Wallis H. Clark

Jelly Layer Formation in Penaeoidean Shrimp Eggs

Etude histologique et chronologique de la formation de la couche gelatineuse des œufs de crevettes Penaeoidea par microscopies optique et electronique a transmission

Light and electron microscopic studies on osmoregulatory tissue in the developing brown shrimp, Penaeus Aztecus

Abstract In larval and early postlarval brown shrimp, Penaeus aztecus , portions of the branchial chamber are lined by a tissue which appears ultrastructurally to be modified for osmoregulation. The distribution of this tissue, the larval stages in which it occurs, and its appearance with the light and electron microscope are presented. The significance of the distribution and ultrastructure of this modified tissue is discussed.

In vitro fertilization with non-motile spermatozoa of the brown shrimp Penaeus aztecus

The sperm of the brown shrimp Penaeus aztecus are nonflagellated and non-motile. In vitro fertilization can be obtained when mature eggs removed from female shrimp are added to dense sperm suspensions in seawater and agitated in a manner simulating natural spawning.

An ultrastructural investigation of spermiogenesis and the mature sperm in the anthozoan Bunodosoma cavernata (cnidaria)

Testicular cysts located within the mesoglea of the mesenteries of Bunodosoma cavernata contain cells in all spermatogenic and spermiogenic stages. Cells in early maturational stages occupy the peripheral region of the cyst while spermatids and mature sperm are more centrally located. The young spermatid possesses a large, uncondensed nucleus within cytoplasm containing multivesicular-like bodies, mitochondria, lipid-like inclusions, and a Golgi complex. The sperm flagellum is present in this early stage of spermiogenesis, arising from the distal centriole which is surrounded by two pericentriolar specializations, centriolar satellites, and a system of branching processes. During spermiogenesis, the nucleus condenses to form the compact nucleus of the mature sperm. The Golgi complex produces “donut” shaped vesicles which become located near the nucleus. No distinct acrosome is formed. The pericentriolar processes persist during the development of the spermatozoon and are associated with a cytoplasmic collar which surrounds the anterior region of the tail.

Fine structure of the midgut epithelium in the developing brown shrimp, Penaeus aztecus

The midgut epithelium of larval and early postlarval brown shrimp has been studied with light and electron microscopy. Ultrastructurally the features of the midgut do not change during these stages of development. On the basis of electron density, two epithelial cell types can be distinguished, and these are referred to as light and dark cells. The dark cells contain more rough endoplasmic reticulum and more free ribosomes than the light cells. Mitochondria in the dark cells have a matrix which is less electron dense than the mitochondrial matrix of the light cells. Both cell types have a microvillous border with a surface coat. The microvilli lack microfilaments within their core, and a terminal web is not differentiated in the stages examined. Tubular smooth endoplasmic reticulum is abundant in the basal portions of the cells. Electron dense, membrane bound vesicles are consistently seen in association with the Golgi apparatus, apical cell surface, and gut lumen and therefore are believed to be secretory granules. Cells in the anterior portion of the midgut often contain very large lipid droplets in the cytoplasm.

Ultrastructural observations of the muscle insertion and modified branchiostegite epidermis in the larval brown shrimp, Penaeus aztecus

Abstract Fine structural observations on muscle insertion in arthropods are extended to the order Decapoda. The three regions of a muscle insertion (cuticle, epidermis and muscle) are discussed for the larval forms of the decapod, Penaeus aztecus . These regions are contrasted to muscle insertions of insects and arachnids which have been previously reported in the literature. In addition, a modified epidermal cell located in the branchiostegite of the larval shrimp is discussed. The epidermal cell of the branchiostegite is modified in a manner similar to the epidermis of the muscle insertion. The two epidermal cell types are contrasted and the significance of their modifications is discussed.