Demographics of horseshoe crab populations in Kota Kinabalu Sabah Malaysia with emphasis on Carcinoscorpius rotundicauda and some aspects of its mating behaviour

Robert R., . and Muhammad Ali S. H., . and Amelia-Ng P. F., . Demographics of horseshoe crab populations in Kota Kinabalu Sabah Malaysia with emphasis on Carcinoscorpius rotundicauda and some aspects of its mating behaviour. pp. 375-388.

Survey results of two populations of Carcinoscorpius rotundicauda at a fishing ground and within a protected area were compared so as to establish effects of human activities on the species. Tachypleus tridentatus and Tachypleus gigas were also found in both sites but in substantially less abundance. The operational sex ratios were male-biased at both sites; 5.50 (n 52) at the fishing ground (Site 1) and 2.58 (n 68) at the protected area (Site 2). Size distributions at both sites were similar of which females were approximately 16 larger than males. A captive experiment was conducted where pair-forming behaviour ofC. Rotundicauda was observed for 30 days. Amplexus were most frequently formed when the sex ratio was balanced lasting for 2.44 2.03 days and eight days maximum. Female body size and amplex-forming frequency were positively correlated (r 0.678 n 7 p 0.10) attributable to fitness projected by the phenotype. Solitary males did not exhibit aggression towards paired males allowing the latter to retain mate exclusivity for considerable periods. Anthropogenic pressures caused an unnatural shift in the population structure of local horseshoe crabs that could lower their reproductive success making eventual extirpation possible.

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Abstract

Survey results of two populations of Carcinoscorpius rotundicauda at a fishing ground and within a protected area were compared so as to establish effects of human activities on the species. Tachypleus tridentatus and Tachypleus gigas were also found in both sites but in substantially less abundance. The operational sex ratios were male-biased at both sites; 5.50 (n 52) at the fishing ground (Site 1) and 2.58 (n 68) at the protected area (Site 2). Size distributions at both sites were similar of which females were approximately 16 larger than males. A captive experiment was conducted where pair-forming behaviour ofC. Rotundicauda was observed for 30 days. Amplexus were most frequently formed when the sex ratio was balanced lasting for 2.44 2.03 days and eight days maximum. Female body size and amplex-forming frequency were positively correlated (r 0.678 n 7 p 0.10) attributable to fitness projected by the phenotype. Solitary males did not exhibit aggression towards paired males allowing the latter to retain mate exclusivity for considerable periods. Anthropogenic pressures caused an unnatural shift in the population structure of local horseshoe crabs that could lower their reproductive success making eventual extirpation possible.

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Item Type:	Article
AGROVOC Term:	Horseshoe crabs
AGROVOC Term:	Copulation
AGROVOC Term:	Fishing areas
AGROVOC Term:	Animal husbandry methods
AGROVOC Term:	Spawning
AGROVOC Term:	Habitats
AGROVOC Term:	Mangroves
AGROVOC Term:	Anthropogenic factors
AGROVOC Term:	Anthropogenic influence
AGROVOC Term:	Animal offspring
Geographical Term:	Malaysia
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	26 Apr 2025 03:13
URI:	http://webagris.upm.edu.my/id/eprint/21362

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