Observations of the pirate perch, aphredoderus sayanus (gilliams), with comments on sexual dimorphism, reproduction, and unique defecation behavior

Analysis of variance results showed significant differences in measurements on 71 specimens of Aphredoderus sayanus comparing standard length (F = 21.91, P < 0.0001), maximum depth (F = 8.44, P = 0.006), and standard length to body depth ratio (F = 9.11, P = 0.004), indicating that this fish is sexually dimorphic with females being larger and more full-bodied than males. In laboratory observations, a pair of A. sayanus created a nest and successfully spawned, which strengthens the argument that this fish might not be a branchial brooder but instead might be a nest builder with the female releasing adhesive eggs in the proximity of the nest. On three separate daytime occasions, A. sayanus ventured outside its refuge approximately to the point that only its head and anus were exposed, defecated, and then backed into its refuge. The jugular position of the anus might allow adult A. sayanus to partially leave its refuges to defecate to avoid altering water quality and without fully exposing itself to predators. This unique defecation behavior might explain the evolutionary reason for the position of the anus in adult A. sayanus.