摘要:

The kind of physical gill known as a plastron is a gas film of constant volume and an extensive water‐air interface. Such films are held by hydrofuge structures, and they resist wetting at the hydrostatic pressures to which they are normally subjected in nature. In well‐aerated water a plastron enables the insect to be immersed indefinitely. A plastron is here recorded for the first time in adult beetles of the suborder Myxophaga. In both known genera of the family Torridincolidae a plastron is present on the abdomen. InPtyopteryxof Brazil the plastron forms a diffraction grating that is responsible for the iridescenceoithe abdomen. The structure of the plastron ofTorridincolaof Rhodesia is like that of some other beetles, and it is not iridescent. Among adult beetles plastron respiration has been independently evolved in at least eight quite different groups, and within some of these groups it has been evolved on more than one occas

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb03074.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

An examination has been made of the length frequency distribution of ammocoetes of the Sea lamprey,Petromyzon marinusL. collected during April, July, August and October. A comparison of the frequency distributions for the individual collections and a study of gonadal development within certain length ranges suggests that the duration of the larval period cannot be less than five years.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb03075.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The sea‐birds breeding in the Galapagos Islands show a diversity of breeding cycles. Some species have rigidly fixed annual breeding while others breed throughout the year but have peaks of breeding at less than annual intervals. The eight species which have non‐annual breeding are probably breeding as often as possible with the interval between the end of a breeding attempt and the start of the next being the time needed to moult the wing and tail feathers. Only one species is definitely known to breed and moult at the same time.Although there are well marked seasonal fluctuations in the sea temperature, regular sampling failed to demonstrate any regular fluctuations in the surface plankton. The available evidence suggests that food for some sea‐birds is erratic and unpredictable. Some non‐annual breeding species have their breeding synchronized by severe food shortages which delay breeding, presumably because females cannot find enough food to form eggs, until conditions improve.Timing of the breeding season in annual breeders is less easily explained but some species may be feeding well away from the islands in areas where there is a regular fluctuation in the food supply. Most of the annual breeders have prolonged breeding seasons and in two species breeding is out of phase on different islands. Perhaps species are influenced by some weak annual variation in food supply which makes it disadvantageous to breed in a few months of t

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb03076.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The results of four attempts at yearly intervals to estimate populations ofAmolops lamtensis(Blgr.) along 360 m of forest stream are discussed and the most consistent estimates are obtained using Jolly's (1965) method of analysing such data. Observations of movement within the population indicate that most frogs are recaptured close to the original point of capture although a few show considerable downstream movement, possibly as a result of being swept away by the current. The recapture expectations are not, however, random and there is a strong indication that larger frogs are more liable to recapture. There is also evidence that frogs are available for recapture for different lengths of time, and it is likely that this leads to an under‐estimate of the total populatio

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb03077.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The structure and mechanisms of the jaws of 18 species of flatfish have been investigated. Clear adaptations to different modes of feeding were found. The mechanisms of the jaws of Soleidae, Cynoglossidae, and Rhombosoleinae are highly specialized and the representatives of the two latter groups have some interesting jaw muscles of doubtful homology.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb03078.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The atlas‐axis complexes of four of the major groups of the mammal‐like reptiles are discussed. These represent the four principal types of occipital condyle found in the Synapsida: hemispherical in the pelycosaurs, kidney‐shaped in the gorgonopsids, trefoil‐shaped in the dicynodonts and double in the cynodonts. In each case the possible movements of the skull are analysed in detail. It is shown that the central theme of the wide variation of this structure found within the synapsid reptiles is the manner in which the problem of achieving rotation of the head about a longitudinal axis was solved.An attempt is made to elucidate the functional evolution of the atlas‐axis complex within these reptiles and the significance of the differences between the reptilian and the mammalian complexes

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb03079.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

Two species of root‐piercing insect,Notiphila riparia(Ephydridae) andErioptera squalida(Tipulidae) are described. The insertion of the spiracles into the plants is dependent on a firm environment which provides the main bracing element for the movements of the spiracles. The structural features of root‐piercing spiracles are described. The spiracles are long enough to reach the gas spaces of the roots of the plants on which the insects are commonly found. The plant epidermis may act as a limiting factor in the respiration of the insects. The emergence of the adults ofErioptera squalidainvolves a change in buoyancy in the pharate adult as the adult emerges at the surf

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb03080.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY