摘要:

AbstractSpecimens ofHolopus rangii(order Cyrtocrinida) were collected by submersible at depths of several hundred meters in the Caribbean and fixed for light and electron microscopy. The presence of an anus is confirmed. However, the chambered organ and glandular axial organ peculiar to crinoids are lacking. The gut lumen sometimes includes partially digested prey items up to several hundred micrometers in diameter, and we propose thatHolopusmay feed raptorially by rapidly closing its arms over demersal zooplankton. Electron microscopy of the arm reveals a radial nerve and a radial haemal channel, which light microscopy previously failed to demonstrate. The cuticle includes bacteria that are probably symbiotic. The ten brachial nerves of the aboral nervous system unite pairwise to form five calyx nerves. The calyx nerves, one in each radial position, are connected by a pentagonal, interradial commissure and then continue to the attached end of the body where they end blindly without forming an aboral nerve center. The absence of the aboral nerve center and related internal organs strengthens the argument that no basal ossicles are included in the skeleton of the calyx and suggests thatHolopusmay have evolved from stalked cyrtocrinid ancestors by saltatory loss of major body parts.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01070.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe occurrence and structure of adipocytes in the larvae of two lamprey species,Geotria australisandPetromyzon marinus, were examined by electron microscopy. Adipocytes from both species possessed large electron‐dense inclusions which histochemical and energy dispersal X‐ray analyses show as containing iron. The greatest concentration of inclusions in adipocytes was found in the nephric fold ofG. australis. While some iron is present in the cytoplasmic matrix as ferritin, the majority is seen in large ammocoetes in membrane‐bound dense aggregations of haemosiderin. The wide variety of inclusion types seen in smaller larvae may reflect on the method of formation of these inclusions within the cell. Because of the high level of iron loading in the larval lamprey nephric fold, this readily accessible tissue may provide a valuable model for studies of iron metabolism in verteb

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01071.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractOrgan heavy metal levels, and ultrastructural localization were examined in the marine prosobranch molluscLittorina saxatilisfrom a metal‐contaminated site. Copper and zinc are localized in the digestive gland, stomach and kidney. The digestive gland does not appear to be a significant site of iron accumulation. High levels of copper and zinc in the stomach may indicate significant uptake from the food. Relatively high heavy metal levels in several organs were reflected in the presence of a variety of metal‐containing aggregates (granules) within the tissues. In common with other invertebrates two broad classes of granule were present. The first appears to be proteinaceous, with a high sulphur content. This type contained copper and iron and was found in the stomach, kidney, pore cells, and rectum. The second type was inorganic and mineralized, containing phosphorus. They contained calcium, zinc and manganese, and were observed in the kidney and digestive gland. Differences in the number of metals were observed between the various granule types, possibly reflecting specific pathways involved in metal sequestrat

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01072.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractOntogenetic changes in the visual cell layer of the duplex retina during growth of the eye of the deep‐sea teleostGempylus serpens, the snake mackerel, are illustrated by comparing the retina of a small specimen with that of a previously studied adult fish.The small specimen has tightly packed cones spanning the whole width of the visual cell layer and small rods situated in its vitread part. Over most of the retina the cone population consists of single cones arranged in a very regular hexagonal mosaic. The temporalmost retina has a cone population consisting mainly of twin cones arranged in meridional rows.Growth of the eye is associated with an increase in the thickness of the visual cell layer and the density of rods and a total elimination of the densely packed single cones, the retina of the adult fish possessing only a temporally located population of double cones.The radical differences between the retina of the small and adult snake mackerel are probably associated with the different light regimes encountered by small and large specimen

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01073.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the present ultrastructural study we have extended previous reports on the histological organization and cell components of the lymphohaemopoietic masses occurring in the cranium, mainly in the orbit, the preorbital canal, and the suprapalatal and coiacoid areas of the holocephalanChimaera monstrosa. Mature and developing granulocytes, monocytes, macrophages, lymphocytes and plasma cells occur in a reticular and/or fibroblastic supporting stroma inside the cartilaginous skeleton. Heterophils, which are the most abundant granulocytes in the cranial tissue, contain two distinct cytoplasmic granular populations, whereas eosinophils show one uniformly electron dense granule type. Heterophils and eosinophils may differentiate from a common precursor producing granules of each cell type in relation to the activity of rough endoplasmic reticulum and Golgi complex. The presence of macrophages, lymphocytes and developing and mature plasma cells suggests an important role of the cranial lymphohaemopoietic tissue in eliciting the immune responses. A phylogenetical relationship between this tissue and the higher vertebrate bone marrow is proposed on the basis of histological similarities between the cell microenvironments governing haemopoietic differentiation in these organs.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01074.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe ultrastructural study of the RA mutant of the Mediterranean fruit fly,Ceratitis capitata, has been analysed in relation to morphofunctional aspects of the cystic cells. These cells appear to be essential to the normal differentiation of the germ cell and participate actively in the release of mature sperm cells from the cysts. Abnormalities in these cells result in the disorganization of the bundles of spermatic cells, leading to their destruction and elimination, thereby contributing to the diminished fertility of this mutant. Abnormalities of the cystic cells have not yet been reported for any infertile dipteran mutants.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01075.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe ultrastructural organization of the proboscis in two species of free‐living Platyhelminthes,Psammorhynchus tubulipenisandCytocystis clitellatusis very alike but differs from previously described species. Both sheath and cone epithelium are composed of two circumferential belts. Only the basal cone epithelium is syncytial, while no nuclei were found in the distal belt of the sheath epithelium. The sheath epithelium is characterized by numerous infoldings of the basal plasma membrane. The nuclei present in the bulb belong to the proximal belt of the sheath epithelium and the apical cone epithelium. Nuclei of the basal cone epithelium are located insunk behind the proboscis bulb. The insunk cell parts pierce the septum of the bulb laterally near the proximal end. Different types of gland necks and sensory cells pierce the epithelia. Associated with the distal belt of the sheath epithelium, two sensory organs are found, containing multiciliary receptors with modified axonemata. Differences in organization of the proboscis musculature are described and compared with the organization in other species. The systematic position of both species is discussed in the light of the new finding

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01076.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY