Direct evidence for embryonic uptake of paternally-derived nutrients in two pipefishes (Syngnathidae: Syngnathus spp.).

Seahorses, sea dragons and pipefishes of the teleost family Syngnathidae are unique in that embryos develop within specialized brooding structures of the male. We enriched brooding Syngnathus fuscus and Syngnathus floridae males with injections of L-lysine-[(15)N(2)] and 16:0-palmitic acid 1-[(13)C] to demonstrate embryonic uptake of paternally-derived nutrients. While all embryos demonstrated amino acid enrichment, late stages showed significantly higher [(15)N], indicating greater utilization of paternal resources as yolk reserves diminished and embryonic energy demands increased. Limited embryonic [(13)C] uptake, defined as less than 10% of adult enrichment, in 75 and 81% of S. floridae and S. fuscus respectively signified rapid lipid metabolism and thus the need for greater enrichment. Interspecific differences in embryonic uptake of paternally-derived nutrients were not demonstrated. However, interspecific differences in egg nutrient reserves and fry size but comparable fry nutrient levels along with data from a published paternal exposure study indicate paternal transfer in S. fuscus most likely compensates for the comparative egg nutrient deficiency. This study is the first to our knowledge to provide direct evidence for the functional significance of the brood pouch in nutrient provisioning. These results add comparative information on the diversity of Syngnathid paternal care and further our understanding of paternal influence on development.