摘要:

The acoelOtocelis luteola, when cultivated with either of two species ofNavicula, reaches maximum size and sexual maturity in 13 to 20 days. The proximal portion of the vagina and its opening are the first reproductive structures to appear. When a small invagination of the ventral epidermis forms the definitive genital pore and genital atrium, the opening of the vagina is displaced to the dorsal side of the atrium. The male copulatory organ, an eversible cirrus that will occupy part of the seminal vesicle and join the genital atrium, develops soon afterward, and the distal portion of the vagina, apparently without a lumen, becomes evident. After sperm have been formed, they are delivered by right and left channels to the seminal vesicle; a conspicuous sperm-filled space thus develops around the cirrus. The sclerotized nozzle of the seminal bursa is distinct by this stage, and enlarging oocytes soon become conspicuous. During final stages of differentiation, oocytes enlarge further. The granule-filled distal portion of the vagina arches over the seminal vesicle, reaching the seminal bursa. In a worm that has been inseminated, active sperm will be seen in one or more spaces within the bursa, which is otherwise rather vaguely delimited. If a mature specimen is starved, it regresses to a stage similar to that of one that has just hatched. Most reproductive structures are resorbed in an order inverse to that in which they differentiated. The cycle of differentiation and dedifferentiation has been repeated as many as seven times, and can perhaps be repeated indefinitely. Furthermore, some mature worms, after being isolated, remained normal for two years and were sexually competent when mated.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652408

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Stimulation of ovarian growth was accomplished by administration of leucine-enkephalin in the fresh water field crabOziotelphusa senex senex.The ovarian index was significantly increased in the crab after leucine-enkephalin injection, but the oocyte diameters were not significantly altered, indicating that leucine-enkephalin stimulated more oocytes to mature. In contrast, injection of methionine-enkephalin significantly decreased the ovarian index and oocyte diameters.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652409

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Four zoeal, the megalopal and the first crab stage are described and illustrated forPlacetron wosnessenskiiSchalfeew (Hapalogastrinae). Morphological differences found in some of the developmental sequences between members of the two subfamilies of the Lithodidae are reviewed.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652410

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The spermatozoon from testes ofLoxosoma pectinaricolaconsists of a head region composed of a long tapering nucleus with homogeneous chromatin. In some mature spermatozoa the nucleus has an anterior acrosome-like extension. A deep basal invagination in the nucleus contains a centriole and the proximal part of the flagellar axoneme. The midpiece consists of two long mitochondrial rods that are connected to each other by a thin mitochondrial lamella. The mitochondrial material surrounds a non-membrane-bounded rod of electron-dense material which also partly surrounds the axoneme. This rod runs parallel to the axoneme. A manchette of microtubules surrounds the nucleus and the mitochondrial material during elongation and nuclear condensation. The tail consists of an axoneme with the usual 9+2 arrangement of microtubules bounded by the plasma membrane. Spermatozoa have been found in the intercellular space in the tissue of the tentacular membrane, indicating possible sperm transport to the ovaries.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652411

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Development of a holothurian,Cucumaria japonica, is examined. Holoblastic radial equal cleavage results in formation of a coeloblastula. Gastrulation begins on the second day. It is represented by an invagination and accompanied by immigration of the mesenchyme cells and marks the start of development of the vitellaria larva. The archenteron immediately divides into rudiments of the hydrocoel, the somatocoel and the rudiment of the gut. No unified enterocoel is formed. Ends of the hydrocoel fuse to form a ring canal on which five primary tentacles, radial canals, a polian vesicle, and a hydroporic canal are formed. The somatocoel divides into right and left somatocoels, which then fuse to form a united coelomic sac, encircling the gut. The ventral mesentery then disappears. Thus, by day 6 the pentactula is completely formed. At day 10 the tentacles move from the ring canal to the radial canals, and the somatocoel gives rise to two derivatives: the preoral and anal coelomes. By the end of the second week of development, three parts can be distinguished in the alimentary canal, and a longitudinal muscle band begins developing in the mid-ventral ambulacrum. At the stage of two months, a rudiment of the respiratory system appears.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652412

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Sperm ultrastructure and the number of sperm per bundle were studied in twoDrosophilaspecies from the tripunctata radiation,D. dunniandD. cardini.The number of sperm per bundle in both species was found to have an unusual frequency distribution, as none of the bundles obeyed the 4(2”) rule proposed for species with definitive spermatogonia division. The absolute and relative size of the cross sectional areas of the mitochondrial derivatives ofD. dunniandD. cardinisperm was found to be somewhat different fromD. hydei(repleta radiation), and very different fromD. melanogasterof the Sophophora radiation. Lastly, a mass of residual material and a desmosome-like attachment plaque were demonstrated between the axoneme and the large mitochondrial derivative inD. dunniandD. cardinisperm. This study highlights the importance of ultrastructural studies of spermatogenesis in the analysis of the phylogeny ofDrosophila.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652413

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Larval development in decapod crustaceans is marked by variable growth patterns and changes in weight and biochemical composition. Larvae of the stone crab,Menippe adina, were mass-reared under laboratory conditions (28 °C; 20%0S) from hatching to the megalopa stage. Growth inM adinais exponential throughout the larval stages (y = 10.395e01592x, R2=0.98). Dry weight increased by 16-fold from the first to fifth zoeal stage (ZI-ZV), and by day 22 the average weight for megalopae was 272.5±48.6 μg. Iatroscan lipid class analysis revealed that polar lipids (>64%) and neutral lipids, of which steryl esters (>20%) were dominant, represent the major lipid classes in larvae at every stage. Free fatty acids and free sterols were present in small amounts, but there was no trace of diacylglycerols. Triacylglycerols represented on average 3% of total lipids. Total lipids of zoeae and megalopae contained substantial concentrations of palmitic (16:0), stearic (18:0), eicosapentaenoic (20:5ω3), oleic (18:1ω9) and arachidonic (20:4ω6). Proximate biochemical composition revealed conspicuous variations during metamorphosis that appear cyclic in nature.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652414

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Earlier work showed the existence of sialic acid (SA) in the prothoracic glands (PGs) ofGalleria mellonella(Karaçali et al., 1997). In this paper we investigated the role of SA during the degeneration process of PGs. Neuraminidase-digested larval PGs were incubated within the hemolymph collected from same age larvae. Light and electron microscopic observations showed incomplete capsule formation by the accumulation of hemocytes around desialylated gland cells, but not in the control group. Desialylated larval PG cells were recognized as a foreign structure or non-self by hemocytes. The result indicates that SA acts as a mask for hemocytic receptors during the larval period under normal conditions. However, in the absence of SA, the glands start to degenerate. We provide an explanation for the role of SA in the recognition process of hemocytes that initiates the degeneration of PGs in pupal cells and show the functionality of SA in insects, confirming that SA is a universal molecule.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652415

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Study of gonads of the mesopelagic ctenophoreBathocyroe fosterirevealed that the animals are dioecious for at least part of their life span. Specimens were collected using the Johnson Sea-Link I and II submersible vehicles during the periods of October 4–11, 1988, off the Bahamas Banks and July 18–20, 1991, off Cape Hatteras at depths of 550–900 m. Each animal was provisionally sexed by scanning all comb rows with a dissecting microscope. The provisional sex was confirmed after preparation of squashes of ad-tentacular and ab-tentacular comb rows for eggs and sperm at various magnifications using dark field optics and histological sections. With two exceptions, only one type of gamete was found in any sexual specimen and all comb rows bore the same type of gamete on both sides of the gastrovascular canal. UnlikeOcyropsis, the only other dioecious, planktonic ctenophore known,Bathocyroehas a gonad location typical of all other ctenophores. Our observations suggest that ctenophore dioecy is not restricted to the epipelagic, oceanic habitat and is not a property of a single genus with atypically located gonads. Dioecy has apparently evolved secondarily at least twice in habitats largely occupied by a group of related ctenophores which are all simultaneous hermaphrodites.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652416

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652417

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor