Hair-fan patterns in the Chaetognatha

Abstract

Chaetognaths are important marine predators which rely on external sensory hairs to receive prey-produced vibrations, enabling them to recognize and locate their food. Hair-fan patterns are mapped for both larvae and adults of Sagitta hispida, Sagitta enflata, and Spadella schizoptera, for several sizes of Sagitta elegans, and for adults of Spadella cephaloptera. The fans are arranged in regular transverse and longitudinal rows with the pattern species specific, but similar, for all species studied. Larvae possess relatively longhair fans at hatching and the number of fans increases with size in the species of Sagitta, but is constant in juveniles and adults of the species of Spadella.