SANTINI, F.; Mus�um National d’Histoire Naturelle, Paris: How easy is it to lose a fin? Patterns of morphological evolution in pufferfish and allies (Tetraodontiformes, Teleostei)

Tetraodontiformes (pufferfish, triggerfish, ocean sunfish) are a small clade (approx. 400 species) of spiny-rayed fishes that have fascinated natural historians since Aristotle due to their highly modified skeletal and external morphology. Fusions, reduction in size and loss of complexes of bones, such as the dorsal and pelvic fins, have occurred convergently in several lineages within this clade during its evolutionary history. This simplification of the skeletal system is, however, matched by a number of muscle -and perhaps nerve – duplications, particularly evident in the cranial region. Recently two species of pufferfish have become the first non-human vertebrates to have their entire genome sequenced, and much speculation has been made by genome scientists of the fact that the reduced genome size in pufferfish could somehow be linked to, and possibly be responsible for, their very modified morphology. During this talk I will use the results of a recent comprehensive revision of the fossil record of Tetraodontiformes and allied groups, that lead to a new hypothesis for the phylogenetic relationships among the main tetraodontiform lineages, to illustrate how morphological modules can be identified within the skeletal system of these fishes, how some of these modules can be modified -likely through processes taking place during the early stages of development – until their final disappearance in adult individuals, and to formulate some hypotheses about the relationships between morphological complexity and developmental regulatory genes in this clade, hypotheses that could probably be tested experimentally using developmental genetic methods.