The role of multimodal communication in reproduction of a live-bearing fish

Bristow, McKenna
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Complex signals, such as multimodal signals, are putatively more common than single signals, because organisms either have multiple traits to convey, or have multiple back-up signals to ensure signal reception. In nature, these signals occur together in tandem and interact. Behavior and physiology are largely regulated by the endocrine system, which is susceptible to external stimuli, thus information received from the external environment exerts a heavy influence on behavior and physiology. Aquatic organisms, in particular, are prone to influence from multiple external cues, because they are immersed in a medium that is full of chemical signals which have been excreted through urine, feces, and mucous. Yet, studies generally investigate one signal and one response at a time. My thesis investigated complex signaling in a live-bearing fish, Poecilia latipinna, to understand how multimodal signals (multiple signals received through different sensory modalities) affected behavioral and physiological responses. Poecilia latipinna use visual signals in mate choice, however there is evidence that visual signals alone do not account for all variation in mate choice. Chemical communication may also play a role in reproduction in this species. I hypothesized that multimodal signals, visual and chemical signals specifically, drive both behavioral and physiological responses in P. latipinna. First, I tested male and female associative preference for two cue modalities, vision and olfaction, by placing individuals into a two-choice maze, and providing either visual, visual + chemical, chemical, or no cues of mature individuals of the opposite sex. Males and females only had an associative preference for visual and visual + chemical cues. To determine physiological response to putative chemical cues, male and female P. latipinna were exposed to water-borne hormone extracts from the opposite sex. At 0, 0.5, and 1.5 hrs, we took water samples from each fish and quantified primary sex steroids released by each individual over time. We quantified estradiol (E2), progesterone (P), and prostaglandin F2α (PGF2α) in females, and testosterone (T) and 11-ketotestosterone (11-KT). We found that female P. latipinna decreased release of E<sub>2</sub> in response to male chemical cues. E<sub>2</sub> decreases prior to ovulation in many teleost species, thus our results indicate that male cues alter female physiology which helps coordinate reproduction. We did not find significant differences in release rates for 11-KT, T, P or PGF2α. Combined, these results and previous research suggest that communication in this species is multimodal. Prior studies on this species had focused on the importance of visual signals in driving behavior but we now know that chemical signals from males drive a physiological response in females that is related to reproduction. This research indicates that important signals or cues have been overlooked in the study of mating behavior in these fish and likely others and highlights the importance of measuring multiple types of responses to multimodal communication.
Animal communication, Chemical communication, Multimodal, Live-bearing fish, Reproductive physiology, Reproductive behavior
Bristow, M. L. (2019). <i>The role of multimodal communication in reproduction of a live-bearing fish</i> (Unpublished thesis). Texas State University, San Marcos, Texas.