摘要:

Some dynamic patterns of clustering in the mangrove‐dwelling hermit crabClibanarius laevimanuswere studied during a semi‐lunar tide cycle in Kenya. Clusters composed of hundreds of quiescent individuals occurred at every low tide, developing either on the mangrove prop roots or in the open (but always within a 4‐m belt from the mangrove fringe). They disbanded at ebb tide, when most animals migrated in lines towards feeding grounds. There they grazed on vegetable debris during high water. When the tide receded, they came back home in crowded groups. The position of aggregating sites remained constant throughout the tides, as well as their number and size, and the shape of clusters was stable with time. Individual hermits often changed clusters (only rarely they were found scattered), but transfers only occurred between aggregations where shell size range matched the shell worn by the moving crab. Dispersal was slower than predicted by random walk models. Questions were aimed on the proximate and ultimate factors underlying this spatial strategy which contrasts the nomadic behaviour shown by the sympatricC. longitarsus.

ISSN:0091-181X    

DOI:10.1080/10236249209378820

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Activity‐rhythm data from four species of semiterrestrial, intertidal crabs collected in Woods Hole, Massachusetts, USA, and Dunedin, New Zealand were investigated using a battery of sensitive digital signal analysis techniques. The animals were tested in a variety of constant lighting regimens, constant darkness, and at a variety of temperatures. In all species a small number of animals showed ultradian rhythms not attributable to either circatidal or circalunidian oscillations.

ISSN:0091-181X    

DOI:10.1080/10236249209378821

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Sets of sole larvae and juveniles were subjected, under DD, LL or DL conditions, to a variety of constant salinities, salinity gradients and cyclic variations of salinity. Animals were observed during several days in cylindrical vertical tanks and their swimming activity was recorded automatically with opto‐electronic IR barriers. Analysis of actograms, periodograms and actotaxigrams demonstrated effects of salinity on behaviour. Salinity variations induced an exogenous rhythm of activity and changes in the distribution patterns of larval and juvenile sole. Nevertheless, sole activity and distribution depended more on nycthemeral light variations than on salinity variations. The ecological consequences of salinity variations in the settlement of juvenile sole in coastal and estuarine areas are discussed.

ISSN:0091-181X    

DOI:10.1080/10236249209378822

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The effect of shelter on the salinity preference behaviour of red and green colour forms of the shore crabCarcinus maenas(Crustacea: Decapoda) was investigated in the laboratory and the field. Red colour forms which are in a state of prolonged intermoult are less tolerant of low salinity than green colour forms and are absent from estuaries. In choice chamber experiments green crabs remained longer at low salinity if a shelter was available, but salinity preference behaviour of red crabs was unaffected by the presence of shelters. In an estuary the upper limit of distribution towards freshwater of green crabs was higher where shelters were made available. These results are discussed in relation to distributional differences and retention within the estuary.

ISSN:0091-181X    

DOI:10.1080/10236249209378823

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0091-181X    

DOI:10.1080/10236249209378819

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor