摘要:

Deroceras caruanae(Pollonera 1891) possesses an endogenous cycle of activity and inactivity entrained by the cycle of night and day.D. caruanaeremains inactive on the undersurface of experimental feeding panels during daylight hours and as dusk approaches undertakes a phase of crawling bringing it into contact with food on the upper surface of the feeding panel at night. As dawn approaches, the slugs retire to the undersurface of the panel. In total darkness, the slugs lose their normal rhythm of light and dark regulated phases of activity and inactivity. The rhythm is retained (albeit out of phase with slugs experiencing a normal light‐dark sequence) in constant illumination. The relative feeding rates ofD. caruanaehave been correlated with this cycle of activity and inactivity.Structural and functional changes in the organs of digestion, notably the digestive diverticula, have been correlated with the cycle of night and day, the cycle of activity and inactivity and feeding. The digestive tubules undergo a sequence of cytological changes over the course of 24 hours that primarily involves the digestive cells. These cells absorb and intra‐cellularly digest food in the hours of daylight and in late evening commence–and at night complete–a process of breakdown releasing fragmentation spherules and excretory concretions into the stomach. The fragmentation spherules, by the release of unused intra‐cellular enzymes, possibly assist in the primary extra‐cellular digestion of food in the crop on the next feeding cycle.The digestive diverticula comprise three cell types; digestive cells, calcium cells and thin cells. The function of these cell types is discussed and the structure of the digestive diverticula ofD. caruanaecompared with that of other pulmonates.Finally a co‐ordinated scheme of the processes of activity and inactivity, and feeding and digestion is constructed showing how such processes are inter‐related and affected by environmental variables; most notable among these is the cycle o

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03938.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Three hundred and twenty‐twoClethrionomys glareolusfrom 17 localities in England, Wales and southern Scotland were typed for haemoglobin and two phenotypes were discovered. They have been designated HbS and HbF. The latter is more electronegative at physiological pH. The nature of the molecular difference between the phenotypes was examined and it was concluded that HbF polymerises more readily than does HbS. Haematological investigations showed that although the red cells of animals with HbF contain more potassium, thereby ensuring electrostatic neutrality, there has not been concomitant dilution of the cell contents. It is suggested that the osmotic stress imposed by this high concentration of particles might be reduced byin vivopolymerisation of haemoglobin. HbS was found to predominate in the north of Britain and HbF in the south. As none of the populations sampled contained animals of both types, it is not yet known whether there is a north‐south cline in haemoglobin type, or a sharp disjunct

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03939.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The principal bones, muscles and tendons of the legs have been measured in a selection of running birds, ranging in size from 0–1 kg quail to 40 kg ostrich. Maximum stride frequencies of the same species have been determined from films. Allometric equations have been derived. Most of the exponents agree well with McMahon's (1973, 1975a) theory of elastic similarity, which is discusse

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03940.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Ostriches have been filmed running fast in their natural habitat. A female ostrich has been dissected and the principal bones, muscles and tendons in a leg have been measured. It is calculated that stresses up to 240 kN m−2and 40 MN m−2, respectively, act in the digital flexor muscles and their tendons during running. Tensile and compressive stresses up to about 70MNm−2and 110 MNm−2act in the tibiotarsus. A large proportion of the energy which would otherwise be required for running is probably saved by elastic storage in tendons. Comparisons are made with the legs of flying birds and of an

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03941.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

As the Crocodilia are the only non‐mammalian vertebrates with tooth sockets, the attachment tissues of the teeth were studied inCaiman scleropsmainly at the ultrastructural level and were compared with those of mammals. All three attachment tissues (alveolar bone, cementum and periodontal ligament) in the Caiman showed both similarities and differences with their mammalian counterparts. Highly organized, lamellated structures, probably representing specialized sensory nerve endings were observed within the Caiman ligament. No such structure has ever been described in the mammalian ligamen

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03942.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

In some areas of the Red fox's range, such as northern Sweden, the number of yearling vixens which breed each year is dependent on food availability, and in years of poor food supply a high incidence of barren yearling vixens may occur. But most previous studies on Red fox reproduction record an overall low incidence of barren vixens, and it has therefore been assumed that most vixens breed in their first year. The present study shows that in suburban London, an area of high fox population density in which food availability is not limited, 52% of yearling vixens fail to breed. Possible reasons for this are discussed. It is also shown that senescence reduces the reproductive capability of vixens in their fifth and sixth breeding seasons.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03943.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Recent collections of the primitive bullomorph,Colpodaspis pusilla(Gastropoda, Opisthobranchia), have provided material for an anatomical investigation and the redefinition of the genus. A full description of a new species from the Indian Ocean is included and the relationship ofColpodaspisto other bullomorphs discussed.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03944.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The alimentary system, reproductive system and central nervous system ofHermaea variopicta(Costa) are described for the first time. Its gut resembles that ofHermaea bifida(Montagu), type species of the genus; the radula is considered in detail. Its diaulic reproductive system is described in morphological and functional terms. The central nervous system has three ganglia on the visceral loop. The anatomical evidence supports the opinion of Lemche&Thompson (1974) thatHermaeopsisCosta, former genus ofH. variopicta,should be discarded. However, the division of the genusHermaeainto two subgenera,HermaeaandPlacida,is not recommended.H. variopictaappears to be more primitive thanH. bifida.In the discussion, the origin of hermaeid and stiligerid lines from a common ancestral stock is suggested, to which is added a new theory of the evolution of stiligerid penial styles.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03945.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Otter faeces were collected at monthly intervals from around two lakes near the River Dee in Aberdeenshire in 1975 and 1976. They were analysed to show the frequency of occurrence of identifiable undigested items and also the relative bulk of these different items. Statistical differences were recorded in frequency of occurrence. The main food was eel in both years with small perch also important in January to June and amphibia in the spring. A reduction in the frequency of eel in the faeces was associated with fewer observations of otters.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03946.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

In Britain since the late 1940s, the Sparrowhawk (Accipiter nisus) and Peregrine(Falco peregrinus)have laid eggs with unusually thin shells. DDT and its metabolites have been blamed. This paper reports how various properties of modern shells differ from those of older shells of normal thickness.For the shells of both species, there were roughly proportional reductions in thickness of the two main component layers, the mammillary and palisade layers, suggesting that thin shells resulted from a decreased rate of deposition. In addition, in modern Sparrowhawk shells, the resistant surface layer was especially deficient perhaps due to a further reduction in deposition rate or to slight premature termination. Shell thinning was associated with a proportionately greater decrease in shell strength. For the Peregrine, porosity, measured as the rate of passage of water vapour, was lower for the thin shells than for normal shells. This difference could not be explained by a change in the area of the pore channels, since the modern shells did not have fewer pores and the pore channels were the same size and shape in the two samples of shells. However, in the thin shells of both species, mammillae height increased relative to mammillary layer thickness, and in the Peregrine shells the extent of this increase was related to the change in porosity.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03947.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY