My, What Big Teeth You Have: Coral Gobies and Corals

Citron Coral Goby (Gobiodon citrinus). Photo: D. Knop

Coral gobies and corals – a case of co-evolution?

Hoping to answer these and other questions about the coral gobies, family Gobiidae, and their host stony corals,  Jürgen Herler of the Department for Theoretical Biology at the University of Vienna has embarked on a three-year research project to clarify whether the cohabitation of fish and cnidarian has benefits for both sides (mutualism), whether only the gobies profit from it (commensalism), or whether the “tenants” may even harm the coral (parasitism).

It is well known that the little fishes hide from larger predators among the fingerlike branches of stony corals, most notably Acropora spp. Herler says that there are also indications that coral-eating species such as butterflyfishes (Chaetodontidae) avoid corals inhabited by marine gobies; gobies have poisonous skin, and perhaps this makes the coral unpalatable. When asked whether maybe the marine gobies quite simply don’t like their home being nibbled and actively attack the butterflyfishes, he replied that this had never been observed, although the gobies have a number of amazingly large teeth – for reasons as yet not understood.

Co-evolution?

Is there a reciprocal evolutionary dependence between coral gobies of the family Gobiidae and their host corals?

Herler is interested above all in the criteria by which the goby species and other fishes associated with corals choose their home – a coral – and whether the coral in question also profits from the cohabitation.

It is also interesting that coral gobies avoid dead corals, and are also less commonly encountered in damaged specimens. So does the coral live longer and perhaps grow even faster if it has “tenants”?

Herler says that if that is the case then marine gobies might serve as indicators of the health and stability of reef systems, which is particularly interesting as reef ecology is gaining in importance in these times of climate change and the disappearance of coral reefs worldwide.

The question of the “accommodation preferences” of the gobies is relevant for research into the evolutionary history of the coral/fish relationship. Highly specialized animals are particularly seriously affected by environmental fluctuations. It is therefore in their own interests to adapt to particularly non-susceptible coral species.

Reciprocal adaptation?

Skull of an approximately 1¼ inch (30 mm) long coral goby of the genus Gobiodon, cleared and stained for morphological investigation. Note large canine teeth.  Photo: J. Herler, University of Vienna

New 24-7 camera recording system

Marine biologist Herler, who is collaborating closely with the Egyptian Suez Canal University as well as universities in Australia and Germany, travels to the Red Sea for the necessary fieldwork for the project. They have worked together with Egyptian and German colleagues to establish a research station, the Dahab Marine Research Center (DMRC), in Sinai. The scientists are working mainly in shallow water.

Because strong winds are prevalent on the Red Sea the waves are often very high, and hence they are trying to do as much of the research as possible in the laboratory and conduct experiments there. In addition they are also installing a new micro-camera recording system that Herler has developed together with Austrian and German technicians, and which is currently being tested in the lab. The system has several advantages: the researchers are less dependent on the weather, there is no disturbance by observers on the reef, a lot of time is saved and can instead be used for experiments, and the videos can be analyzed at any time and anywhere.

If all goes as planned then these timid little gobies, virtually impossible to observe in the field, will soon be being filmed around the clock.

Excerpt from CORAL Magazine, Reef News.
Source: IDW

Further reading: Scott Michael's species account of the Yellow Clown Goby.