摘要:

Observations on populations ofRhysida nuda togoensisandEthmostigmus trigonopodusin Zaria, Nigeria, show that growth rates are very rapid and life cycles shorter than in centipedes from temperate regions.R. nuda togoensisreproduces when one year old and, in all probability,E. trigonopodusdoes so as well.It is suggested that both species are enabled to continue feeding in damp areas after the rains have ended by virtue of their mobility and large size (with consequent greater resistance to desiccation). Increasing aridity drives them into crevices in the soil where a relatively rich fauna may persist through the dry season. The young appear at the beginning of the rains, thereby having the entire rainy season available for feeding.The taxonomy ofR. nuda togoensisis discussed and the distribution of both species in Nigeria is described. They are virtually absent from the dry sudan savanna vegetation belt.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01732.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

A technique for the study of the ontogenetic development and the sequential changes in structure of the gonad ofMonopterus albusduring natural sex reversal was established by making successive biopsy examinations on gonadal tissue of individual animals at regular time intervals. Results obtained from the present investigation provided some direct and conclusive evidence that anatomical transformation from an ovary, through a transitory intersexual phase, to a testis occurred as a natural process in the life cycle of individuals in this species, and confirmed most of the previous observations derived from studies based upon body‐size and sexuality correlation. This biopsy approach will form a basis for further investigations on the effects of various experimentations, such as hormone administration, hypophysectomy, photo‐stimulation and thermo‐stimulation, on sex differentiation and sex changes in this protogynous hermaphroditic

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01733.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The morphology of thefeedingapparatus in several genera of carcharhinid sharks (Carcharhinus, Rhizoprionodon, Hypoprion, Prionace, GaleocerdoandNegaprion) was studied in both fresh and preserved states. The actions of the cranial musculature were determined through electrical stimulation. The feeding behaviours of representatives of the generaCarcharhinus, NegaprionandGaleocerdowere studied under controlled conditions by direct observation as well as photographically. The cranial anatomy of carcharhinid sharks is characterized by a relatively reduced chondrocranium and a greatly hypertrophied musculature. The hyostylic jaw suspension serves to allow substantial cranial kinesis, particularly with respect to the upper jaw. Protraction of this skeletal element is accomplished in at least two ways, depending on the external and internal forces applied to the palatoquadrate cartilage. Under one set of conditions upper jaw protraction serves to allow precision when feeding on benthic organisms. Under quite different conditions upper jaw protraction allows the jaw to cut deeply through food items too large to be swallowed whole. The feeding mechanism found in these sharks, therefore, seems to be well adapted to deal with a wide variety of food types.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01734.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Morphological aspects of squid (Loligo, Lolliguncula) mantle relevant to locomotory function were studied. Methods used included polarized light microscopy of frozen sections of untreated tissue taken from animals immediately after death and electron microscopy.The mantle consists of circular and radial muscles arranged in alternating rings along the whole length of the mantle. The muscle is obliquely striated. Connective tissue fibres are found in the body of the muscle and in the outer and inner tunics. The outer tunic consists of layers of large collagenous fibres. The fibres run in superimposed right‐ and left‐handed helical courses that lie at an angle of 27° to the long axis of the animal. The tunics and the intramuscular connective fibres are thought to resist length changes in the mantle while permitting the changes in girth required for the jet power stroke. Both the intramuscular and the tunic fibre systems may provide elastic energy for the return phase of the jet cycle. Tunic fibres appear to be a geodesic tensile reinforcing system ensuring smooth shape changes in the ma

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01735.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Behavioural and morphological characteristics of all members of the stork family are summarized. References are given to other papers where these subjects are discussed in greater detail for each group of storks. Based on the evidence now available, a revised classification is suggested (Table II) which divides the Ciconiidae into three tribes, six genera, and 17 species. The following genera (of Peters, 1931) are synonymized with other existing genera:Ibis, Sphenorhynchus, Dissoura, Euxenura, andXenorhynchus.It is further suggested thatScopusshould be placed in a suborder of its own and thatBalaenicepsbe placed in a monotypic family adjacent to the Ciconiidae, pending further study.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01736.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

There is some apprehension about the possible effect of the introduced American minkMustela visonupon the indigenous British fauna, either as a predator exerting new and excessive pressure upon native prey species, or as a carnivore competing for prey resources against native carnivores. Concern is also felt by preservers of game, and by keepers of small domestic animals (poultry and rabbits) about the mink's potential as a pest. To investigate the food habits of the mink in England and Wales the alimentary canals of 1165 trapped animals were examined, yielding 204 samples for analysis. The resulting information provides a general picture of the mink's diet, including seasonal variations. Comparisons were possible with similar work carried out in other countries, and with the diets of other British carnivores. Tentative conclusions were reached regarding the broad pattern of food relationships between the mink and other British animals, wild and domestic.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01737.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Feral American mink (Mustela vison) thrive in Scotland. The potential impact of the mink on the native fauna was investigated through its food. Fifty‐five stomachs and 33 scats were analysed by identifying the indigestible remains. Fish formed the main prey (49% occurrence) and birds and mammals 28% and 23% respectively. Most of the fish eaten were Salmonidae (brown trout and salmon). No remains of eels were found.Mink may compete with otters for food, but the smaller prey taken by the mink and its greater use of land separates it from the otter. Mink seem to be occupying a vacant feeding niche in Scotlan

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01738.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Evidence is presented which shows that in traversing the heart of the Tuatara, systemic venous blood is selectively distributed to the pulmonary arches. This selective distribution of deoxygenated blood into the pulmonary circuit occurs despite the poorly developed primary ventricular septum and the lack of a secondary septum, and yet it appears to be as effective as that seen in reptiles having these anatomical attributes.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01739.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

A detailed kinematic analysis of the mantle movements of swimmingLolliguncula breviswas made. Some data were also obtained onLoligo pealei.The qualitative and quantitative data provided are of use in discussing mechanisms of squid mantle function.Several possible mechanisms of squid mantle re‐expansion were proposed and investigated. The inhalant phase of jet propulsion is probably effected by contraction of the radial muscles, since thinning of the mantle wall accompanies re‐expansion. The radial muscles may cause mantle re‐expansion by contracting alternately with the circular muscles in response to nerve impulses, or by contracting alternately with the circular muscles in response to stretch cycles effected by mantle wall thickening in the power stroke, or by contracting continuously through both power and recovery strokes. Elasticity of the mantle tissue may contribute to mantle re‐expansion. Neither pressure pumps nor a Bernoulli effect mechanism are effectors of mantle re‐

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01740.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Scales from four specimensof Latimeria chalumnaewere examined in a dissecting microscope and then X‐rayed. Some were demineralized and prepared for routine histology. Others were cleared in cedarwood oil. Ground sections of plastic embedded scales were micro‐radiographed and electronmicrographs made of araldite embedded frozen scales. Corresponding 1 μm thick serial sections were examined in the light microscope.The greater part of the scale is composed of layers of unmineralized isopedine surmounted by the exposed portion of the scale which is pigmented and ornamented by a series of denticles of tubular dentine tipped with enameloid. Between these two parts is a thin ridged bone‐like layer. In the electron micrographs the isopedine was seen to consist of layers of densely packed collagen fibres; the orientation of which was uniform in each layer but varied markedly from layer to layer. Only few cells were found between the fibre bundles.The X‐rays revealed numerous concentric annulae and, lying approximately at right angles to these, a further series of ridges radiating from the centre of the scales.It is suggested that the basal unmineralized isopedine and the ridged layer of bone‐like tissue covering it represents a highly modified cosmoid scale on which the denticles and pigmented layer have become su

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01741.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY