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

Gonadal Degeneration Is Mediated by Apoptotic Processes in the Semelparous Gray Side-Gilled Sea Slug Pleurobranchaea maculata

AbstractSpecies undergoing postreproductive death experience great changes in their reproductive organs, which are driven by numerous physiological processes. To assess whether apoptotic processes are involved in the dynamics of the reproductive organs of Pleurobranchaea maculata, the gonadal structure of this semelparous side-gilled sea slug was studied using light and scanning electron microscopy. Apoptotic cells at different gonadal developmental stages were detected by in situ TUNEL assay. Apoptosis was primarily focused on spermatogonia during gonadal cell proliferation, probably as a regulatory mechanism that maintains homeostasis in reproductive cells. Visible gonadal degeneration at the end of the reproductive period is accompanied by apoptosis of the basal lamina cells of the acini, suggesting that apoptotic processes are involved in the gonadal degeneration observed in P. maculata.

Ultrastructure of ovotestis of young and adult pulmonate mollusk, Macrochlamys indica Benson, 1832

Macrochlamys indica is a hermaphrodite terrestrial pulmonate mollusk. Transmission electron microscope studies were done on the ovotestis of young and adult (older) M. indica which are elaborated in this paper. The ovotestis contains numerous lobes each of which contains many ovoid shaped acini which are occupied by stages of spermatogenesis and a single oocyte. In younger snails, the acini contain stages of developing spermatogenesis, whereas each acinus of older snails is composed of single large oocyte and few stags of spermatogenesis. The number of Sertoli cells is high in the acini of younger snails than in older snails. Details of the cellular organization of the Sertoli cell are described. Some long thin threads extend from the acinar boundary to acinar lumen. The anterior end of these threads is either free or directly connected to the developing cells of spermatogenesis. There are two types of cells in the interacinar space of the ovotestis in both younger and older snails. One cell is small oval interstitial cell and other is thin elongated periacinar cell. The acinar boundary contains secretory cells with deeply stained nucleus. In the acinus of older snails, the Sertoli cells do not form any barrier between oocyte and spermatogenic cells. Functions of the periacinar cell and interacinar cell are discussed. It is found that the spermatogenesis is highly active in younger snails with single dormant oocyte while process of oogenesis predominates in the older snails. The reproductive strategy of this pulmonate species thus depends on the individual's body size and their maturity.

Morphologic effects of in vivo acute exposure to the pesticide methoprene on the hepatopancreas of a non-target organism, Homarus americanus

Methoprene is a pesticide widely used for mosquito control. It is an endocrine disruptor, acting as an analog of juvenile hormone. While targeting insect larvae, it also impacts non-target animals including crustaceans. Anecdotal reports suggested that methoprene has unintended effects on adult arthropods. Earlier, we documented effects in adult lobsters at the metabolic and gene expression levels. In this study we have documented morphologic corollaries to our prior observations. We examined the light and electron microscopic changes in the hepatopancreas of adult lobsters following in vivo acute exposure to methoprene. Changes by light and electron microscopy levels were evident following exposure to sub-lethal concentrations of methoprene for 24h. Tissue from exposed animals showed the formation of extensive cytoplasmic spaces (vesiculation) with disruption and loss of specific subcellular organelles. The findings provide morphologic correlates to the metabolic and genomic alterations we have observed in previous investigations.

Ultrastructure of somatic tissues in the ovaries of a chaetognath (Ferosagitta hispida)

Transmission electron microscopy reveals that the ovaries of Ferosagitta hispida contain four somatic tissues. A myoepithelial ovary wall, continuous with a thin layer of peritoneocytes lining the coelomic cavity, encloses a fluid-filled ovarian space in which oocytes develop. Lamellar extensions of a "follicular reticulum" branch throughout the ovarian space and ensheath developing oocytes. This tissue has been overlooked in most previous studies of chaetognath ovaries. A bipartite oviductal complex extends the length of each ovary just within the lateral ovary wall. It consists of a flattened, blindly ending cellular tube, herein referred to as the cellular sheath, and an enclosed syncytium. Sheath cells secrete an electron-dense product into the ovarian space. Those sheath cells directly bordering the syncytium are contractile and are joined to the to the syncytium by gap junctions and microvillar interdigitations. The syncytium contains a complex of membrane-bounded lumina. The latter sometimes enclose sperm received during mating or ovulated eggs. Thus the syncytium serves both as a seminal receptacle and as a duct for passage of eggs to the outside. Contrary to several classical reports, the cellular sheath and syncytium of the oviductal complex do not separate at ovulation to form a temporary oviductal lumen.