Structure of the ovotestis and evidence for heterosynthetic incorporation of yolk precursors in the oocytes of the nudibranch mollusc, Spurilla neapolitana.

The ovotestis of Spurilla neapolitana consists of a series of spherical lobes, each of which is composed of radially arranged, sac-like acini or follicles. The male and female portions of each acinus are separated by ovarian follicle cells and testicular accessory cells. A thick basal lamina serves as a barrier between adjacent acini.

Ultrastructure of the "pigment knob" of Pleuromamma spp. (Copepoda: Calanoida).

The calanoid copepod genus Pleuromamma is easily distinguished from all other copepods by the presence of a rounded, dark-red cuticular structure ( = pigment knob) that protrudes from the left or right side of the second thoracic segment in both sexes. The present study of the pigment knob reveals a complex ultrastructure consisting of various cell types within three distinct areas that are bathed by hemolymph from the lateral sinus. The knob is covered by a greatly expanded cuticle through which a pore passes.

The ultrastructure of oogenesis and yolk formation in Labidocera aestiva (Copepoda: Calanoida).

Yolk formation in the oocytes of the free-living, marine copepod, Labidocera aestiva (order Calanoida) involves both autosynthetic and heterosynthetic processes. Three morphologically distinct forms of endogenous yolk are produced in the early vitellogenic stages. Type 1 yolk spheres are formed by the accumulation and fusion of dense granules within vesicular and lamellar cisternae of endoplasmic reticulum.