Aspects of internalanatomy and reproduction in the copepoda

The functional morphology of the muscular, digestive, circulatory, and nervous systems is reviewed and compared in the
Copepoda, with emphasis on the Calanoida. Recent ultrastructural data are provided with respec t to the reproducti ve system in marine
calanoids.
Paired dorsal and ventral longitudinal muscles constitute the main muscle bands of both the rnetosome and urosome. The digestive
tract consists of a mouth, esophagus, midgut, hindgut, and an anus. The extensive midgut is morphologically divided into three zones
characterized by various cell types. A simple heart enclosed in a large pericardial cavity comprises part of the open circulatory
system. Hemolymph flows from an anteriorly directed aorta through various sinuses in the head. These are continuous with the
perivisceral cavity, from which the hemolymph is returned to the pericardial cavity. The nervous system consists of a brain, a ventral
nerve cord with ganglia in each met asomal segment, and a giant nerve network.
The male reproductive tract is composed of a single test is and a genital duct which is divided into the ductus deferens, seminal
vesicle, spermatophore sac, ductus ejaculatorius and gonopore. Spermatogenesis res ults in disc - shaped, aflagellate spermatozoa that
lack acrosomes. In the female, a single ovary extends into two oviducts that terminate at a pair of spermathecae and a single genital
opening. Yolk formation in the developing oocytes involves both autosynthetic and heterosynthetic processes.