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Prospecting the Photosynthetic Flatworm Symsagittifera roscoffensis as a Novel Fish-Feed

Nathan J. Thomas Orcid Logo, Kam Tang Orcid Logo, Christopher Coates

Aquaculture Journal, Volume: 3, Issue: 2, Pages: 149 - 167

Swansea University Authors: Kam Tang Orcid Logo, Christopher Coates

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DOI (Published version): 10.3390/aquacj3020013

Abstract

Symsagittifera roscoffensis is an intertidal Acoel flatworm that forms a symbiotic relationshipwith the alga Tetraselmis convolutae. Members of the genus Tetraselmis are known to have a high nutritionalvalue and have been widely used to enrich intermediate prey for fish within the aquacultureindustr...

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Published in: Aquaculture Journal
ISSN: 2673-9496
Published: MDPI AG 2023
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa63540
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Abstract: Symsagittifera roscoffensis is an intertidal Acoel flatworm that forms a symbiotic relationshipwith the alga Tetraselmis convolutae. Members of the genus Tetraselmis are known to have a high nutritionalvalue and have been widely used to enrich intermediate prey for fish within the aquacultureindustry; therefore, S. roscoffensis could be a good candidate as a trophic shortcut to deliver algalnutrition to fish. In this study, we investigated the likelihood of five ornamental tropical freshwaterand six ornamental marine fishes to consume this worm, either as live feed or in freeze-dried form. Wealso tested the ability of S. roscoffensis to form a symbiotic relationship with alternative algal species,analysing the nutritional profile of S. roscoffensis when grown in different media. All the experimentalfish consumed live worms to some degree, with the exception of one species (Meiacanthus grammistes);the response time to the worms ranged from 1.1–68.6 s for freshwater ornamental species to 1–24 s formarine ornamental species, and in most cases, this was comparable to or shorter than their responsetime to the reference diet Artemia. The fishes showed no negative effects after consuming the worms.We obtained similar results with freeze-dried worms in terms of the number of worms eaten, responsetime, and feeding time. Symsagittifera roscoffensis was able to form a symbiotic relationship withall the tested algal species of the genus Tetraselmis, but not with members of other genera. Wormsgrown in nutrient media (f/2 and f/4) had significantly higher contents of protein, pigments, andtotal and polyunsaturated fatty acids, including eicosapentaenoic acid (20:5n 3) and -linolenicacid (18:3n 3), than those grown in seawater. These results show that S. roscoffensis was acceptableto many ornamental fish species, delivering key algal ingredients that are beneficial to fish health;hence, it is a promising alternative to conventional fish feeds for the ornamental pet trade.
Keywords: photosymbiosis; acoel worm; ornamental fish; nutrition; algal switching; fish health
College: Faculty of Science and Engineering
Funders: RWIF (RIG1036-125)
Issue: 2
Start Page: 149
End Page: 167