Functional and comparative morphology of the pectoral fins among scorpaeniform fishes

2009 2009

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Abstract (summary)

Many benthic fishes use their pectoral fins for both swimming and substrate contact. Each behavior imposes different, potentially conflicting functional demands on the pectoral fins. It has been hypothesized that benthic fish decouple these demands through morphological and functional regionalization of the fins, but this hypothesis had not been experimentally tested. In this study, I demonstrated functional regionalization of the pectoral fin in the longhorn sculpin, Myoxocephalus octodecimspinosus, a benthic scorpaeniform fish. The ventral region of the pectoral fin is used during substrate contact; the dorsal region is used during swimming. I characterize a previously undescribed swimming behavior during which the pectoral fins are held in a steady, laterally extended posture while the dorsal, anal and caudal fins are used for propulsion. I also investigate the functional morphology of individual pectoral fin rays. I find that the curvature of the fin rays is higher in the ventral versus dorsal region of the fin, regardless of behavior. The fin rays of longhorn sculpin possess a previously undescribed morphology in cross-section. Specifically, the hemitrichia, or bony halves that make up the fin rays, are cylindrical in cross-section proximally and crescent-shaped distally. The cylindrical segments in the proximal regions of the fin rays of longhorn sculpin provide resistance to bending, which may confer strength and support for weight-bearing substrate-contact behaviors. Further, the ventral fin rays, which are used for substrate contact, have a higher proportion of their total length made up of cylindrical segments. Finally, I used a comparative approach to examine the distribution of morphological specializations and habitat (benthic or pelagic) of the pectoral fins among scorpaeniform fishes. I identified three discrete characters of the pectoral fins that are associated with a benthic habitat for analysis; (1) an asymmetrical fin membrane among ventral fin rays, (2) the presence of fin rays that are unbranched distally, and (3) the presence of ventral pectoral fin rays that are free of fin membrane. Each of these characters has evolved more than once among scorpaeniform fishes and is more common among benthic than pelagic fishes.

Indexing (details)

Organismal biology
0287: Morphology
0472: Organismal biology
Identifier / keyword
Biological sciences; Fin rays; Functional regionalization; Pectoral fins; Scorpaeniformes; Sculpin
Functional and comparative morphology of the pectoral fins among scorpaeniform fishes
Taft, Natalia K.
Number of pages
Publication year
Degree date
School code
DAI-B 70/09, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Fernandes, Cristina Cox
Committee member
Gillis, Gary B.; Lauder, George V.; McCormick, Stephen D.
University of Massachusetts Amherst
Organismic & Evolutionary Biology
University location
United States -- Massachusetts
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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