摘要:

L.africanaand L.knysnaensisare regarded as two morphs of a single species which exhibits a genetic cline along the south‐eastern coast of southern Africa. The dark brown morphknysnaensisdominates the western, cooler end of the cline and is replaced by the pale blue morphafricanaat the warmer end of the cline. These conclusions are based on evidence from the latitudinal distributions, the complete range of intermediate forms regarding shell colour and shell morphology and the lack of differences in redular morphology, penial morphology or habita

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1979.tb01084.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Littorina rudiswas collected from stands ofSpartina capensisin saltmarsh habitats within Langebaan and knysna lagoon, Cape Province. It was absent from rocky sores and from saltmarshes east of Knysna. The shell, radular and penial morphology are described.L. rudisfrom both localities bore tessellated colour patterns similar to those of British saltmarsh ecotypes. The Knysna population contained individuals with a unique amber background colour. The shells from Knysna and Langebaan were very thin in accordance with the sheltered habitats. The number of embryos carried in the brood puch was similar in both countries. Sexual maturity was attained at about 4 mm shell length; the male and female modal sizes were 4.9 mm and 5.1 mm respectively at Langebaan. No. published records were found forL. rudisin South West Africa. Some possible origins of the South AfricanL. rudispopulations are discussed.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1979.tb01085.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

A large number of larval, metamorphosing and adult nonarasitic lampreys,lampetra planeri, were collected from three different rivers and placed in a morphological series. The characteristic changes were then described and used to propose a sequence of Stages (1–9). The first signs of metamorphosis (Stages 1–2), which could occasionaly be found as early as late June, are characterized by the eruption and enlargement of the eyes. This is followed by rapid transformation of the the oral hood into an oral disc, and changes in the shape of the pharyngeal region (Stages 2–5). Pronounced alterations in body pigmentation, enlargement of the fins and the development of teeth occur during Stages 4 to 6. The vast modifications involved in Stages 2 to 6 take place relatively repidly in the period between approximately mid‐July and mid‐September. The subsequent changes which occur more slowly, eventually lead to the production of immature (Stage 7) and sexually mature adults (Stage 8). Mature males are characterized by the presence of a urinogenital papilla, while the females posses a post‐cloacal fin‐like fold and greatly distended trunk. Spawning took place between late March and late April with the spent animals (Stage 9) dying soon afterwards.The above sequence of Stages was then compared with those found in a smaller sample of the parasitic and ancestral speciesL. fluviatilis. The early metamorphosing stages in both species are apparently indistinguishable but clear differences atart to appear at Stage 5 when the body surface ofL. fluviatilisis assuming a distinct silvery sheen. This trend becomes more marked in Stages 6 and 7, at wich time the river lamprey also has a more pronounced eye and disc and a slimmer trunk. Stage 7 inL. fluviatilisrepresents animals migrating to the sea in either the autumn or spring to commence their trophic phase. On the other hand this Stage inL. planerimay be regarded as representing a massive contraction of adult Stages and is in many ways similar to the early upstream migrants of para

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1979.tb01086.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Representatives of the various Stages (1–9) in the metamorphosis and short adult life of the brook lamprey,Lampetra planeri, were used to provide quantitative data to describe the pattern of changes that take place during this period of the life cycle. During the transformation of the oral hood into an oral disc, this ventral region of the snout first declines in length before increasing markedly. The branchial region declines in length and remains relatively smaller than in the ammocoete, a feature probably correlated with the concomitant internal changes in the pharynx which permit a change from a unidirectional to a tidal respiratory flow. The eye increases in size only through the initial Stages (1–5). The main period of fin enlargement occurs rather later in metamorphosis than the above changes.During maturation the two initially separate dorsal fins increase further in height and eventually become separated only by a notch. Differences between the two sexes are found in the relative size of the disc and fins, the larger structures of the male probably being related to their greater activity in spawning behaviour. Measurements on metamorphosedL. fluviatilisconfirm that in this species the eye and disc are relatively larger than inL. planeri.Data are presented which illustrate that in collections taken during the metamorphosis of both species the males are smaller and slightly more numerous than the females and that transformation is initiated at a longer length inL. planerithan inL. fluviati

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1979.tb01087.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The structure of the braincases and associated nerves and blood‐vessels is described.Typhlopscombines primitive lacertilian features, notably the retention of a palatine artery, with specialisations such as the structure of the recessus scalae tympani.Leptotyphlopsis more completely snake‐like, but the two genera show in common a specialised intracranial course of the hyomandibular branch of the facial nerve, due to lateral closure of the juxtastapedial recess by the overgrowing crista circumfenestralis. The lateral closure of the juxtastapedial recess is considered as an adaptation to burrowing habits. The Vidian canal in scolecophidians is poorly defined, due to the lack of lateral ascending wings of the parasphenoid. This might constitute an archaic character contradicting the descent of snakes from any Recent lacertilian gr

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1979.tb01088.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY