Rabbitfish

Description and ecology

All rabbitfish have large, dark eyes and small, somewhat rabbit-like mouths, which gives them their name. Most species have either bright colors or a complex pattern. The largest rabbitfish grows to about 53 cm (21 in), but most species only reach between 25 and 35 cm (9.8 and 13.8 in).

Another unusual feature among rabbitfishes is their pelvic fins, which are formed from two spines, with three soft rays between them. The dorsal fin bears 13 spines with 10 rays behind, while the anal fin has seven spines and nine rays behind; the fin spines are equipped with well-developed venom glands.

All rabbitfish are diurnal; some live in schools, while others live more solitary lives among the corals. They are herbivorous, feeding on benthic algae in the wild. However, Siganus rivulatus was recently observed feeding on jellyfish (Scyphozoa) and comb jellies (Ctenophora) in the Red Sea. Also Siganus fuscescens have been observed eating prawns and other baits, suggesting that some species are opportunistic omnivorous feeders. They are pelagic spawners. Many are fished for food, and the more colorful species—especially the foxfish—are often kept in aquaria.

In aquaria, they eat a variety of fresh vegetables and algae. Care must be taken during aquarium maintenance and cleaning, as rabbitfishes are often easily frightened and will use their venomous spines in defense. Their venom is not life-threatening to adult humans, but causes severe pain.

Taxonomy

In 2007 Kurriwa et al., outlined a way to split the genus—if the scientific community so desires:

Other lineages might exist and make obsolete the somewhat weak distinction between the second and third groups. Also, it is not known where the type species S. rivulatus would fall, hence names for these three subgenera or genera are not established at present.

Hybridizaton has played a role in the evolution of the Siganidae, as evidenced by comparison of mtDNA cytochrome b and nDNA internal transcribed spacer 1 sequence data. Evidence exists of interbreeding between S. guttatus and S. lineatus, as well as between S. doliatus and S. virgatus.

Also, either females of the last common ancestor of S. puellus and the S. punctatus interbred with females ancestral to the main non-foxface lineage, or males of the former hybridized with females of the last common ancestor of S. punctatissimus and the foxfaces, while males of the latter mated with females of the original foxface species.

An individual was found that looked like a slightly aberrant blue-spotted spinefoot (S. corallinus). On investigation, it turned out to be an offspring of a hybrid between a female of that species and a male masked spinefoot, which had successfully backcrossed with the blue-spotted spinefoot.

Species

As noted above, several presumed species are suspected to actively interbreed even today; these might warrant merging as a single species. This applies to the white-spotted spinefoot (S. canaliculatus) and the mottled spinefoot (S. fuscescens), and to the blotched foxface (S. unimaculatus) and the foxface rabbitfish (S. vulpinus). Alternatively they might be very recently evolved species that have not yet undergone complete lineage sorting, but their biogeography suggests that each group is just color morphs of a single species. On the other hand, the morphologyically diverse Blue-spotted Spinefoot (S. corallinus) might represent more than one species; orange individuals are found at the north of its range, while yellow ones occur to the south, and these two may be completely parapatric. Some species of spinefoot have a very painful sting on each of their barbs, but some are a good eating fish.

There are currently 29 recognized species in this genus: