Conspecific Chemical Cues Modulate Reproductive Physiology and Behavior in a Live‐Bearing Fish

Abstract

Chemical communication in aquatic environments plays a crucial role in mating by facilitating conspecific recognition, mate selection, and coordination of reproduction. Aquatic chemical communication is well‐understood in a handful of model species; moreover, none of the models are live‐bearing fish. We studied chemical communication in a live‐bearing fish, Poecilia latipinna, using behavior and physiology to identify potential cues and mating responses. We hypothesized that this species uses chemical communication to coordinate reproduction. We tested male behavioral response to conspecific cues using a two‐choice arena, with water‐borne steroid extracts from mature females and a control solution on either side. To quantify physiological response, males and females were individually placed in tanks containing 5 L of water for 4 hrs, and exposed to a control or water‐borne extracts of mature individuals of the opposite sex. At 0, 0.5, 1.5, and 4 hrs, we took 1 L water samples from each tank and extracted them for steroid analysis via solid‐phase extraction. We quantified estradiol (E2), progesterone, and prostaglandin F2α (PGF2α) in females, and testosterone (T) and 11‐ketotestosterone (11‐KT) in males using enzyme‐linked immunosorbent assays. At the end of the experiment, we sacrificed the fish, collected gonads, and fixed them in Bouin for histology. Gonads were serially cut at 7 μm, then stained with hematoxylin‐eosin to quantify maturation stages and with specific antibodies for main steroidogenic enzymes (3β‐hydroxysteroid‐dehydrogenase, 11 β‐hydroxylase, aromatase, and 17,20‐lyase) to localize steroidogenic sites.We found that male P. latipinna can detect female chemical cues, as males spent 178.4% more time on the side where female cues were released. However, males exposed to female cues showed no physiological response. Neither T nor 11‐KT was differentially released by males after being exposed to female cues. In females, we found that control fish had a cyclical pattern of hormone release rates, and these cyclical patterns were altered in treatment females. Progesterone and PGF2α show opposite cycling patterns in treatment females (i.e. when control females increased release, treatment females decreased). While the physiological cause for these cycles has not yet been investigated, the mirrored cycling between treatment and control females suggests that male cues alter hormone release cycles. Control females also have cyclical release of E2, but in treatment females cycling is suppressed. Estradiol decreases prior to ovulation in many teleost species, thus our results indicate that male cues alter female physiology to coordinate reproduction. Preliminary analysis of gonadal tissue for both males and females indicate differences in steroid synthesis between control and treatment fish. These results suggest that water‐borne steroids are acting as a chemical cue, and modulate hormone release and production in conspecifics. This study demonstrates some of the effects of chemical cues on behavior and reproductive physiology in this species, indicating that chemical communication plays a role in the coordination of reproduction in P. latipinna, and provides new insights into the potential mechanisms and origins of chemical cues in live‐bearing fish.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.