摘要:

The short‐acting muscle relaxant suxethonium (bis‐ethyl succinylcholine chloride) has been used successfully to immobilize a number of domestic and zoo animals. It has been compared with suxamethonium, and acute experiments were carried out to provide information on its mode of action at the neuromuscular junction in ruminants. The species for which an appropriate dosage to produce immobilization has been found are: sheep, goat, dog, pig, red deer, Formosan deer, and collared peccary. A simple field respirator is described for the emergency resuscitation of animals. The problems relating to the use of this type of drug are discus

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05211.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

A brief account is given of a field trial to immobilize wild red deer on the island of Rhum. The difficulties of estimating the weight of a wild animal, and the range and technical limitations of the apparatus are discussed. A number of deer were satisfactorily caught and marked and the potentialities of the method are described.

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05212.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

The placentation ofTupaiais of particular interest for two main reasons, first because of the suggested relationship of the Tree shrews (Tupaiidae) to the Lemuroidae—a relationship which has been much discussed and on which widely divergent views have been expressed—and second becauseTupaiais the only mammal so far described in which the foetus is provided with a double (so called bidiscoidal) placenta of the entothelial chorial type.The placental sites are easily recognizable in the virgin uterus as two localized areas of the endometrium, respectively dorsal and ventral, and characterized by the absence of uterine glands. On pregnancy supervening the endometrium of each site undergoes a marked decidual reaction forming the maternal component of (1) a temporary omphalopleural (yolk sac) placenta—the foetal component of which is furnished by the vascular omphalopleure—and of (2) the definitive allantoic placenta. The allantois growing down as a flattened lobe on either side and penetrating between the attached trophoblast of the vascular omphalopleure and its mesodermal and endothelial layers ensuring the replacement of the vitelline vessels of the vascular omphalopleure by the allantoic vessels and thus forming a relatively simple labyrinthine endothelio chorial p

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05213.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

The development of the gonad and the processes of sex differentiation have been studied in the ammocoete ofLampetra planeri, with particular emphasis on the mode of differentiation of the male gonads. After an initial undifferentiated stage during the first larval year, meiotic changes appear, particularly in cell nests, and from these germ cells and from isolated gonocytes, growing oocytes are developed. The initial phase of differentiation is regarded as a female stage, during which auxocytosis occurs on a variable scale in probably all gonads. This is followed in definitive males, by the degeneration of germ cells that have already differentiated in a female sense, either at the early meiotic prophase, or later in the cytoplasmic growth period of the occyte. Even in morphologically differentiated testes, meiotic activity and oocyte growth may be observed, although on a diminishing scale, throughout the greater part of the larval period. More extensive and synchronous atresia of growing oocytes may occur comparatively late in the larval period, giving the appearance of sex inversion. These cases are regarded as examples of abnormally retarded differentiation. Other presumptive male gonads are derived from gonads consisting predominantly of meiotic cysts, which have persisted beyond the age when auxocytosis is normally completed in definitive females. In some cases the future male gonad can be recognized at an early stage by certain morphological and histological criteria, irrespective of the condition of the germ cells. The views of Okkelberg (1921) and D'Ancona (1943, 1949) on the supposed existence of intersexual gonads have been discussed in relation to the quantitative analysis of gonad types. The author believes that the sexual indeterminacy attributed to these animals is illusory and that once differentiation has begun, its course and direction are irreversible. In male differentiation there is some evidence of renewed activity in the peritoneal epithelium of the gonad surface and it is suggested that the somatic elements of the testis may have some inductive effect tending to inhibit the further differentiation of bipotential germ cells in a female direction. No continuity exists between the undifferentiated cell nests of early stages and the cysts of germ cells in the mature testis. The former should not, therefore, be regarded as male elements in an hermaphrodite gonad. At early stages of differentiation, potential male ammocoetes are those in which the gonads are composed predominantly of meiotic cysts, or in which regression is taking place at various phases of oogenesis. The critical period for oocyte growth and for male differentiation occurs at lengths of 60 to 70 mm when the ammocoetes are at the beginning of their third year. From 50 mm upwards the proportion of female gonads consistently exceeds 50% of the total of all types. Analysis of ammocoete populations suggests that there is normally a slight excess of females, but that the sex ratios do not vary widely from one stream to another. No evidence has been found to suggest that environmental factors play any part in sex differentiation or that the sex orientation of the gonad is labile and indeterminate.

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05214.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

The development of the gonads has been studied in ammocoetes of the landlocked sea lamprey,Petromyzon marinus.Up to lengths of about 70 mm, the gonads remain undifferentiated: the germ cells proliferating to form first small groups and finally large cysts of germ cells. At lengths of 70 to 80 mm, over 70% of all gonads examined were of the cystic type. Measurements made on large numbers of animals at this stage indicate the presence of two distinct groups with smaller and larger gonads. These represent the future male and female gonads respectively. These size differences are thought to correspond to differences in germ cell numbers in the two sexes. In a few cases the sex of the gonads can be distinguished at lengths of 71 to 80 mm, but differentiation is not generally complete below lengths of 100 mm. Differentiation is preceded or accompanied in both sexes by the appearance of growing oocytes. The frequency distribution for oocyte counts in bimodal, the lower numbers representing the future male gonads. During auxocytosis and differentiation large numbers of germ cells undergo degeneration; the majority at the zygotene or pachytene stage. In definitive females, the surviving oocytes represent only 20 to 30% of the total number of germ cells in the cystic gonad. Oogenesis begins within the cysts which are broken up by the invasion of somatic elements. The presence of large cysts is therefore without relevance to the future sex of the gonad.The extensive regression of germ cells in the future male gonads results in an actual decrease in size during differentiation. The somatic characters that distinguish the earlier male gonads ofLampetra planeriare less developed inmarinus.In size and histological structure these often resemble the undifferentiated gonads of earlier larval stages. The male germ cells are derived from residual undifferentiated elements which survive the extensive regression at the cystic stage. At first the male gonads contain only a few isolated germ cells which proliferate slowly throughout larval life. At metamorphosis there is a very marked acceleration in the division of the male germ cells. Male germ cells retain their undifferentiated character throughout the larval period. In regard to the mode,of sex differentiationmarinusis more differentiated thanplaneri.This is supported by the existence of a sex dimorphism in gonad size (and probably germ cell numbers) preceding morphological and histological differentiation, and by the evidence of bimodality in oocyte numbers. The vastly reduced fecundity of the brook lamprey compared with that of the sea lamprey is associated with significant differences in the pattern and phasing of gonad development in the two species. Inplaneri, germ cell proliferation begins earlier than inmarinus, but is shorter in duration, terminating in auxocytosis and differentiation. This results in an enormous reduction in the total numbers of germ cells. Expressed as a percentage of the total numbers, the proportion undergoing regression during sex differentiation is thought to be similar in both species. The difference in the number of germ cells which survive as oocytes in the female gonads of the two species is thus a direct consequence of precocious oocyte development and the earlier curtailment of the gonial divisions in the brook lamprey ammocoete.

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05215.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Fifteen species are recorded, among which one subgenus, seven species and one “form” are described as new. The list comprisesXenylla crassipilasp. n.X. cf. yucatanaMills,X. (Paraxenylla) manglesubgen. et sp. n.Willemia brevispinaHüther,Onychiurus gambiariussp. n.Tullbergiacf.fovetaBonet.T. occidafricanasp. n.Pseudanuridacf.bogoyawlenskyBeckerFriesea giglioliisp. n.Brachystomella parvulaformadivisanov. B.contortaDenis,Pseudachorutes niloticusWahlgren.Aethiopella tournieriDelmare,Arlesia delamareisp. n., andNeanura (Bilobella) guineensesp. n. Body chaetotaxy in illustrated for all species where this has not previously been studied and in several cases represents the first published information on this character for the g

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1965.tb05216.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY