The distribution of exocrine glands in Lepeophtheirus salmonis and Caliguselongatus (Copepoda : Caligidae)

The morphology, function and distribution of exocrine glands of copepods ha ve rarely been studied in detail and almost nothing is known about them in the sea lice species L. salmonis and C. elongatus. This study utilised a no vel application of a light-microscopy staining technique to reveal a variet y of glands in nauplius, copepodid, chalimus, preadult and adult stages. Th e stain, 3',3-diaminobenzidine tetrahydrochloride (DAB), applied to fresh m aterial, differentiated a population of exocrine glands and enabled a study of their distribution. The stain was successful in highlighting the ducts and pores associated with the larger glands. The locations of gland sub-pop ulations were conserved in all life-stages, although glands in the swimming legs were found to be better represented in mobile and free-swimming stage s i.e. copepodids, preadults and adults. Glands associated with the mouth-t ube were also located. Other, nonglandular, peroxidase-positive regions wer e also highlighted by the stain. These regions were found mainly in preadul t and adult stages where they formed characteristic bi-symmetrical patterns on the cuticle of the dorsal surface. A study of some calanoid copepods su ggested that peroxidase-positive glands are a feature peculiar to caligid c opepods. This staining technique has proven useful for elucidating the onto geny of gland populations in caligids.