic species in Spain, which could be living in the whole Galician coast. Anyway, its natural distribution area is North America.

THIS ALSO HAPPENS IN THE MEDITERRANEAN

Until now, we have explained species that live far from the place we life, but the truth is that this behaviour also happens in some Mediterranean species. Some examples are the starlet cushion star (Asterina gibbosa) and the ornate wrasse (Thalassoma pavo).

The ornate wrasse is one of the most colourful fishes in the Mediterranean sea. In that case, they are born females, but according to the sex ratio, they can change to males.

Ornate wrasse (Thalassoma pavo) (Picture: Matthieu Sontag, Creative Commons).

REFLECTION

If you are one of those who thing that sex change in human beings is unnatural, you have read some examples of animals that change their sex.

All you need is Biology is a LGTB-friendly blog and we love everbody equally. More love and respect, and less hate!

REFERENCES

• Acerca ciencia: Los animales que cambian de sexo 
• Alvarado, A (2010). Cambio de sexo en algunas especies animales. Revista Digital Universitaria, Vol. 11, núm. 8
• Catálogo Español de Especies Exóticas Invasoras: Crepidula fornicata 
• Darwin Book Cats: Fun Fish Fact: Some fish change sex
• Hickman, Roberts, Larson, l’Anson & Eisenhour (2006). Principios integrales de zoología. Mc Graw Hill (13 ed).
• Tree of life web project: An Exploration of the Clowfish
• National Geographic (2002, abril). A bordo de burbujas.
• Picture cover: Alexander Vasenin, Creative Commons

Tardigrades: animals with superpowers

The smallest bears in the world have almost superhero abilities. Actually, they are not bears: water bears is the popular name of tardigrades. They are virtually indestructible invertebrates: they can survive decades without water or food, to extreme temperatures and they have even survived into outer space. Meet the animal that seems to come from another planet and learn to observe them in your home if you have a microscope.

WHAT IS A TARDIGRADE?

Water bear (Macrobiotus sapiens) in moss. Colored photo taken with a scanning electron microscope (SEM). Photo by Nicole Ottawa & Oliver Meckes

Tardigrades or water bears, are a group of invertebrates 0.05-1.5 mm long that preferably live in damp places. They are especially abundant in the film of moisture covering mosses and ferns, although there are oceanic and freshwater species, so we can consider they live anywhere in the world. Even a few meters away from you, in the gap between tile and tile. In one gram of moss they have find up to 22,000 individuals. They are found in Antarctica under layers of 5 meters of ice, in warm deserts, hot springs, in mountains 6,000 meters high and abyssal ocean depths: they are  extremophiles. It is estimated that over 1,000 species exist.

MORPHOLOGY

Its popular name refers to their appearance, and the scientific name to their slow movements. Their bodies are divided into five segments: cephalic, with its tube-shaped mouth (proboscis) with two internal stilettos and sometimes simple eyes (ommatidia) and sensory hairs, and the remaining 4 segment with a pair of legs per segment. Each leg has claws for anchoring to the ground.

Bottom view of a Tardigrade where the five segments of the body are observed. Colored photo taken with a scanning electron microscope (SEM). Photo by Eye Of Science/Science Photo Library

Tardigrade (Echiniscus sp.) In which you can see the claws. Colored photo taken with a scanning electron microscope (SEM). Photo de Eye Of Science/Science Photo Library

Look at this video of Craig Smith to see tardigrade’s movements in more detail:

FEEDING

With its mouth stilettos, tardigrades perforate plants and absorbe the products of photosynthesis, but they can also feed absorbing the cellular content of other microscopic organisms such as bacteria, algae, rotifers, nematodes… Some are predators too and can eat whole microorganisms.

Their digestive system is basically the mouth and a pharynx with powerful muscles to make sucking motions that opens directly into the intestine and anus. Some species defecate only when they shed.

Detail of the mouth of a tardigrade. Colored image of scanning electron microscope (SEM). Photo by Eye Of Science/Science Photo Library

INTERNAL ANATOMY

They have no circulatory or respiratory system: gas exchange is made directly by the body surface. They are covered by a rigid cuticle which can be of different colors and is shed as they grow. With each moult, they lose oral stilettos, to be segregated again. They are eutelic animals: to grow they only increase the size of their cells, not their number, that remains constant throughout life

REPRODUCTION

Tardigrades generally have separate sexes (are dioecious) and reproduce by eggs (are oviparous), but there are also hermaphrodites and parthenogenetic species (females reproduce without being fertilized by any male). Fertilization is external and development is direct: they don’t have larval stages.

Tardigrade egg. Colored image of scanning electron microscope (SEM). Photo by Eye of Science/Science Photo Library

TARDIGRADE’S RECORDS

The tardigrades are incredibly resilient animals that have survived the following conditions:

• Dehydration: they can survive for 30 years under laboratory conditions without a single drop of water. Some sources claim that resist up to 120 years or have been found in ice 2000 years old and have been able to revive, although it is likely to be an exaggeration.
• Extreme temperature: if you boil one tardigrade survives. If you put it to temperatures near the absolute zero (-273ºC), survives. Their survival rate ranges from -270ºC to 150ºC.
• Extreme pressure: they are capable of supporting from vacuum to 6,000 atmospheres, ie 6 times the pressure in the deepest point on Earth, the Mariana Trench (11,000 meters deep).
• Extreme radiation: tardigrades can withstand bombardment of radiation at a dose 1000 times the lethal to a human.
• Toxic substances: if they are immersed in ether or pure alcohol, survive.
• Outer space: tardigrades are the only animals that have survived into space without any protection. In 2007 the ESA (European Space Agency) within the TARDIS project (Tardigrades In Space) left tardigrades (Richtersius coronifer and Milnesium tardigradum) for 12 days on the surface of the Foton-M3 spacecraft and they survived the space travel. In 2011 NASA did the same placing them in the outside of the space shuttle Endeavour and the results were corroborated. They survived vacuum, cosmic rays and ultraviolet radiation 1,000 times higher than that of the Earth’s surface. The project Biokis (2011) of the Italian Space Agency (ASI) studied the impact of these trips at the molecular level.

HOW DO THEY DO THAT?

The tardigrades are able to withstand such extreme conditions because they enter cryptobiosis status when conditions are unfavorable. It is an extreme state of anabiosis (decreased metabolism). According to the conditions they endure, the cryptobiosis is classified as:

• Anhydrobiosis: in case of environmental dehydration, they enter a “barrel status” because adopt barrel shaping to reduce its surface and wrap in a layer of wax to prevent water loss through transpiration. To prevent cell death they synthesize trehalose, a sugar substitute for water, so body structure and cell membranes remain intact. They reduce the water content of their body to just 1% and then stop their metabolism almost completely (0.01% below normal).

  

  Tardigrade dehydrated. Photo by Photo Science Library

• Cryobiosis: in low temperatures, the water of living beings crystallizes, it breaks the structure of cells and the living being die. Tardigrades use proteins to suddenly freeze water cells as small crystals, so they can avoid breakage.
• Osmobiosis: it occurs in case of increase of the salt concentration of the environment.
• Anoxybiosis: in the absence of oxygen, they enter a state of inactivity in which leave their body fully stretched, so they need water to stay perky.

Referring to exposures to radiation, which would destroy the DNA, it has been observed that tardigrades are able to repair the damaged genetic material.

These techniques have already been imitated in fields such as medicine, preserving rat hearts to “revive” them later, and open other fields of living tissue preservation and transplantation. They also open new fields in space exploration for extraterrestrial life (Astrobiology) and even in the human exploration of space to withstand long interplanetary travel, ideas for now, closer to science fiction than reality.

ARE THEY ALIENS?

The sparse fossil record, the unclear evolutionary relatedness and great resistance, led to hypothesis speculating with the possibility that tardigrades have come from outer space. It is not a crazy idea, but highly unlikely. Panspermia is the hypothesis that life, or rather, complex organic molecules, did not originate on Earth, but travelled within meteorites in the early Solar System. Indeed, amino acids (essential molecules for life) have been found in meteorites composition, so panspermia is a hypothesis that can not be ruled out yet.

Photo by Eye Of Science/Photolife Library

But it is not the case of tardigrades: their DNA is the same as the rest of terrestrial life forms and recent phylogenetic studies relate them to onychophorans (worm-like animals), aschelminthes and arthropods. What is fascinating is that is the animal with more foreign DNA: up to 16% of its genome belongs to fungi, bacteria or archaea, obtained by a process called horizontal gene transfer. The presence of foreign genes in other animal species is usually not more than 1%. Could be this fact what has enabled them to develop this great resistance?

DO YOU WANT TO SEARCH TARDIGRADES BY YOURSELF AND OBSERVE THEM IN ACTION?

Being so common and potentially livIng almost anywhere, if you have a simple microscope,  you can search and view living tardigrades by yourself:

• Grab a piece of moss of a rock or wall, it is better if it is a little dry.
• Let it dry in the sun and clean it of dirt and other large debris.
• Put it upside down in a transparent container (such as a petri dish),  soak it with water and wait a few hours.
• Remove moss and look for tardigrades in the water container (put it on a black background for easier viewing). If lucky, with a magnifying glass you’ll see them moving.
• Take them with a pipette or dropper, place them on the slide and enjoy! You could see things like this:

REFERENCES

• Pequeños pero invencibles
• Revelan más secretos del indestructible tardígrado
• Meet the miniature water bear: nature’s ultimate survivor or an alien from another planet?
• Tardígrados, los animales que desafían toda preconcepción biológica
• Tardigrada.es
• Los tardígrados, ositos de agua
• Tiny animal survive exposure to space
• Anhydrobiosis in invertebrates
• “Alien” water bears amaze scientists
• Tardigrada (Astronoo)
• La criptobiosis en el phylum Tardigrada
• El animal “más resistente de la Tierra” se prueba en el espacio
• Cover photo by Oliver Meckes

The Queens of the Garden; flowers with crown

If you believed that crowns only belonged to kings and queens, you were totally wrong. In this article you will see that some flowers, as the daffodils, also wear crowns and they are worthy of them! In addition, not all flowers are wearing the same one, because there are many different ones, of all sizes and colours. And these singular structures are the reason that some of this plants are cultivated to plant in the gardens.

INTRODUCTION

First of all, we have to present the Amaryllidoideae‘s subfamily (Fam. Amaryllidaceae) because is here where we will find these royal flowers wearing crowns.

The members of this subfamily are perennial or biennial and herbaceous plants with bulbs or rarely with rhizome (underground stems that are usually elongated and with horizontal growth, similar to roots, and that usually contains reserve substances stored). These plants tend to present long narrow leaves that surround a portion of the stem, with parallel nerves, hairless, deciduous, also they are flat and with entire margins, smooth.

A picture of a daffodils (Narcissus) as an example of an Amaryllidoideae member.

THEIR FLOWERS

Now that we get an idea of how these plants are, we have to know the flowers characteristics. That is, how are the flowers:

• Hermaphrodite: both male and female reproductive organs are present.
• Bracteate: each flower has a specialized leaf that is originated in its armpit.
• They can grow in solitary or grouped.
• No differentiation between petals and sepals. Therefore, in this case there isn’t difference between corolla and calyx, but it is a perianth formed by two whorls of petaloid tepals. In each whorl are 3 tepals and in total 6 per flower. These may be free or connected together. When the latter happens, crowns can be formed, as explained in the next section.

Flower parts: 1. petaloid tepal ; 2. crown; 3. floral bract (Miguel Ángel García‘s modified picture).

CROWNS’ DIVERSITY

The Amaryllidaceae group consists of 59 different genera. But not everyone is fit to wear crown. And now, you will know which of them are allowed and where they appear.

PARACOROLLAS

In Europe, the Mediterranean region and western Asia exists one of the most popular flowers with crown. It’s about the daffodil (Narcissus), one plant of the most used in gardening and surely the commonest queen of the gardens. This genus comprises a long crown or a funnel-shaped cup. Its origin is petaloid, that is, part of the tepals are fused to give rise to this structure. This type of crown is called paracorolla.

Narcissus (Author: Blondinrikard Fröberg).

STAMINAL CROWNS

On the other hand, within the same territory, there is the Pancratium gender. But this one presents a totally different crown; in this case the origin is staminal. That is, the bases of the stamens are enlarged and fused together to form the funnel.

Pancratium illyricum (Author: Tigerente).

Furthermore, the genera Calostemma and Proiphys occur between the centre and east of Asia and in Australia. These ones also carry staminal crowns (as in the previous case).

Calostemma luteum (Author: Melburnian).

Proiphys amboinensis (Author: Tauʻolunga).

OTHERS CROWNS

Moreover, within the same distribution as the two examples above, Lycoris appears. But, this one wears a smaller crown as it’s formed only by the joining of the tepals’ bases. This leads to tiny tube.

Lycoris aurea (Public Domain).

Finally, in America is where we find a big variety of genera and different crowns, differently formed (but, some as in the previous cases). The members of this territory are: Clinanthus, Pamianthe, Paramongaia, Hieronymiella, Placea, Hymenocallis, Ismene, Leptochiton, Eucrosia, Mathieua, Phaedranassa, Rauhia and Stenomesson

Pamianthe peruviana (Author: Col Ford and Natasha de Vere).

Placea amoena (Author: Dick Culbert).

Phaedranassa tunguraguae (Author: Michael Wolf).

Ismene amancaes (Author: Mayta).

Hymenocallis caribaea (Author:Tatters ❀).

Eucrosia bicolor (Author: Raffi Kojian – http://www.gardenology.org).

Clinanthus variegatus (Author: Melburnian)

Now that you know the different royal crowns, which one would be the queen of your garden?

REFERENCES

• Aguilella & F. Puche. 2004. Diccionari de botànica. Col·leció Educació. Material. Universitat de València: pp. 500.
• Bolòs, J. Vigo, R. M. Masalles & J. M. Ninot. 2005. Flora manual dels Països catalans. 3ed. Pòrtic Natura, Barcelona: pp. 1310.
• Guía de Consultas Diversidad Vegetal. FACENA (UNNE).Monocotiledoneas- Asparagales: Amaryllidaceae.
• W. Byng. 2014. The Flowering Plants Handbook: A practical guide to famílies and genera of the world. Plant Gateway Ltd., Hertford, UK.
• Apuntes de Fanerógamas, Grado de Biología Ambiental, UAB.
• Guía de Consultas Diversidad Vegetal. FACENA (UNNE).Monocotiledoneas- Asparagales: Amaryllidaceae.

Flowers wearing turban, the Tulip fever

The spring beginning has allowed some of you to enjoy the beautiful colours of those flowers that have already bloomed. This time I’m going to talk about one of the most colourful, simple, but wonderful flowers you probably already will have had the opportunity to observe in many gardens or in nature. It is the tulip. Besides introduce you this plant, in this article I will make a more detailed description of its morphological parts. I think it’s a good example to start learning vocabulary, because its structure is quite clear and simple. Therefore, if you are interested in learning some technical vocabulary, now it’s a perfect chance. But, do not think I’m just going to talk about the technical aspects, because reading this article you will also be able to learn the history behind the tulips. And as you will see, these flowers caused a good fever!

Artistic image of several tulips (Photo taken by Adriel Acosta).

 INTRODUCTION

The tulips (Tulipa sp.) are flowers that when are closed seem a turban. This plants have been very popular and well-known for very long time, because of its high ornamental interest.

Its genus is distributed in the central and western Asia, in the Mediterranean and in Europe. It is known that its origin belongs to the centre of Asia and, from there, their distribution has been expanded naturally and by human actions. And, although about 150 species are known in the nature, human intervention has greatly increased the species list. Caused both by hybridization (forcing the offspring of two interesting species) and by selective breeding (choosing the offspring which has more value).

Tulip crop in Amsterdam (Photo taken by Rob Young). 

 THE TULIP FEVER

As already mentioned above, tulips are one of the most ornamental plants used, both in decoration as in landscaping. And while the tulip crop is rather old, the boom occurred in Europe during the seventeenth century. Giving rise to what is known as Tulip mania or the Tulip fever. In those moments, especially in Netherlands and France, a high interest in the cultivation of these plants awoke. The fever was so great that people were selling goods of all kinds to buy tulip bulbs, even reaching up to sell the most valued as the house or farm animals.

The cause of this was originated in the Netherlands, where the single-coloured tulip bulbs were being sold at that time. But afterwards, the Eastern bulbs that give rise to flowers with variegated colours appeared. And they were very attractive. Although the cause was uncertain in that moment, it was known that if a single-coloured bulb touched other marbled-coloured bulb, the first one would turned into a marbled-coloured bulb. This caused the tulip’s price began to increase and soon after occurred the first speculative bubble in history.

Nowadays, we know that the cause is due to a virus which is transmitted from some bulbs to others; this virus is known as Tulip breaking virus.

Anonymous gouache on paper drawing, 17th century, of the “Semper Augustus”. A representation of one of the most popular tulips which was sold at record price in Netherlands (Public Domain).

MORPHOLOGICAL CHARACTERS

 The plant

 Tulips are geophytes, that is, they have resistance bodies underground to survive during unfavourable seasons, the winter. These organs are bulbs, which have been used on crops to preserve these plants.

Its leaves are linear or linear-lanceolate, i.e., they are long, narrow and acute. Parallel venation can be observed on its leaves, so a nerve is by side other and with the same direction. Their arrangement is usually in rosette: this means that the leaves are born agglomerated in the bottom of the plant above the bulb, and at the same level. Even so, you can sometimes see some leaves along the stem, cauline ones. These are sessile, without petiole, and wrap a little the stem.

To cultivate tulips, we can use their bulbs or fruits. These seconds are capsules, a dried fruits, opened due the action of some valves. At first, the seeds are hooked inside these capsules and then are released and distributed on the environment.

Tulip (Photo taken by Adriel Acosta).

The flowers

Tulips appear in early spring, due they are plants adapted to very dry Mediterranean climate or cold areas.

As you have seen, the flowers are solitary or appear to 3 gathered in one stem. They are usually large and showy, hermaphrodite, therefore, they have both male and female reproductive organs, and are actinomorphous, that is, they can be divided symmetrically for more than two planes of symmetry.

These flowers have 3 inner tepals and 3 external that are free among them, without being bound or fused. We talk about tepals when the sepals (calyx pieces) and petals (corolla parts) are similar between them. In this case, the tepals are petaloid, because they adopt typical colours and shapes of the petals.

In the inner part of the flower, we can see 6 stamens divided equally into 2 whorls; being these two closely spaced between them, so they seem to arise from the same point. And right in the centre, surrounded by these stamens, there is the gynoecium, female part of the flower. This gynoecium consists of the ovary and 3 stigmas attached to this directly. The stigmas are this part of female reproductive organs where it should arrive pollen to fertilize the ovaries.

Parts of tulip flower: 1. Sepal, 2. Petal, 3. Stamen, 4. Female reproductive organ (ovary and 3 stigmas) (Photo taken by Adriel Acosta).

 As you have seen in this article, some flowers have caused curious stories and a great impact on our society. Also, you have had the opportunity to observe in detail the tulip’s structure. One more time, I wish you liked it.

REFERENCES

• A. Aguilella & F. Puche. 2004. Diccionari de botànica. Colleció Educació. Material. Universitat de València: pp. 500.
• Bolòs, J. Vigo, R. M. Masalles & J. M. Ninot. 2005. Flora manual dels Països catalans. 3ed. Pòrtic Natura, Barcelona: pp. 1310.
• Notes of Phanerogamae and Applied Plant Physiology, Degree of Environmental Biology, Ambiental, UAB
• F. Schiappacasse. Cultivo del tulipan. http://www2.inia.cl/medios/biblioteca/seriesinia/NR21768.pdf
• Fundación para la Innovación Agraria; Ministerio de Agricultura. 2008. Resultados y Lecciones en Tulipán. Proyecto de Innovación en XII Región de Magallanes. Flores y FOllajes/ Flores de corte (11).