摘要:

Males of the nematomorphParachordodes wolterstorffifrom the New Forest, Hampshire, England have been examined entire, in thick sections and in cuticle preparations by light (differential interference contrast) and scanning electron microscopy. Surface features, internal organization and cuticular fibres are described and illustrated. Surface ornamentation is very varied. The fibres are made up of two fibrils twisted together left‐handed and are arranged in up to 45 layers. Fibres in alternate layers from right‐ and left‐hand helices round the worm. Helicity and stiffness of fibres, body pressure, attachment to substratum and phylogeny are disc

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02096.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The cuticles of many worms contain a cylindrical trellis made of layers of collagen fibres wound round the body in left‐ and right‐hand helices. This kind of extensible skeletal structure imposes various constraints on a worm's behaviour, and some of these are examined, using the nematomorphParachordodes woltersforffiias the main example. Upon extension or shortening of the cuticle, neighbouring fibres in one layer will eventually touch and so limit further movement; this in turn affects the extent of shortening, elongation, bending and coiling of the whole worm. Simple equations relate: the angle between a fibre and the worm's long axis; fibre spacing and radius; worm body radius and radius of curvature. The relevance to the life of the worm of fibre arrangement, matrix properties and volume changes is discus

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02097.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Forty‐eight intestinal tracts, extracted from both sexes of California sea lions, Harbour seals and Northern elephant seals, were measured. The majority of intestinal tracts were removed from stranded animals that died from various causes. The sea lions and elephant seals, approximately equal in size, were larger than the Harbour seals. All species possess a small intestine which is significantly longer than even the entire gastrointestinal tract of herbivores of comparable size. Elephant seal small intestines, averaging approximately 25 times the seal's body length, were considerably longer than the small intestines of either sea lions (averaged more than 18 times the body length) or Harbour seals (averaged nearly 16 times the body length). However, the large intestines of elephant seals were shorter than either of the other two species. Among the sea lions and Harbour seals the large intestines were approximately equal in length. Sea lions and Harbour seals also showed a close correlation between standard length and total intestinal length. Among elephant seals these two parameters showed greater variability. The functional significance of the extremely long small intestine remains unclear. Certainly, the large body mass and high energy requirements of these animals has contributed to the development of a long intestinal tract. It also appears likely that diet and the high motility rate of digesta influenced the intestinal development. Comparatively, the significantly shorter large intestine of elephant seals probably relates to this species' remarkable capabilities in water conservation and metabolic water retentio

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02098.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The burrowing mechanisms of two soft‐bodied marine invertebrates,Polyphysia crassa(Annelida: Polychaeta) andPriapulus caudatus(Priapulida) were re‐examined and extended utilizing computer image analysis. Predetermined points on sequential photographs of animals burrowing in methylcellulose (an artificial medium of high transparency) were digitized and stored asx, ycoordinates from which were calculated segment length, width, and volume in addition to producing real and straightened images of the animal on a plotter. Both species are adapted to soft substrata and both utilize a direct peristaltic wave to advance the body into a cavity or loosened area formed by anterior structures.Polyphysiadisplaces and loosens the substratum with lateral scraping movements of its anterior six segments (the “head region”) whilePriapulusmakes a large cavity anteriorly by the forceful eversion and dilation of the praesoma. UnlikePriapulus, Polyphysiautilizes a different method of locomotion when moving on the mud surface as opposed to burrowing, the former involving two direct peristaltic waves at a time and negligible internal pressures resulting in nearly continuous advance. However when burrowing,Polyphysia, likePriapulus, utilizes a single direct peristaltic wave alternating with phasic pressure pulses which advance the animal in step‐wis

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02099.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The morphological variation of the Hooded crow at Trondheim, Norway, was studied, based on a sample of 734 birds collected during a six year period. Mouth colour, plumage colour, skull thickness and feather length were found to be characters which could readily be used to separate juveniles from adults. Females aged 15–19 months had a thinner skull roof than older female birds. Low coefficients of variation were found for the lengths of the third primary and of the tail feathers. A discriminant analysis showed that of the various body dimensions studied bill height and bill length distinguished the sexes most precisely. A high degree of sexual dimorphism was also found to exist in body weight and in the thickness of the skull roof.Those body structures which develop at about the same stage during the juvenile growth period were associated with the same principal component, viz. the lengths of bony structures, parts that develop early on in life, were intercorrelated (wing bones, tarsus, bill basis and the width of foramen magnum). The lengths of the primaries and of tail feathers were also intercorrelated, structures which develop late.The mean body weight of the Hooded crow population studied in Norway was intermediate between that of the Hooded crow in Germany and of the Carrion and Hooded crows in England and Scotland. No such differences were found in wing length. Norwegian Hooded crows have shorter tails than German ones, but their bills are much larger, in particular for the females. Therefore, the degree of sexual dimorphism in bill size seems to be reduced at high latitude

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02100.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Polyvillous cells are differentiated bipolar cells in the epidermis ofLampetraspp., which are not innervated and are interpreted as a type of ionocyte. They bear numerous apical microvilli, capped by mucus. In some examples the apex bulges at the surface of the epidermis, in others it is sunken into a crypt or may even appear to be internal to the cell. It is supposed that these variations correlate with the maturity of the individual cell. Cytological features aiding recognition of the polyvillous cells by electron microscopy are the presence of numerous membrane fragments in the secretion above the short irregular apical microvilli, coated apical invaginations or vesicles, mitochondria with well developed cristae and internal granules, and in many cases a plasma membrane which appears more electrondense than that of the neighbouring epithelial cells

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02101.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The epidermis cfLampetraspp. contains several kinds of differentiated cell; one innervated variety is characterized by bearing a group of large apical microvilli which project from the surface of the skin. InLampetra planerisuch oligovillous cells are numerous under the oral hood of the ammocoete larva, on the papillae fringing the dorsal fin and bordering the gill vents of the adult, and at the tip of the male genital papilla. Elsewhere on the head, body and fins they are present but more scattered, which appears to be the condition also in adult anadromousLampetra fluviatilis. There are differences in the number and dimensions of the microvilli found on oligovillous cells, but each is supported by a stout core of actin filaments extending a variable distance down into the cytoplasm. Under the apex of the cell there are microtubules and numerous vesicles which are thought to be concerned in the renewal of the membrane on the microvilli. Beside and proximal to the nucleus is a system of channels of rough endoplasmic reticulum, and a stack of membranous cisternae which appears to have been derived from the endoplasmic reticulum. A nerve fibre is associated with the base of the cell which is indented by a spur‐like process from the neurite. Typical “synaptic vesicles” are not found in the cell but irregular vesicular or canalicular profiles are associated with the cell membrane adjoining the neurite spur. The space between the cell and neurite membranes contains extracellular material with a characteristic appearance of prickle‐like densities on the cell side meeting densities on the neurite membrane. Variations in the cytology of oligovillous cells can be explained in terms of a cycle of development and de‐differentiation. Certain cells with vesicles throughout the cytoplasm and with a narrow apex without microvilli are interpreted as degenerate examples. The oligovillous cells are thought to be chemosensory

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02102.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

There is much variation in the extent of tracheation of the wings of adult Lepidoptera. This is surveyed. Significantly more tracheal branching is found in species with pupal cocoons. No correlation of tracheation with wing length is apparent. The concentrations of oxygen and carbon dioxide in the air inside cocoons ofAntheraea pernyiGuér. (Saturniidae) before emergence are measured. Oxygen supply is probably not limited by the cocoon. Respiration rates per unit mass of wings ofA. pernyiare similar to those of the whole, resting adult. The possible adaptive significance of this tracheation and its variation is discussed

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02103.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

For the first time rickettsia‐like micro‐organisms are illustrated infecting most tissues of second‐stage juveniles ofGloboderu rostochiensis. They were seen only inside host cells, except for the few degenerating forms in the intestinal lumen. They were most common in the non‐contractile (sarcoplasmic) region of body wall muscles. A study of the oesophageal glands of the nematode suggested that micro‐organisms present within these glands would be unlikely to pass out of them and that the nematode would not act as a vector of these micro‐organisms to its host plants. No micro‐organisms were found in the genital primordia of the nematodes. Stored, hatched juveniles appeared to contain more microorganisms than newly hatched juveniles, indicating an increase in the intensity of the infection subsequent to hatching. No obvious signs of pathogenicity were observed in the nematodes. Uninfected juveniles apparently live longer than infected onesin viro, probably because infected juveniles exhaust their lipid reserves sooner than uninfected juveniles. The possible effect of the micro‐organisms on their nematode hosts and their potential as biological control agent

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1983.tb02104.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY