Thitipramote, N., Suwanjarat, J., Leigh, C. and Breed, W.G. 2011. Variation in sperm morphology of a murine rodent from South-East Asia: the Greater Bandicoot Rat, Bandicota indica. -Acta Zoologica (Stockholm) 92: 201-205.In most mammals the male gamete, the spermatozoon, has a fairly consistent, species-specific shape although in a few species some variability is evident. The present study set out to determine the extent of sperm variability in a population of a South-East Asian murine rodent, Bandicota indica, that was sampled during both the breeding and non-breeding periods. We found that, regardless of the time of year when the animals were obtained, males had sperm present in the cauda epididymides but a high degree of variability was always evident including the presence of some grossly abnormal forms. The abundance of abnormal sperm tended to be greater during the non-breeding period. These animals also have relatively small testes, thus the occurrence of the variable sperm populations is consistent with the hypothesis that depressed levels of intermale sperm competition result in a relaxation of the genetic control of male germ cell maturation during spermiogenesis and thus the production of polymorphic sperm populations.
This study investigated some aspects of the reproductive biology of male and female greater bandicoot rats, Bandicota indica, in southern Thailand from September 2004 to September 2006. In females, body, uterine and preputial gland weights, occurrences of pregnancies and placental scars, and in males, testicular weights and histology, and sizes of accessory sex glands, were recorded. Pregnancies occurred predominantly, but not exclusively, in the wet season, with a higher incidence pregnancies in the second, than in the first, dry season. Uterine and preputial gland weights tended to be lower in the first, but not the second dry season, with placental scars occurring at all times of year. Males tended to have heavier testes in the wet season but some seminiferous tubules contained sperm even in the dry season. Seminal vesicles, but not prostates and preputial glands, tended to be heavier in animals in the wet season. We conclude that the greater bandicoot rat in southern Thailand shows maximal reproductive activity in the wet season with some reproductive activity, albeit variable from year to year, occurring in the dry season depending upon environmental conditions. This study has also shown that females, as well as males, have large preputial glands, and that males invariably have small testes regardless of the time of year. These observations suggest a similar timing of reproduction, but a different breeding biology and perhaps social organisation, from that of the sympatric ricefield rat, Rattus argentiventer
In this paper spermatogenesis and sperm ultrastructure of the cockle Anadara granosa are studied using transmission electron microscopy. The spermatocyte presents electron-dense vesicles and the arising axoneme that begins to form the flagellum. During spermatid differentiation, proacrosomal vesicles appear to migrate towards the presumptive anterior pole of the nucleus; eventually these vesicles become acrosome. The spermatozoon of Anadara granosa is of the primitive type. The acrosome, situated at the apex of the nucleus, is capshaped and deeply invaginated at the inner side. The spherical nucleus of the spermatozoon contains dense granular chromatin and shows invagination at the posterior poles. The centriole shows the classic nine triplets of microtubules. The middle piece consists of the centriolar complex surrounded by five giant mitochondria. It is shown that the ultrastructure of spermatozoa and spermiogenesis of Anadara granosa reveals a number of features that are common among bivalves.
During a tributyltin (TBT)-exposure experiment, the ultrastructural features of oogenesis have been examined in TBT-induced imposex females of Babylonia areolata and compared with those of the normal female. The results obtained from such experiment demonstrates that B. areolata exhibits a low to moderate intensity of imposex because all VDSI values are never higher than 3. Ultrastructures of germ cell development including oogonia, pre-vitellogenic, early vitellogenic, late vitellogenic and mature oocytes show that oogenesis in imposex female is similar to that of normal females except for the presence of numerous lipid droplets in the cytoplasm of the oocytes and the follicle cells in imposex females, indicating the degeneration of their oocytes. Vitellogenesis in B. areolata involves both auto-and heterosynthetic processes that resemble those of the basal gastropods and the pulmonates. In addition, the presence of cortical granules and microvilli are unique structures of this species.
Abstract. Species of the Potamididae occupy the full range of aquatic habitats and differ not only in the morphology and size of their shells but also in sperm morphology. In the past, several species were classified as Cerithiidae. Characters of the developing and the mature spermatozoa have been used to gain better insight into their taxonomy. Cerithidea obtusa (Lamarck 1822) is the most dominant brackish water gastropod of the mangrove forests in Southern Thailand. Spermatological data are scarce in this species. In order to confirm its taxonomic position within the Potamididae, euspermatogenesis and euspermatozoa are examined by transmission electron microscopy. The morphological changes during spermiogenesis such as nucleus condensation, acrosome formation and development of the midpiece are described.
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