May 18, 2012 Graham

How Prawns Lure Prey – The Scientist

An interesting study on how female guppies’ likeness for the colour orange is used by predatory shrimp to lure them close.

“This is the first significant advance on predatory lures for 100+ years and the first experiment really addressing why a lure should actually work,” John Endler, an evolutionary ecologist at Deakin University in Australia, wrote in a email. Endler, who was not involved with the research, co-authored a study in 1990 that linked female preference for orange guppies with the prevalence of orange-colored males.

That predators might have co-opted a prey species’ color preference in order to entice that prey is a “new, interesting twist” on color bias, which states that animals evolve preferences and even high visual acuity for colors relevant to their survival and reproduction, added Greg Grether, a behavioral ecologist at the University of California, Los Angeles, who was not involved in the work. Grether’s work, for example, has shown that female guppies’ love of orange pushed male guppies to maintain the right orange shade.

Read more here – How Prawns Lure Prey | The Scientist

February 5, 2012 Graham

Multiple Evolution Events of ‘Blind’ Cavefish – Science News

The blind cave fish is commonly found in many shops and has been a favourite in the hobby for many years. It exists in various caves in Mexico and has long been known to be the same species as the Mexican tetra, Astyanax mexicanus found above ground. Now a new study by a team of researchers from Portugal, America, and Mexico has shed some light into how they came to be.

It seems that the various underground populations are more closely related to the above ground form than to other populations of blind fish. In other words the blind form has evolved multiple times. A striking example of what is known as convergent evolution. Not only that but a significant amount of cross breeding between the two forms still takes place. The fact that the blind form still persists in spite of a constant influx of genes from the sighted form is evidence for a very strong selection pressure against eyes within the environment of the caves. Blind fish are clearly able to produce more offspring in the caves than are sighted fish.

Strange places fish live – BBC

English: Common Clownfish (Amphiprion ocellari... — Clownfish - via wikipedia

A nice piece from the BBC illustrating the wonderful variety of fish behaviour. Some of these fish are quite familiar to us yet much of their life remains to be discovered.

A Great Barrier Reef pearlfish has been filmed by the BBC living inside a sea cucumber‘s bottom. But it is not the only fish with a somewhat unusual home. Where are some of the other strange places fish live?

Read it here – BBC Nature.

BBC’s new Great Barrier Reef documentary serves up some serious eye candy [Documentaries] (io9.com)

November 30, 2011 Graham

How fish choose their mates

When male guppies choose females to mate with, it seems they can be quite choosy.

Males decide how much effort they put into courtship and which females to court based on how many others they have recently encountered and how attractive they were, according to a new study into the mating tactics of tropical fish.

Cichlid Male Nannies Help Out, Especially If They’ve Been Sneaking

Some species of cichlid form groups with younger fish looking after babies. Often these fish are unrelated to the larger , more dominant fish.

Cooperative breeding of this kind has puzzled evolutionary biologists for a long time as it is costly and often does not generate obvious fitness benefits to subordinates. In the case of Neolamprologus. pulcher, the main benefit for subordinates to stay in a territory of dominant breeders seems to be the protection gained against predators provided by the large group members.

This study shows a direct relationship between the relatedness of these helper fish to the offspring and the amount of care they provide.

More here.

November 30, 2011 Graham

Monogamy and pair bonding practiced among certain fish species

With some species of cichlid fish the male takes eggs into his mouth and nurtures both them and the developing young. Up until now it’s not been certain if he was the genetic parent of the young or had been fooled into looking after them by the female.

The study, led by a research team at Kyoto University‘s Graduate School of Science, has found a solution to the mystery of whether mouthbrooding females transfer their young to any male fish in their school or specifically to their mating partners, by proving that the male fish the females shift the young to are indeed the genetic fathers of the young.

More here.

November 27, 2010 Graham

Discus Fish Parent Young – Science Daily

Few fish are famed for their parenting skills. Most species leave their freshly hatched fry to fend for themselves, but not discus fish. Jonathan Buckley from the University of Plymouth, UK, explains that discus fish young feed on the mucus that their parents secrete over their bodies until they are big enough to forage.

Most aquarists know that young discus graze the mucus from the sides of their parents so this article will come as no surprise. Rather more interesting is the discovery of changes in the composition of the mucus produced by the parent fish.

Buckley found a huge increase in the mucus’ antibody and protein levels when the parents laid their eggs, similar to the changes seen in mammalian milk around the time of birth. The protein and antibody levels remained high until the third week and returned to pre-spawning levels during the fourth week after hatching.

Much as human infants get extra protection from breast-feeding so to do young discus fish benefit from the “milk” they get from their parents. Any discus breeder will confirm that fish reared away from their parents rarely do well.

Read the full article here.

October 9, 2010February 7, 2018 Graham

Male mate choice in Pelvicachromis taeniatus – BioMed Central

Studies addressing the adaptive significance of female ornamentation have gained ground recently. However, the expression of female ornaments in relation to body size, known as trait allometry, remains unexplored. Here, we investigated the allometry of a conspicuous female ornament in Pelvicachromis taeniatus, a biparental
cichlid that shows mutual mate choice and ornamentation. Females feature an eye-catching pelvic fin greatly differing from that of males.

This is a nice paper that offers a neat explanation for the large pelvic fins found in female kribs. Anyone who has kept and bred P. taeniatus will agree entirely with the arguments made in this paper. The female uses her pelvic fins to exaggerate the colour and size of her belly to the male. Males are attracted to gravid females – the more gravid the higher the attraction. It follows that females with bigger, more colourful pelvic fins will be more likely to attract males and thus be more likely to pass on the genes for bigger more colourful pelvic fins. Thus over the generations the female pelvic fins will tend to get larger and more colourful.

Pelvicachromis taeniatus female — Female showing the exaggerated pelvic fins

Of course if the pelvic fins are too large they will interfere with the females ability to swim, catch food and avoid predators. A balance will therefore occur between the forces of sexual selection – bigger and more colourful and natural selection – correct size for efficient swimming.

Read the whole paper here.

September 28, 2010 Graham

Behavioral and Genetic Changes Helped Cavefish Survive – Science Daily

University of Maryland biologists have identified how changes in both behavior and genetics led to the evolution of the Mexican blind cavefish (Astyanax mexicanus) from its sighted, surface-dwelling ancestor.

Image via Wikipedia

The blind cave fish of Mexico – Astyanax mexicanus is a popular and unusual aquarium fish. It’s one of around 80 species of blind cave fish found throughout the world. What makes this fish really interesting is that the fish from which it evolved is still swimming around in the surface waters of Mexico. In fact the blind form has evolved so recently that full speciation has not yet occurred and the two forms, sighted and blind, are considered to be the same species and can even interbreed.

Progress on Vaccine for whitespot – Science Daily

Tests of the potential vaccine against “Ich” ― the dreaded “white-spot” disease that plagues fish in commercial fish farms, public aquariums, pet fish retail outlets, and home aquariums ― are raising hopes for finally controlling the disease, scientists reported at the 240th National Meeting of the American Chemical Society (ACS).

If this can be developed into a useable and affordable product for aquarists it could well transform the hobby. White spot (Ichthyophthirius multifiliis) is responsible for untold numbers of fish deaths each year. An absolutely brilliant piece of news.

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