摘要:

Minnows (TeJeosiei:Phoxinus phoxinus(L.)) were exposed on a black background for varying periods to allow melanophore formation. The ages and times of appearance of melanophores were photographically determined. The background responses of the newly‐formed melanophores were assessed microscopically in fixed preparations of animals killed in liquid nitrogen at different time‐intervals. The results were interpreted according to the generally accepted belief that rapid and slow colour changes indicate nervous and hormonal mediation respectively. The age of the newly‐formed melanophores appeared to influence their background responses, the older melanophores being more responsive. It is suggested that the sensitivity to hormonal control develops first in the life of a pigment cell, to be followed later by sensitivity to nervous control. Nervous control, however, does not appear simultaneously for W/B and B/W adaptations but develops first for the latter. This differential development is considered to provide evidence for double innervation of melanop

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03158.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The development of the thyroid gland was studied in various larval and metamorphic stages of three Iraqi anurans of the generaBufo, HylaandRana.At comparable stages of development, differentiation of the gland occurs earlier in the last two genera than inBufo.It is suggested that the development of the thyroid during prometamorphosis is closely related to the histogenesis of the pronephric system in these genera.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03159.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Long‐tailed field mice (Apodemus sylvatkus) live on the Castle Rock in the centre of Edinburgh city, which has been cut off from open country for nearly one and a half centuries. However they do not differ significantly from mice caught 4 km away on the edge of Edinburgh. The Edinburgh samples have different frequencies in 5 out of 20 nonmedical skull variants when compared with a Durham sample, and in eight when compared with a Perthshire one. The most likely explanation for the lack of differentiation of the Castle Rock sample is that it is a relic of a population once continuous with the main breeding population of Britain, that has survived in its restricted area despite its small number

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03160.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The Manini is a widely distributed surgeonfish that is often abundant on reefs. It has two modes of existence, scattered individuals or dense column‐forming schools, which may be seen on the same day at different places on the reef. In Hawaii schooling is a tactic used for getting to the bottom to feed when the bottom is held by territory‐holding food competitors. Mixed‐species “flocks” are an extension of this tactic. In atoll situations habitat partitioning exists, with the Maninis feeding in the intertidal area away from competitors; there, schooling is anti‐predato

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03161.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The microanatomy of the skin of an air‐breathing fish,Notopterus notopterusis described and related to the distribution of various histochemical constituents involved in keratinization.In addition to distinct unicellular mucous glands, secreting sulphated acid mucopolysaccharides, the epidermis of TV.notopterusis mainly composed of polygonal cells containing sulphated acid mucopolysaccharides, concentrated in the distal peripheral areas of the cells. The mucopolysaccharide contents of these polygonal cells gradually increase as they mature and move towards the outer surface. They may ultimately form a part of the protective keratinized layer.The mature keratinized cells give positive reactions with Papanicolaou's stain, contain cystine bound SS groups, cysteine bound SH groups, calcium and moderate amounts of sulphated acid mucopolysaccharides. These cells having flat pyknotic nuclei undergoing karyolysis, are fused together at their lateral margins to form an intact sheet which is frequently seen sloughing off from the underlying epidermal cells.The process of cornification inN. notopterusis comparable to that of the amphibians and the aquatic reptile–the turtle.There exists a well developed lymphatic system in between the cells of thestratum germinativumhaving lymphatic spaces often penetrating deep into the middle layer. This is an adaptation which contributes largely to the protective function of the fish skin.The layers between the scales and the basement membrane contain sulphated acid mucopolysaccharides. This together with keratinization has been correlated with the peculiar mode of life of the fish, often facing the problems of desiccation.The epidermis is anchored on the dermis by fine strands of collagen fibres connecting the basement membrane and the scales, and by numerous fine papilla‐like projections of the basement membrane projecting in between the cells of thestratum germinativum.Numerous fine elastic fibres in the connective tissue pockets in which scales are lodged, provide for free movement of the scales when the body of the fish is bent during swimming.Pit organs singly or in groups are found distributed in the epid

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03162.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Siamopaludina martensiandFilopaludina sumatrensishave typical viviparid reproductive systems with dimorphic spermatozoa and copulatory right tentacle in the male, and a large pallial brood‐pouch in the female. Females outnumber males as in several other viviparids. Brood‐pouches contained overall monthly averages of 0–14 developing young inS. martensi, 9–23 inF. sumatrensis, more than half of which were well‐developed, later juveniles. Brood‐pouch counts and ovary condition of both species varied in broad accordance with monthly rainfall, giving an irregularly seasonal pattern of annual change resembling those of several terrestrial Malayan snails. Juveniles emerge from the brood‐pouch mostly at night. Alteration of aquarium conditions leads to temporarily accelerated release of young but does not permanently raise brood‐pouch counts or r

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03163.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

A study of the seasonal variation of circulating immunoreactive hormone (ir LH) was undertaken in captive Herring gulls (Lams argentatus) by estimating the hormone concentration in monthly plasma samples with a radioimmunoassay to chicken LH.In the mature gulls (in 4th or 5th year), the ir LH concentration increased significantly through the spring (from 0.71 to l.94ng/ml in males and from 0.59 to 2.34ng/ml in females). The ir LH peak in the females may occur marginally later. In younger birds, only a slight elevation of the hormone level was apparent. A subsequent small summer peak of ir LH was found only in mature male gulls. Another major feature of the annual secretion pattern was the dramatic increase found in all groups of gulls in the sample taken at the end of November. This level had fallen to near basal values only a month later in all birds except the mature male gulls.Throughout the winter, spring and summer, the circulating ir LH in the immature birds remained below that found in their mature counterparts.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03164.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Descriptions and measurements are given for the circulating blood cells of four species of alcids, namelyAlca torda, Uria aalge, Uria lomvia, andFratercula arctica.Differential white cell counts were also made on the blood of these birds and on the blood of a fifth species,Cepphus grylle. Great variations were noted in the percentage of each cell type found in individual birds, while means and first and third quartiles varied between species. The results indicate that the blood picture of individual birds of the species examined, would be of little value in assessing “condition” of birds in either field or in the laboratory. Red blood cell counts were made forF. arcticaadults, while haematocrit values and clotting times were determined for this species and forU. aalge(adults and chic

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03165.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Attention is drawn to the fact that cephalopod skin contains reflecting elements (irido‐phores, leucophores) in addition to the well‐known chromatophores; and the reflexion of monochromatic light from small areas all over the arm, head and body skin inOctopus vulgarisandSepia officinalisis demonstrated. It is emphasized that the chromatophores of these species contain pigments only at the yellow‐red (‐black) end of the spectrum so that no combination of their activities could cause the skin to take on the blue or green tinge occasionally seen in the living animal. The function of the chromatophores in cryptic “colouration” is largely limited to tone‐matching, colour‐matching being dealt with by the reflecting elements. These, when they are revealed by retraction of the overlying chromatophores, automatically reflect incident light of whatever wavelength and thus enable what is probably a colour‐blind animal to take on the colour as well as the tone of

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03166.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The total parasite load, helminths and arthropods, was measured in wild antelopes (Antilopinae and Alcelaphinae) in Kenya. Two parasite faunas were present, one consisting of endemic species and the other of species introduced into Africa with human livestock, presumably within the last 2000 years. There was little evidence of natural immunity to helminthic infection and gazelle restricted by ranching died of acute helminth infection. The helminth fauna of antelopes was dissimilar from that of zebra and giraffe which graze in the same savannah area, although species of tick were shared. New host records from Kenya are given forBigalkenema curvispiculumGibbons,Paracooperia raphicerciOrtlepp,Trichostrongylus axeiCobbold andT. colubriformisGiles fromGazella thomsoniiGilnther,B. curvispiculumfromG. grantiBrooke,Cooperia fulleborniHung fromConnochaetes taurinusBurchell andMoniezia expansaRudolphi fromGiraffa camelopardalis tippel‐skirchiL. The implication of parasitic infection to conservation programmes and the possible future erosion of the conservation areas in East Africa is discussed briefl

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1974.tb03167.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY