Influence of salinity and cadmium on the survival and osmoregulation of Callianassa kraussi and Chiromantes eulimene (Crustacea: Decapoda)

  • M Thwala
  • BK Newman
  • DP Cyrus

Abstract

This study investigated the influence of salinity and cadmium on the survival and osmoregulatory capability of two decapod crustaceans, Callianassa kraussi and Chiromantes eulimene. Callianassa kraussi was able to survive in salinities of 5–55 over 96 h, whilst C. eulimene survived in 0–55 over the same time period. The 96-hour cadmium LC50 for both species decreased progressively at salinities above and below their respective isosmotic conditions, with the decrease being slightly more pronounced below compared to above isosmotic salinity. A hypo-iso-osmoregulatory strategy was followed by C. kraussi as it hyper-osmoregulated at salinities between 5 and 25 and osmoconformed at salinities greater than 25. Chiromantes eulimene followed a hyper-hypo-osmoregulatory strategy; it hyper-regulated in salinities from 0 up to isosmotic conditions at about 28 (c. 780 mOsm kg–1), followed by hypo-regulation up to 55. The effect of cadmium exposure on the osmoregulatory capacity of C. kraussi was more pronounced at hyper-regulating salinities (5–25) whilst on C. eulimene the influence was more pronounced at salinities above the isosmotic point (28). The influence of salinity and cadmium on both survival and osmoregulation of the two crustaceans are discussed by outlining the chemical and physiological mechanisms involved.

Keywords: hyper-osmoregulation, hypo-iso-osmoregulation, LC50, osmolality, osmotic capacity, toxicity

African Journal of Aquatic Science 2011, 36(2): 181–189

Author Biographies

M Thwala
Department of Zoology and Coastal Research Unit of Zululand, University of Zululand, Private Bag 1001, KwaDlangezwa 3886, South Africa; Current address: CSIR, Natural Resources and the Environment, PO Box 395, Pretoria 0001, South Africa
BK Newman
Department of Zoology and Coastal Research Unit of Zululand, University of Zululand, Private Bag 1001, KwaDlangezwa 3886, South Africa; Current address: CSIR, Natural Resources and the Environment, PO Box 17001, Congella 4013, South Africa
DP Cyrus
Department of Zoology and Coastal Research Unit of Zululand, University of Zululand, Private Bag 1001, KwaDlangezwa 3886, South Africa
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Articles

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eISSN: 1727-9364
print ISSN: 1608-5914