摘要:

Recoveries and sight‐records were made from 2700 Upland and 470 Ruddy‐headed geese marked in the Falkland Islands between 1977 and 1980 in order to describe the movements of these island populations. First‐year male Upland geese tended to be sighted further from natal areas than first‐year females, once independent of their parents. Second‐year Upland geese were sighted further from shedding sites than adults throughout the year. This age‐related difference was also found for Ruddy‐headed geese in spring. Breeding adults of both species were rarely sighted more than 5 km from their territories. Upland adults moved furthest from their breeding territory during Sate summer and autumn. Significantly more long‐distance (over 20 km) movements were recorded for Ruddy‐headed geese compared with Upland geese, and were mostly carried out by geese in their second or third year, for both species. The mobility of the geese makes attempts to reduce the population on certain pastures by cu

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05631.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Supernumerary upper second deciduous premolars and lower second molars are reported in lynx,Lynx lynx lynx(L.), from Norway at frequencies comparable with the situation reported from lynx populations in other countries. Other authors have interpreted these anomalies as true atavisms in response to altered environmental conditions, and consequently as being contradictory with Dollo's law. The author suggests an alternative interpretation of the appearance of supernumerary teeth, which brings such phenomena in line with Dollo's law and the recent modern synthesis of evolution.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05632.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Statocyst structure in representatives of each, as currently recognized, family of the bivalve sub‐class Anomalodesmata has been investigated.Three types are recognized—A, B and C. Type A is possessed only byPholadomya Candida, a representative of the ancient Pholadomyacea. Type C is found only in the Cuspidariacea. Type B, possessed by all other anomalodesmatans is divided, on the basis of statolith structure, into three sub‐types—B1, B2and B3.Type A statocyst is extraordinarily complex with a capsule penetrated by nerve endings and a multicellular statolith. Such a sophisticated structure is adjudged essential for a bivalve that is postulated to lie angled on its back in the sediment and to collect subsurface deposits via the pedal gape, using the foot as a suction piston.Type B statocyst comprises a large, multicellular capsule of ciliated cells as the sensory receptors. Variations in structure relate to whether or not there is a single, large, statolith (B1), a large statolith and other statoconia (B2), or numerous crystal‐like statoconia, one of which may be enlarged into a statolith (B3).Type C statocyst comprises a small capsule of but four or five cells in transverse section, each of which is swollen and lined by microvilli. A large, oval statolith is not freely mobile within the lumen and probably confers little fine orientation discrimination.It is concluded that statocyst structure has some phylogenetic significance, widely separating the Pholadomyidae from other anomalodesmatans and indicating that the Cuspidariacea may have a separate origin from the other deep‐water ‘septibranch’ predators. Type B3statocyst (crystal‐like statoconia) appears typical of the Clavagellacea, but is also possessed byMyadora striata.All other anomalodesmatans possess either Type B1or B2statocysts, and with so much variation between and within constituent genera, families and superfamilies, little adaptive significance is attached to form. All other bivalves investigated to date have a statocyst structure of Type B, this probably representing ‘primitive’ conditions. Earlier conclusions from studies of other bivalves that type B2or B3is more primitive than B1cannot be substantiated, because more comprehensive studies of these phylogenies may reveal a wider diversity of form than i

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05633.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

In seasonally breeding mammals, the hormone melatonin, produced at night by the pineal gland, is known to be important in transducing the effect of photoperiod in timing reproduction. In the Bennett's wallaby, an unimplanted unilaminar blastocyst is held in a state of seasonal diapause from mid‐winter to mid‐summer. Here we show that an implant of the hormone melatonin rapidly terminates seasonal diapause in this species. Blastocyst reactivation is not accompanied by a significant reduction in levels of the hormone prolactin, thereby refuting earlier suggestions that this hormone is responsible for maintaining seasonal embryonic diapa

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05634.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

PipistreUus mimusWroughton exhibits a clearly defined breeding season at Varanasi (25°N, 83°E). Morphological specializations of the Graafian follicles consist of a hypertrophied discus proligerus resulting in the reduced antral cavity, and post‐partum oestrus. The females appear to store spermatozoa in their genital tracts during November and December. Other interesting features associated with reproduction in this species are that the corpus luteum regressed soon after implantation and there is a very short period of lactat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05635.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Theropod dinosaurs and birds share a specialized ankle joint in which the proximal tarsal series. the astragalus and calcaneum is braced against the tibia by an ascending process. This feature has been used since T. H. Huxley's time (1870) to support the proposal that birds evolved from dinosaurs. However, according to Martin, Stewart&Whetstone (1980), the avian tarsus is not homologous with that of theropods. They argue that while the ascending process in theropods is continuous with the astragalus inArchaeopteryxand all later birds, it is an independent ossification associated primarily with the calcaneum. A preliminary study of tarsal ontogeny in birds (McGowan, 1984), undertaken to resolve this problem, revealed two developmental pathways, one exemplified in ratites and the other in carinates. The ratite condition corresponded to that of theropods, the bony ascending process being part of the astragalus, while in carinates the corresponding process was part of the calcaneum. The present study, based on more extensive material, reveals that, although the carinate process becomes associated with the calcaneum during later development, there is evidence that it originates as a cartilaginous process from the astragalus and is therefore homologous with the ratite condition. As the avian tarsus is homologous with that of theropods, and ofArchaeopteryx, it may be used to support a close phylogenetic relationship among them.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05636.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Although the avian furcula is generally regarded as a dermal bone, this view was challenged by Lansdown (1968a), who postulated that it is a cartilage bone. His reinterpretation was predicated upon histochemical data, derived from embryological observations made on the Japanese quail, and is deserving of further investigation as it bears importantly upon the interpretation of the homology of the furcula, and upon aspects of avian phylogeny and the origin of the flight apparatus.Employing the same investigative methods as Lansdown (1968a), together with additional techniques, his interpretations have been reconsidered and no support for his suggestions has been found. The furcula of the quail, instead, has the early developmental characteristics of a typical dermal bone and conforms with the developmental details seen in the chicken.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05637.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Geographical variation in male carcass weight, and sexual dimorphism in size was studied in 19 populations of Norwegian moose (Alces alces(L.)).Significant age‐specific variation in male carcass weight was found for all the populations studied up to the age of 4 1/2 years, but in some populations maximum weight was not reached until at least 5 1/2 years. Increase in the mean weight of females after the age of 2 1/2 years was not significant. Only a weak relationship existed between mean yearling and adult bull weights in a population. However, within both the southern (62°N) parts of the country, yearling carcass weight was a good predictor of adult bull weight in a region.Adult bull weight in a region was best predicted from the increment in mean carcass weight observed between 1 1/2 and 3 1/2 years of age. Within a region, variation in age‐specific carcass weight between cohorts of bulls from different years was also well predicted from annual variation in growth increment.Those patterns reveal a sexual difference in strategy of body growth. The adult weight of females is probably strongly determined by the weight gained by the time of onset of reproduction. The males have available a longer period for growth in body weight. They are therefore able to compensate for low weights early in life by increased gain of weight in later years, that provide good conditions for growth.Geographical variation in the degree of sexual dimorphism in size correlated only poorly with adult male size. We suggest that the sexual size‐dimorphism is a result of reproductive constraints of the female, i.e. in populations living in poor conditions and having small body size, the onset of reproduction prevents further gain in body

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05638.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Data on lion home range size, pride size, density, group size, cub survival, litter size and adult sex ratio were extracted from studies carried out in 10 habitats. The data were compared with five measures of food supply: mean prey biomass, prey biomass during the season of greatest abundance, prey biomass during the season of least abundance, biomass of middle‐sized prey species (i.e. those with mean adult live‐weights between 50 and 250 kg), and the mean size of carcasses fed on by lions. The results indicated that range size is inversely correlated with the abundance of prey during the period of least abundance, but not with overall prey abundance. Range size showed no consistent variation with pride size or with minimum metabolic requirements. Pride size (measured in terms of average number of animals per pride and average number of adult females) and cub survival strongly correlated with lean season food abundance. No relationship was found between group size or litter size and any of the measures of food supply Adult sex ratio did not vary consistently with food supply or lion density, although the data did suggest that prides inhabiting small, circumscribed reserves may experience less inter‐male competition and this, in turn, may affect the adult sex

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05639.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The structure of the mouthparts and foregut of some caraboid beetles has been correlated with their type of feeding mechanism. These may be adapted to fragmentary feeding, fluid feeding (where pre‐oral digestion is important), or to mixed feeding (a large category which ranges from a mainly fluid to a mainly solid intake). Head structures concerned with feeding have been discussed in relation to these methods; they include the mandibles, maxillae, labrum‐epipharynx and anterior foregut, proventriculus, labium‐hypopharynx and the head floor. Different types of head floor were denned in relation to gular structure, in particular the presence or absence of the mid‐gular apodeme. Convergent evolution of feeding mechanisms was noted amongst both fragmentary feeders and fluid feeders; in the latter group, sucking pumps have been evolved in the Carabitae,Scarites, Cicindelidae, Paussini and some other caraboids. It was suggested that head shape in caraboids may reflect locomotory adaptations more frequently than feeding adap

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb05640.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY