Abstract:
:Sixty-seven specimens of the common North Atlantic asteroid, Asterias vulgaris, were collected at seasonal intervals over a 2-year period and their testes observed with both light and electron microscopy. In the germinal epithelium, a predictable series of interactions between versatile somatic cells and germinal cells is repeated annually in relation to sequential events in spermatogenesis. For example, massive proliferation and differentiation of spermatogenic cells depend on the elaboration of thousands of spermatogenic columns, which are distinct cellular subdivisions of the germinal epithelium. Each fully developed column is composed of at least one somatic cell surrounded by ≈︁ 400 germinal cells. Such columns form only after intensive spermatogonial mitosis begins in the germinal epithelium. Single annual periods of spermatogenic proliferation and differentiation are initiated from 1 to 3 months out of phase in different individuals and overlap incompletely. Therefore, it is possible to observe testes that are entirely in the proliferative phase, entirely in the differentiative phase, or in both phases simultaneously. Detailed ultrastructural observations and preliminary autoradiographic data demonstrate that columns maintain their height for a variable period of time as germinal cells are generated near their bases, pass along their lengths, and differentiate near their tips; therefore, simultaneous proliferation and differentiation of more than one generation of germinal cells occur in the same column. Finally, formation of primary spermatocytes ceases basally, (terminating proliferation), and remaining columns degrade completely as germinal cells composing them differentiate or are phagocytized (terminating differentiation and spermatogenesis); resulting spermatozoa ultimately accumulate in the expandable lumen. It is proposed that spermatogenic columns provide the structural basis for organization of the microenvironment of small groups of spermatogenic cells (≈︁ 400 at a time) during proliferation and differentiation. Preliminary evidence from A. vulgaris and other species also suggests that somatic cells are temporally pluripotent and are variously involved in the formation, structure, and activities of columns, in extensive phagocytosis, and probably in contributing intrinsic (e.g., 1-methyl adenine and steroids) and mediating extrinsic (e.g., gamete shedding substance and nutrients) microenvironmental factors influential during spermatogenesis in asteroids. The prodigious spermatogenic capabilities of asteroids apparently depend on the generation of spermatogenic columns, on the progressive interaction of germinal and somatic cells before, during, and after columns form, and on the predictable effects of microenvironmental factors received and interpreted at the structural level of the spermatogenic column.
journal_name
J Morpholjournal_title
Journal of morphologyauthors
Walker CWdoi
10.1002/jmor.1051660107subject
Has Abstractpub_date
1980-10-01 00:00:00pages
81-107issue
1eissn
0362-2525issn
1097-4687journal_volume
166pub_type
杂志文章abstract::The tubular accessory gland consists of a simple secretory epithelium surrounded by a muscular coat. Over the pupal instar, the gland increases ten-fold in volume and 15-fold in length. Pupal development is divisible into a phase of mitosis and one of cell growth. During the mitotic phase, cytoplasmic membranes are sp...
journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1051720109
更新日期:1982-04-01 00:00:00
abstract::Homology is resemblance caused by a continuity of information. In biology it is a unified developmental phenomenon. Homologies among and within individuals intergrade in several ways, so historical homology cannot be separated sharply from repetitive homology. Nevertheless, the consequences of historical and repetitiv...
journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1051730307
更新日期:1982-09-01 00:00:00
abstract::The Hawaiian Drosophilidae possess spectacular diversity in male foreleg modifications, many of which are unknown in other Diptera. The greatest diversity in foreleg morphology is in the antopocerus, modified tarsus, and ciliated tarsus clade (AMC Clade), a group of 95 species. The modified tarsus flies are divided in...
journal_title:Journal of morphology
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更新日期:2010-01-01 00:00:00
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journal_title:Journal of morphology
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更新日期:2002-11-01 00:00:00
abstract::Larval and juvenile air breathing fish may experience nocturnal and/or seasonal aquatic hypoxia. Yet, whether hypoxia induces respiratory developmental plasticity in larval air breathing fish is uncertain. This study predicted that larvae of two closely related anabantid fish-the facultative air breather the Siamese f...
journal_title:Journal of morphology
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abstract::The morphology of ctenostome bryozoans remains little investigated with only few species having been subject to more detailed studies. From all the seven main different superfamilies, only few representatives have been studied. The superfamily Arachnidioidea has particularly been neglected concerning detailed morpholo...
journal_title:Journal of morphology
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更新日期:2020-12-01 00:00:00
abstract::Previously we showed that type XII collagen (col XII) is highly upregulated in the regenerating newt (Notophthalmus viridescens) forelimb. Here, using immunohistochemistry and in situ hybridization, we studied the pattern of expression of col XII during early stages of adult newt tail regeneration. The results show th...
journal_title:Journal of morphology
pub_type: 杂志文章
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更新日期:1996-11-01 00:00:00
abstract::Eggs of Xenopoecilus sarasinorum possess two distinct types of filaments on the surface of the egg envelope (chorion), long, attaching filaments restricted to the vegetal pole and weak, nonattaching filaments around the animal pole (micropyle). Both types are formed during oogenesis. After mature eggs were spawned thr...
journal_title:Journal of morphology
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更新日期:2008-06-01 00:00:00
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journal_title:Journal of morphology
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更新日期:1984-10-01 00:00:00
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journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1052040103
更新日期:1990-04-01 00:00:00
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journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.10915
更新日期:2011-03-01 00:00:00
abstract::South American Pipidae show a unique reproductive mode, in which the fertilized eggs develop in temporarily formed brood chambers of the dorsal skin after eggs have been deposited on the back of the female. We studied the skin incubation of Pipa carvalhoi using light microscopy and scanning electron microscopy. The sk...
journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.10759
更新日期:2009-11-01 00:00:00
abstract::The structure, attachment and subsequent metamorphosis of larvae of the marine bryozoan Bugula neritina were studied by light and electron microscopy. Two points of larval anatomy are of special significance to proper interpretation of the metamorphosis: 1 Two cytologically similar blastemal tissues, each laden with f...
journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1051340307
更新日期:1971-07-01 00:00:00
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journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1051940203
更新日期:1987-11-01 00:00:00
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journal_title:Journal of morphology
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更新日期:2010-02-01 00:00:00
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journal_title:Journal of morphology
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更新日期:1992-08-01 00:00:00
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journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.10964
更新日期:2011-08-01 00:00:00
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journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.10203
更新日期:2004-05-01 00:00:00
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journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1051440207
更新日期:1974-10-01 00:00:00
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journal_title:Journal of morphology
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更新日期:1989-02-01 00:00:00
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journal_title:Journal of morphology
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journal_title:Journal of morphology
pub_type: 杂志文章,评审
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更新日期:2000-07-01 00:00:00
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journal_title:Journal of morphology
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更新日期:1996-04-01 00:00:00
abstract::The light microscopic analysis of serial sections of the subcommissural organ (SCO) of the rainbow trout (Salmo gairdneri) shows that the form of the groove-like (in cross section) organ varies over its total length. Its rostral origin is a tunnel-like structure anterior to the orifice of the hollow pineal stalk. The ...
journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1051960307
更新日期:1988-06-01 00:00:00
abstract::For the first time the scanning electron microscope was used to compare developmental changes in scorpion embryos and the first and second stadia. In the buthid species of this study, Centruroides vittatus, and all other scorpions, the newborn climb up on their mother's back and remain there without feeding for severa...
journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.10227
更新日期:2005-07-01 00:00:00
abstract::The brine shrimp, Artemia (Crustacea, Anostraca), is a zooplankton that is commonly used in both basic and applied research. Unfortunately, Artemia embryos are often cultured under conditions that alter early development, and reports based on these cultures oversimplify or fail to describe morphological phenotypes. Th...
journal_title:Journal of morphology
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doi:10.1002/jmor.20344
更新日期:2015-03-01 00:00:00
abstract::The postembryonic development of the turtle carapace was studied in the aquatic Еmys orbicularis and the terrestrial Тestudo graeca. Differences in the structure of the bony shell in aquatic and terrestrial turtles were shown to be associated with varying degrees of development of epidermal derivatives, namely, the th...
journal_title:Journal of morphology
pub_type: 杂志文章
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更新日期:2019-10-01 00:00:00
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journal_title:Journal of morphology
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doi:10.1002/jmor.10632
更新日期:2008-07-01 00:00:00
abstract::We provide a detailed description of the larval morphology of the Great Basin spadefoot toad (Scaphiopus intermontanus), a species with documented morphological variability in larval structures associated with feeding. We based our findings on laboratory-raised individuals fed a herbivorous diet. We characterized the ...
journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1094
更新日期:2002-05-01 00:00:00
abstract::The structure of the thumus in adult specimens of a marine teleost, the cling fish Sicyases sanguineus, has been studied by light and transmission electron microscopy. Most cling fishes have an outer thymus located beneath the opercular epithelium. A few of them, however, have a large inner thymus besides a poorly dev...
journal_title:Journal of morphology
pub_type: 杂志文章
doi:10.1002/jmor.1051770103
更新日期:1983-07-01 00:00:00