摘要:

The carotenoid pigments of the hepatopancreas, ovaries and epidermis ofCarcinus maenaswere investigated. The following pigments were identified: β‐carotene, δ‐carotene, echinenone, isocryptoxanthin, canthaxanthin, lutein, zeaxanthin, flavoxanthin and astacene.The relative abundance of these pigments in the three tissues and the presence of possible hydroxy and keto intermediates suggest the metabolism of astaxanthin from β‐carotene. The metabolic pathway inCarcinusis discussed in relation to recent studies on other inver

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02871.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

In Lake AlbertDaphnia lumholtziis found in two forms. One has a pointed anterior prolongation, or helmet, on the head. The other has a shorter rounded head, and was originally described as a separate species,D. monacha. The latter form dominates the zooplankton in the middle of the lake where planktivorous fish are rare or absent. The helmeted form becomes commoner near the margins of the lake and reaches its greatest abundance in Ndaiga Lagoon, where planktivorousfish are common. The possession of a helmet is associated with a reduction in the size of the carapace compared to the round headed form. The carapace with its contained eggs is the most conspicuous part of a cladoceran, so that the helmeted forms are at an advantage in the presence of planktivorous fish which locate their prey by sight. The mid‐lakemonachaforms are larger than specimens of the same form in Ndaiga Lagoon, where it is shown thatAlestes baremosefeeds selectively on the larger specimens of themonachaform.The helmeted form produces more, but smaller eggs than themonachaform. The total brood volume (= mean egg volume x mean number eggs per female) is greatest in the midlakemonachaforms. The selective advantages of variations in egg size and the possession of a helmet are discussed. It is concluded that the data from Lake Albert support the hypothesis of Brooks (1965) concerning the adaptive significance of helmet development inDaphni

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02872.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Bulinus nyassanusandB. succinoidesare both endemic to Lake Malawi and for many years were known only from their shells. Recent collections of living material have made possible a study of the anatomy of both species and the application of biochemical and immunological techniques have indicated their affinities withinBulinus. Some interesting aspects of their ecology have also been revealed.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02873.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Norway lemming droppings remaining from the high 1963 population in Jämtland (mid‐Sweden) were examined microscopically for an evaluation of food species present. The findings from this were compared with the occurrence of these species growing on the mountains. It is tentatively concluded that lemmings are exercising a degree of selectivity in their choice of food species, but the reasons for this choice still remain obscu

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02874.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The structure and growth of the polyplacophoran shell, characteristically consisting of eight plates surrounded by a girdle, is examined in the light of current views on the relationships of mantle and shell in the Bivalvia. The periostracum and outer and inner calcareous layers of the shell of the latter group are homologous with the cuticle, tegmentum and articulamentum respectively of the shell of the Polyplacophora. The margin of the mantle consists of a large marginal fold, which secretes the cuticular girdle, and a small accessory fold bearing mucous cells. These are functionally comparable with all three folds of the mantle margin found in other molluscs, although anatomically the marginal fold of the chitons probably represents only the inner surface of the outer fold of the mantle margin.The cuticle not only forms the girdle, which bears calcified spines or spicules, but also extends between the shell plates. The principal part of the cuticle consists largely of mucopolysaccharide material but there is also a thin discrete inner region which is similar chemically to the periostracum of other molluscs. The cuticle, possibly without spines, probably covered the entire dorsal surface of a primitive placophoran and beneath this, plates developed. As these grew the cuticle became worn away except marginally and between the plates. It is suggested that a covering of mucus over the visceropallium may have been the forerunner of the molluscan shell and the possibleevolutionary relationships of the shell throughout the Mollusca are discussed.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02875.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The Atheriniformes is an order of teleost fish which consists of the Atherinoidei (sand smelts etc.), Cyprinodontoidei (tooth‐carps) and Exocoetoidei (halfbeaks etc.). Some of its members have protrusible upper jaws and some do not. Photographs have been taken of two species of Cyprinodontoidei feeding, to discover how they use their jaws, which are protrusible. The anatomy and mechanisms of the jaws of these and of various other Atheriniformes have been studied. The terminology of the kinematics of machines is used in a general discussion of the mechanisms of teleost jaws. Anatomical similarities between the jaws of Acanthopterygii, Cyprinoidei and Atheriniformes are noted and discusse

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02876.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

A study of the jerboa,Jaculus jaculus butleri, was made in the desert near Khartoum, Sudan. The species, habitat and method of capture are described. Information is given on the population and reproduction, and a “pattern of generations” is suggested. Details are given on the behavioural attitudes and activities of the jerboa, moulting, vocal noises, ectoparasites and predat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02877.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Measurements by nieans of an oxygen electrode of the rate of oxygen consumption of a wide variety of common intertidal invertebrates show that at least two rates of uptake can be distinguished in the intact animal. First, there is a rapid rate of oxygen uptake corresponding with activity and second there is a slower rate which corresponds with periods of quiescence and which alternates with the fast rate. Intermediate rates correspond with intermediate rates of overt activity. The maximal and minimal rates of oxygen uptake are affected differently by temperature change. The fast rate corresponding to activity (“active metabolism”) increases with temperature in approximate agreement with Arrhenius's law. The slow rate corresponding to quiescence (“maintenance metabolism”) does not vary with temperature over much of the range 7 to 22.5d̀C. It is concluded that, contrary to common belief, the intertidal invertebrates studied have a “basal metabolic rate” with a Q10of approximately one over much of the normal environmental temperature range and in this respect are well suited to life in a habitat where rapid fluctuations in tempe

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02878.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

In Newell&Northcroft (1967) evidence was presented which showed that the metabolism of certain intertidal invertebrates at rest does not vary greatly with temperature change. The following work was undertaken to determine whether temperature‐independent metabolism could be demonstrated in suspensions of mitochondria extracted from poikilotherm tissue and whether it could be inferred that there was any difference in the ability of poikilotherms from different habitats to adjust toshort‐term temperature change.It was found that the rate of reaction/temperature curve of mitochondria isolated from the skateRaiahad a flattened region below 10°C but above this the rate of oxidation of succinate and pyruvate increased regularly with temperature. The curve for intertidal forms had a gradual slope extending as high as 20°C in the musselMytilus eduliswhile in the terrestrial snailHelix aspersathe gradual slope reached 27.5°C after which the rate of oxidation of substrate increased sharply before declining towards higher temperatures. Finally, the curve for mitochondria isolated from the desert locustSchistocerca gregariashowed a gradual slope up to 35°C after which a sharp increase in the rate of oxidation of substrate occurred. Thus the extent of the gradual slope corresponds with the normal environmental temperature range to which the tissues of the poikilotherms are subjected and the general form of theR‐Tcurve is such that rapid fluctuations within the normal environmental temperature range have relatively little effect on the rate of mitochondrial

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02879.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Previous references to “necking” behaviour, and the main features of the study area are briefly outlined.“Necking” behaviour in giraffe takes place only in all male herds. When the animals are in a head to head posture the intensity is either high or low, but when animals take up a head to tail posture the actions are always of high intensity and appear to have greater sexual significance.The significance of “necking” is discussed, and it is suggested that these ritualized actions form an important sexuo‐social bonding mechanism whereby a hierarchy is created amongst the males,and movement between strictly bachelor and mixed herds helps to maintain contact between the sexesin this poly

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1967.tb02880.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY