Influence of sex and habitat on the size and shape of anal and dorsal fins of the blackstripe topminnow Fundulus notatus

Background/Question/Methods

In fish, the anal and dorsal fins serve multiple functions, including those related to swimming, display, and reproduction.  As such, they are likely to be targets of both natural and sexual selection.  Many fish species occupy different habitats, yet how environmental differences influence multi-use traits is largely unknown.  This work examined the size and shape of the anal and dorsal fin in the blackstripe topminnow Fundulus notatus from lake and stream habitats across multiple ages and sexes.

Results/Conclusions

Differences in the size and shape of anal and dorsal fins were sex-specific and not related to habitat differences. Males have longer and more pointed anal fins and longer, larger and more pointed dorsal fins than females. These sex differences occur predominantly in the older age class. The angle (i.e. pointedness) of the dorsal and anal fins is tightly correlated suggesting that fins follow a similar growth trajectory as individuals become sexually mature.