Masaei Takeda

SCANNING ELECTRON MICROSCOPY OF ENDODERMAL SENSORY CELLS OF HYDRA MAGNIPAPILLATA

Abstract.The free surface of the endoderm of Hydra magnipapillata was observed by scanning electron microscopy in order to analyze the fine structure of the apical receptive sites of the sensory cells. Endodermal sensory cells had a small round exposed surface provided with a single cilium. Two types of sensory cells, tufted and papillary, could be distinguished from each other by their apical features. The former projected 50 or more microvilli on their apical surface, which was at level with the surface of neighboring epithelial cells. The latter displayed a rounded swelling on their apex, on which 10–30 microvilli of various lengths were found pointing random directions. Both types of receptor regions were compared with those of previously reported sensory cells in Hydra ectoderm and in the gut epithelium of other animal species.

Remarkable papillomas in white sturgeons,Acipenser transmontanus, reared in an aquarium

Papillomatous growths on the ventral surface of the body and paired fins of the white sturgeon,Acipenser transmontanus Richardson, were described histologically with the aid of light and electron microscopy. Contrary to the usual state of intact squamous epithelium being equipped with microridges, no such surface structures were apparent in the papillomatous tissue. The growths appeared to be an aberrant elevations of proliferated dermal tissue, which sustains the hyperplastic Malpighian layer consisting of the stratum spinosum (prickle cell layer) and sbasale. Many intercellular bridges were found, constructed from prominent projections, with distinct demosomes and many tonofilaments. The likely causative agent was mechanical irritation between the small aquarium tank and growing sturgeon, since no viral and/or parasitic inclusion bodies were encountered in the cells.

Histology of the ink tube and its associated organs in a unicornfish,Eumecichthys fiskii (Lampridiformes)

Histological examination of the ink tube (=sac) and melanoid ink production in the unicornfish,Eumecichthys fiskii (Taeniosomi), were conducted on a female specimen, 1050 mm in total length, caught off Sado Island. Sea of Japan, on 16 December, 1996. The ink tube, apparently derived from a primitive gut, was constructed from the connective tissue capsule, muscularis, submucosa and a single layer of cuboidal cells reminiscent of an intestinal villus. Although the site and process of differentiation of melanoid granules could not be determined. variously-sized melanoid clumps were detect-ed between the spaces of the villus-like cell cords. Melanoid ink excreted from the ink tube was attached to the surfaces of the latter, the intestine and the pouch associated with swim bladder. No ink was encountered in the intestinal canal.

Histological Studies on Some Organs of Two Male Dealfishes, Trachipterus ishikawae, Caught on the Beach of Shirahama, Wakayama Prefecture, Pacific Coast of Japan

The testis, thyroid, kidney, exocrine pancreas, endocrine pancreas (=Brockmann body), spleen and liver of two dealfishes, Trachipterus ishikawae, collected on the beach of Shirahama, Wakayama Prefecture, Pacific coast of Honshu, Japan, were examined histologically. The specimens measured 2.30 m (specimen A) and 1.65 m (specimen B) in total length. The testicular lobes were atrophied and sclerotized, having the appearance of an aggregation of numerous protuberances (or spherules), each spherule corresponding to a lobule containing a number of cysts, although some of the latter had collapsed and/or merged with each other. Each cyst contained sperms and spermatids, relict sperms being found in the spermiduct. The thyroid gland, an amorphously soft body, located dorsally on the ventral aorta and its afferent branchial arteries, was composed of many variously-sized follicles. Each follicle comprised a large amount of smooth colloid, surrounded by a flat epithelium consisting of cubic cells. The overall condition indicated an inactive state. In the kidney, a great deal of stromatous tissue, including AF positive lipid grains, and a small number of glomeruli were apparent. In both specimens, the thread-like loose connective tissue comprising the exocrine pancreas attached to and running parallel with the liver, stomach, Brockmann body and spleen, were composed of acini with zymogen-rich pyramidal cells. Details of cell types in the Brockmann body were difficult to determine. Fatty deposits were absent from the liver of specimen A, which was characterized by rich stromatous tissue and dilated sinusoids. However, rich fatty deposits were found in several portions of the liver of specimen B. Well-developed stromatous tissue and nodules of red- and white pulps were recognized. It was concluded that the two specimens were spent and debilitated males.