ISSN:0035-919X    

DOI:10.1080/00359198409519477

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The anatomy of the siphons ofSolen marginatusandS. capensishas been described by both light and electron microscopy. Externally the siphon is annulated, each annulation corresponding to a region within the siphon wall where connective tissue is reduced. When disturbed, animals first shed a few terminal segments of siphon before proceeding to escape by burrowing rapidly. Observations and histological sections before and after autotomy have shown that loss is achieved with rapid contraction of the circular and radial muscles of the siphon wall about one of the weakness planes. This action compresses, elongates and breaks the longitudinal muscle fibres, which run for the full length of the siphon across the autotomy planes. Although valve adductions accompany autotomy, loss of segments of siphon can occur without any mechianical aid.

ISSN:0035-919X    

DOI:10.1080/00359198409519478

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Selected species of phytoplankton, including species that often give problems in identification with light microscopy, are discussed and illustrated with scanning electron microscopy from samples collected in the Benguela upwelling system. The species represent two choanoflagellates, one chrysophyte, two prasinophytes, one cryptomonad and fifteen diatoms. Structure of the cells as they appear in SEM is compared with previous published knowledge on their structure from light microscopy as well as electron microscopy. Identity of the South African specimens is, thereby, authenticated and compared with the species as they are known from other regions.

ISSN:0035-919X    

DOI:10.1080/00359198409519479

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The uptake of dissolved organic matter by the whelkBullia digitalishas been monitored using a mixture of radioactive amino acids. Efflux as well as influx was measured and attention paid to the sites of uptake, which proved to include the surface of the foot as well as the gill. A net rate of amino acid influx of over 1 x 10−3μg hr−1was calculated for a standard animal of 750 mg dry tissue mass, from a solution of just over 1 μg ℓ−1. It is concluded that, under natural conditions, utilization of dissolved amino acids and other dissolved organic matter could account for a fairly high proportion, certainly more than 15 per cent, of the metabolic needs of the animal and may be essential as a nutrient source for young juveniles.

ISSN:0035-919X    

DOI:10.1080/00359198409519480

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Short-term (6 h) behavioural responses ofPerna pernaexposed to different concentrations (0,2, 0,4, 0,6, 0,8 ppm) of copper in sea-water (35‰) have been investigated.Pernadoes not respond to copper until exposed to 0,2 ppm. The initial response to all concentrations is a sharp adduction followed by a period of rapid valve movements. The animals never completely close their valves; nevertheless the heart rate gradually decreases suggesting isolation of tissues by use of the mantle edge. The responses exhibited byPernaare compared to those of other species.

ISSN:0035-919X    

DOI:10.1080/00359198409519481

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Abnormally high cadmium concentrations in the tissues ofBullia digitalisfrom Ou Skip, on the west coast of the Cape Province, are confirmed, while high zinc levels are reported for the first time. Values of cadmium and zinc inB. rhodostomafrom the south coast are similar to those reported by previous authors, being about 25 per cent of the levels recorded from Ou Skip. The two species do not differ markedly in their abilities to accumulate the two metals. There is a close correlation between cadmium and zinc concentrations on both west and south coasts. A possible association of high tissue levels with cells of upwelling water is briefly discussed.

ISSN:0035-919X    

DOI:10.1080/00359198409519482

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Temperature data housed in the South African Data Centre for Oceanology are analysed for the area covering the Agulhas Bank and surrounding ocean. In particular, the vertical temperature structures during summer and winter are compared and contrasted. The Agulhas Current forms a major influence in the east and south, while major differences also emerge with conditions on the shallower shelf and the western areas. Recent temperature sections are shown, and satellite imagery is also used to identify features on the Bank.

ISSN:0035-919X    

DOI:10.1080/00359198409519483

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0035-919X    

DOI:10.1080/00359198409519484

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0035-919X    

DOI:10.1080/00359198409519486

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor