No Sexual Dimorphism in Pumpkinseed (/Lepomis gibbosus/) Gut Microbiomes

Abstract:

Gut microbiomes of freshwater fish are shaped primarily by their environment, with developmental stage and diet also being significant contributors. Among sexually dimorphic fish, no significant differences have been observed between the gut microbiomes of males and females. However, a recent publication on yellow drum (Nibea albiflora) first identified sex-specific differences in fish gut flora structure and function. As part of continuing work on centrarchid fish biology in Presque Isle Bay, Erie County, PA, we explored whether sexually dimorphic gut microbiomes were present in pumpkinseed (Lepomis gibbosus), a common freshwater fish native to the northeastern quarter of the United States. Pumpkinseeds are physically sexually dimorphic, with males being larger and more colorful and females having more pronounced vertical bars. Pumpkinseeds are also behaviorally dimorphic in that females are sexually selective during mating. Intestinal tissues from twelve size-matched adult pumpkinseeds, six males and six females, were digested to isolate bacterial DNA. The bacterial 16S V4 region was amplified, sequenced, and analyzed. Stomach contents from each fish were also examined and compared between sexes. No significant differences between male and female microbiomes were observed across multiple measures, nor were differences in stomach contents. These results suggest that male and female pumpkinseeds have similar gut microbiomes and diets and support previous studies that failed to uncover sexually dimorphic gut floral communities across freshwater fishes. It is likely that the gut microbiomes were similar due to the fish being collected from Presque Isle Bay during the same sampling event as well as the similar diets each fish consumed.