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Does human infringement at the spawning grounds challenge horseshoe crab eggs and their embryogenesis?
Bryan Raveen Nelson1, Behara Satyanarayana2, Moh Julia Hwei Zhong3, Faizah Shaharom4.
Horseshoe crabs come ashore to search for surf-protected areas with loosely
packed sediments to spawn. This enables the buried horseshoe crab eggs to have sufficient
oxygenation and moisture to complete their embryogenesis. Under these circumstances,
Balok, on east Peninsular Malaysia (South, South China Sea) was frequently visited
by Tachypleus gigas (Müller, 1785) for their spawning. It became doubtful whether
horseshoe crab embryogenesis could complete under stressful habitat conditions onset
human infringement through physical infrastructure placement on the beach. In addition,
the absence of biological evaluating tools triggered the idea to evaluate the health of
horseshoe crab spawning grounds using parasitic worms as sensitive indicators. In this
study, field visits were made between 2009 and 2014 to trace horseshoe crab nests. Upon
successful excavation, the eggs were collected carefully from the nests using plastic hand
shovel. Meanwhile, nematodes (Ascaris spp. and Dolicholaimus spp.) and polychaetes
(Glycera spp. and Lumbrineris spp.) as well as poor conditioned eggs including those in
black (unfertilized/desiccated) or red (bacteria infected eggs), were also recorded from
the horseshoe crab nests. The assumed healthy green-yellow green horseshoe crab eggs
were brought back to the laboratory and acclimatized for 2 days under 28 ‰ salinity and
28 ºC prior the laboratory culture. The number of days in reaching third embryonic moult
(Stage-20), hatching of first-instar trilobite larvae and moulting into second-instar was
recorded for 40 days. While the field visits of 2011 documented 5-6 worms (nematode and
polychaete) per horseshoe crab nest, during 2013, it increased to 6-11 worms. It was clear
that physical alterations that took place at the beach during 2011 such as construction of
erosion barriers, parking lot and then, the fish jetty during 2013 were responsible for the
increased worm intrusion into horseshoe crab nests. The higher abundance of nematodes
and polychaetes were significantly correlated (P < 0.05) with the increasing number of
black and red eggs after the year 2011, when human infringement became active at Balok.
Together, the duration for horseshoe crab embryogenesis to reaching Stage-20 and the
duration to hatching into the trilobite larvae were both, delayed up to 5 days and, the
egg hatching viability was reduced up to 63% after nematodes and polychaetes trespassed
the horseshoe crab nests. With this, poor environment health affects the quality of buried
horseshoe crab eggs. Hence, conservation and management efforts are necessary to
prevent loss of T. gigas population and their spawning area at Balok, the most documented
horseshoe crab spawning ground on east Peninsular Malaysia.
Affiliation:
- Universiti Malaysia Terengganu, Malaysia
- Universiti Malaysia Terengganu, Malaysia
- Universiti Malaysia Terengganu, Malaysia
- Universiti Malaysia Terengganu, Malaysia
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Indexation |
Indexed by |
MyJurnal (2021) |
H-Index
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4 |
Immediacy Index
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0.000 |
Rank |
0 |
Indexed by |
Scopus 2020 |
Impact Factor
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CiteScore (0.9) |
Rank |
Q3 (Geography, Planning and Development) Q4 (Pollution) Q4 (Management, Monitoring, Policy and Law) |
Additional Information |
SJR (0.175) |
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