Functional morphogenesis from embryos to adults: Late development shapes trophic niche in coral reef damselfishes.

The damselfishes are one of the dominant coral reef fish lineages. Their ecological diversification has involved repeated transitions between pelagic feeding using fast bites and benthic feeding using forceful bites. A highly-integrative approach that combined gene expression assays, shape analyses, and high-speed video analyses was used to examine the development of trophic morphology in embryonic, larval, juvenile, and adult damselfishes. The anatomical characters that distinguish pelagic-feeding and benthic-feeding species do not appear until after larval development. Neither patterns of embryonic jaw morphogenesis, larval skull shapes nor larval bite mechanics significantly distinguished damselfishes from different adult trophic guilds. Analyses of skull shape and feeding performance identified two important transitions in the trophic development of a single species (the orange clownfish; Amphiprion percula): (a) a pronounced transformation in feeding mechanics during metamorphosis; and (b) more protracted cranial remodeling over the course of juvenile development. The results of this study indicate that changes in postlarval morphogenesis have played an important role in damselfish evolution. This is likely to be true for other fish lineages, particularly if they consist of marine species, the majority of which have planktonic larvae with different functional requirements for feeding in comparison to their adult forms.

Morphogenesis of the zebrafish jaw: development beyond the embryo.

The zebrafish has emerged as an important model for vertebrate development as it relates to human health and disease. Work in this system has provided significant insights into the variety of genetic signals that direct the cellular activities and tissue interactions necessary for proper assembly of the pharyngeal skeleton. Unfortunately our understanding of craniofacial development beyond embryonic stages is far less complete. Stated another way, we know a great deal about the early patterning of the skull, but we know comparatively little about how mature craniofacial shape is determined and maintained over time. Here we propose ways to expand the current molecular genetic paradigm beyond the embryo to gain an understanding of the processes and mechanisms that guide growth and remodeling of mineralized craniofacial, skeletal, and dental tissues. First, we discuss sources of adult mutant phenotypes that can be used to study of postembryonic development. Next, we review salient quantitative methods that are necessary to define complex adult phenotypes. We also discuss how other organismal systems can be used to inform and complement studies in zebrafish. We conclude by discussing the implications for such studies within the context of furthering an understanding of the etiology and pathophysiology of human craniofacial malformations, as well as informing an understanding of adaptive craniofacial variation among natural populations.

Exploring the radiation of a diverse reef fish family: phylogenetics of the damselfishes (Pomacentridae), with new classifications based on molecular analyses of all genera.

The damselfishes (Perciformes, Pomacentridae) are an important family of marine reef fishes that occupy a range of ecological positions in the world's oceans. In order to determine the evolutionary pattern of their radiation, we used multiple methods to examine molecular data from 104 species representing all extant genera. The analysis of 4291 DNA nucleotides (1281bp were parsimony informative) from three nuclear genes (rag-1, rag-2 and bmp-4) and three mitochondrial genes (12s, 16s and nd3), produced well-resolved phylogenies with strong evidence for a monophyletic Pomacentridae, and support for five major damselfish clades. We found that the monotypic subfamily Lepidozyginae evolved early in the pomacentrid radiation. The placement of the genus Altrichthys indicates that brood care has evolved at least twice among the damselfishes. The subfamilies Chrominae and Pomacentrinae, and the genera Abudefduf, Chromis, Chrysiptera, Plectroglyphidodon, and Stegastes, were always found to be polyphyletic, and monophyly was rejected for the genus Amphiprion by almost every analysis. All phylogenetic studies of the Pomacentridae have indicated that their taxonomy is in need of revision at multiple levels. We provide a new classification scheme wherein each subfamily is now monophyletic, and this reorganization is consistent with all previous molecular studies of the damselfishes. The Chrominae are restricted to the genera Chromis and Dascyllus; the Pomacentrinae now represent a lineage of 16 genera that constitute a major, and relatively recent, radiation of coral reef fishes throughout the Indo-West Pacific; we erect the new subfamlies Abudefdufinae and Stegastinae; we relegate the anemonefishes (the Amphiprioninae sensu Allen) to the tribe Amphiprionini within the Pomacentrinae, and synonomize the genus Azurina with Chromis.