Feeding behaviour in some teleosts is triggered by single amino acids primarily through olfaction

Abstract

The present study investigated behavioural responses of naı¨ve rainbow trout Oncorhynchus mykiss, lake charr Salvelinus namaycush, lake whitefish Coregonus clupeaformis and goldfish Carassius auratus to food extracts as well as selected amino acids (at 10 À6 M) and related chemicals in a flow-through behaviour trough. Cysteine, the most potent olfactory stimulating amino acid determined electrophysiologically, enhanced locomotor activity, an initial arousal behaviour, in all species examined, in exactly the same fashion as did food extracts. The increased locomotor activity was followed by distinct species-specific search behavioural patterns: 1) bottom searching in rainbow trout; 2) surfacing and jumping in lake charr; 3) exploratory behaviour against the trough window in lake whitefish; 4) gravel pecking in goldfish. Olfactory-stimulating neutral amino acids alanine and serine and gustatory-stimulating imino acid proline were effective, to varying degrees, in eliciting feeding behaviour. Arginine and glutamate suppressed the locomotor activity in rainbow trout, but triggered feeding behaviour in the other species. Agmatine, a decarboxylated arginine, stimulated feeding behaviour in all species tested, except rainbow trout. The observed behavioural responses were in close accordance with the electrophysiological threshold and specificity. Together, the present data demonstrate that single amino acids and closely related chemicals initiate feeding behaviour primarily by olfaction, and interchangeably and complemented by gustation, in naive fishes.

Sensory evolution in blind cavefish is driven by early embryonic events during gastrulation and neurulation

“…Chemosensory detection of amino acids depends on both gustatory and olfactory sensory modalities (Hara, 1994). In most fish species, the detection threshold of the taste buds is in the micromolar range (Hara, 1994(Hara, , 2006(Hara, , 2015, higher than the concentrations used here. However, as CF possess more taste buds than SF on their lips and face (Schemmel, 1967;Varatharasan et al, 2009;Yamamoto et al, 2009), we needed to ascertain that the observed response to amino acids was truly olfactory mediated.…”

Coordinated shift of olfactory amino acid responses and V2R expression to an amphibian water nose during metamorphosis

“…Amino acids constitute an important odor class in aquatic organisms, signalling the presence of food [8,11]. To examine the fate of olfactory responses during metamorphosis of Xenopus laevis we monitored responses to amino acids at three ontogenetic stages, 57/58, 61/62 and 66+ (beginning metamorphosis with functional ORNs already present in the MC, midmetamorphosis, and post-metamorphosis, respectively; see Fig.…”

“…Remarkably, ORNs activated by amino acids, a major odor group for fish and frogs [8][9][10][11], show a similar spatial distribution as the V2R and TRPC2 expression [6]. It may be expected that amino acid responses and possibly V2R expression do not remain unaltered during metamorphosis, as there appears to be no use for receptors to detect water-borne odorants such as amino acids in the air nose of an adult frog.…”

Chemosensory reception, behavioral expression, and ecological interactions at multiple trophic levels

“…Amino acids are abundant in tissues of marine and freshwater invertebrates (Sutcliffe, 1962;Firling, 1977;Edwards, 1982;Herzog and Liappis, 1987;Carr et al, 1996;Zimmer et al, 1999), and they act as feeding stimulants/ attractants for diverse predatory species (Carter and Steele, 1982;Carr, 1988;Valentincic and Captrio, 1994;Coman et al, 1996;Hara, 2006;Keiichiro et al, 2006). In the present study, worm (Eisenia rosea Gates 1942) prey of adult newts (Taricha torosa Rathke 1883) were collected on three occasions (April 14, August 26 and October 12, 2004) from natural streamside sediments at the field study site.…”