Date Awarded

Summer 2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Advisor

Jan R McDowell

Committee Member

Kevin C Weng

Committee Member

Ryan B Carnegie

Committee Member

Bruce B Collette

Abstract

Batrachoidiformes, the toadfishes, are benthic fishes that inhabit nearshore subtidal and intertidal habitats, characterized by their dorsoventrally flattened bodies and large pectoral fins. These fishes lack dispersive larvae, and larval development is retained in nests guarded by their parents. To date, 82 species and 23 genera are accepted as valid. Previous studies recognized a single family, Batrachoididae, with four subfamilies: Batrachoidinae, Porichthyinae, Thalassophryninae, and Halophryninae. Interrelationships among subfamilies, however, are unresolved and interrelationships among species are problematic. Despite being a conspicuous member of the coastal fauna, the internal morphology of most species of Batrachoidiformes is unknown, being intraspecific and ontogenetic variations not reported for most species. Several characters used in previous analyses were found to have problematic construction or be intraspecifically variable. This new study reassessed the morphology of 66 species of 22 genera, representing most of the diversity of subfamilies of Batrachoidiformes. This investigation also endeavored in accounting for intraspecific and ontogenetic variations, in order to recognize the potential phylogenetic characters. The first chapter investigated the caudal skeleton of Batrachoidiformes, the posteriormost region of the axial skeleton. Results found high intraspecific variation in this region, especially in the shape of the epurals and the parhypural flange. Despite the high intraspecific variability, potentially informative characters were identified, such as the presence of a hypurapophysis-like process in seven genera of Halophryninae. The second chapter investigated the series of intermuscular bones and tendons within Batrachoidiformes. Variation in this series of sesamoid bones is not only poorly known in toadfishes, but teleost fishes in general. Results show that variation in intermuscular bones is high and potentially phylogenetically informative. For example, Batrachoidinae, Thalassophryninae, and Halophryninae have the origin of the first epineural articulating with the neural spine of the first vertebra. In Porichthyinae and other representatives of Percomorphacea the origin of the first epineural articulates with the neural arch of the first vertebra. The third chapter described the early ontogenetic changes of the skeleton of Porichthys notatus (Porichthyinae). These completely novel descriptions include tables of sequence of ossification and appearance of cartilages. The fourth chapter is the phylogenetic analysis. Previous characters were modified and new characters were proposed, resulting in a dataset of 191 morphological characters. One of the main results of this analysis is that Halophryninae is not monophyletic, with Allenbatrachus, Batrachomoeus, and Halophryne being more closely related to Porichthyinae, Thalassophryninae, and Batrachoidinae. This new phylogenetic arrangement and its supporting synapomorphies are discussed, including potential implications in the classification within this order.

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