Researchers from Emory University have identified the first fish to have switched from ultraviolet vision to violet vision, i.e. the ability to see blue light. This fish in question – a type of scabbardfish – is also the first example of an animal where a deleted molecule has resulted in a change in visual spectrum.

Many species, including humans, have violet vision but our common vertebrate ancestor had UV-vision and could not sense the blue colour spectrum.

All fish studied before the scabbardfish have been found to have UV vision. The scabbardfish is believed to have switched from UV vision to violet vision by deleting the molecule at site 86 in the chain of amino acids that makes up the opsin protein.

“Normally, amino acid changes cause small structure changes, but in this case, a critical amino acid was deleted,” Yokoyama explains.

Vision is of particular interest to evolutionary geneticists since it is a comparatively straight-forward sensory system with a low number of genes involved. Human vision is for instance made possible by no more than four genes.

“It’s amazing, but you can mix together this small number of genes and detect a whole color spectrum,” says evolutionary geneticist and research team leader Shozo Yokoyama. “It’s just like a painting.”

In their study, the Emory researchers linked molecular evolution to functional changes and the possible environmental factors driving them.

“This multi-dimensional approach strengthens the case for the importance of adaptive evolution,” says Yokoyama. “Building on this framework will take studies of natural selection to the next level.”

The Scabbardfish spends most of its life at a depth of 25-100 meters and at these depths UV light is less intense then violet light, something which may have prompted the change in vision. Living deep down in the ocean will however not necessarily make you benefit from a vision switch; the Lampfish has for instance retained its UV vision – most likely because it swims up to the surface at night to feed on translucent crustaceans that are easier to locate if you have UV vision.

“The finding implies that we can find more examples of a similar switch to violet vision in different fish lineages,” says Yokoyama. “Comparing violet and UV pigments in fish living in different habitats will open an unprecedented opportunity to clarify the molecular basis of phenotypic adaptations, along with the genetics of UV and violet vision.”

The article has been published in the October 13 issue of Proceedings of the National Academy of Sciences.

http://www.pnas.org

In addition to evolutionary geneticist Shozo Yokoyama, the research team also included post-doctoral fellow in biology Takashi Tada and post-doctoral fellow in biology and computational chemistry Ahmet Altun.

“No matter how exquisite it may seem, as if it were some sort of magic, evolution is at most a good trick… and there is a way to make it work. In case of turtle evolution, a major part of the trick was found to be embryonic folding.”

Dr Shigeru Kuratani
Riken Center for Developmental Biology

Ever wondered how the turtle got its shell? So has a Japanese team of scientist and they decided to investigate the subject by comparing turtle embryos with those of chicks and mice.

In turtles, it is the ribs that grow outward and fuse together to form the shell, formally known as the carapace. Having your ribs folded around your body is such a great leap from being a soft bodied animal that scientists have long puzzled over how this change happened in the course of evolution. Just like mammals and birds, turtles hail from a soft-bodied ancestor without any external carapace.

Through their embryological studies, the Japanese team of researchers from the Riken Center for Developmental Biology in Kobe, Japan, was able to identify the key event in the development of a turtle embryo that changes its fundamental “body plan”; the moment when the upper part of its body wall folds in on itself, forcing the ribs outward. This folding process results in a thickening of the deep layer of the turtle’s skin that maps out the position of the shell. As the turtle embryo grows bigger, the folding prevents the ribs from growing inwards.

“In the early embryo, the muscles and skeleton are in similar positions to those of the chicken and mouse”, Dr Kuratani explains.

Last year, a 220-million-year-old fossil was found in China, consisting of a fossilized turtle with an incomplete shell covering the underside of it body.

“The developmental stage of the modern turtle, when the ribs have not encapsulated the shoulder blade yet, resembles the (body) of this fossil species,” says Dr Kuratani.

The team has not yet been able to determine what causes the folding to happen in the first place

“That belongs to a future project,” says Dr Kuratani.

“Small fish may have small brains but they still have some surprising cognitive abilities”, says Dr Jeremy Kendal* from Durham University’s Anthropology Department.

Dr Kendal is the lead author of a new study showing that Nine-spined stickleback fish (Pungitius pungitius) can compare the behaviour of other sticklebacks with their own experience and make choices that lead to better food supplies.

“‘Hill-climbing’ strategies are widely seen in human society whereby advances in technology are down to people choosing the best technique through social learning and improving on it, resulting in cumulative culture”, says Dr Kendal. “But our results suggest brain size isn’t everything when it comes to the capacity for social learning.”

Around 270 Nine-spined sticklebacks were caught from Melton Brook in Leicester using dip nets. After being divided into three experimental groups and one control group, the fish were housed in different aquariums and the fish in the experimental groups were subjected to two different learning experiences and two preference tests in a tank with a feeder placed at each end.

1.) The fish were free to investigate both feeders during a number of training trials. One feeder (dubbed “rich feeder”) always handed out more worms than the other one (dubbed “poor feeder”). The fish were then tested to see which feeder they preferred.
2.) In the second training trail, those fish that come to prefer the rich feeder could see other fish feeding. During this stage, the rich and poor feeders were swapped around and the rich feeder either gave even more worms than before or roughly the same or less. During the second test, the fish were once again free to explore the tank and both feeders. Around 75 per cent of the Nine-spined sticklebacks had learned from watching the other fish that the rich feeder, previously experienced first hand themselves as the poor feeder, gave them more worms. In comparison, significantly fewer sticklebacks favoured the feeder that appeared to be rich from watching other sticklebacks if they themselves had experience that the alternative feeder would hand out roughly the same or more worms.

Further testing showed that the sticklebacks were more likely to copy the behaviour of fast feeding fish.

“Lots of animals observe more experienced peers and that way gain foraging skills, develop
food preferences, and learn how to evade predators”, Dr Kendal explained. “But it is not always a recipe for success to simply copy someone. Animals are often better off being selective about when and who they copy. These fish are obviously not at all closely related to humans, yet they have this human ability to only copy when the pay off is better than their own.”

The study, which has been published in the journal Behavioral Ecology, was carried out by scientists from St Andrews and Durham universities and funded by the Biotechnology and Biological Sciences Research Council. The lead author of the study, Dr Kendal, is a Research Council UK Fellow.

We often think of evolution as something extremely slow that takes place over the course of thousands or even millions of years. The truth is however that certain adaptations can occur very quickly, sometimes over the course of just a few generations.

Male Guppy. Copyright www.jjphoto.dk

Eight years later, a time period equivalent of less than 30 guppy generations, the guppies living in the low-predation environment had adapted to this environment by producing larger and fewer offspring with each reproductive cycle.

“High-predation females invest more resources into current reproduction because a high rate of mortality,
driven by predators, means these females may not get another chance to reproduce,” explained Gordon, who works in the lab of David Reznick, a professor of biology.

The guppies living below the barrier waterfall where there were a lot of predators did not show any signs of producing fewer or larger offspring.

“Low-predation females, on the other hand, produce larger embryos because the larger babies are more competitive in the resource-limited environments typical of low-predation sites”, Gordon said. “Moreover, low-predation females produce fewer embryos not only because they have larger embryos but also because they invest fewer resources in current reproduction.”

The paper will be published in the July issue of The American Naturalist.

Swanne Gordon’s research team included David Reznick and Michael Bryant of UCR; Michael Kinnison and Dylan Weese of the University of Maine, Orono; Katja Räsänen of the Swiss Federal Institute of Technology, Zurich, and the Swiss Federal Institute of Aquatic Science and Technology, Dübendorf; and Nathan Miller and Andrew Hendry of McGill University, Canada.

Financial support for the study was provided by the National Science Foundation, the Natural
and Engineering Research Council of Canada, the Le Fonds Québécois de la Recherche sur la Nature
et les Technologies, the Swedish Research Council, the Maine Agricultural and Forestry Experiment
Station, and McGill University.

Two new species of the genus Leporinus has been described from the Araguaia-Tocantins River system in the Amazon basin: Leporinus unitaeniatus and Leporinus geminis.

Brazilian ichthyologists Julio Garavello and Geraldo Santos describe them both in a paper* published in the most recent issue of Brazilian Journal of Biology.

Leporinus unitaeniatus

Leporinus unitaeniatus derives its name from its distinguishing colour pattern; uni is the Latin word for one and taenia means ribbon. This fish is adorned with a conspicuous longitudinal dark brown bar along the lateral line on the flanks. Other distinguishing characteristics are the slender and elongated body, the narrow snout, and the small eyes. The mouth is sub-inferior and filled with elongated, incisor-like teeth forming a straight cutting edge. There are 42–44 lateral line scales; 6 scale rows above and 5 scale rows below the lateral line; and 16 circumpeduncular scales.

Picture credit: http://www.scielo.br

Leporinus geminis

Juvenile Leporinus geminis fish look very similar to juveniles of the close relative Leporinus unitaeniatus, hence the name Leporinus geminis. Geminius is the Latin word for twin.

Leporinus geminis is decorated with three large and vertically elongated brown blotches on the trunk and has one inconspicuous dark bar on the body. The body is deep, the snout is blunt, and the eyes are large. The mouth is sub-inferior and fitted with large incisor-like teeth forming a curved cutting edge. There are 40–42 lateral line scales; 5.5 or 6 scale rows above and 5 scale rows below the lateral line; and 16 circumpeduncular scales.

Picture credit: http://www.scielo.br

* Garavello, JC and GM Santos (2009) Two new species of Leporinus

Agassiz, 1829 from Araguaia-Tocantins system, Amazon basin, Brazil (Ostariophysi, Anostomidae). Brazilian Journal of Biology 69, pp. 109–116.

Chinese ichthyologists Yang, Chen and Yang have described three new species of snow trout in a paper[1] published in the journal Zootaxa[2]. All three species have been described from material previously identified as one single species, Schizothorax griseus. True trouts belong to the Salmoninae subfamily in the Salmonidae family, but snow trouts are members of the family Cyprinidae.

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Schizothorax

New species: Schizothorax beipanensis

Schizothorax heterophysallidos

Schizothorax nudiventris

Schizothorax beipanensis

Schizothorax beipanensis is found in southern China where it inhabits the Beipan River drainage, a part of the Pearl River drainage. It has been encountered in both slow-flowing deep pools and fast-flowing rivers with clear water and over a wide range of different bottom substrate, from mud and sand to rocks, boulders and pebbles.

Schizothorax beipanensis differs from its close relatives by having well-developed upper and lower lips (the lower lip is actually tri-lobed), no horny sheath on the lower jaw, and a continuous postlabial groove with a minute median lobe.

Schizothorax heterophysallidos

Just like Schizothorax beipanensis, the snow trout Schizothorax heterophysallidos is found in the Pearl River drainage in southern China, but it lives in the river drainage of Nanpan, not Beipan. Schizothorax heterophysallidos lives in small streams where the bottom consists of sand and pebbles.

The name heterophysallidos is derived from the unusual swim bladder of this fish; physallis is the Greek word for bladder and heteros means different. In addition to the swim bladder (the posterior chamber of the air bladder is three to six times longer than the anterior chamber), Schizothorax heterophysallidos can be recognized on its well-developed and trilobed lower lip, thin upper lip, and blunt snout. It has a continuous postlabial groove with a minute median lobe and the last unbranched dorsal-fin ray has a strong lower part. In mature specimens, the abdomen lacks scales.

Schizothorax nudiventris

Schizothorax nudiventris also lives in southern China, but in the upper parts of the Mekong River drainage. The Mekong basin is one of the richest areas of biodiversity in the world. More than 1200 species of fish have been identified here and the number is believed to increase as the area becomes more thoroughly explored by science.

Schizothorax nudiventris has a well-developed and trilobed lower lip, thin upper lip, blunt snout, and continuous postlabial groove. The body is decorated with irregular black spots on the sides, and the last one-quarter of the last unbranched dorsal-fin ray is soft. In mature specimens, the abdomen has no scales, and it is this feature that has given the fish its name nudiventris. Nudus is the Latin word for naked, while venter means abdomen.

Born in the Netherlands in 1947, Marc van Roosmalen is a Brazilian primatologist of Dutch birth living in Manaus, Brazil. After studying biology at the University of Amsterdam he did four years of doctoral fieldwork in Suriname studying the Red-faced Spider Monkey. Since then, van Roosmalen has devoted his life to the scientific exploration of the South American flora and fauna.

Marc van Roosmalen is described as a hand-on naturalist and has spent long periods of time doing research work in the Amazonian rainforest, while simultaneously producing prolific amounts of scientific papers, books, reviews, and wildlife documentaries. His work has led to the discovery and description of several new species, such as Callibella humilis, the dwarf marmoset, the second smallest monkey in the world, and Lecythis oldemani, a tree belonging to the Brazil Nut family. From 1986 to 2003, van Roosmalen served as senior scientist at the National Institute for Amazonian Research (INPA) under the Brazilian Ministry of Science and Technology.

Parallel to his research work, van Roosmalen is a dedicated conservationalist trying to protect the Brazilian rainforest from destruction by humans. During the late 1980s, he launched “The Center for the Rehabilitation and Re-introduction of Endangered Wildlife” in the federal Rio Cuieiras Nature Reserve; a centre where all kinds of animals, but especially monkeys confiscated from the illegal pet trade, were rehabilitated in the local rain forest. In 1999, he founded the NGO “Amazon Association for the Preservation of High Biodiversity Areas” (AAPA) and began purchasing areas of pristine rainforest in regions harboring extremely high biodiversity and/or animals and plants new to science.

For his outstanding work in South America, van Roosmalen has received several honors and was knighted as Officer in the Order of the Golden Ark by Prince Bernhard of the Netherlands in 1997. At the turn of the millennium, van Roosmalen was selected as one of the worldwide recognized “Heroes for the Planet” by Time Magazine.

You can read about van Roosmalen’s current predicament in our interview with him which is found here. More information can also be found in this Wired article and this article published by the Smithsonian institution.

“For if there are out there big tree-dwelling, ground-dwelling and even aquatic mammals not known to science – a dwarf tapir, a giant peccary, a white deer, a dwarf manatee, another river dolphin, to name a few – what do we really know about its flora and fauna? Very Little. About its ecology – the utterly complex web of relationships between plants and animals? Even less. Then what do we know about the sustainability of this ecosystem? Absolutely nothing.”

– Marc van Roosmalen

According to a new study from Uppsala University, the origin of fingers and toes can be traced back to a type of fish that inhabited the ocean 380 million years ago. This new finding has overturned the prevailing theory on how and when digits appeared, since it has long been assumed that the very first creatures to develop primitive fingers were the early tetrapods, air-breathing amphibians that evolved from lobed-finned fish during the Devonian period and crawled up onto land about 365 million years ago.

Lead author Catherine Boisvert[1] and co-author Per Ahlberg[2], both of Uppsala University in Sweden, used a hospital CT scanner to investigate a fish fossil still embedded in clay. “We could see the internal skeleton very clearly, and were able to model it without ever physically touching the specimen,” says Ahlberg. The scan revealed four finger-like stubby bones at the end of the fin skeleton. The bones were quite short and without joints, but it was still very clear that they were primitive fingers. “This was the key piece of the puzzle that confirms that rudimentary fingers were already present in the ancestors of tetrapods,” Catherine Boisvert explains.

The scanned fossil was that of a meter-long Panderichthys, a shallow-water fish from the Devonian period. Panderichthys is an “intermediary” species famous for exhibiting transitional features between lobe-finned fishes and early tetrapods, while still clearly being a fish and not a tetrapod. The specimen used was not a new finding; it had just never been examined with a CT scan before.

So, why have researchers for so long assumed that digits were something that evolved in tetrapods without being present in their fishy ancestors? The main reason is the Zebra fish (Danio rerio), a commonly used model organism when vertebrate development and gene function is studied. If you examine a Zebra fish, you will find that genes necessary for finger development aren’t present in this animal. Researchers therefore assumed that fingers first appeared in tetrapods and not in fish.

It should be noted that similar rudimentary fingers were found two years ago in a Tiktaalik, an extinct lobe-finned fish that lived during the same period as Panderichthys. Tiktaalik is however more similar to tetrapods than Panderichthys.

The Panderichthys study was published in Nature on September 21.