Bos AR et al. (2011), Ontogenetic habitat shift, population growth, a...

ECB-ART-43204

Mar Biol 2011 Jan 01;1583:639-648. doi: 10.1007/s00227-010-1588-0.

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Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea).

Bos AR , Gumanao GS , van Katwijk MM , Mueller B , Saceda MM , Tejada RL .

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Archaster typicus, a common sea star in Indo-Pacific regions, has been a target for the ornamental trade, even though little is known about its population biology. Spatial and temporal patterns of abundance and size structure of A. typicus were studied in the Davao Gulf, the Philippines (125°42.7''E, 7°0.6''N), from February 2008 to December 2009. Specimens of A. typicus were associated with intertidal mangrove prop roots, seagrass meadows, sandy beaches, and shoals. Among prop roots, specimens were significantly smaller and had highest densities (131 ind. m-2) between November and March. High organic matter in sediment and a relatively low predation rate seemed to support juvenile life among mangroves. Size and density analyses provided evidence that individuals gradually move to seagrass, sandy habitats, and shoals as they age. Specimens were significantly larger at a shoal (maximum radius R = 81 mm). New recruits were found between August and November in both 2008 and 2009. Timing of recruitment and population size frequencies confirmed a seasonal reproductive cycle. Juveniles had relatively high growth rates (2-7 mm month-1) and may reach an R of 20-25 mm after 1 year. Growth rates of larger specimens (R > 30 mm) were generally <2 mm month-1. The activity pattern of A. typicus was related to the tidal phase and not to time of day: Specimens moved over the sediment surface during low tides and were burrowed during high tides possibly avoiding predation. This is one of the first studies to document an ontogenetic habitat shift for sea stars and provides new biological information as a basis for management of harvested A. typicus populations.

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Genes referenced: LOC100887844

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References [+] :

McEdward, Life Cycle Evolution in Asteroids: What is a Larva? 1993, Pubmed, Echinobase

	Fig. 1. Map of Davao Gulf with study area magnified on right. Isobaths in 300-m intervals. Circles along shore represent mangroves. Exact location in Philippines can be found in Bos et al. (2008b)
	Fig. 2. Archaster typicus. Mean density (individuals m−2) with SD of visible sea stars in 1-m2 quadrats (n = 6) in seagrass and sand in Samal Island observed hourly on 15–16 September 2008. Water depth (m) shows tidal amplitude (solid line). Horizontal bar indicates period from sunset to sunrise
	Fig. 3. Archaster typicus. Mean density (individuals m−2; filled circle) and mean biomass (g m−2; open circle) with SD in mangroves, seagrass, and sand between August 2008 and December 2009

	Fig. 5. Archaster typicus. Radius frequencies (pooled data for mangrove, seagrass, and sand) in Samal Island around every full moon between February 2008 and December 2009
	Fig. 6. Archaster typicus. Mean radius (mm) of cohorts as result of a modal progression analysis (open circle, n = 6,279; pooled data for mangrove, seagrass, and sand) and radius increments of enclosed specimens (filled circle, n = 28) between January 2008 and December 2009
	Fig. 7. Archaster typicus. Growth rates (mm month−1) from natural population (open circle, n = 39; thin regression line, r 2 = 0.469) and enclosed specimens (filled circle, n = 116, and filled inverted triangle, n = 49; dotted regression line, r 2 = 0.243). Thick regression line represents natural population and enclosed sea stars excluding selected juveniles (G = 0.178 + 5.734e−0.048R, n = 155, r 2 = 0.497)