A Look at Cirri Presence and Preference: Utilizing Field and Laboratory Studies to Explore a Novel Appendage in Hippocampus zosterae
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Authors
Bland, Paige
Issue Date
2026-01-16
Type
Thesis
Language
en_US
Keywords
Ecology , Evolution (Biology) , Animal science , Marine biology , Natural selection , Sexual selection in animals , Academic theses
Alternative Title
Abstract
Dwarf seahorses (Hippocampus zosterae) are a cryptic species displaying filamentous appendages, known as cirri, which have been historically assumed to have evolved for camouflage purposes. To investigate potential patterns in cirri presence in H. zosterae, photos from monthly sampling over a year-long period in Tampa Bay, Florida were analyzed to deduce which environmental parameters could be correlated with cirri. Cirri presence on wild caught seahorses was quantified using a scoring system of cirri on three head areas and one body area that summed to an overall cirri score for each fish. Preliminary results indicated that females had more cirri than males, and that fish with more cirri were present during the wet season, coinciding with the breeding season of H. zosterae. The sexual dimorphism identified in this trait for dwarf seahorses led to a hypothesis centered around cirri’s potential role in mating preferences. To determine if cirri are a sexually selected trait, wild seahorses were brought into the laboratory for mating trials consisting of three size-matched seahorses: a male, a highly ornamented female, and a less ornamented female. We developed a novel methodology for photographing female seahorses to measure cirri counts, length, and surface area and documented the potential loss of cirri in a captive setting. Our genetic results confirmed the highly ornamented female was chosen in 17 out of 19 trials, supporting our hypothesis that this trait serves as a sexually selected trait with males showing a mating preference for females with greater cirri. Drastic cirri loss was recorded for females over 21 days in captivity, prompting new hypotheses that cirri function as a condition-dependent trait involved in mate signaling, and may serve as an indicator of seahorse health and survival.
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This dissertation is protected by the Copyright Laws of the United States (Public Law 94-553, revised in 1976). Consistent with fair use as defined in the Copyright Laws, brief quotations from this material are allowed with proper acknowledgement. Use of the materials for financial gain with the author's expressed written permissions is not allowed.