Check the evolution in your own body

42% of the US population and 11.5% of the Spanish people do not believe in evolution. However, there are different evidence that Darwin was right, some of them in your own body. Have you had your appendix or wisdom teeth removed? Find out in this post which vestigial organs you have inherited from your ancestors.

WHAT ARE VESTIGIAL STRUCTURES?

Vestigial structures (often called organs althouth they are not organs properly) are body parts that have been reduced or have lost its original function during the evolution of a species. They can be found in many animals, including humans.

Orca skeleton in which vestiges of the hind limbs can be seen. This is a proof of its terrestrial origins. Photo: Patrick Gries

Vestigial structures were fully functional in the ancestors of these species (and in the homologous structures of other existing species), but currently its function is practically useless or it has changed. For example, the second pair of flying wings in some insects such as flies have lost their function and they have been reduced to balance organs (halteres). If you want to know more about the evolution of flight in insects click here.

Besides physical structures, vestigial features can also manifest itself in behavior or biochemistry processes.

WHY ARE THEY  EVIDENCE OF EVOLUTION?

Natural selection acts on species favoring features that increase their survival and eliminating the ones with no benefits, for example when changes appear in the habitat. Individuals with unfavorable characteristics will die or will breed less and that feature will be removed after some generations, while favorable traits will remain as their carriers can pass them to the next generation.

Sometimes there are features that are neither favorable nor unfavorable, so they continue appearing in the next generations. But all has a cost structure (energy, risk to become infected, develop tumors…), so selective pressure continues acting to eliminate something that is not conducive to the success of the species. This is the case of vestigial structures, which “take longer” disappear throughout evolution. Their existence reveal that in the past these structures had an important role in our ancestors.

FIND YOUR VESTIGIAL TRAITS

THE NICTITATING MEMBRANE

We talked about it in How animals see the world. The third eyelid is a transparent or translucent membrane that protects and moisten the eye without losing visibility. It is common in amphibians, reptiles and birds. Among primates, it is only functional in lemurs and lorises.

Nictitating membrane or third eyelid of a masked lapwing (Vanellus miles). Photo: Toby Hudson

In humans the plica semilunaris is a remnant of the nictitating membrane. Obviously we can not move it but still has some lacrimal drainage function and helps on the eye movement (Dartt, 2006).

Plica semilunaris. Photo: unknown

DARWIN’S TUBERCLE AND EAR MUSCLES

10% of the population has a thickening in the ear, a vestige of the common pointy ear in primates. This structure is called Darwin’s tubercle and has no function.

Variability of Darwin’s tubercle at the top of the ear (0 = absent).  Credit.

Comparison between the ear of a yellow baboon (Papio cynocephalus) and ours. Credit

Also, primates (and other mammals) have mobile ears to lead the pinna toward the sound source: surely you have noticed it in your house dog or house cat. Humans (and chimps) no longer have that great mobility, although some people may move slightly pinna. It has been proven with electrodes these muscles are excited when we perceive a sound that comes from a particular direction (2002).

Auricular muscles responsible of movement of the pinna. Credit

The occipitofrontalis muscle has lost its function to prevent the head from falling, but participates in facial expression.

PALMARIS LONGUS MUSCLE

16% of Caucasians do not have this muscle on the wrist, neither 31% of nigerian people neither 4,6% of chinese people. It can even appear in one arm and not in the other or be double.

It is believed that this muscle actively participated in the arboreal locomotion of our ancestors, but currently has no function, because it does not provide more grip strength. This muscle is longer in completely arboreal primates (like lemurs) and shorter in land primates, like gorillas (reference).

And do you have it or not? Try it: join your thumb and pinky and raise your hand slightly.

I have two palmaris longus in the left arm and one on the right. Photo: Mireia Querol

WISDOM TEETH

35% of people do not have wisdom teeth or third molar. In the rest, its appearance is usually painful and removal is necessary.

I don’t have the third molar. Photo: Mireia Querol Rovira

Our hominin ancestors had them, much bigger than ours. A recent research explains that when a tooth develops, emits signals that determine the size of the neighboring teeth. Reducing the mandible dentition and the other along evolution has resulted in reduced molars (and eventually the disappearance of the third).

Comparison between the dentition of a chimpanzee, Australopithecus afarensis and Homo sapiens. Look at the reduction of the last three molars between afarensis and sapiens, Credit

THE TAILBONE

If you touch your spine till the end, you will reach the coccyx or tailbone. It is three to five fused vertebrae, vestige of the tail of our primate ancestors. In fact, when we were in the womb, in the early stages of embryo development a 10-12 tail vertebrae formation is observed.

Different stages in human embryonic development (1 to 8) and comparison with other species. Credits in the image.

Subsequently it is reabsorbed, but not in all cases: it has been reported 40 newborns with a tail.

Infant born with tail. A mutation has prevented the growth inhibition of the tail during pregnancy. Credit

Although we have no tail, currently these bones serve as anchors of some pelvic muscles.

Tailbone position. Photo: Mireia Querol Rovira

SUPERNUMERARY NIPPLES (POLYTHELIA)

It is estimated that up to 5% of the world population has more than two nipples. These “extra” nipples can be presented in different ways so sometimes are confused with freckles or moles. They are located in the mammillary line (from the axilla to the groin), exactly in the same position as other mammals with more than two breasts (observe your house dog, for example). Usually the number of breasts corresponds to the average of offspring that has a mammal, so extra nipples would be a vestige from when our ancestors had more offspring per birth. Usual is 3 nipples, but has been documented a case of up to 8 nipples in a person.

Additional nipple below the main one. Credit

FIND YOUR VESTIGIAL REFLEXES AND BEHAVIOURS

PALMAR AND FOOT SOLE GRASP REFLEX

Surely you’ve experienced that if you bring anything into the hands of a baby, automatically he grabs it with such a force that would be able to hold his own weight. This reflex disappears at 3-4 months of age and is a remnant of our arboreal past and the way to grab the hair of the mother, as with the other current primates. Watch the next video in 1934 on a study of twins (minute 0:34):

On the feet there is also a reflex of trying to grab something when the foot of a baby is touched. It disappears at 9 months of age.

By the way, have you noticed how easily children climb on any handrails or higher zones in a playground?

GOOSEBUMPS

Cold, stress or intense emotion (eg, listening to some music) causes the piloerector muscle to raise the hair giving the skin the appearance of a plucked chicken. It is an involuntary reflex in which some hormones, like adrenaline (which is released in the mentioned situations) are involved. What utility had this to our ancestors and has in modern mammals?

• Increasing the space between the skin and the external surface, so that hot air trapped between hair helps on maintaining temperature.
• Looking bigger to scare off potential predators or competitors.

Chimpanzee with hair bristling in a display before a conflict. Photo: Chimpanzee Sanctuary Northwest

Obviously we have lost hair in most parts of the body, so although we retain the reflex, it has no use to us or to keep warm or to ward off predators. The hair has been preserved abundantly in areas where protection is necessary or due to sexual selection (head, eyebrows, eyelashes, beard, pubis…), but in general, can also be considered a vestigial structure.

There are more vestigial structures but in this post we have focused on the most observable. In future posts we will discuss other internal structures, like the famous appendix or vomeronasal organ.

REFERENCES

• Proof of evolution that you can find on your own body
• 10 Vestigial Traits You Didn’t Know You Had
• Darwin was right
• Los reflejos de prensión palmar y plantar
• Resuelto el enigma de las muelas del juicio
• Politelia bilateral familiar

Cetaceans of the Mediterranean Sea

Did you know that in the Mediterranean Sea habitually lives 8 species of cetaceans, among dolphins and whales; in addition to other visitor and spontaneous species, such as the killer whale? In this post, a new version of “Cetaceans in the Catalan coast“, the first post published in this blog, I will give more information about the cetaceans that live in this small sea. 

INTRODUCTION

Cetaceans originated 50 million years ago in the ancient Tethys Sea, from terrestrial mammals. Approximately, there are 80 living species in the world, but only 8 of them live habitually in the Mediterranean and other species are present only in some seasons or sporadically.

HABITUAL CETACEANS OF THE MEDITERRANEAN SEA

STRIPED DOLPHIN 

Striped dolphin (Stenella coeruleoalba) is a cetacean with a black or bluish grey colouration in the back and white in the ventral part. There is a black line from the eye to the anal region through each side, and another one from the eye to the pectoral fin. Mediterranean striped dolphins are slightly smaller than their neighbours from the Atlantic, and achieve a maximum length of 2.2 m.

Striped dolphin (Stenella coeruleoalba) (Picture: Scott Hill National Marine Mammal Laboratory, Creative Commons).

They may live in big groups, till hundreds of individuals. Anyway, in the observations that I have done in the Mediterranean, groups included from 5 to 50 animals. They are very acrobatics and they can jump 7 meters above the sea surface.

Striped dolphins are common in both Mediterranean basins, specially in the open sea, being so many abundant in Ligurian Sea, Gulf of Lion, Alboran Sea (between Andalucía, Spain, and Morocco) and the Balearic Sea (between the Iberian Peninsula and the Balearic Islands).

This is the most abundant species in the Mediterranean (about 117,000 animals in the western basin), but they are in a vulnerable status of conservation due to the affection by morbillivirus, pollutants such as organochlorine compounds and fishing devices.

BOTTLENOSE DOLPHIN 

Bottlenose dolphins (Tursiops truncatus) maybe are the most known for the population because they are the protagonist of some movies and they are the most common cetacean in captivity.

Bottlenose dolphin (Tursiops truncatus) (Picture: Gregory Slobirdr Smith, Creative Commons).

Their robust body is grey, clearer in the sides and white in the abdomen. Bottlenose dolphins are 4 m long.

Their groups, integrated by females and offspring or young males, range from 2 to 10 animals. They live in all the coasts of the Mediterranean Sea.

Their conservation status in the Mediterranean is vulnerable. It is though that their population is about 10,000 animals. Competence with commercial fisheries, bycatch and water pollution are among their threats.

SHORT-BEAKED COMMON DOLPHIN 

Short-beaked common dolphin (Delphinus delphis) is easily recognisable for the colouration of its body: dorsal region is dark and sides are cream-coloured or yellow, and constitute a V in the half of the body. Like striped dolphins, they are also small animals (2-2.5 m).

Short-beaked common dolphin (Delphinus delphis) (Picture: JKMelville, Creative Commons).

They live in numerous groups in open waters, from 10 to 200 animals, but sometimes groups of several thousands have been seen.

They enjoy with boats:

Despite their name, it is difficult to observe them because they are endangered in the Mediterranean. In the last 40 years, their population have been reduced by half. There are several reasons: lack of preys due to competence with fishers, bycatch, habitat degradation, sound pollution and high concentrations of pollutants.

FIN WHALE

Fin whale (Balaenoptera physalus) is the biggest whale in the Mediterranean and the second one in the world.

Fin whale (Balaenoptera physalus) (Picture: Circe)

Fin whale’s head is V-shaped, wide and flatten. It is dark grey in the back and white in the abdomen, but asymmetric in the jaws: left side is dark grey and right side is white. Dorsal fin is short and placed in the last third of the body. In the moment of diving, caudal fin is not shown out of the water. Blow may be 8 meters height and narrow. Their maximum length is 24 m.

They are usually seen alone or in small groups (normally mother and calf) in open waters. In the Mediterranean, they are most frequently sighted between Balearic Islands and Ionian Sea, being specially abundant in the Gulf of Lion.

According to IUCN, it is a vulnerable species in the Mediterranean, but it is endangered worldwide. The Mediterranean population includes 5,000 adults. They are victims of strikes with ships, high DDT concentrations, acoustic pollution due to seismic surveys and bycatch.

Have you seen this fin whale rescue from Fuerteventura?

SPERM WHALE

Sperm whales (Physeter macrocephalus)  are the biggest toothed whales and one of the biggest cetaceans in the Mediterranean.

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

Sperm whales have a rounded or triangular hump instead of a dorsal fin, which is followed by six exaggerated “knuckles”. An important clue for its identification is the blow: it is a bushy blow directed low, left and forwards. Head, which is square, represent 1/3 of the total length of the body. It is dark or grey, with the lower part of the mouth white. To dive, they show the caudal fin out of the water. They may be 20 long.

Their groups are composed by females and their offspring, other groups of young males and adult males are solitary. The number of animals per group ranges from 10 to 15, but smaller groups also exist. They are usually seen in oceanic waters of all the Mediterranean.

It is an endangered species in the Mediterranean due to they are accidentally captured in fishing nets, by strikes with vessels and the annoyance provoked by marine traffic. It is estimated that live some thousands in the Mediterranean.

Have you seen this video of a sperm whales that “adopt” a deformed cetacean?

RISSO’S DOLPHIN 

Risso’s dolphin (Grampus griseus) is grey when is born, but becomes paler with age for the presence of scars that do not disappear. They might measure 4 m.

Risso’s dolphin (Grampus griseus) (Picture: Rob, Creative Commons).

Generally, they live in groups of 3-50, despite sometimes groups of some thousands have been spotted. In the Mediterranean, it is widely distributed in open waters, being more abundant in the western basin, where they prefer continental slope and submarine canyons.

Their status of conservation is unknown, but bycatch and acoustic and chemical pollution affect them.

LONG-FINNED PILOT WHALE

Long-finned pilot whale (Globicephala melas) is the biggest dolphin species in the Mediterranean, since it may achieve 6 m. Black in general, this pilot whale has a anchor-shaped ventral patch. Its flippers measure one fifth of the length.

Long-finned pilot whale (Globicephala melas) (Picture: Wikiwand).

Their groups range from 10 to 60 animals, but also several thousands. Groups include several generations of females with their calves. In the Mediterranean, it is abundant in the western basin, specially in the Strait of Gibraltar and Alboran Sea.

There is deficient data to evaluate its status of conservation. Anyway, it is known that are threatened by bycatch, strikes and acoustic and chemical pollution.

CUVIER’S BEAKED WHALE

Cuvier’s beaked whales (Ziphius cavirostris) are dark grey or brown, paler in the head. Their head is bulky, and the beak is not much marked. They may be 7 m long.

Cuvier’s beaked whale (Ziphius cavirostirs) (Picture: WDC).

They usually live in groups of 2-7 individuals or alone, in deep oceanic waters.

It is difficult to observe them due to the little activity in surface, reason that can explain why there are not enough information to evaluate their conservation status. It is known that are specially sensible to acoustic pollution, both military activities or seismic surveys. Moreover, the ingestion of plastic and bycatch also affect them.

KILLER WHALES IN THE MEDITERRANEAN?

Killer whales (Orcinus orca) are one of the most fascinating cetaceans. They live in polar and tropical waters, from the coast to open sea.

Killer whale (Orcinus orca) (Picture: Jose J. Díaz)

In the Mediterranean, however, they are only considered residents in the Strait of Gibraltar, with a size population of 32 whales. Their presence in the Strait, it is believed that is linked to the presence of bluefin tuna, their food.

Did you know that they use different dialects to communicate each other? Did you know that homosexual behaviours have been described in this species? Albino killer whales have been reported.

Their status of conservation is unknown, but direct death by fishers, reduction of their preys, annoyances and habitat degradation are among the causes of their reduction.

REFERENCES

• CRAM: Cetacis
• Day, T (2008). Guía para observar ballenas, delfines y marsopas en su hábitat. Ed. Blume
• Gobierno de Canarias: Curso de Observación de Cetáceos
• IUCN (2012). Marine Mammals and Sea Turtles of the Mediterranean and Black Seas. Gland, Switzerland and Malaga, Spain: IUCN
• Kinze, CC (2002). Mamíferos marinos del Atlántico y del Mediterráneo. Ed. Omega
• Lleonart, J (2012). Els mamífers marins i els seus noms. Terminàlia, 5, 7-25
• Notarbartolo di Sciara G. (compilers and editors) (2006). The status and distribution of cetaceans in the Black Sea and Mediterranean Sea. IUCN Centre for Mediterranean Cooperation, Malaga, Spain.
• Cover picture: Scuba Diver Life

Evolution for beginners 2: coevolution

After the success of Evolution for beginners, today we’ll continue  knowing the basics of biological evolution. Why  exist insects that seem orchids and vice versa? Why gazelles and cheetahs are almost equally fast? Why your dog understands you? In other words, what is coevolution?

WHAT IS COEVOLUTION?

We know that it is inevitable that living beings establish symbiotic relationships between them. Some depend on others to survive, and at the same time, on elements of their environtment as water, light or air. These mutual pressures between species make that evolve together, and as one evolve as a species, in turn it forces the other to evolve. Let’s see some examples:

POLLINATION

The most known process of coevolution is pollination. It was actually the first co-evolutionary study (1859) by Darwin, although he didn’t use that term. The first to use the word coevolution were Ehrlich and Raven (1964).

Insects existed long before the appearance of flowering plants, but their success was due to the discovery that nectar is a good reserve of energy. In turn, the plants found in the insects another way more effectively to carry pollen to another flower. Pollination by the wind (anemophily) requires more production of pollen and a good dose of luck to at least fertilize some flowers of the same species. Many plants have developed flowers that trap insects until they are covered with pollen and then set them free. These insects have hairs in their body to enable this process. In turn some animals have developed long appendages (beaks of hummingbirds, butterflies’ proboscis…) to access the nectar.

Darwin’s moth (Xantophan morganii praedicta). Photo by Minden Pictures/Superstock

It is the famous case of the Darwin’s moth (Xanthopan morganii praedicta) of which we have already talked about. Charles Darwin, studying orchid Christmas (Angraecum sesquipedale) saw that the nectar was 29 cm inside the flower. He sensed that there should exist an animal with a proboscis of this size. Eleven years later, Alfred Russell Wallace reported him that the Morgan’s sphinxs had proboscis over 20 cm long, and a time later they were found in the same area where Darwin had studied that species of orchid (Madagascar). In honor of both it was added “praedicta” to the scientific name.

There are also bee orchids that mimic female insects to ensure their pollination. To learn more about these orchids and the Christmas one, do not miss this post by Adriel.

The bat Anoura fistulata and its long tongue. Photo by Nathan Muchhala

But many plants not only depend on insects, also some birds (like humming birds) and mammals (such as bats) are essential to pollination. The record for the longest mammal tongue in the world is for a bat from Ecuador (Anoura fistulata); its tongue measures 8 cm (150% of the length of its body). It is the only who pollinates one plant called Centropogon nigricans, despite the existence of other species of bats in the same habitat of the plant. This raises the question of whether evolution is well defined, and occurs between pairs of species or it is diffuse due to the interaction of multiple species.

PREDATOR-PREY RELATIONSHIPS

The cheetah (Acinonyx jubatus) is the fastest vertebrate on land (up to 115 km/h). Thomson’s gazelle (Eudorcas thomsonii), the second (up to 80 km/h). Cheetahs have to be fast enough to catch a gazelle (but not all, at risk of disappearing themselves) and gazelles fast enough to escape almost once and reproduce. The fastest gaelles survive, so nature selects in turn faster cheetahs, which are who eat to survive. The pressure from predators is an important factor that determines the survival of a population and what strategies should follow the population to survive. Also, the predators will find solutions to possible new ways of life of their prey to succeed.

Cheetah hunting a Thomson’s gazelle in Kenya. Photo by Federico Veronesi

The same applies to other predator-prey relationships, parasite-host relationships, plants-herbivores, improving their speed or other survival strategies like poison, spikes…

HUMAN AND DOGS … AND BACTERIA

Our relationship with dogs since prehistoric times, it is also a case of coevolution. This allows, for example, to create bonds with just looking at them. If you want more information, we invite you to read this post where we talk about the issue of the evolution of dogs and humans in depth.

Another example is the relationship we have established with the bacteria in our digestive system, essential for our survival. Or with pathogens: they have co-evolved with our antibiotics, so using them indiscriminately has favored these species of bacteria to develop resistance to antibiotics.

THE IMPORTANCE OF COEVOLUTION

Coevolution is one of the main processes responsible for the great biodiversity of the Earth. According to Thompson, is responsible for the millions of species that exist instead of thousands.

The interactions that have been developed with coevolution are important for the conservation of species. In cases where evolution has been very close between two species, if one become extint will lead to the extinction of the other almost certainly. Humans constantly alter ecosystems and therefore biodiversity and evolution of species. Just declining one species, we are affecting many more. This is the case of the sea otter (Enhydra lutris), which feeds on sea urchins.

Sea otter (Enhydra lutris) eating sea urchins. Photo by Vancouver Aquarium

Being hunted for their fur, urchins increased number, devastated entire populations of algae (consumer of CO2, one of the responsible of global warming), seals who found refuge in the algae nonexistent now were more hunted by killer whales… the sea otter is therefore a key species for the balance of this ecosystem and the planet, as it has evolved along with urchins and algae.

Coevolutive relations between flowers and animals depend on the pollination of thousands of species, including many of agricultural interest, so we must not lose sight of the seriousness of the issue of the disappearance of a large number of bees and other insects in recent years. A complex case of coevolution that directly affects us is the reproduction of fig.

TO SUMMARIZE

As we have seen, coevolution is the evolutionary change through natural selection between two or more species that interact reciprocally.

It is needed:

• Specificity: the evolution of each feature of a species is due  to selective pressures of the feature of the other species.
• Reciprocity: features evolve together.
• Simultaneity: features evolve simultaneously.

REFERENCES

• Massa R (2007). Atlas ilustrado del origen de la vida: La evolución de las especies. Jaca Book spa, Milano.
• Muchhala N. Nectar bat stows huge tongue in its rib cage. Nature (2006) vol. 444 (7120) pp. 701-702
• Coevolución: patrones y procesos
• Celebrando a Darwin
• Los 10 mamíferos más rápidos de la tierra
• La coevolución y las enseñanzas de Darwin
• Coevolución
• Las nutrias marinas pueden salvar nuestro planeta

Cetaceans with dialects: the killer whale and the sperm whale

Last week, the press was full of news about a recent article that highlight that sperm whales in the Eastern Pacific have distinct dialects. For this reason, the post of this week will explain what a dialect is (in cetaceans), which cetaceans have dialects in addition to sperm whales and which is the explanation to this. 

INTRODUCTION

The first question to be answered is “What is a dialect?”. This question is not simple because sometimes this concept is confused with another one: geographic variation. While dialects are song differences between neighbouring populations of potentially interbreeding individuals, geographic variations refer to differences in song over long distances and between populations which normally do not come together. In the case of dialects, the explanation of their presence is social learning, while in geographic variations the reason can be found in their genes. The function of dialects is to be an acoustical signature that help maintain cohesion and integrity of groups and as an inbreeding avoidance mechanism.

CETACEANS WITH DIALECTS

To date, dialects have been described in two cetacean species: killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus). These two species have several features in common:

• They live in matrilineal groups, that are highly stable groups of individuals linked by maternal descent that protect themselves against predators and other dangers.
• They live in multilevel societies, that consist of hierarchically nested social levels. From the upper to the lowest level, there are three levels: vocal clans, social units and individuals. This kind of societies are also present in human and other primates and in African elephants.

KILLER WHALE DIALECTS

Dialects have been found in resident killer whales from the northeastern Pacific, Norway and Kamchatka. In this species, these dialects consists on repertories of several call types that are different among pods. Each pod have distinctive features in the call repertories and, therefore, each pod has a particular dialect. Pods that share part of the repertories constitute acoustic clans. So, each clan is acoustically different. Pods from different clans can overlap and interact and new pods can be formed by fission of other pods, which turn out in divergence of dialects.

Killer whales (Orcinus orca) are one of the cetacean species with dialects (Picture: Oceanwide Science Institute).

SPERM WHALE DIALECTS 

Sperm whales have repertories that varied in the proportional usage of different coda types and classes. Sperm whale codas are stereotyped sequences of 3-40 broad-band clicks usually lasting less than 3 seconds in total, which functions are to help maintain group cohesion, reinforce bonds, aid negotiations and collective decision-making. These groups with distinct dialects also interact. To give a particular example, in the South Pacific and the Caribbean, there are six sympatric acoustic clans based on coda sharing, which simultaneously differ in movement and habitat use patterns and in feeding success.

Dialects have been described in sperm whales (Physeter macrocephalus) (Picture: CBC News).

ORIGIN OF DIALECTS IN CETACEANS

A recently published article in the magazine Nature suggests a mechanism that may explain the origin of multilevel societies in sperm whales. As we have seen, it is in these societies where dialects are present in cetaceans. So, here we will explain the origin of multilevel societies in sperm whales as an example.

In sperm whales, the upper level of the multilevel society are clans of individuals that communicate between them using similar codas. These clans are originated from cultural transmission via biased social learning of codas, when they learn the most common codas (conformism) from behaviourally similar individuals (homophily). Thus, the result are groups with increasingly homogeneous behaviour with a strong integration. The cultural transmission plays a key role in the partitioning of sperm whales into sympatric clans (clans that live together but without interbreeding). So, it is in these clans where distinctive behavioural patters may appear, like dialects. The lower level, social units, are originated from ecological, cognitive and time constraints and benefits.

Multilevel societies. Individuals (stars and filled circles) are the lowest level and in association (black lines) with other individuals they constitute social units (empty black circles). Socials units with acoustic similarity (orange lines) form vocal clans (blue and green). It is in vocal clans where dialects can emerge (Picture: Marc Arenas Camps).

HUMPBACK WHALES: A DIFFERENT CASE

The differences in the songs of humpback whales (Megaptera novaengliae) cannot be considered dialects since they happen between geographically isolated populations. Due to a geographic and reproductive isolation, these differences have appeared as a result of genetic distinctions among populations.

REFERENCES

• Cantor, M; Shoemaker, LG; Cabral, RB; Flores, CO, Varga, M & Whitehead, H (2015). Multilevel animal societies can emerge from cultural transmission. Nature Communications. 6:8091. DOI: 10.1038/ncomms9091
• Conner, DA (1982). Dialects versus geographic variation in mammalian vocalizations. Animal Behaviour. 30, 297-298
• Dudzinski, KM; Thomas, JA & Gregg, JD (2009). Communication in Marine Mammals. In Perrin W, Würsig B & Thewissen JGM (edit.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
• Ford, JKB (2009). Dialects. In Perrin W, Würsig B & Thewissen JGM (edit.). Encyclopedia of Marine Mammals. Academic Press (2 ed).

Homosexuality is so animal

Fortunately for LGTB collective, greater and greater countries and societies understood that homosexuality is something natural and that it is not an illness. Anyway, despite this is true, it is also true that it is necessary to work hard to achieve equality on lesbian, gay, transexual and bisexual rights and to eradicate the false belief that homosexuality is unnatural. In the next weeks, in cities all over the world like Barcelona and Madrid will take place LGTB Pride parties. For this reason, this article hope to show clear examples that homosexuality is not exclusive of human, but present in many animals. So, there is no reason to continue believing in the argument that homosexuality is unnatural! 

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INTRODUCTION

Homosexuality is a fact present in many animal species. In fact, it has been documented in 1,500 of the more than 1 million described animal species (Bagemihl, 1999). Without going any further, a study of the California University demonstrated that in all the analysed species there were some individuals with homosexual traits or behaviours, including worms, flies, birds, dolphins and chimpanzees, among others.

In the animal kingdom, the concept “homosexuality” refers to any sexual behaviour between same sex animals, like copulation, flirt, mating, genital stimulation and young breeding. In the case of humans, it is more complex than this because there is much more factors and feelings are involved in this.

From the biological point of view, it is supposed that the goal of any species is its perpetuation. So, which is the function of homosexuality? There are many theories about it and they are not particular because for each species there is one explanation or another. Let’s explain three of them! Marelen Zuk, professor in biology at the University of California, propose that not producing their own offspring, homosexuals could help to breed and take care of their relatives, what also contributes to genetic pool. According to the biologist and phsycologist Janet Mann from the Georgetown University, it is a way of creating links and alliances between individuals. Finally, in the case of fruit fly and other insects, the evolutionary biologist Nathan Bailey suggest that the reason of their homosexuality is the lack of the gene that let them to distinguish between both sex. There is also the possibility that homosexuality doesn’t have any function. At any rate, homosexual behaviour may have evolutionary consequences, but it is still being studied.

PINGUINS

On February 2004, New York Times published that Roy and Silo, two male chinstrap penguins (Pygoscelis antarctica) from the Central Park Zoo, coiled their necks, vocalized one to other and had sex. When they were exposed to females, they rejected them. Moreover, zookeepers gave them a fertile egg in order they incubate them and when the little penguin was born they feed her until she was able to live by herself. This is not an isolated case because it have happened more in this and other zoos, like in Bremerhaven Zoo (Germany), Faunia (Spain) and Dingle Ocean World (Ireland).

But this is not exclusive of captive animals. A research done on Adélie penguin (Pygoscelis adeliae) found homosexual behaviours in some of their young individuals. Another research was carried on king penguin (Aptenodytes patagonicus), in which it was observed that 28.3% of males flirted with other males. The reason in this case seems to be an excess of males or high testosterone levels. Anyway, it was found two partners (male-male and female-female) in which one knew the vocalization of the other.

Penguins are a good example of birds with homosexual behaviours (Picture from Listverse).

BONOBOS

The bonobo (Pan paniscus), apes very close to humans, are a good example of homosexual behaviours. They are so sexual. It has been observed that, in captivity or free, half of their sexual relationships are with same sex animals. In addition, females have sex with other females almost every hour. The main function of this is to strengthen links between animals. In the case of males, in order to reduce the stress after a fight, a penis fight takes place, that consists on rubbing their genitals together.

In bonobos, same sex relationships may be done to strengthen social links (Picture from BBC).

KILLER WHALES

Homosexual interactions between male killer whales (Orcinus orca) are an important part of their social life. When resident groups join together during summer and autumn to feed, males show flirting, affectionate and sexual behaviours between them. Normally, interactions take place one to one and lasts for an hour, but it can be longer. In this interactions, they caress, chase and carefully push one to the other. Another amazing behaviour is the beak – genital orientation, but it also take place between males and females. Just under the water surface, one male swims in an upside down position, touching the genital zone of the beak. Then, they dive together in a double helix spiral. This happens several times, but they interchange their positions. It is not strange to see them with the erected penis during this interaction. Despite it happens in all ages, it is specially abundant in young animals.

Killer whales (Orcinus orca) are cetaceans with homosexual behaviours (Picture from WorldPolicy)

GUPPIES

A research made on guppies (Poecilia reticulata) demonstrated that the lack of females in the environment during a long period of time produce that males prefer other males even when there are females in the environment. Not only this. When males that had been with females during a long period of time are deprived from females for a short time (two weeks) they prefer males instead of females.

Male guppies prefer other males when there is no females in the environment during a long period of time (Picture from GuppyFish).

DRAGONFLIES

Some studies lay bare that there is a high rate of mating between same sex individuals in dragonflies. The reasons could be the lack of individuals of the other sex or that female tricks to avoid sexual advances of males could produce that males look for same sex individuals. One specific example is blue-tailed damselfly (Ischnura elegans), in which 17% of males of wild populations prefer male partners.

17% of male blue-tailed damselfly (Ischnura elegans) prefer other males (Picture: L. B. Tettenborn, Creative Commons).

SOME EXAMPLES MORE

• Studies on wild occidental gull (Larus occidentalis) show that between 10 and 15% of females are homosexual. It has been seen that they show flirting rituals between them and that they set nets together. They only copulate with males to produce fertile eggs, but then go with their initial partner.
• On domestic sheep, 8% of males from a flock prefer other males despite the presence of females. But this could benefit other males because they can present the same genes and pass to next generation. But this also benefits females by doing them more fertile.
• The king of savannah, the lion, also have homosexual behaviours. It has been observed wild male and female lions with this behaviour, include mating.

• In some species of seahorse, homosexual behaviours between females are frequent, more than heterosexual.

CONCLUSION

Homosexual behaviours are no only in humans, but they are more complex in people. The reason that lead to the development of these behaviours in animals are several: lack of females, to stablish harder links… but there are some examples in which the behaviour is permanent. Moreover, it has been seen that this behaviours are not artificial due to the captivity of animals, like humans in prison, but they haven in wild animals too. So, homosexuality happens in many animals and cannot be considered unnatural. In addition, if it is the result of natural forces it cannot be considered immoral. 

REFERENCES

• ABC: Los pingüinos gay de Madrid, a punto de ser padres
• Bagemihl, B (1999). Biological Exuberance: Animal Homosexuality and Natural Diversity, New York: St. Martin’s Press, 752 pp.
• Bailey, NW & Zuk M (2009). Same-sex sexual behaviour and evolution. Trends Ecol Evol. 24 (8): 439-46 
• BBC: ¿Existen realmente los animales homosexuales? 
• BBC: Penguins flirt with homosexuality 
• BBC: Todos los animales son homosexuales
• Field, K & Waite TA (2004). Absence of female conspecifics induces homosexual behaviour in male guppies. Animal Behaviour, 68, 1381-1389
• Hay una lesbiana en mi sopa: Conoce a Missy y Penélope, las pingüinas lesbianas de Irlanda 
• National Geographic: Damselfly Mating Game Turns Some Males Gay
• Quo: Relaciones homosexuales en el reino animal
• The New York Times: Love that dare not squeak its name
• WayBack Machine: Gay Penguins Resist “Aversion Therapy”
• WorldPolicy: Homosexuality in Marine Mammals 

Reasons to watch marine mammals in captivity (or maybe not)

The topic we are discussing this week is marine mammals in captivity, a very controversial subject. While some people totally agree with this practice because they defend that are beneficial (not only economical), others are against it.

INTRODUCTION

In the discussion about marine mammals in captivity; zoos, aquaria and and dolphinaria maintain that their shows have such a great value in conservation, people learn a lot and that marine mammals have a good life. On the contrary, animal protection groups and more and more scientists defend their lives are impoverished, people don’t receive a good information of the species and that captures of wild animals negatively impacts populations and habitats.

CAPTIVITY OF MARINE MAMMALS IS EDUCATIONAL (OR MAYBE NOT!)

Despite in some countries is compulsory to offer educational values in their shows, there is less evidence that the industry spreads information about marine mammals and their habitats. There are more than 1,600 centres in United States and just a negligible part are actually involved in educational and conversational issues, since most of them just aspire to entertain their visitors.

Tricks performed by sea lions, dolphins or whales are exaggerated variations of their natural behaviours and cause the audience loose the notion of the place they are: inside pools confined by Plexiglas. In a survey of 1,000 US citizens, the respondents overwhelmingly preferred to see captive marine mammals expressing natural behaviours rather than performing tricks and stunts.

Contrast of the behaviour between a killer whale (Orcinus orca) and a sea lion. In the right, the natural behaviour, which consists on a killer whale capturing a sea lion (Picture: Daniel Bianchetta). In the left, artificial behaviour in which a sea lion gives food to a killer whale.

In general, almost nothing is explained  about natural behaviours, ecology, demographics or population distribution during the shows. In addition, it has been demonstrated that the information is sometimes incorrect of distorted. For example: SeaWorld doesn’t use the word “evolution” as many visitors consider the theory of evolution to be controversial, they fool in the explanation of the drooping fin syndrome in killer whales or about their life span in captivity.

Another example is that many actions performed by dolphins in shows or observed being directed toward visitors or trainers that are portrayed as play or fun (such as the rapid opening and closing of the mouth and the slapping of the water surface with the tail flukes or flippers) are actually displays that in wild animals would usually be considered aggressive.

Aggressive behaviour of a dolphin, slapping the water surface with the tail flukes(Picture from Sara's Cetacean Stories).

So, the exhibition of marine mammals does exactly the opposite of what the industry rhetoric claims: instead of sensitizing visitors to marine mammals and their habitats, it desensitizes humans to the cruelty inherent in removing these animals from their natural habitats and holding them captive.

ZOOS HELP TO THE CONSERVATION OF SPECIES (OR MAYBE NOT)

Zoos, aquaria and dolphinaria have increasingly promoted themselves as conservation centres, emphasizing their role as Noe ark. In fact, they do no more than produce new individuals of a limited group of species and do not maintain true conservation programs.

While several zoos have programs to breed endangered species in captivity with the intention that these animals be used in restocking depleted populations, this is not the case with dolphins. Only one facility attempted a captive breeding program for baiji or Yangtze river dolphins (Lipotes vexillifer).

Baiji or Yangtze river dolphin (Lipotes vexillifer) (Picture: Mark Carwardine, Arkive).

Moreover, the number of centres that invest money in conservation programs are few in number and the amount of money is less that 1% of their benefits. Fewer than 5 to 10 percent of zoos, dolphinaria and aquaria are involved in conservation programs, either in natural habitat (in situ programs) or in captive settings (ex situ).

Nevertheless, in Europe these centres are obliged for law to develop conservation programs to free the animals breeding in captivity to the nature. The truth is that the overwhelming majority of marine mammal species currently being bred in captivity is neither threatened nor endangered. In addition, the success of these programs would be in the capability to introduce the animals in the nature, what has been done in few chances.

What is worse is that many dolphinaria and aquaria are buying animals directly captured in the wild populations.

CAPTURE OF WILD ORGANISMS

All cetacean capture methods are invasive, stressful and potentially lethal, despite the method generally considered the better consists on chasing them by small boats and then herded together and encircled by a net. The process is so traumatic that mortality rates shoot up six-fold in the first five days of confinement. The dolphins not selected and released from the net may experience a similar risk of dying once the capture operators have left the area.

Capture of dolphins in Japan during a seine-net capture (Picture: Adrian Mylne, Reuters)

The most violent and cruel method of collecting cetaceans for dolphinaria is the drive fishery, used primarily in Taiji and Futo, Japan. A fleet of small ships produce underwater noise with metal pipes to force the dolphins to go into shallow water. Some of the animals are set aside for the public display facilities, while the rest are killed for human and pet food and other products.

Dolphin slaughter in Taiji (Japan) (Picture: unknown author).

ZOOS, AQUARIA AND DOLPHINARIA HAVE PROGRAMS TO HELP STRANDED ANIMALS (OR MAYBE NOT)

The one area of activity in which dolphinaria and aquaria can legitimately claim to serve a conservation function is work involving rescue, rehabilitation and release of stranded marine mammals. Indeed, there are some very good stranding rehabilitation programs, but the interests are not always clear.

Usually, the real interest is to promote a good reputation of themselves, so they promote themselves as altruists centres that care for marine mammals in the wild. In addition, they use a stranding as proof that marine mammals’ natural habitat is a dangerous place full of human-caused and natural hazards. The public receives a skewed picture in which an animal’s natural environment is hostile and captivity is a benign alternative.

Also disturbing is the fact that these industries appear to evaluate each animal in terms of display potential. Species that are highly desirable or rarely observed in captivity may be determined to be unsuitable for release.

MARINE MAMMALS IN CAPTIVITY ALLOW RESEARCH (OR MAYBE NOT)

Almost always, dolphinaria and aquaria claim that they foster research and scientific study of marine mammals, thereby contributing to both education and conservation. However, much of what can be learned from captive marine mammals has in fact already been learned (reproductive physiology length of gestation, visual acuity and general physiology). Moreover, most of the results given by studies made on captivity animals have been demonstrated to not be correct, specially those related with behaviour.

There may be some research questions that the study of captive animals can answer most directly, but due to advancements in technology such as biopsy darts, electronic tags and underwater video, as well as improvements in capture and release techniques, it can be studied in wild animals.

Use of a metabolic dome to study the metabolism of sea lions (Picture from Vancouver Aquarium).

REFERENCES

• Kleiman, D.G.; Thompson, K.V.; & Kirk Baer, C. (2010) Wild Mammals in Captivity. Principles and Tecniques for Zoo Management. The University of Chicago Press (2 ed).
• Rose, N.A; Parsons, E.C.M & Farinato, R. (2009). The case against Marine Mammals in Captivity. The Humane Society of the United States and the World Society for the Protection of Animals (4 ed)

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The awesomest fish: the sunfish

This week I want to dedicate this post to common sunfish (Mola mola), one of the biggest bony fishes in the planet and the one with the smallest brains compared with its body. Curiously, an individual of 200 kg had a brain of just 4 grammes (like a walnut)! 

INTRODUCTION

Nowadays, there are four species of sunfishes, which are all included in the Molidae family: the Roundtailed or Common mola (Mola mola), the Southern ocean sunfish (Mola ramsayi), the Sharp-tailed mola (Masturus lanceolatus) and the Slender mola (Ranzania laevis). Today, I will talk about the Common mola (Mola mola) because it is the commonest.

 Roundtailed or Common mola (Mola mola) (Foto:Per-Ola Norman, Creative Commons)
Sharp-tailed mola (Masturus lanceolatus) (Foto: NOAA/PIRO Observer Program, Creative Commons)
Slender mola (Ranzania laevis) (Foto: NOAA/PIRO Observer Program, Creative Commons)

COMMON MOLA (MOLA MOLA)’S DESCRIPTION

Common mola’s body have been somehow truncated leaving them little more than a large head with long fins atop and below. Not having in consideration the fins, its body is less than twice as long as it is deep. The tail is not exactly a tail; it consists on expansions of the dorsal and anal fin rays and it is rounded. Skin is gritty and is covered with mucus. Its body is typically silvery in color with slight sheen and can exhibit changeable spotty patterns.

Common mola (Mola mola). Picture made by Blanca Figuerola (Visit her site).

Teeth of each jaw are joined forming an only piece, with an small mouth compared with the body.

The average size for an adult is 1.8 m (from the mouth till the end of the tail) and 2.4 m from each end of the fins. The average weight is one tonne. They hold the record for the world’s heaviest bony fish: a 3.1 meter long specimen weighted in at 2,235 kg.

REPRODUCTION

Sunfishes have a high reproductive potential, as a female of 1.4 meters long can produce 300 million eggs in its single ovary, which are tiny. They have three larvae stages and in the last, the body is covered by bony rays, which are lost when they achieve the adult age.

DIET

Common mola eats a variety of foods, being the most common prey items of gelatinous zooplankton like jellyfishes, Portuguese man-o-war, ctenophores and salps. In addition, they feed on squids, sponges, serpent star bits, eel grass, crustaceans, small fishes and eel larvae.

DISTRIBUTION

They live in all tempered seas and oceans worldwide. They usually live in open sea, but sometimes they move closer the coast, from the surface to 300-400 m deep.

PARASITES AND PREDATORS

It has been detected more than 50 species of parasites in sunfishes, from very different groups, including shark larvae. Moreover, it has been found parasites in their parasites.

On the other side, due to its size, they have few predators, just killer whales and sea lions. Sea lions exhibit a behaviour related to sunfishes. They eat their fins and they abandon the body and sinks to the bottom, where are ate by starfishes.

REFERENCES

• http://oceansunfish.org/
• http://australianmuseum.net.au/ocean-sunfish-mola-mola
• http://www.cibsub.cat/bioespecie-mola_mola-32823
• http://www.fishbase.org/summary/Mola-mola.html

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Albinism in cetaceans

This publication talk about albinism in cetaceans and give some examples about it.

WHAT IS ALBINISM?

Albinism is a group of inherited conditions resulting in little or no pigment (hypopigmentation) in the eyes or in the eyes, skin and hair. Mammals’ pigmentation depends on the presence or absence of melanin in the skin, hair and eyes. Melanin is produced by amino acid tyrosine thanks to enzyme tyrosinase, whose alteration cause albinism. The other case is the overproduction, known as melanism, and the result is overly dark animals.

ALBINO CETACEANS

Albino marine mammals have been reported for 21 cetacean species (Fertl et al. 1999; Ferlt et al. 2004) and 7 pinniped species (Rodriguez & Bastida, 1993; Bried & Haubreux, 2000). Some cetacean species are sperm whales (Physeter macrocephalus), bottlenose dolphins (Tursiops truncatus) and killer whales (Orcinus orca).

Chédiak-Higashi Syndorme is a type of albinism that consists on diluted pigmentantion patterns that appear pale gray eye, white blood cell abnormalities and a shortened life span. It was detected on Chimo, a female killer whale (picture).

Chimo, an albino killer whale (Picture: Orcinus orca).

Albinism means some associated problems to marine mammals: it reduces the heat absorption in colder waters, it eases the detection for depredators, it increases the eye and skin sensibility to sunlight and it reduces the visual communication.

REFERENCES

• FERTL, D; PUSSER, L. T.; & LONG, J. J. (1999) First record of an albino bottlenose dolphin (Tursiops truncatus) in the Gulf of Mexico, with a review of anomalously white cetaceans. Mar. Mamm. Sci. 15, 227-23
• PERRIN, W. F.; WÜRSIG, B; THEWISSEN, J. G. M. Encyclopedia of Marine Mammals (Ed. Academic Press, 2ª edició)