摘要:

AbstractWe have analyzed morphological changes affecting the lympho‐hemopoietic organs of the anadromous sea lamprey,Petromyzon marinusthroughout its life span. For this analysis, ammocoetes (2–4 years), premetamorphosing lampreys (nearly 5 years), metamorphosing lampreys, macrophtalmia stages (young adults) and parasitic adults (nearly 7 years) were used. The principal lympho‐hemopoietic organs in the ammocoete are typhlosole, larval opisthonephros and nephros‐associated adipose tissue. After metamorphosis, these organs degenerate, and their lympho‐hemopoietic tissue is replaced by dense connective tissue. The supraneural body and to a lesser degree, the definitive opisthonephros, are the main blood‐forming organs in adult lampreys. During larval life, lympho‐hemopoietic cells appear in the branchial area, associated with pharyngeal epithelium. These loci are not morphologically homologous to the thymus gland of jawed vertebrates. These results are discussed, with special emphasis on the importance of cell microenvironments in eluciding changes in different blood‐forming loci throughout the life cycle and their significance for the lamprey's

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb00805.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe oogenesis of the common prawnP. serratusis described. The reproductive cycle is annual and there is little evidence for a second spawning period. Oogenesis under the electron microscope follows a typical crustacean pattern and has been divided into seven stages according to the structure of the oocytes. The production of yolk is mainly intra‐oocytic, with a small extra‐oocytic contribution. Yolk, in the form of small granules, arises within the lamellar elements of the rough endoplasmic reticulum. These were then transformed into finely granular yolk bodies. Lipid droplets, as in other crustacean species, arisede novoin the cytoplasm and there is no association between lipids and cell organel

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb00806.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractSpermiogenesis inPalaemon serratusis described. The mature sperm has an atypical form and is highly modified. In early stages of spermiogenesis mitochondria, golgi complexes, stacks of annulate lamellae and endoplasmic reticulum are present but disappear later in development. Two modified mitochondria are present in the mature sperm. This latter consists of a cup‐shaped nucleus, a cross‐striated “spike”, has a centriole and lacks an acrosome. The nucleus contains membrane‐bounded vesicles which arise by pinocytosis. The “spike” may be a flexible posterior organ which suggests a mode of fertilization requiring lim

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb00807.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe stalk of the pentacrinoid larva of a feather star (Comanthus japonica) is described for the first time by transmission electron microscopy. One end of the stalk bears the calyx and the other end is cemented to the substrate by attachment cement consisting of a meshwork of 5 nm filaments. The stalk is supported by a scries of skeletal ossicles pierced by a central canal: short intercolumnal ligaments connect adjacent skeletal ossicles and central through‐going ligaments run the length of the central canal. At the end of the stalk nearest the calyx, the chambered organ and the closely associated axial organ are histologically similar to those of adult crinoids. Presumed neurosecretory neurons are associated with the intercolumnal ligaments, and the following kinds of nerves run down the central canal: (1) a large stalk nerve in each of the five interradii; (2) smaller coelomic nerves in each of the five radii in association with the epithelium of tubular aboral extensions of the chambered organ; (3) a very small nerve associated with the aboral extension of the axial organ in the stalk axis. This axial organ extension is surrounded by a haemal channel. Because of the small size of the stalk, none of the nerves or the haemal channel were described in previous light microscopic studies. The discussion gives special attention to the controversial motility of the pentacrinoid stal

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb00808.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb00809.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY