摘要:

AbstractThe vomeronasal organ in the frog, genusRana, is composed of three interconnected cavities; superior, middle and inferior, which are separated from and anterior to the principal olfactory cavity. The superior cavity is found just underneath the external naris and forms a vestibule both for the principal olfactory organ and the vomeronasal organ. The vomeronasal sensory epithelium is located in the medial region of the inferior cavity and contains ciliated cells and microvillous receptor cells. Inspection of microscopic sections of frogs that had been swimming in fluorescent colorants revealed fluorescence on the surface of the vomeronasal organ, but not on that of the olfactory organ. Observationsin vivoshow that water enters via the external naris by two fissures, one on each side of the movable nasal lid, passes the middle cavity to flow via the sensory epithelium of the inferior cavity. The design of the frog nose makes it possible for this amphibious animal to sample the chemical composition of its environment; above water the frog can inhale air and expose its olfactory organ to volatile substances; in water the vomeronasal organ samples water‐borne substances. These new findings are discussed in relation to the air/water interface and the position of the amphibians in the evolution of terrestrial vertebrate

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01232.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThree layers of different electron density can be distinguished in the periostracum. Periostracal units of up to 900 nm length are merged into the outer fibrous layer and binding of gold‐labelled lectin‐WGA indicates the presence of chitin because it is labile to chitinase treatment.The periostracum is formed by the epithelia of the groove and the belt at the mantle edge. The distal and basal epithelium of the groove consists mainly of type A cells with an extended Golgi apparatus and apical vesicles. The presence of peroxidase and phenol oxidase indicates a function in tanning of the periostracum. In the proximal epithelium of the groove, type B cells with protruding apices add more material for periostracum formation. Type C cells secrete single periostracal units which are formed within single vesicles or larger vacuoles. Type D cells secrete electron‐dense vesicles which also contain WGA‐positive material.The distal cells of the belt are characterized by predominating strands of the rER while subapical vacuoles, to some of which WGA binds, dominate in the cells of the central part. In the belt, phenol oxidase and peroxidase can be localized in cisternae of the rER and the Golgi apparatus. Numerous control incubations indicate that, indeed, two different enzymes are lo

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01233.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractSerotonin‐containing cells are described by immunohistochemistry throughout lancelet ontogeny. Such cells are first detected in the 2‐day larva: these are (1) enterochromaffin cells in the inner epithelium of the gut and (2) anterior serotonergic neurons at the rostral end of the nerve cord. In the 6‐day larva, relatively low levels of serotonin appear in ventro‐lateral perikarya and cell processes of intraspinal serotonergic neurons scattered along the nerve cord. In the 18‐day (early metamorphic) larva, antero‐lateral serotonergic neurons are detected near the rostral end of the nerve cord as two small, bilateral clusters of perikarya with axons that descend the nerve cord; at later developmental stages, these axons extend almost to the posterior end of the body. In the 21‐day (mid‐metamorphic) larva, serotonin can no longer be detected in the anterior serotonergic neurons, but serotonin‐containing cells are found subjacent to the inner epithelium of the digestive caecum and in the peribranchial epithelium covering the primary gill bars. In the discussion, we suggest that the anterior serotonergic neurons may play a role in larval photoreception and that the antero‐lateral serotonergic neurons may be homologous to vertebrate hindbrain neurons with axons descending the spinal cord to modulate undulation (if this homology is valid, the anterior limit of the lancelet hindbrain would be roughly 100 μm behind the rostral ti

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01234.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractF‐actin and tubulin behaviour was investigated using fluorescence probes and electron microscopy in the course of spermatogenesis in two gamasid mites,Porrhostaspis lunulataMüller (Parasitidae) andPergamasus truatellusAthias‐Henriot (Pergamasidae). In spermatogonia and primary spermatocytes of both species, the proteins were localized mainly in the intercellular bridges and, in lesser quantities, in the cytoplasm. Overall, actin was present along the plasma‐lemmal contact sites of the gonial cells.At the beginning of spermatid elongation, actin could be detected in two regions: in perinuclear cytoplasm and under the plasmalemma. Subplasmalemmal actin, visible as threads running along acrosome‐adhering protrusions of the nuclear envelope, is supposedly located within the electron‐dense material filling the subacrosomal gap. Tubulin was found on both sides of each actin thread; its location was consistent with two sets of microtubules adhering to the inner acrosomal membrane. Their involvement in acrosome shaping is suggested.As spermatid elongation terminated, the previous pattern of proteins disappeared. InPergamasus, however, actin emerged briefly near the centrifugal ends of spermatids (granular bodies zone).In spermatocyte‐containing cysts, actin and tubulin fluorescence (more pronounced inPorrhostaspis) was associated with intercellular junctions between the cyst cells. In both species, diffuse actin fluorescence was also detected in the cytoplasm of cyst cells assembling elongated spermatids; the reaction was intensified at the end of the elongation process, when the cytoplasm of cyst cells aggregated around the centripetal ends o

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01235.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe functional anatomy of the extremely complex copulatory organs of the millipedeCraspedosoma transsilvanicumVerhoeff, 1897, was investigated by scanning electron microscopy and serial semi‐thin sectioning after fixation of the animals by freezingin copula.There is no male organ for sperm transfer which inserts into the receptacula seminis. Sperm secretion is only brushed over the openings of the receptacula by cuticular projections of the anterior gonopods (‘brush’). Other parts of the gonopods (projections of the cheirites, podosternite) bring the brush and the openings of the receptacula in the proper position.Examination of the gonopods from series ofCraspedosomafrom locations near Vienna showed that there are intermediary specimens between the nominal speciesC. transsilvanicumandC. alemannicumVerhoeff, 1910. Obviously, a mechanical isolation mechanism, as supposed by Verhoeff, does not exist between these nominal species.At the beginning of a copulation, the male forces the female into the mating position. When touched by males, the females try to evade them by rolling up. The possibilities are discussed that females thereby test the actual fitness of males, and that males use their clasper‐like copulatory organs to prevent females from e

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01236.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe head and branchial regions of larval and adult lampreys and hagfish were studied histologically in serial sections. The most remarkable feature in these extant agnathans was the occurrence of large blood‐sinuses. In larval lampreys, blood‐sinuses are well developed in the velum, an organ that functions to introduce water and accompanying food particles from the mouth into the gill and alimentary regions. The sinuses in the velum may act to transduce the force of contraction of velar muscles to the stroke‐like movement of the velum; without these sinuses muscular contractions might simply cause the velum to collapse. In adult lampreys, blood‐sinuses are well developed in the peribranchial space that surrounds the branchial (gill) sac and is surrounded by the branchial pouch. It is possible that the force of contractions of the branchial‐pouch muscles is transduced effectively to the branchial sac via the peribranchial blood‐sinus and facilitates the expiration of water through the external gill pores. If the peribranchial sinus were absent, the muscular contraction might deform the branchial sac in an inappropriate manner. In the hagfish, the blood‐sinus system is also well developed in the velum and peribranchial space, although the peribranchial sinus lies outside the muscular branchial pouch. In agnathans, the blood‐sinus system may function, at least in part, as a kind of hydrostatic skeleton that transduces the force generated by muscu

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01237.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe mesodermal male genital system and the spermatophore ofZygaena trifolii(Insecta, Lepidoptera, Zygaenidae) have been studied histologically. Whereas the long unpaired duct, the ductus mesospermaticus, has been found to consist of at least six distinctly different regions, the tissues and secretions of the seminal vesicles and the accessory glands were found to be quite uniform. Several of the different regions are separated from each other by epithelial septa (constrictions). The external structure and the internal organization of the spermatophore are described. Based on histological comparisons, the correlation between the contents of the spermatophore and the different parts of the male system is given.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01238.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThree different types of presumed unpigmented ocelli have been found in the anterior end ofParenterodrilus taenioides, a small gutless interstitial polychaete. The type‐1 ocelli are located in the palps and four ocelli have been found along the length of each palp. The type‐2 and type‐3 ocelli lie close together in the head segment and are located in posterior ganglionic expansions of the brain. There is one pair of the minute type‐2 ocelli but at least two pairs of the type‐3 organs, which are the largest ocelli. In each ocellus the sensory cells are of the ciliary type and possess two cilia whose plasma membranes branch into numerous microvilli. With the exception of the type‐1 ocelli they consist of a sensory cell and a supportive cell. In each ocellus the supportive cell forms a thin cup‐shaped envelope around the densely packed ciliary branches. The type‐1 ocelli consist of a single cell forming an intracellular vacuole (phaosome) which contains less densely packed microvillus‐like structures. In particular, the structure of these ocelli is compared with that in other polychaetes, with special emphasis on the remaining genera of

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01239.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractEarly juvenile stadia are described in four species of family Cambalopsidae.Hypocambala helleriSilvestri, 1897, andH. anguinea(Attems, 1900) show normal relationships between numbers of podous and apodous rings, and numbers of leg‐pairs.Glyphiulus granulatus(Gervais, 1847) andTrachyiulus tjampeanus(Attems, 1903) have a deviating stadium (probably stadium III) in which most of the podous rings (10–13 rings inG. granulatus, 19 rings inT. tjampeanus) have only one leg‐pair. No trace of the anterior leg‐pair, nor of its sternum, could be found in these rings. At the moult to the next stadium (?IV), the normal, diplopodous condition is restored. The term haplopodous diplopods is suggested for the deviating juveniles ofG. granulatusandT. tjampeanus.The haplopodous condition creates potential problems for palaeontology and indicates a closer relationship betweenGlyphiulusandTrachyiulusthan reflected in current classifi

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1993.tb01240.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY