Vol. 57, 2018 (update: 2018.05.23; 06.20) Distinct Size and Distribution Patterns of the Sand-sifting Sea Star, Archaster typicus, in an Urbanised Marine EnvironmentYong Kit Samuel Chan1,*, Tai Chong Toh2, and Danwei Huang1,2 doi:10.6620/ZS.2018.57-28
1Department
of Biological Sciences, National University of Singapore, Singapore
117543, Republic of Singapore (Received 13 December 2017; Accepted 2 May
2018; Communicated by Benny K.K. Chan) Yong
Kit Samuel Chan, Tai Chong Toh, and Danwei Huang (2018) Archaster typicus
is a microphagous sea star ubiquitous throughout sandy shoals of the
Indo-Pacific. Along highly urbanised coasts, loss of sandy habitats
through land reclamation and degradation of adjacent mangrove forests
and seagrass meadows, which serve as nurseries for A. typicus, could lead to local
extinction of this species. To determine the population status of A. typicus
in Singapore, we performed belt-transect surveys at three modified
shores, then compared size structure, clustering patterns and
ontogenetic shifts within the Central Indo-Pacific region. We found
that A. typicus individuals
were, among other things, larger in Singapore (79.2 ± 14.2 mm) than the
rest of the Central Indo-Pacific region with further differences
amongst Singapore’s sites. Sea stars of this species were also greatly
clustered in smaller areas within the transects, with most transects
presenting small Nearest Neighbour Index values of < 1. While
ontogenetic shifts were noted in previous studies, no juveniles have
been recorded in the nursery habitats of mangroves and seagrasses, with
limited size and mating seasonalities. Although A. typicus
appears to have grown in size considerably on reclaimed beaches in
Singapore, the lack of any apparent ontogenetic connectivity here may
threaten the sea star populations in the near future, particularly in
the context of growing coastal development in Southeast Asia. Key words: Asteroidea, Population ecology,
Artificial shores, Intertidal ecology, Archaster typicus. *Correspondence: Tel: (+65) 6516 2699. E-mail:
samuelc@u.nus.edu |