Polyunsaturated fatty acids in fish tissues more closely resemble algal than terrestrial diet sources

• Published in: Hydrobiologia Vol. 848; no. 2; pp. 371 - 383
• Main Authors: Ebm, Nadine, Guo, Fen, Brett, Michael T., Bunn, Stuart E., Kainz, Martin J.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.01.2021; Springer; Springer Nature B.V
• Subjects: Algae; Animal tissues; Aquatic ecological zones; Aquatic invertebrates; Aquatic organisms; Arachidonic acid; Benthos; Biomedical and Life Sciences; Body organs; Composition; Consumers; Diet; Docosahexaenoic acid; Ecology; Eicosapentaenoic acid; Fatty acids; Fish; Fish as food; Fish oils; Fishes; Freshwater; Freshwater & Marine Ecology; Freshwater fish; Headwaters; Inland water environment; Invertebrates; Leaves; Life Sciences; Lipids; Macroinvertebrates; Muscles; Omega-3 fatty acids; Organs; Polyunsaturated fatty acids; Primary Research Paper; Rivers; Storage; Streams; Terrestrial environments; Tissue; Unsaturated fatty acids; Vertebrates; Zoobenthos; Zoology; Stream food webs; Headwaters; Fish eyes; Food quality; Docosahexaenoic acid; Fish brain
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/s10750-020-04445-1

The River Continuum Concept implies that consumers in headwater streams have greater dietary access to terrestrial basal resources, but recent studies have highlighted the dietary importance of high-quality algae. Algae provide consumers with physiologically important omega-3 (n-3) polyunsaturated fatty acids (PUFA), particularly eicosapentaenoic acid (EPA). However, terrestrial plants and most benthic stream algae lack the long-chain (LC) n-3 PUFA docosahexaenoic acid (DHA, 22:6n-3), which is essential for neural development in fish and other vertebrates. We sampled subalpine streams to investigate how the PUFA composition of neural (brain and eyes), muscle, and liver tissues of freshwater fish is related to their potential diets (macroinvertebrates, epilithon, fresh and conditioned terrestrial leaves). The PUFA composition of consumers was more similar to epilithon than to terrestrial leaves. Storage lipids of eyes most closely resembled dietary PUFA (aquatic invertebrates and algae). However, DHA and arachidonic acid (ARA, 20:4n-6) were not directly available in the diet but abundant in organs. This implies that algal PUFA were selectively retained or were produced internally via enzymatic PUFA conversion by aquatic consumers. This field study demonstrates the nutritional importance of algal PUFA for neural organs in aquatic consumers of headwater regions.