Phylogenetic analysis of the pearlfish tribe Carapini (Pisces : Carapidae)

Fishes of the tribe Carapini (Encheliophis and Carapus) share a noteworthy peculiarity: they shelter in holothurian echinoderms or bivalve hosts. Some species are considered parasitic, others commensal. This study focuses on the phylogeny of the tribe, using two other Carapidae species as an outgrou p (Snyderidia canina and Onuxodon fowleri). Insofar as possible, the select ed anatomical and behavioural characters where chosen in an ecomorphologica l perspective, as features that could be responses to various lifestyle-rel ated constraints. Our character selection also took into account the fact t hat some features are (presumably) linked. Such features were grouped toget her as a single trait to avoid their overvaluation. This methodology enabled commensals to be separated from parasites, the for mer belonging to Carapus and the latter to Encheliophis. Carapus species re flect in their morphology the constraints imposed by a diet of hard, mobile , elusive prey, showing predator-type features: a strong dentition, a wide mouth opening, a robust food intake apparatus. On the other hand, the endop arasitic Encheliophis species show a generally weaker buccal apparatus and narrow mouth opening, in relation to the different constraints of their lif estyle where the diet constraints are less pronounced: they eat body parts of their host. Changes in both generic diagnoses are proposed and three spe cies are transferred from Encheliophis to Carapus.