An aquatic vertebrate can use amino acids from environmental water

Abstract

Conventional food-web theory assumes that nutrients from dissolved organic matter are transferred to aquatic vertebrates via long nutrient pathways involving multiple eukaryotic species as intermediary nutrient transporters. Here, using larvae of the salamander Hynobius retardatus as a model system, we provide experimental evidence of a shortcut nutrient pathway by showing that H. retardatus larvae can use dissolved amino acids for their growth without eukaryotic mediation. First, to explore which amino acids can promote larval growth, we kept individual salamander larvae in one of eight different high-concentration amino acid solutions, or in control water from which all other eukaryotic organisms had been removed. We thus identified five amino acids (lysine, threonine, serine, phenylalanine, and tyrosine) as having the potential to promote larval growth. Next, using 15 N-labelled amino acid solutions, we demonstrated that nitrogen from dissolved amino acids was found in larval tissues. These results suggest that salamander larvae can take up dissolved amino acids from environmental water to use as an energy source or a growth-promoting factor. Thus, aquatic vertebrates as well as aquatic invertebrates may be able to use dissolved organic matter as a nutrient source.

Metabolites from Microbes Isolated from the Skin of the Panamanian Rocket Frog Colostethus panamansis (Anura: Dendrobatidae)

“…Phenylalanine 3 is an essential amino acid, known to be directly taken up from water, which promotes larval growth in the salamander Hynobius retardatus [ 59 ]. Considering that microbes can be transmitted vertically through parental care to the embryos [ 60 , 61 ], if such vertical transmission occurs in C. panamansis during egg attendance and tadpole transport, phenylalanine bacterial producers might serve as growth promoters at the larval stages of this frog.…”

Invasive investigation: uptake and transport of l-leucine in the gill epithelium of crustaceans

“…While waterborne amino acid uptake has been studied in 10 different marine invertebrate taxa, now including four arthropod species, the identification of amino acid transporters in marine invertebrates relies heavily on mammalian models ( Stephens, 1988 ; Glover et al , 2011 ; Katayama et al , 2016 ; Blewett and Goss, 2017 ). As such, little is known about the exact transporters present on invertebrate gill epithelia; however, most mechanistic evidence suggests a combination of SLC6 family Na + /AA cotransporters on the basolateral and apical membrane, allowing amino acid transport across the gill epithelia ( Wright, 1987 ; Applebaum et al , 2013 ; Blewett and Goss, 2017 ).…”