Microscopic morphology of the antennule and antenna of the marine isopod Cirolana harfordi

Abstract

ABSTRACT The use of scanning electron microscopy on the cuticle outgrowths called setae (that contain sensilla) in crustaceans is useful for, understanding how crustacean species sense their environment and for taxonomic studies. So far, most of the setal morphology studies have been performed on decapod crustaceans such as lobsters and shrimps and there has been a comparative lack of such research on marine isopods, from which terrestrial isopods such as woodlice or slaters have evolved. In the current study, electron microscopy was used to study the antennal setae of the marine isopod Cirolana harfordi using magnification powers of up to 40, 000. C. harfordi displayed a number of setal types including setae that had a sub-terminal pore that contained a cupule-shaped structure and plumose setae which are pennate in structure and have two rows of setules along the setal shaft in a fashion analogous to a palm leaf. These plumose setae may be useful to the animal in detecting water currents. Differences in the structure and placement of setae on the antennae of C. harfordi as compared to two other marine isopods, Bathynomus pelor and Natatolana borealis (that have had a comprehensive study of antennae setal morphology performed on them in previous studies) indicate that scanning electron microscopy of isopod setae may be useful in taxonomic studies of isopods.