摘要:

About 30 species are described, with keys for identification and notes on distribution. The chief genera arePileolariaandSpirorbiswith 12 and 5 species respectively, of which nearly half appear to be endemic. Endemic species are mostly centred in California, where seasonal changes in sea temperature are minimal. The remainder fall into two groups each of nine species, a northern group of Circeinae,Pileolaria (Jugaria)andSinistrellaspecies and a southern group comprising otherPileolariasubgenera,Spirorbis, ProtolaeospiraandJanua.The two groups overlap to some extent and all their species extend to the W. Pacific or other oceans, the northern forms via the Arctic, the others apparently through transport by shipping.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03973.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Dugesia polychroa, D. lugubrisandPlanaria torvapreyed upon snails of differing morphologies and while theDugesiaspp. fed approximately in proportion to snail abundance,PL torvawas more selective onPotamopyrgus jenkinsi.The incidence of feeding on four snail taxa by theDugesiaspp. was significantly correlated and differed strikingly from that ofPI. torvawhere feeding was related to its annual life cycle. Large peaks of feeding coincided in theDugesiaspp. for the four snail types; this was attributed to snail vulnerability being increased by environmental disturbance. Comparison of feeding byDugesiaspp. in the presence and absence ofPI. torvaindicated that severe competition was occurring for food withPI. torvahaving a food refuge inP. jenkinsi.The distribution ofPI. torvain Britain is largely confined to productive habitats in the Glasgow‐Edinburgh and East Anglia regions. It is concluded that historical rather than ecological events have played the major part in its distribution to date. The strong association ofPL torvawith port areas and the canal system suggests that it is a recent introduction via the timber trade with Fennoscani

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03974.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

A method for measuring the glycogen content of the hepatopancreas ofCepaea hortensisis described. Glycogen content was determined for snails from field population cages and from a nearby natural population. Results showed that caged snails possessed lower levels of glycogen than did the natural population, while the lowest levels of glycogen were associated with higher snail densities in the cages. There is evidence for an increase in glycogen content ofC. hortensisduring the late summer in nature and in experimental populations. The results are discussed with regard to the selective effect that glycogen may have onCepaeaand to the interpretation of events occurring in populations ofCepaeathat glycogen assay could provide.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03975.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Two lakes lie in a caldera at the top of Jebel Marra. One is shallow and highly saline, with a dense bloom of planktonic blue‐green algae and a zooplankton consisting entirely of rotifers. The other is over 100 metres deep, is less saline, with a sparse phytoplankton of diatoms, and the dominant zooplankter isEucyclops gibsoni.The marginal fauna of the deep lake includes a number of widespread insects, but is unusual in that it includes an aquatic glowworm (Family Lampyridae).In the shallow lake there is a superabundance of oxygen in the upper two metres, but no oxygen below six metres, except when strong winds mix the lake so that there is then about 40% saturation throughout the water column. In the deep lake it was found that after strong winds there was only about 12% saturation in the top 30 metres of water. The restricted fauna of these lakes appears to be a result of the combined effects of isolation, salinity and a variable oxygen regim

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03976.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The longevity of original scales and the process and consequences of scale regeneration in the euryhaline Common goby,Pomatoschistus microps(Kroyer), has been studied by monthly sampling of two populations. Scale regeneration comprises four stages: formation of a new growth centre, a regenerated area in the form of a wide central irregular area lacking concentric circuli: formation of short and widely spaced circuli at the outermost region of the regenerated area: a check in regenerated scale growth on reaching the size of the original scales: and the commencement of normal growth similar to that of the surrounding original scales. Growth of regenerated scales within 30 days was not sufficient to attain the same size of the original ones. The average percentage of regenerated scales in successive months during the life span ofP. micropsis about 20% in immature fish and sharply increases up to about 60% of the total scales during the breeding season. The correlation between sharp increases in regenerated scales and the breeding season is also confirmed on examining scales from two other gobioid species,Gobius paganellusandGobius cobitis.It is suggested that the loss of a large number of scales may result in the check in body growth during the breeding season.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03977.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03978.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03980.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03981.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03982.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1979.tb03983.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY