摘要:

The occurrence, size and maturity changes ofEubothrium crassum(Bloch) have been studied in smolts and adultSalmo salarL. andS. truttaL. of the River Exe and other Devon rivers. Adult parasites are found only in salmon and sea trout migrating up river to spawn, and range in size from small and immature to large and mature, though rarely gravid, worms. It is concluded that they are acquired and only become fully mature in the sea and gravid worms are lost on or before arrival in the rivers. During the upstream migration of salmon there is a selective loss of larger and more mature parasites and the survivors do not increase in length or mature, due to the intestine becoming a progressively more unfavourable habitat as the period of fasting continues. As few salmon return to the sea, most parasites in fresh‐water die before breeding. In sea trout, which feed in fresh‐water, parasites continue to grow and probably mature on return to the sea. It is suggested that parasites found in adult Atlantic and Pacific salmon in rivers are rarely, if ever, the same worms that are carried to sea by smolts but are of marine origin and are residues of a marine life cycle, and that two biological races ofE. crassumexist, a marine and a fresh‐wate

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01684.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

Twenty non‐metrical variants are described in the skulls of Grey seals (Halichoerus grypus). Ten of these have been classified in samples of 47 skulls from Orkney and 18 from the Hebrides. The frequencies of one variant were “significantly” different (P≏1%) in the two samples. This result means that there is some genetical distinctiveness between the two samples and suggests a way of characterizing and hence comparing seal

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01685.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The display of the Standard‐winged nightjar is described and figured. In display flight of the male the “standards” (the greatly elongated second primaries) are lifted nearly vertically above the wing, and it is probable that this is achieved aerodynamically as well as muscu

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01686.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

This two‐year study of the breeding and moulting cycles of a small bird,Pycnonotus goiavier, was made on Singapore Island, which is near the equator and has a very uniform climate. There are well‐marked breeding and moulting seasons in the population, and it is suggested that these protein‐demanding processes are timed to occur within the period of increased insect abundance in the first half of the year. Seasonal changes in the weight of the flight muscles indicate a cycle in the protein level of the body. This cycle might serve as an internal regulator of the reproductive

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01687.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The Indian gerbil,Tatera indica(Hardwicke) has been successfully maintained under laboratory conditions for 18 months, during which time over 250 vaginal cycles were recorded and 30 litters were born. Under laboratory conditions this animal had four‐to‐five‐day oestrous cycles and sterile mating induced a ten‐day pseudopregnancy. Anoestrus was not infrequent and was characterized by the absence of corpora lutea and large follicles from the ovaries and the atrophy of the uterus.The mean length of pregnancy was 22.3 days (range 18–30 days) and the litter size varied from two to seven young (mean 4.76 young). Mating at the post‐partum oestrus resulted in delayed implantation if a litter of three or more young was being suckled. Under these circumstances pregnancy lasted 36 days (range 34–40 days).Implantation was interstitial and mesometrial. The chorioallantoic placenta was discoidal, labyrinthine and haemochorial probably becoming haemoendothelial just before term.Daily injection of ovine prolactin inhibited the occurrence of oestrus and caused enlargement of the corpora lutea in three of five animals. It is suggested that prolactin might be the luteotrophic hormone in

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01688.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The examination of bovine bone samples from prehistoric and medieval settlements may be undertaken for both zoological and archaeological information. Interpretation of samples displaying bi‐ or trimodalism however, has been hindered by the absence of modern comparative material from animals of known age, sex, breed and plane of nutrition. Two such modern samples have been collected and their metrical attributes described, prior to a consideration of their relevance to the problems encountered in interpreting prehistoric bone sample

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01689.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The reproduction of the possum,Trichosurus vulpecula(Kerr), was investigated on Banks Peninsula, Canterbury, from 1963 to 1965. The majority of births occur in the autumn, but there is a minor breeding season in the spring. After undergoing an anoestrous period during the summer most females enter oestrus around April. A small proportion of females give birth to a second young during September or October. Reproductive periodicity was also found to occur in the male possum. Although spermatogenesis continues throughout the year in the sexually mature animal there is a marked change in the size of the prostatic urethra at particular periods of the year which correspond to those in which the majority of females are undergoing oestrus. The mean weight of the prostate shows a sixfold increase during the autumn. However only very small changes take place in the size of the testis and epididymis. Changes in size and activity of the prostate correspond with marked changes in the interstitial tissue of the testis. Leydig cells, responsible for the secretion of testosterone, show a great increase in number in animals in which the prostate is enlarged. Associated with the growth of the prostate are changes in the behaviour of the possum. The body weight and fat deposits of the male possum drop markedly at the time of the autumn breeding season.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01690.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

Planaria torvawas described originally by O. F. Müller in 1774 under the generic nameFasciola.The synonyms arising since have been critically evaluated and the many varied morphological descriptions of this species are reviewed. The identity of this species in Britain has been confirmed by detailed examination of external and internal anatomy and it is shown thatPlanaria torfrida, described from Britain by Perkins (1928), is a synonym ofPlanaria torva. Dugesia lugubris(Schmidt, 1862) is the species most likely to be confused withPlanaria torvaand convenient methods of separating these species are described. The validity of all available British records has been examined and new localities described.Planaria torvaoccurs in England, Scotland and Ireland but has a markedly discontinuous distribution. There are real concentrations of habitats in the Edinburgh and Glasgow areas where the species also forms a larger proportion of the triclad population than usual. The species is markedly eurytopic and occurs in a wide range of lotic and lentic habitats, although most of them are calcium rich by British standards. It is not yet possible to offer a sound explanation for these facts because the ecology ofPlanaria torvais insufficiently known

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01691.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The eruption and wear of the cheek teeth of male Fallow deer from a park and wild population has been studied for age determination purposes. It was found possible to age accurately up to 48 months animals whose date of death was known, whether they were from a wild or park population. It was found that up to at least this age individual and environmental differences affecting animals born in successive years did not mask those resulting fromthe restricted seasonal breeding of this species.Antler development and body weight were studied in relation to the ages obtained and were found to be of limited value for age estimation.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb01692.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY