摘要:

Sexual dimorphism of tympanate auditory systems in insects has bees described in only a few taxonomically isolated cases. However, widespread sexual dimorphism occurs in the ultrasound‐sensitive, midline ear of the praying mantis.In dimorphic species, it is always the female mantis that shows a reduction in ultrasonic hearing. The dimorphism may be mild—a difference in tuning and small reduction in sensitivity—or extreme with no evidence of audition in the female. In all but the mildest cases, the reduction in hearing is accompanied by significant anatomical divergence from the male ear structure. Two distinct metathoracic groove (‘ear’) types are linked to hearing reduction in the females.Anatomical evidence of auditory sexual dimorphism appears in 34% of the 183 mantis genera examined. The dimorphic genera are widely but non‐uniformly distributed within three of the four largest mantis families.Auditory sexual dimorphism is closely correlated with dimorphism in wing length. In general, mantises with functional wings have sensitive ultrasonic hearing while those with short wings do not. These findings support the hypothesis that ultrasonic hearing in mantises is part of a defensive system against attack by echolo

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04017.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Habitat use and foraging behaviour of resident merlins(Falco columbarius)wintering in Saskatoon, Canada, were studied over a five‐year period. Birds were trapped through the winter and selected individuals fitted with radio transmitters to monitor continously their location, movements and activities from roost departure until re‐entry. Merlins maintained individual home ranges in winter, with extensive overlap between neighbouring birds in some cases. Yearling home ranges were not significantly different in size from those of adults. The winter home ranges of adults were closely associated with their previous nest site. Both adults and yearlings made significantly greater use of Residential habitat in the city than expected based on the area available in their home ranges. However, while adults remained largely in the two oldest habitat types, yearlings were also found in more recently built areas of the city. Home ranges held within the city were sometimes combined with foraging areas in the adjacent countryside. The use of foraging areas in farmyards and cattle feedlots outside of the city was most notable in adults, although some yearlings apparently learned this strategy in their first year. Merlins also used Commercial‐Industrial habitat for hunting at levels much higher than expected from its availability in their home ranges. Diets in summer and winter had a high degree of overlap; house sparrows(Passer domesticus)and bohemian waxwings(Bombycilla garrulus)made up a large proportion of the diet during both seasons. Hunting activity peaked at 09:00 and 16:00 h, reflecting the replenishment of energy stores lost over‐night, and the storage of energy in preparation for the next over‐n

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04018.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The Central AmericanLoxocemusand the pythons are assigned to sister subfamilies Loxoceminae and Pythoninae, within the weakly characterized family Boidae. They share the character of the left cerebral artery foramen being larger than the right. Within the Henophidia, paired subcaudal scales associate these subfamilies withXenopeltisand the Uropeltidae.Twenty‐nine discrete variables were coded as 52 binary characters. Nine continuous (meristic) variables were examined. A method is described by which 18 binary characters were selected from seven of these variables, for inclusion in the data set. WithLoxocemusandXenopeltisas outgroups, the data were analysed by a compatibility method. The Pythoninae are resolved into tribes Pythonini and Moreliini on the basis of complementary synapomorphies. The Pythonini have only the genusPython, for the African and Asiatic species, includingreticulatusandtimoriensis.The Moreliini have all of the Australasian species, in two genera:AspiditesandMorelia.A phylogenetic analysis of the two tribes is presented, with incomplete resolution of the Moreliini. The two tribes overlap in the areas of the Moluccas and Timor. It is postulated that:Loxocemusplus Pythoninae represent a Laurasian stock; south‐east Asia was the primary centre of radiation of the Pythoninae; by the Miocene dispersal to Australasia had occurred, where there was a second radiat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04019.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

It is shown experimentally that diet composition affected the sizes of several digestive organs in juvenile rabbits collected from the wild. Stomach weight, small intestine volume and colon length were larger in rabbits reared on diets higher in fibre. Small intestine weight, however, was lower.Analysis of natural variation in wild adult rabbits showed that all digestive organs (except for the appendix) were larger in rabbits living on chalk soils than in those living on sand or clay. Seasonal variation was more marked in males than in females, probably because of the sexes' different breeding requirements. Thus most male digestive organs were smaller between December and June than at other times of year. Female digestive organs did not show this pattern, and were largest in May/June, when the demands of pregnancy and lactation are highest. However, food quality may have been important too. Food quality is probably highest in April, and most digestive organs were then smallest (both sexes). The dry weights of stomach and small intestine did not fit these patterns. Stomach weight increased with the presence of the nematode parasiteGraphidium strigosumand small intestine and caecal volumes with the presence of cestodes. Numbers of nematodes(Trichostrongylus retortaeformisandPassalurus ambiguus)in the caecum or colon, however, had no effects on organ sizes.Data are presented on variation in intensity and prevalence of these helminth parasites with season and soil type.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04020.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

OttersLutra lutrain Shetland feed almost exclusively in the sea. Their diet was assessed from direct observations of 13, 313 dives, of which 27% were successful, and 2028 prey could be identified. The results are compared with published data on the availability offish for different seasons, time of day, state of tide, and different types of coast. The most frequently taken prey was eelpoutZoarces viviparus(34%), but they were relatively small, and rocklingsCiliata musteladominated the diet in terms of biomass (18%, against eelpout 15%). Small eel‐shaped, bottom‐living species dominated in the diet at all times, but of those, otters took the larger fishes in the populations (median weight of prey 28 g). The size and species composition of prey of males was the same as that of females with cubs, but females without cubs took smaller fish.In spring, prey was smaller than at other times, and otters were least successful when diving. Diving success and mean prey weight was highest in winter, although prey availability was highest in summer.Eelpout were caught mostly along sheltered coasts, rocklings in more exposed areas. It is argued that for optimal exploitation of the seasonal availability of different species of prey, otters need to use different types of coast, and the size of their ranges would be related to the spacing of coastal types.Most fishes were caught in daytime, and around high tide otters fed less than at other times; hunting therefore took place during periods of inactivity of prey. For the main prey species,Ciliata mustela, it was estimated that otters took a substantial part of the total populat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04021.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Observations were made of the early differentiation of the gonad in the grey short‐tailed opossum,Monodelphis domestica, using light and electron microscopy. An investigation was made also of the effects of neonatal treatment with oestradiol benzoate on sexual differentiation.Neonates were removed from the nipple at various times after birth (0‐14 days), killed and karyotyped to determine the genetic sex. Some individuals were then fixed in buffered formalin, embedded in paraffin and prepared for light microscopy. Alternatively the mesonephri and gonadal anlagen were dissected free of tissue, fixed in buffered 2.5% glutaraldehyde and prepared for electron microscopy. Twenty‐two offspring from nine litters were examined.At birth, pups were sexually undifferentiated and had rudimentary indifferent gonadal anlagen. By three days after birth, the gonad rudiments of males exhibited the first formation of sex cords with the coalescing of presumptive Sertoli cells. The sex cords of males were well defined by six days. By contrast, the gonads of female pups failed to display defined sex cords up to two weeks after birth.An unusual feature was the initial appearance of a scrotal bulge in males as early as two days after birth, thus preceding any obvious morphological gonadal differentiation.In all 34 pups were coated with oestradiol (1‐2 μg per application) for various lengths of time. Some individuals were allowed to reach maturity so that growth rate and sexual behaviour could be studied.Oestradiol treatment had a profound effect on male neonates, but no apparent effect on female neonates. Testis development was inhibited with the failure of the rudimentary gonad to form sex cords. With the exception of near‐normal scrotum development, external and internal genitalia were completely feminized. Treated males allowed to reach maturity had growth rates similar to control females and exhibited oestrous behaviour in the presence of a control male.The results suggest that gonadal differentiation in marsupials can be profoundly influenced by exogenous hormone. The early development of a scrotal bulge, preceding morphological differentiation, and the lack of an effect of oestradiol on scrotal formation would indicate that the differentiation of this somatic tissue may not be dependent on gonadal det

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04022.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The sequence of tooth wear was determined from skulls of fallow deer of known age. A system for scoring molariform tooth wear has been devised so that small but readily recognizable wear changes of the individual cusps may be recorded and used to assess the age of animals of unknown birth dates. The technique can be readily adapted for other ruminant species with the appropriate database.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04023.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04024.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY