Phylogeny, ontogeny and gonad microstructure of the gobioid fishes (Teleostei: Perciformes)

Gobioidei includes over 2000 species of primarily benthic, marine fishes, distributed throughout the world tropics, subtropics and temperate zones. Although they are a significant portion of the marine fish fauna, the relationships and biology of gobies are not well-studied because of their small size, tendency towards morphological reduction and paedomorphosis and often cryptic habitats. This work includes a series of studies on the phylogeny, larval development and gonad structure and evolution of the gobioid fishes. I use morphological character data and cladistic parsimony methods to hypothesize relationships of species within Microdesmidae, and I examine previous hypotheses of microdesmid sister taxon relationships. Monophyly of Microdesmidae and all included genera is confirmed, but the sister taxon relationship between Microdesmidae and Ptereleotridae is not recovered. Larval development in microdesmids is investigated through a series of captive rearing studies; I compare the results of these studies to existing museum collections of larval microdesmids. All known larvae of microdesmid species are described, variation in larval meristics is discussed, and larval characters are interpreted in light of the previous phylogenetic hypothesis. I examine histologically the structure of the reproductive system in microdesmids and other morphologically reduced gobies to determine the effect of miniaturization and reduction on the evolution of the gonads and gametes. Gonad structure in gobies varies from that seen in other perciforms, but the most significant departure is seen in the extreme paedomorph Schindleria praematura. In S. praematura, paedomorphic reduction is associated with drastic rearrangements of the gonad accessory tissues in both males and females, but the morphology of the gametes is not affected. I also examine the phylogeny of goby groups based on the complete sequence of the mitochondrial ND1 and ND2 genes. Topologies recovered by parsimony analysis of the nucleotide and translated amino acid datasets differ, and previous morphological character analyses are explored in light of both hypotheses. The molecular phylogeny suggests that major changes to the current taxonomy are indicated, and serves as a framework for future morphological and molecular phylogenetic studies.