Rabbitfish.

Rabbitfishes or spinefoots are perciform fishes in the family Siganidae. There are 28 species in a single genus, Siganus. In some classifications, the species with prominent face stripes – colloquially called foxfaces – are separated in the genus Lo. But this is now known to be erroneous; indeed some other species like the Masked Spinefoot (S. puellus) show a reduced form of the stripe pattern. Rabbitfishes are found in shallow lagoons in the Indo-Pacific and eastern Mediterranean.

Description and ecology

Rabbitfishes grow to about 40 cm (15 in) and have small, rabbit-like mouths, large dark eyes, and a shy temperament which gives them their name; the scientific name Siganus is simply the Latin term by which Mediterranean rabbitfishes were known in Ancient Rome. Most species have either bright colors or a complex and interesting pattern.

Another unusual feature among rabbitfishes is their pelvic fins, which are formed from two spines, with 3 soft rays between them. The dorsal fin bears 13 spines with 10 soft rays behind, while the anal fin has 7 spines and 9 oft rays behind; the fin spines are equipped with well-developed venom glands. All rabbitfish are diurnal, some live in school, while others live more solitary lives among the corals. They are herbivorous, feeding on benthic algae in the wild. They are pelagic spawners. Many are fished for food, and the more colorful species – especially the foxfishes – are often kept in aquaria.
In aquaria, they should be fed 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 poisonous spines in defence. Their poison is not life-threatening to adult humans, but is likely to cause severe pain.

Systematics

As mentioned above, separation of Lo is unwarranted; it is embedded in a subgroup of Siganus. However, a way to split the genus – if the scientific community desires so – has been outlined in 2007:

•    An ancient group containing e.g. S. Woodlandi
•    Another fairly small group containing e.g. the White-spotted-Mottled Spinefoot (S. canaliculatus/S. fuscescens) complex.
•    The bulk of the genus, including the foxfaces.

But other lineages might exist and render the somewhat weak distinction between the second and third groups void. Also, it is not known where the type species S. rivulatus would be placed, 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. There is by now evidence of interbreeding between the Orange-spotted (S. guttatus) and the Golden-lined Spinefoot (S. lineatus), as well as between the Barred (S. doliatus) and the Barhead Spinefoot (S. virgatus).

Also, either females of the last common ancestor of the Masked (S. puellus) and the Gold-spotted Spinefoot (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 the Peppered Spinefoot (S. punctatissimus) and the foxfaces, while males of the latter mated with females of the original foxface species.

Also, either females of the last common ancestor of the Masked (S. puellus) and the Gold-spotted Spinefoot (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 the Peppered Spinefoot (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.