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TURBID WATERS VS. CLEAR CHOICES: EXPLORING THE WORLD OF DWARF SEAHORSE MATE SELECTION**

Abstract

Algal-induced turbidity can alter several important aspects of reproduction and sexual selection. This experiment investigated the effects of algal turbidity on the mate choice of dwarf seahorses (Hippocampus zosterae) who exhibit conventional sex-roles and are indicator species for threatened seagrass ecosystems. The experimental design consisted of an equal 1:1 sex ratio and two sex-biased treatments: female-biased (2F:1M), and male-biased (1F:2M) in clear and turbid water (n=8, 128 seahorses) to quantify mate choice parameters in sex-biased treatments and determine if turbidity impacts mate preference. The parameters surveyed included body measurements and mating activity levels of seahorses. Sexual dimorphic body measurements include females with significantly greater presence of cirri, larger snout length, head length, and trunk length; males possessing significantly larger tail length, body width, and crown areas. However, due to low intrasexual morphometric variation, we used body mass to test for mate size preference, resulting in trends of approximately 75% of matings in clear water being size assortative, whereas matings were random in turbid treatments. Since morphometric traits do not fully explain mate choice and appear to not be under sexual selection, we predict that courtship activity levels could be a more reliable indicator of mate choice, which previous syngnathid studies have already shown. To test this, the mating behavioral analysis is on-going using BORIS software for morning, noon, and night for 20 minutes each. The mating behavior ethograms include quivering, pointing, pumping, holding tails, brightening, and competitive behaviors among the fishes. The preliminary results suggest courting mainly occurs during the early morning hours on the first two mornings, resulting in copulations within 48 hours together. This study’s results will help us better understand mate choice criteria in dwarf seahorses for wild populations, in varied sex ratio conditions, when visually hindered by eutrophication.

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