摘要:

All epifaunal and shallow‐burrowing, intertidal macrofauna on an exposed sandy beach appear to undergo tidal migrations which vary in extent but are all upshore on the incoming tide and downshore on the outgoing tide during day and night. In the crustaceans this is probably endogenous rhythmic behaviour and they show increased activity at night. In the molluscs this movement is not synchronised by an intrinsic mechanism but results from behavioural responses to changing physical conditions. The large wedge clam,Donax serra,shows no tidal migrations but does show a semilunar rhythm of movement from just above mean tide level (MTL) during springs to the low tide level during neap tide

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03379.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Fixation of trout gills with different concentrations of glutaraldehyde has shown that the more concentrated solutions (25%) tended to produce clearer material for inspection under the scanning electron microscope. All gradations in surface sculpturing, from microvilli to microridges of about 13– 7–0 μm length have been observed, and their distribution on different parts of individual secondary lamellae is described. The possible significance of the types of sculpturing and their distribution is discussed in relation to the likely pattern of water flow across the secondary lamella during gill ventila

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03380.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Three types of the A‐neurosecretory cells (NSCs) were found in the pars intercerebralis (PI) of the adult brain of four species of tsetse flies(Glossina palpalis, G. pallidipes, G. austeniandG. morsitans).The typical formula of their composition is: 8 A1‐, 14 A2‐ and 4 A3‐cells. After permanganate oxidation, the neurosecretory materials (NSMs) of Al‐ and A3‐cells are rich in strong acid groups. The A2‐NSM contains both strong and weak acid groups after this treatment; besides, it retains a weak affinity to acid dyes. In addition to the A‐cells, the PI ofGlossinaspecies seems to include a number of NSCs of the type B.The data obtained indicate a great similarity of the NSC composition in the PI ofGlossinaand other related higher dipterans.In addition to the NSCs, giant neurons and particular cells with large cytoplasmic inclusions were also found in the PI ofGlossina.The cells with large cytoplasmic inclusions correspond apparently to vacuolated cells previously observed in the brain of some flies. It is suggested that the considerable complication in reproductive biology which took place in tsetse flies had no effect on the composition of the NSCs in their PI when compared to that in related species with more ordinary cycles

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03381.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Seven different measurements of fox skulls from animals of known sex were recorded for 571 fox skulls from Wales and South‐East England. A multivariate technique, discriminant function analysis, is used to classify the skulls according to sex and regional origin. Differences detected suggest that male skulls tend to be larger, and that skulls from Wales are larger than those from South‐East England. The classifications are presumed to reflect true differences between sexes and regi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03382.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The literature of mammalian splanchnology contains but a single reference to the tonsillar morphology of the Rhinocerotidae, viz. Owen's (1852) cursory description of the faucial (palatine) tonsil in an Indian rhinoceros{Rhinoceros unicornis).Herein a fuller account is given of the tonsillar formations present in the lateral food channel of another Indian rhinoceros specimen and of specimens of the Sumatran rhinoceros(Didermocerus suma‐trensis),the African White rhinoceros(Ceratotherium simum)and the African Black rhinoceros(Diceros bicornis).Attention is drawn to the invariable presence of tonsillar tissue in the rhinoceros pyriform fossa and to its frequent manifestation therein as an anatomically discrete and hitherto unrecognized organ, the laryngopharyngeal tonsil. This structure, functionally supplementary to the faucial tonsil, would appear to develop independently from the lympho‐thymic primordium of the embryonal third pharyngeal pouch. Its anatomy is described and its morphological significance is discus

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03383.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Lyonsia hyalinaConrad possesses “radial mantle glands” of a complex structure located deep within the periostracal groove. They occur along the mantle edge in alignment with slightly raised striations of the periostracum, are deeply staining and are composed of three cell types. Secretory and supportive cells, which are flask‐shaped, alternate throughout the gland, while a third cell type is ovoid and borders the gland. A sulfated mucopolysaccharide is secreted over the periostracum by the glands and functions in adhesion of sand grains to the

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03384.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The scorpion,Paruroctonus mesaensis(Vaejovidae) has seven instar stages and moults six times. There is no post‐reproductive moult. The average growth ratio between successive instars is 1–38. The average rate of weight increase is 000249/day. This rate fluctuates seasonally: it is highest in spring and lowest in winter and summer. Growth rate is a function of ambient burrow temperature and prey abundance. Body size is determinate. The growth rate of the pectines is significantly greater in males as compared with females. Analysis indicates that the pectines are a secondary sexual trait in males.Animals mature from 19 to 24 months of age. Matings were observed from May through October. Gestation lasts 10–14 months. First surface appearance of newborn (instar II) is synchronous throughout the population and occurred in early August for five consecutive years. Some females were observed to be gravid for at least three consecutive years. Gravid females carry an average of 48–8 embryos. However, on the average only 19–9 young/female survive to appear on the surface. Factors which may be responsible for this observed decrease include resorption of embryos; death at birth, eclosion or first moult; and maternal and sibling cannibalism. The influence of various environmental factors on reproduction were analyzed. The number of newborn appearing on the surface and the population biomass of newborn showed a high positive correlation with precipitation and vegetat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03385.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The mechanics of feeding inSalmo gairdneriandHoplias malabaricus,two generalized predaceous teleosts, was studied using high‐speed movies (200 frames per second). InHoplias,the feeding mechanism is characterized by an extreme anterior swing of the maxilla and rapid depression of the hyoid occurring synchronously with mandibular depression and neurocranial elevation. A similar feeding sequence is observed inSalmoalthough the movements of the head are neither as extreme nor as rapid.The anterior swing of the maxilla, usually attributed to mandibular depression, increased when the ligamentous connection of the maxilla to the mandible was severed. A mechanical model of the jaw was constructed to elucidate the functional interrelationships of the neurocranium, maxilla and mandible.Films of the “holostean”Amia calvafeeding show that the feeding mechanism is of a fundamentally different nature than that of primitive teleost fishes. Extreme anterior swinging of the maxilla occurs synchronously with jaw opening but branchiostegal expansion and hyoid depression only reach a maximum well after the jaws have begun to close. The existence of a highly efficient levator operculi—opercular series—mandible coupling is hypothesized on the basis of the rapid initial jaw opening.This pattern of feeding movements inAmiahas necessitated a revision of current theories on the nature and significance of the

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03386.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY