The Repository @ St. Cloud State

Open Access Knowledge and Scholarship

Date of Award


Culminating Project Type


Degree Name

Biological Sciences - Ecology and Natural Resources: M.S.




College of Science and Engineering

First Advisor

Matthew P. Davis

Second Advisor

Matthew A. Tornow

Third Advisor

Jennifer Y. Lamb

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Keywords and Subject Headings

Phylogenetics, Geometric Morphometics, Systematics, Marine, Bioluminescence, Hatchetfishes


Within the Actinopterygii (ray-finned fishes), the Stomiiformes (dragonfishes and their allies) include 444 species of fishes found in pelagic deep-sea habitats world-wide. Within Stomiiformes, the family Sternoptychidae (deep-sea hatchetfishes) includes 78 species within ten genera. The deep-sea hatchetfishes all possess ventral bioluminescent photophores, which are hypothesized to be used for camouflage in the deep sea. The sternoptychids are commonly known for having deep bodies that resemble a hatchet, although seven genera in this family exhibit a more slender-body. Previous phylogenetic studies have examined the evolutionary relationships of this family of fishes predominately based on morphological data. Few molecular-based studies have examined the evolutionary relationships of the sternoptychids. This study investigates the evolutionary relationships of Sternoptychidae using a genome-scale dataset with ultraconserved elements (UCEs) and protein-coding gene fragments. This dataset is then combined with previously published morphological data to infer a total evidence hypothesis for the evolutionary relationships among deep-sea hatchetfishes. The phylogenetic analyses infer the Sternoptychidae to be a monophyletic family, although these results differ from previous phylogenetic studies regarding the monophyly of the subfamilies ‘Maurolicinae’ and Sternoptychinae. The ‘Maurolicinae’ consists of seven slender-bodied genera (Araiophos, Argyripnus, Danaphos, Maurolicus, Sonoda, Thorophos, Valenciennellus) and Sternoptychinae includes three deep-bodied genera (Argyropelecus, Polyipnus, Sternoptyx). The hypothesis of relationships presented herein for the family infers a polyphyletic ‘Maurolicinae’ with Maurolicus inferred to be nested within the subfamily Sternoptychinae. To investigate the evolution of body shape in the deep-sea hatchetfishes, patterns of body-shape were quantified in 684 digitized specimens using a geometric morphometric approach with seven homologous landmarks and 106 semi-landmarks. The relative warp analysis clustered species within genera together in relationship to their deep or slender body-shape. The geometric morphometric analysis provides continuous characters of body shape that allowed for a species-level ancestral character state reconstruction in combination with the total evidence phylogeny. The results presented herein infer a slender-bodied common ancestor for the family Sternoptychidae with three independent transitions to deeper bodies.



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