Modified sperm in echinoderms from the bathyal and abyssal zones of the deep sea

Mature sperm morphology has been described for 23 species of bathyal echinoderms from Bahamian watersand one abyssal species from Hawaii. The sperm of the holothuroids, asteroids and ophiuroids weresimilar to those reported in shallow-water species. Among echinoids, however, sperm head length (acrosome,nucleus and middlepiece) was significantly correlated with the upper limit of their known depthranges. Sperm head length was also significantly and positively correlated with egg diameter in echinoidsand holothuroids but not in asteroids. The longest sperm yet reported in echinoderms (26 µm) is describedfrom the Bahamian echinoid, Aspidodiadema jacobyi A. Agassiz.