Analysis of Grain-Size Selection by Deposit-Feeding Holothurians and Echinoids (Echinodermata) from a Shallow Reef Lagoon, Discovery Bay, Jamaica

Abstract

The size-frequency distribution of sediments from the foreguts of the aspidochirote holothurians Isostichopus badionotus, Holothur~a rnexlcana and H. arenicola, and the spatangoid echinoids Meoma venlricosa and Plagiobr~ssus grandis, collected in the field, closely resembled those of sediments sampled adjacent to each animal. The differences in graphic mean grain size fell within the range of variability of the available sediment. Laboratory experiments using 2 grades of poorly sorted sand confirmed that I badionotus, H. mexicana, H. arenicola, H. grisea, Actlnopyga agassiziand the apodous holothurian Euapta lappa did not discriminate between different size grains. Small and large specimens of the first 3 species showed no difference In the spectrum of grain sizes ingested In the laboratory. Critical evaluation of previous reports reveals no unequivocal evidence of selective feeding by deposit-feeding holothurians. In general, deposit-feeding holothurians and spatangoids appear to be incapable of exercising any preference for particular grain sizes. The significance of the differences in surface texture of the buccal podia between holothurian species is unclear, but texture does not appear to b e related to size of food particles in any simple way. It is suggested that feeding may not b e a purely mechanical process, as previously thought, but that adhesive mucus on the buccal podia might play a role. In contrast to other deposit-feeding taxa, grain size does not appear to b e a significant mechanism for resource partitioning between coexisting species of tropical holothurians; other studies suggest microhabitat differences may be more important.

A Review of Sea Cucumber Aquaculture, Ranching, and Stock Enhancement in China

“…The sea cucumber juveniles are preyed on by crabs and sea breams (Xing and Wang, 2000). Some tropical sea cucumber have fish predators, although there is relatively little predation due to toxins found in the body wall (Hammond, 1982). They are sometimes referred to as the earthworms of the sea because they are responsible for the recycling of detritus and mixing of substrate and they help control the populations of marine pests and pathogens in the sediments.…”

Aggregations and temporal changes in the activity and bioturbation contribution of the sea cucumber Holothuria whitmaei (Echinodermata: Holothuroidea)

“…ha -1 (Massin & Doumen 1986, Conand 1989, Preston 1993, Long et al 1996, Lawrence et al 2004); however, densities of 100 to 275 ind. ha -1 have been reported (Conand 1989, Lokani 1990, Kinch et al 2008.Activity behaviour in sea cucumbers has been linked with feeding (Hammond 1982, Massin 1982a, Shiell & Knott 2008. Feeding in aspidochirotes is achieved by ingesting and stripping sediments of associated organic nutrients (Massin 1982a).…”

“…Consequently, holothurians are strong bioturbators of the upper 5 mm of marine sediments (Bakus 1973, Massin 1982a,b, Aller & Yingst 1985, Amon & Herndl 1991. Estimates of the total bioturbation contribution of sea cucumbers vary but, at greater densities, holothurians are reported to process several tonnes of sediment per annum (Hammond 1982, Uthicke 1999. Apart from the physical manipulation of sediments, sea cucumbers, through their ingestion and metabolism of organic matter, contribute nitrogen-based compounds directly to the sediment/water interface (Massin 1982b, Birkeland 1988, Uthicke 1999, 2001a, thereby enhancing benthic community productivity (Uthicke & Klumpp 1998).…”

“…Estimates of the total bioturbation contribution of sea cucumbers vary but, at greater densities, holothurians are reported to process several tonnes of sediment per annum (Hammond 1982, Uthicke 1999. Apart from the physical manipulation of sediments, sea cucumbers, through their ingestion and metabolism of organic matter, contribute nitrogen-based compounds directly to the sediment/water interface (Massin 1982b, Birkeland 1988, Uthicke 1999, 2001a, thereby enhancing benthic community productivity (Uthicke & Klumpp 1998).Studies of the bioturbation and nutrient recycling contribution of aspidochirotes have traditionally focused on low-to medium-value holothurians (Hammond 1982, Klinger et al 1994, Uthicke 1999, 2001a,b, Ferdouse 2004. Two of the most abundant low-value aspidochirotes of the Indo-Pacific, Holothuria atra and Stichopus chloronotus, are prolific bioturbators of coral reef sediments, processing the upper 5 mm of marine sediments in their habitat at least once per annum (Uthicke 1999).…”

Is there a link between the type of habitat and the patterns of abundance of holothurians in shallow rocky reefs?

“…Quadrats, several meters apart, were haphazardly laid out. Since holothurians remain hidden in the rocky substrate during daytime hours, but begin to merge following nightfall (Hammond, 1982), we decided to carry out all diving during nighttime with the help of underwater lamps. To eliminate the potential effect of the 'habitat complexity' on the spatial patchiness of holothurians, all quadrats were deployed on smooth horizontal rocky surfaces, avoiding as much as possible the presence of structural 'elements' that potentially could increase the complexity of the substrate (pebbles, boulders, caves, crevices, etc).…”