摘要:

In the egg shells of Rhea sp. there are grooves on the surface and it is into these grooves that one or more pore mouths open.Five egg shells ofRhea americanaand four ofRhea darwiniiwere studied in detail in respect of the numbers of pore mouths and the number, length and orientation of the grooves. It was found thatR. americanahad nearly twice as many pore mouths and grooves as hadR. darwinii.Their distribution in both species showed more and longer grooves and more pore mouths in the equatorial regions than in the polar regions of the shell. The grooves were also found to be approximately longitudinally orientated in the equatorial regions but this orientation became less marked towards the polar regions. Not surprisingly longer grooves tended to have more pore mouths than did shorter grooves, but, in addition, broader grooves were associated with greater length too.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03369.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Octopus vulgarisdrills shelled molluscs and measurements showed the radula to be too large to reach into the depths of the holes made. Small teeth were found on the salivary papilla and its seems likely that these are used for excavating the deeper parts of the holes and penetration of the shell.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03370.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Growth rates, mortality and parental care of nestling sparrowhawks were studied in southwest Scotland. Ae Forest was a conifer plantation 200–400 metres above sea‐level, while the Annan valley consisted of farmland, woods, and small plantations on low ground.Nestling sparrowhawks were measured daily from hatching for 21–24 days. Weight, tarsus length and outermost primary feather length were recorded. Nestlings could be sexed by the age of 16 days from the larger size of females, which were significantly heavier than males at one day, had longer tarsi at nine days, and longer primaries at 18 days. Growth rates were calculated using linear regression over standardized periods of about 10 days.Growth rates were independent of brood size, and were negatively correlated with hatching date in one area. Hatching order and growth rate were correlated within broods. The greatest differences in growth rates were found between zones of Ae Forest, and between forest and valley.Twenty‐one per cent of nestlings over two days old died. Causes of mortality were starvation, wet weather, predation and desertion. Most of the mortality occurred in parts of Ae Forest remote from valley woodlands.The presence or absence of the adult female was noted on nest visits. When habitually brooding, until the young were 11 days old, the hen was present on about 85% of visits. By fledging this figure fell to 66% in the valley, and to 32% in the forest.The development of sexual dimorphism is discussed; females gained weight and body size faster than males, which developed various skills sooner.It is suggested that differences in growth rates between parts of the study area were related to food supply. Poor growth rates, high mortality, and lack of parental care all occurred in areas which were remote from sources of abundant prey, as measured by song‐bird

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03371.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Female Spotted hyaenas mimic the male in the possession of a peniform and highly erectile clitoris and false scrotum. Sex hormones have been assayed in the blood plasma, gonads and adrenal glands of male and female Spotted hyaenas and in the blood plasma of Striped and Brown hyaenas. Although the testicular concentration of testosterone greatly exceeds that of the ovaries in Spotted hyaenas, there is no significant difference between the sexes in the mean plasma levels of this hormone, or of the other androgen assayed, andro‐stenedione. In contrast, male Brown and Striped hyaenas have far higher plasma concentrations of testosterone than females.Testosterone levels in twin female Spotted hyaena foetuses were similar to the mean for adult females and it is suggested that high foetal androgen levels are responsible for the appearance of the male sexual facies in adult female Spotted hyaenas. The high plasma androgen levels recorded in adult females may also be associated with their aggression and dominance of male

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03372.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Samplesof Lacerta dugesiiwere collected on the Madeiran islands, measured and scored for number of scales in seven scale rows. Body length is related to age. Scale number varies between the island groups but does not appear to decrease in variance with age. Relative leg length declines in variability with age and varies significantly from one sample to another on Madeira.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03373.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The twenty‐four hour activity cycle of captive coypus was investigated by direct visual observation, automatic recording and by measuring the amount of faeces eliminated at hourly intervals. Coypus were active from just before sunset and the “Zeitgeber” or cue for activity onset may be declining light. The activity period usually ended before sunrise and the interval between the end of the period and dawn was inversely related to temperature. The animals fed and defaecated throughout the active period and 80–86 % of the faecal pellets were produced in water. Refection started shortly after the end of the feeding period, when the animals had returned to the nest, and continued until an hour or two after midday.A model is suggested which involves two passages of food through the gut and a cycle length of 24 hours from ingestion to defaecation. The feeding and defaecation periods were equal in duration, but the refection period was 40% shorter. Hypothetically this may be due to a caecum by‐pass mechanism during the second passage of food through the gut so that the defaecation period, like the feeding period, is controlled by the rate at which food passes through the pyloric sphincter. In contrast the period of refection may be controlled by the rate at which food remains are voided from the caecum. Coypus spent the pre‐dawn and daylight hours on nests and in contact with familiar conspecifics. These behaviours may have the function of temperature maintenance in the coldest part of the night and of avoiding diurna

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03374.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

A study of the Blue starfishLinckia laevigatain the Banda Islands, Moluccas, Indonesia, revealed 62% infestation by the molluscan prosobranch parasiteThyca crystallina.Infestation rate varies directly with the degree of water movement. A marked difference in settlement pattern according to parasite size is observed. The smallest limpets tend to settle on the upper surface of the distal parts of the arms and are randomly oriented. The largest parasites are found on the oral arm surface on the right hand side of the ambulacral groove and facing the starfish mouth. All of the attached parasites were female. Most of the large females had a dwarf male, one tenth the length, attached, under the mantle, at the anterior end. Amongst the small limpets, less than half had made a proboscis hole in the host integument and none had made an attachment disc lesion; of the large parasites 90% had the proboscis embedded in the host and 80% left an attachment disc lesion on the host. Small parasites can move very slowly over the host surface. Larger limpets are probably permanently attached. A detached parasite of any size is probably unable to reattach. There is evidence of an extended parasite breeding period and repetitive settlement on the hosts, which could cause the observed overdispersion without invoking a mature female parasite pheromone.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03375.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Nilaparvata lugens(Stål) andSogatellafurcifera(Horvath) found in light trap samples at Titi Serong Padi Experimental Station, Parit Buntar, Perak, West Malaysia, between 1972–74, were stylopised byElenchussp. The types of changes caused by stylopisation to the secondary and tertiary sexual organs/characters are discussed. The sex of the specimens with extremely reduced secondary sexual organs is analyzed. The development of the male secondary sexual organ from the late fifth instar to a fully developed male is traced. The reasons why the secondary sexual organs of stylopised male Delphacidae are more reduced than females are outlin

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03376.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The adult Bluehead wrasse(Thalassoma bifasciatum)is a facultative cleanerfish that can change its colouration into any one of three: patterns. These patterns correspond to several modes of feeding behaviour which, in turn, can be correlated with the movements of host fishes. The barred pattern occurred on individuals that are far ranging and also on those that formed unstable cleaning groups. These groups tended to form at locations having sharp drops in depth of several metres. Here these groups serviced large groups of host fishes. The striped pattern occurred on solitary individuals with a limited home range. They occurred in very shallow areas and serviced small groups of host fishes. The bright yellow pattern developed when a large food source was discovered and may be related to the attraction of conspecifics.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03377.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Serial sections, injections with india ink and latex, and observations on fresh material, have been used to determine the pattern of blood circulation within the intestine of larval and adult lampreys. Attention has also been paid to resolving the variable terms previously applied to many of the blood vessels, and to the possible functional significance of the differences found between the two life cycle stages. In the larva, the main arterial supply to the intestine consists of a typhlosolar artery, while the venous return is comprised of a posterior and a left and right anterior intestinal vein that usually unite before entering the liver. Although a typhlosolar artery is also present in the adult, the main venous return of the ammocoete is replaced at metamorphosis by a newly formed typhlosolar vein. Moreover, in the ammocoete a considerable amount of blood is discharged into the haemopoietic sponge‐work of the typhlosole and the arterial supply to the intestine is poorly developed. By contrast, the typhlosolar sponge‐work is lost in the adult and a more efficient arterial supply is developed within the lamina propria of the various intestinal regions. Furthermore, vascular couples are developed in the adult which facilitate the flow of blood in opposite directions in the intestinal wall. Since, during both life cycle stages, the arterial blood passes into tissue spaces, there is no true capillary network in the intestine and no evidence was found for the presence of a lymphatic system. It is suggested that the changes which take place in the intestinal blood supply and the internal structure of the gut during metamorphosis result in improvements both to the vascular system and to the assimilation efficie

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03378.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY