TheAquariologist.com blog

Who ever said Corydoras are no schooling fish?

I recently bumped into this video on Youtube. I doubted if I should post it here, but just for those idiots that think that turning a condom into an aquarium is a good idea, here it is. Really, don’t try to do this!

Colisa lalia (Creative Commons)

In my last post I discussed the artificial colouring of ornamental fish species by dye injection. That there are other ways to influence the colour of ornamental fish is shown in a recent paper published in the Animal Behaviour journal. A group of scientists studied the effect of dietary pigments on skin pigmentation, growth and behaviour of male flame-red dwarf gourami, Colisa lalia. The fish were fed either a control diet or one of three different diets, Lucantin Pink, beetroot juice powder or Overseal Carantho powder, daily for 12 weeks. The addition of synthetic astaxanthin (Lucantin Pink) significantly increased red coloration, whereas betalain-based (beetroot juice powder) and anthocyanin-based (Overseal Carantho powder) pigments did not affect skin colour. Fish fed the test diets showed a similar growth than fish fed the control diet.
The increased red coloration also affected the popularity of the C. lalia males. Females C. lalia interacted more and spent more time with males fed the diet containing Lucantin Pink than fish fed the control diet. Such effects were not seen in fish fed the other two test diets.

For more information, see the paper: Baron, M., Davies, S., Alexander, L., Snellgrove, D., Sloman, K.A., 2008. The effect of dietary pigments on the coloration and behaviour of flame-red dwarf gourami, Colisa lalia. Animal Behaviour, 75, 1041-1051.

Dyed glassfish, Parambassis ranga (Creative Commons)

In recent years, some artificially coloured ornamental fish species such as glassfish (Parambassis ranga, formerly Chanda ranga) and Corydoras catfishes (Corydoras spp.) have made their way into fish stores. Most of them are believed to be injected with various coloured dyes to ‘improve’ their commercial value. Many claim that others are fed on dye-rich foods, however, although this is possible there is little evidence to support this. In contrast, recent evidence regarding the production methods for coloured Parrot cichlids, which were once believed to be colour-fed, has since shown that the fish are injected.

Not only should this practice be condemned on ethical ground, it has also been shown that 40% of glassfish that have been injected with such dyes show infection with Lymphocystis virus causing wart-like lesions of the skin of the fish (Burgess and MacMahon, 1998). By comparison, less than 10% of natural, unpainted glassfish studied had Lymphocystis.

Cosmetic manipulation, which confer no benefit to the fish, should be condemned on welfare ground. It devalues living creatures and treats them as if they were some inanimate object that can be decorated purely for whim or commercial gain!

References
Burgess, P., MacMahon, S., 1998. Why it’s cruel to dye. Practical Fishkeeping Magazine. March 1998.

If you are thinking of remarkable fish, the mudskipper must be one of the first to spring in mind. Not only are they able to breathe air, they can also walk on land! Mudskippers are found along intertidal zones living on the margin of land and sea. They have special adaptations to help them dominate a habitat which few other animals can exploit: soft mud with fluctuating water quantities and qualities.

Underwater, mudskippers breathe through gills like other fishes. However, unlike most other fish, mudskippers can’t stay underwater indefinitely. To survive on land, mudskippers can retain water in enlarged gill chambers which lock shut on land. They rotate their eyes to swill the water in the gill chambers around and keep the gills fluffed up and oxygenated. But these critters have more options to acquire oxygen. They can absorb gaseous oxygen through blood-rich membranes at the back of the mouth and throat (buccopharyngeal cavity). They also absorb air through their skin which is rich with blood capillaries, so long as the skin remains moist.Regarding the walking abilities of these fish, mudskippers have arm-like pectoral fins which even have little “elbows”. But they do not move these alternately in the way that we walk. Instead they make little hops by keeping their body rigid and jerking forwards on their pectoral fins.Mudskippers have even more adaptations to life on land. A distinctive feature of mudskippers are their huge goggly eyes at the top of their heads. These eyes sit on stalks and periscope above the water, while the rest of their bodies remain safely underwater. Unlike other fishes, mudskippers prefer to swim with their heads above water, their eyes giving them a good 360 degree view. Fascinating …

Brood care in the three-spined stickleback (Creative Commons)

In my last post I informed you on the existence of personalities in dumpling squid. Today’s post is a variation on that theme. A recent study in Animal Behaviour shows us one of the consequences animal personality has in the three-spined stickleback, Gasterosteus aculeatus.
Scientists studied individual differences in the quality of nest constructions. They hypothesized that if nest construction does reliably reflect builder quality, one would expect consistent variation between individuals in this trait. To test this hypothesis they encouraged male sticklebacks of 4 different populations to complete three consecutive nests. The quality of the nest was based on a number of measurements as total substrate used, construction time, area of the nest, nest compactness, etc. Within populations, the number of threads used, the area of the nest and the mass of substrate deposited on top of the nest were all consistent within males, showing that individual male three-spined sticklebacks differed consistently in the size and composition of the nests they produced. Studies of fitness consequences of nest construction in three-spined sticklebacks will be the subject of future research.

For more information, see the paper: Rushbrook, B.J., Dingemanse, N.J., Barber, I., 2008. Repeatability in nest construction by male three-spined sticklebacks. Animal Behaviour, 75, 547-553.

Carribean reef squid, Sepioteuthis sepioidea (Creative Commons)

Ask any fish freak — we know, or think we know, that our fish have personalities. Who could miss them? Some are aggressive, others are docile; some are bold, others are shy.
In some circles, ascribing personalities to animals is still a cardinal sin of biology and warrants being branded with a scarlet A (for anthropomorphism). Nonetheless, scientists have consistently found evidence of personality traits in species as closely related to us as chimpanzees, and as distant as squid, ants and spiders.
A recent study in Animal Behaviour has looked at developmental processes resulting in shy/bold animals. David Sinn, Samuel Gosling, and Natalie Moltschaniwskyj have measured the behaviour of dumpling squid, Euprymna tasmanica, in two tests, a threat and a feeding test, at five times across their life span. The results showed that how squid behaved in the threat test was not related to their behaviour in the feeding test. However, squid did show a consistent behavioural response within a test over time.
The experiment also showed that different phenotypes (i.e. bold versus shy individuals) displayed different amounts of developmental variation. Shyer animals were more plastic in feeding tests, while bolder animals were more plastic in threat tests. These results suggest that for some animals shy/bold behaviour throughout development is uncorrelated across different tests situations related to risk, while within a test situation, there may still be developmental constraints to changing shy/bold behaviour.

For more information, see the paper: Sinn, D.L., Gosling, S.D., Moltschaniwskyj, 2008. Development of shy/bold behaviour in squid: context-specific phenotypes associated with developmental plasticity. Animal Behaviour, 75, 433-442.

New species of lamprologines from Tanganyika and associated rivers continue to be discovered. With about 80 described lacustrine species, lamprologines comprise roughly half of the cichlid species in Lake Tanganyika. Scientists have recently described a new lamprologine cichlid, Lepidiolamprologus mimicus.
Underwater observation during the period and analysis of stomach contents of samples revealed that this species was exclusively piscivorous and mainly preyed on young and sub-adults of cyprichromine cichlids. In the littoral region of Kasenga, four species of cyprichromine (Cyprichromis leptosoma, C. zonatus, C. coloratus, and Paracyprichromis brieni) form mixed-species schools. When hunting, L. mimicus changed their body coloration, generally looking like female Paracyprichromis brieni. This enabled them to blend into schools of their prey. This is the first instance of aggressive mimicry reported for lamprologines.

For more information, see the paper: Schelly, R., Takahashi, T., Bills, R., Hori, M., 2007. The first case of aggressive mimicry among lamprologines in a new species of Lepidiolamprologus (Perciformes: Cichlidae) from Lake Tanganyika. Zootaxa, 1638, 39-49

Archerfish are remarkable hunters known for their habit of preying on insects and other small animals by shooting them down with water droplets from their specialized mouths. The family is a small one, consisting of seven species in the genus Toxotes; all occur in fresh, brackish, and marine waters from India to the Philippines, Australia, Louisiana and Polynesia.

Scientists had always thought their hunting technique was an unsophisticated skill, based on blasts of water with a “spit and hope” quality. However, recent studies have shown that these fish are able to precisely judge the size and position of prey above the water line, taking into account the distorting effect on light of passing from air to water. Furthermore, the fish also fine-tune the size of each blast. Watch an impressive video of an archerfish catching a fly (3MB).

To be honest, I always thought that archerfish were the only fish capable of water spitting. However, on my never-ending hunt for interesting fish behaviour I came across some old (1968) footage of Dr. Jörg Vierke. It shows that also common Colisa lalia and Colisa labiosa are able to apply this hunting technique. Have a look at the video!