Changes in Sediment Fatty Acid Composition during Passage through the Gut of Deposit Feeding Holothurians: Holothuria atra (Jaeger, 1883) and Holothuria leucospilota (Brandt, 1835).

Prosper L Mfilinge,Makoto Tsuchiya

doi:10.1155/2016/4579794

Prosper L Mfilinge, Makoto Tsuchiya

Open Access

https://doi.org/10.1155/2016/4579794

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Abstract

Sea cucumbers Holothuria atra and Holothuria leucospilota play an important role in the bioturbation of sediment in coral reef and rocky intertidal ecosystems. This study investigated changes in sediment fatty acid (FA) composition during gut passage in H. atra and H. leucospilota. The FA composition did not differ significantly between species. Comparison of FA composition in ambient sediment (AS), foregut (FG), midgut (MG), hindgut (HG), and faecal pellets (FPs) indicated that marked changes in FA composition occurred during passage through the gut of H. atra and H. leucospilota. Saturated fatty acids (SAFAs), monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and branched fatty acids (BrFAs) were significantly higher in FG than in AS, suggesting that both species selectively ingested nutrient rich particles. Significant reduction of SAFAs, MUFAs, PUFAs, and BrFAs occurred in MD and HD, with complete elimination of most PUFAs in FPs. A decrease in PUFAs 20:5ω3, 18:4ω3, 22:5ω3, 22:6ω3, 18:2ω6, 18:3ω3, 18:3ω6, odd-numbered BrFAs, and MUFA 18:1ω7 indicated that algal detritus and bacteria were important part of diet. These results have implications for the fate of specific dietary FAs, especially ω3 and ω6, and the contribution holothurian FPs make to the FA composition of coral reef and rocky intertidal ecosystems.

Highlights

The feeding activity of holothurians plays an important role in the bioturbation of sediments [1, 2] by removing substantial amount of organic matter during gut passage [3]
The results indicated that fatty acid (FA) composition and concentration of the ingested sediments changed during passage through the FG, MG, and HG and after release in the faecal pellets (FPs) for both Holothuria atra and Holothuria leucospilota
MANOVA indicated a significant interaction between species and gut positions (MANOVA, Pillai’s trace, p < 0.0001), which indicated that both species and position of sediment along the gut affect the concentration of Saturated fatty acids (SAFAs), monounsaturated fatty acids (MUFAs), Polyunsaturated fatty acids (PUFAs), and branched fatty acids (BrFAs) (Figure 2)

Summary

Introduction

The feeding activity of holothurians plays an important role in the bioturbation of sediments [1, 2] by removing substantial amount of organic matter during gut passage [3]. This sediment reworking activity is essential, in order to keep coral reef ecosystems clean and healthy. It has been shown that the efficiency of processing of the sediment and the amount of reworked sediment depends on the length and morphology of the digestive tract, particle sizes, and digestive speed of the ingested sediments [2] Because these features vary among the holothurians species, sediment reworking efficiency may be species specific. 20:5ω3 and 22:6ω3 are found in higher quantities in diatoms and dinoflagellates and have been used as diatom and dinoflagellate markers in aquatic environments, respectively [7, 8, 11, 12]

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