Growth and Survival of Larval Sandfish, Holothuria scabra (Echinodermata: Holothuroidea), Fed Different Microalgae

Abstract

This study assessed the nutritional value of four species of microalgae for larval sandfish, Holothuria scabra (Echinodermata: Holothuroidea). Two-day-old larvae were fed either a single diatom (Chaetoceros muelleri, Chaetoceros calcitrans), flagellate (Isochrysis aff. galbana (T-ISO), Pavlova salina), or a ternary microalgal diet (TMD) comprised of 40% C. muelleri, 40% T-ISO, and 20% P. salina for 12 d. On Days 4, 6, and 8 length of larvae fed either C. muelleri, C. calcitrans, or the TMD was significantly greater than in T-ISO and P. salina fed larvae as well as the unfed control larvae. T-ISO fed larvae had a significantly greater length compared to unfed larvae on Days 4, 6, and 8; however, larvae fed P. salina had a significantly greater length compared to unfed larvae on Days 6 and 8 only. Survival of larvae fed either C. muelleri or the TMD was significantly better than the flagellate fed and unfed larvae on Days 4, 8, and 12. There was no significant difference between survival of unfed larvae and larvae fed either T-ISO or P. salina during the 12-d larval culture period. On Day 12, larvae fed either a diatom or the TMD developed in excess of 84% competent doliolariae. Larvae fed C. muelleri had a significantly higher percentage competent doliolariae than larvae from all other treatments except the TMD. Neither larvae fed either T-ISO or P. salina nor unfed larvae developed any competent doliolariae. In conclusion, this study showed C. muelleri to be the most effective of the four microalgae tested as a single microalgal diet for larval H. scabra and, as such, C. muelleri will be used as a reference diet in future studies.

Ingestion and digestion of live microalgae and microalgae concentrates by sandfish, Holothuria scabra, larvae

“…Chaetoceros muelleri has been used as a monospecific diet for sandfish larvae (Battaglene, 1999;Duy, 2012;Knauer, 2011). It is surprising therefore that ingestion of C. muelleri in this study was relatively low by all ages of sandfish larvae when compared to other microalgae.…”

“…Duy, 2010;James et al, 1994;Morgan, 2001) and a poor diet by others (e.g. Battaglene, 1999;Knauer, 2011). The reasons for these contrasting results are unclear but this phenomenon highlights our limited knowledge in this field and lack of consensus towards development of appropriate diets for larval culture of sandfish.…”

“…However, increasing the ration of TISO from a density of 4 x 10 4 cell mL -1 to 8 x 10 4 cell mL -1 was reported to negatively affect growth and development of sandfish larvae, possibly because of resulting changes in pH and levels of un-ionised ammonia (Morgan, 2001). Two other studies have reported that TISO supported poor larval competence at metamorphosis when fed to sandfish auriculariae (Battaglene, 1999;Knauer, 2011) and this may relate to the nutrient composition of this species. Although TISO contains relative high levels of docosahexaenoic acid (DHA, 22:6n-3), it has relatively low levels of eicosapentaenoic acid (EPA, 20:5n-3).…”

“…Our results indicate that C. muelleri is unsuitable as a food for D2 sandfish larvae despite the fact that this species is considered to be a rich source of essential fatty acids which are crucial for the normal development and survival of marine invertebrate larvae (Carboni et al, 2012;Reitan, 2011;Scholtz et al, 2013). More research is required to optimise the use of C. muelleri for feeding later auricularia stages as it has been reported to be a more effective diet for sandfish auricularia larvae than TISO and P. salina (Knauer, 2011). Microalgae ration relative to larval stocking density, for example, is likely to influence rates of ingestion and digestion of C. muelleri.…”

“…and Isochrysis aff. galbana (TISO) used either singly or in combination (Agudo, 2006;Battaglene, 1999;Duy, 2012;Gamboa et al, 2012;James et al, 1994;Knauer, 2011).…”