摘要:

An analysis of the disposition of trichobothria in all the post‐embryonic stages of six British species of Chernetidae, similar to that employed by Gabbutt (1969) in his study of the Neobisiidae, shows that a linear relationship exists between the successive position of named trichobothria. A model, based on growing and non‐growing regions gives a good approximation to the data. The results are considered in relation to the use of trichobothrial position as an adult generic or specific character and as a device for separating the nymphs of this fam

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01719.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

A key is given for identifying the eight species of Mugilidae of the Northeast Atlantic and Mediterranean. The use of Risso's names for four species is justified and explained and recognition is given to Tortonese's discovery thatMugil capurrii(Perugia) is a senior synonym ofM. monodiChabanaud. The relationship ofLiza saliensto certain species of West and southern Africa is held to be additional support for the recognition ofProtomugilPopov as a subgenus ofLizaincluding these species.ChelonRöse, with type‐speciesMugil cheloCuvier (=Chelon labrosus(Risso)), is recognized, following Jordan&Evermann (1917) and Schultz (1946), but its limits are differently conceived so as to includeCrenimugilSchultz rather thanLizaJordan&Swain. The latter is held to comprise about 30 Old World species. The status ofChelon bispinosus(Bowdich) is discussed, with its bearing on possible population‐differences inC. labrosusand the relationship of this species withC. crenilabis.The identity ofLiza seheli(Forskål) is discussed and reasons are given for disagreeing with Wimpenny and others in applying this name to the species found at both ends of the Suez Canal zone. The latter isL. carinata(Ehrenberg in Cuvier&Valenciennes).Myxus maroccensisMohr is believed to be a youngLiza r

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01720.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The planktonic Rotifera are not all cosmopolitan in their geographical distribution. There is a latitudinal variation in the assemblage of planktonic species. Most of this variation can be attributed to species in nine genera, of which some (e.g.Brachionus) are more abundant in warm areas, and others are more abundant in cool areas (e.g.Notholca). The latitudinal change in the assemblage is gradual, but it can be measured by the Sorensen index of similarity.In addition to the latitudinal variation there is evidence of a small group of species restricted to the Americas.Detailed surveys extending over a year or more yield between 30 and 100 species for a given lake or area, except in the high Arctic where the number recorded for Spitzbergen falls to 16. Single samples yield many fewer species, normally ranging from 4 to 26.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01721.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

In the West Cameroonian crater lake, Barombi Mbo, and its inflowing stream there are 17 species of fishes, of which 12, including the 11 cichlids, appear to be endemic. We give a systematic account of the endemics, including four new species and two new genera,KoniaandMyaka.The ecology of the lake is described in relation to the feeding biology of the fishes, studied by underwater observation in the lake and the examination of stomach contents. The cichlids in Barombi Mbo probably evolved there from two or three ancestral populations and now show clear ecological separation in their feeding and breeding. The problem of speciation within the lake is of particular interest because of the apparent absence of physical barriers to account for the genetic isolation of incipient species.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01722.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

InBulinusas in other Planorbidae the basic haploid chromosome number is 18 andB. tropicusbelongs to a group of diploid forms (2n=36) distributed predominately in southern Africa.B. truncatesbelongs to a group of tetraploid forms (2n=72) occurring mainly in northern Africa and extending northwards beyond the limit of the diploid forms. Hexaploid (2n= 108) and octoploid (2n= 144) populations occur in Ethiopia. Observations were made on snails belonging to this polyploid complex collected from 69 localities in Ethiopia. Chromosome numbers were determined in gonad tissue and in embryos. Morphological features studied are the shell (spire length, columella shape, umbilicus, costulation), radula (size of the first lateral tooth and the shape of its mesocone), copulatory organ (presence or absence) and egg size. Biochemical features investigated are the body‐surface mucus, egg‐proteins and esterase iso‐enzymes.Certain diploid populations conform toB. natalensisand others toB. tropicusbut these extremes are connected by intermediates preventing taxonomic subdivision and the entire diploid group is regarded as a northern part of the range of aB. natalensis/tropicuscomplex. Ethiopian tetraploid populations are identified asB. truncatesbecause of similarity to Egyptian snails in morphology and egg‐proteins and the susceptibility of some Ethiopian snails to infection with EgyptianSchistosoma haematobium.The shell spire is comparatively long in many hexaploid and octoploid populations, and distinctive egg‐protein patterns are given by octoploids but these groups do not provide clear‐cut taxonomic species.Hexaploids and octoploids are associated with streams at high altitudes while diploids and tetraploids occur in various habitats, most frequently at lower levels. The comparative rarity of the tetraploidB. truncatesprobably is one of the factors that have apparently prevented the establishment oftruncates‐borne strains ofS. haematobiumin Ethiopia, though present developments are likely to increase the abundance of tetraploid snails and provide opportunities for transmission of

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1972.tb01723.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY