摘要:

Janua (Dexiospira) brasiliensisandJ. (D.) foraminosaare fully described for the first time and compared by a pictorial key with other species ofDexiospiraandPillaiospira. The former is very close toJ. (D.) pseudocorrugata(=“Sptrorbis corrugatus”) and particularly toJ. (D.) nipponica, whilst the latter occupies a central position in the group of five species (includingJ. (D.) steueri) which are characterized by having large four‐lobed juvenile talons.Janua (Janua) pagenstecheriis the most widespread species of the genus, whereasJ. (Leodora) knightjonesiseems to be confined to coral seas. In all, 14 species ofJanuaare recognized, whilst 19 names are here regarded as synonyms or varieties. Eleven other species sometimes placed inDexiospiraorLeodorashould rather constitute the generaCirceis, SinistrellaandRomanchella. These are re‐defined and their affinities are studied.The subgenusDexiospiraseems to be centred in the Indo‐West Pacific, where it reaches maximum species‐diversity and extension into cooler latitudes.J. (D.) pseudocorrugata var. mannarensisis pantropical and overlaps in the Mediterranean with the west European form and in the West Pacific with varspraecepsandfenestrata, and with subspeciesainu, which are characterized by small modifications of the tube or abdo

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1975.tb00812.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The rough periwinkleLittorina saxatilisis considered, in current literature, to consist of various sympatric “subspecies” and “varieties”. These, it has been suggested, are incipient species and are evidence for sympatric speciation.This paper shows that in Wales the “saxatilis” aggregate consists of four separate, fully sympatric species:L. rudis, patula, nigrolineataandneglecta. Differences between these species include proportions, sculpture and size of the shell, range of colour patterns, the anatomy of the genitalia, and isozyme patterns. The possible evidence for incipient species is discussed and rejected.The diversity of penis form amongst the British winkles is remarkable, and it is suggested that in these sympatric species the structure of the penis could be of importance in species recognition.The four species occupy different zones on the shore and three certainly differ also in their methods of reproduction:L. rudisis ovoviviparous and contains embryos throughout the year,patulais ovoviviparous but contains embryos only in winter,nigrolineatais oviparous. The reproduction and dispersal methods of all British winkles are reviewed. The evidence available supports the view that non‐planktonic dispersal is an adaptation which, in species whose shell colour varies considerably from one locality to another, enables each population to become adapted to its local environmental conditions. Ovoviviparity occurs in high‐shore non‐planktonic species, and may be an adaptation to avoid the dangers of egg desiccation. Planktonic dispersal is found in species whose shell colour does not vary as much as in non‐planktonic ones. In these species, it is argued that a common planktonic pool enables a rapid re‐colonization in the case of local decrease in population numbers, and also the rapid dispersal of

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1975.tb00813.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The rough periwinkleLittorina “saxatilis”exhibits a wide range of shell colours. In current literature it is claimed that these colours are not related to the environment, that they arise randomly as genetic accidents and that they have little positive survival value.In a previous paper it has been shown that, in Wales,“saxatilis”consists of four separate, fully sympatric species. This paper reports an investigation as to whether the colour of two of these species,nigrolineataandrudis, is related to the colour of the background. Because of difficulties in quantitatively describing the colour of the background it was decided to concentrate mainly upon one aspect: whether or not the frequency of red shells is larger upon shores consisting of red sandstone than elsewhere in Wales.In both species the association between red shells and red sandstone is highly significant. Allnigrolineatasamples in which red was found at a frequency above 15% are from red sandstone. On red sandstone, red shells of this species were found mainly upon sheltered shores, their frequency decreasing and that of white shells increasing with exposure. This may be because barnacles, which occupy the same vertical zone asnigrolineata, are more abundant upon exposed shores. Partly covering the red rock, barnacles create a white background upon which white shells, rather than red, are cryptic. Yellow shells are found mainly on sheltered shores, where the brown algaFucusis abundant. It was observed that when the tide is in and the algae spread out, a yellow shell situated beneath them is well concealed. Yellow is also found upon barnacles which because of fungal and lichen infections, are dirty yellow. It is suggested that a striped (“nigrolineated”) pattern breaks up the shape of the shell. It also resembles the colour of the dark rock and the dark sutures between barnacle plates.Inrudis80% of the samples containing over 25% red are from red sandstone. Contrast tonigrolineata, in this species the relative frequency of red decreases on sheltered shores. This could be because the brown algaPelvetia, which occupies the same vertical zone asrudis, is more abundant in sheltered conditions and its colour partly covers over that of the rock beneath.The fact that in both species red shells are more frequent upon red sandstone than elsewhere in the study area, suggests that visual selection is restricting their distribution to the background that they match most. Rock pipits and shore‐crabs prey upon winkles. They have colour perception and could be partly responsible for t

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1975.tb00814.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Three species of Sabelliphilidae and four species of Lichomolgidae are reported as associates of scleractinian corals, nudibranchs, polychaetes, asteroids, and holothurians in Mauritius. A sabelliphilid from the polychaeteSabellastarte magnificarepresents a new genus and species. Two previously described lichomolgids are recorded from new hosts. Species ranges are extended from Madagascar and New Caledonia to Mauritius.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1975.tb00815.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY