Defense Date

4-20-2021

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Tracey Sutton, Ph.D.

Second Advisor

David Kerstetter, Ph.D.

Third Advisor

Stephen Kajiura, Ph.D.

Abstract

Dragonfishes (Family Stomiidae) are considered the most numerically important and diverse taxon of higher-level meso- and bathypelagic predators in oceanic food webs, with the subfamily Melanostomiinae contributing 220 of the 317 species. The Stomiidae is also the most speciose fish family in the Gulf of Mexico. The relationship between diversity (both systematic and morphological) and feeding of the Melanostomiinae has not been previously examined due to sample size limitation. Here the diet and morphology of 16 species of dragonfishes in the Gulf of Mexico was examined to address the question, “Does the extraordinary speciation in this most-diverse deep-pelagic fish clade reflect specialization in its primary limiting resource – food?” Gut content analysis revealed three feeding guilds by major prey taxon, with most species grouped into a piscivorous guild and two other guilds that selected for cephalopods. Piscivorous dragonfishes were further categorized into feeding groups by fish family, where four feeding groups were identified. Within this feeding guild, most dragonfishes were grouped into a myctophid-eating cluster, with three additional clusters including predation upon bristlemouths (Family Gonostomatidae), oceanic basslets (Family Howellidae), bigscales (Family Melamphaidae), and dragonfishes. Regarding functional morphology, five morphotype groups were identified, with dissimilarity driven by barbel length, vertical oral gape, and horizontal maxillary oral gape. There were no obvious morphological-dietary relationships amongst melanostomiines, suggesting that morphology and diet are not strictly correlated in extant species. Diet specialization may have influenced the hyperspeciation exhibited by melanostomiines, but other factors like species-specific bioluminescence, interspecific competition, and predator avoidance also influenced this speciation.

Share

COinS