William E. S. Carr

Food Habits of Juvenile Marine Fishes Occupying Seagrass Beds in the Estuarine Zone near Crystal River, Florida

Abstract Quantitative gravimetric analyses of stomach contents were carried out on juveniles of 21 species of fishes that cohabit seagrass beds near Crystal River, Florida. Our analyses were based on dry weights of food items and are expressed as percent of total stomach contents. The species analyzed were Harengula pensacolae, Opisthonema oglinum, Anchoa hepsetus, Anchoa mitchilli, Synodus foetens, Strongylura marina, Hyporhamphus unifasciatus, Oligoplites saurus, Trachinotus falcatus, Eucinostomus gula, Haemulon plumieri, Orthopristis chrysoptera, Bairdiella chrysura, Cynoscion nebulosus, Diplodus holbrooki, Lagodon rhomboides, Microgobius gulosus, Chasmodes saburrae, Menidia beryllina, Trinectes maculatus, and Sphoeroides nephelus. Analyses of stomach contents taken from small, sequentially arranged size classes enabled us to delineate discrete ontogenetic changes in food habits in many of the species. In the 15 species in which planktivorous feeding stages were detected, only zooplankters were consume...

The Molecular Nature of Chemical Stimuli in the Aquatic Environment

Many aquatic organisms possess well-developed chemosensory systems that are adapted to monitoring changes in the chemical composition of the aqueous environment in which they live. For aquatic organisms. specific chemicals in the environment may evoke highly predictable changes in behavior. Facets of behavior known to be affected by external chemicals include those associated with feeding. avoiding predators, recognizing a suitable habitat, reproducing, migrating. and interacting with conspecific organisms. General reviews of this material are provided by Mackie and Grant ( 1974). Daloze, Braekman. and Tursch (1980). and Atema (1985).

Chemically stimulated feeding behavior in marine animals : Importance of chemical mixtures and involvement of mixture interactions.

A review is provided of the chemical components in tissue extracts that elicit feeding behavior in marine fish and crustaceans. For most species, the major stimulants of feeding behavior in excitatory extracts are an assemblage of common metabolites of low molecular weight including amino acids, quaternary ammonium compounds, nucleosides and nucleotides, and organic acids. It is often mixtures of substances rather than individual components that account for the stimulatory capacity of a natural extract. Recent studies using a shrimp,Palaemonetes pugio, are described in which behavioral bioassays were conducted with complex synthetic mixtures formulated on the basis of the composition of four tissue extracts. These results indicate that synergistic interactions occur among the mixture components. The neural mechanisms whereby marine crustaceans receive and code information about chemical mixtures are also reviewed. Narrowly tuned receptor cells, excited only by particular components of food extracts such as specific amino acids, nucleotides, quaternary ammonium compounds, and ammonium ions, are common in lobsters and could transmit information about mixtures as a labeled-line code. However, since physiological recordings indicate that most higher-level neurons in the brain each transmit information about many components of mixtures, rather than about a single component, it is suggested that information about a complex food odor is transmitted as an across-fiber pattern, instead of a labeled-line code. Electrophysiological recordings of responses of peripheral and central neurons of lobsters to odor mixtures and their components reveal that suppressive interactions occur, rather than the synergistic interactions noted earlier in the behavioral studies. Possible reasons for these differences are discussed. Evidence from the behavioral study indicates that the “direction” of a mixture interaction can be concentration-dependent and the synergism may occur at low mixture concentrations, while suppression may occur at high concentrations.

ANTENNULAR CHEMOSENSITIVITY IN THE SPINY LOBSTER, PANULIRUS ARGUS: STUDIES OF TAURINE SENSITIVE RECEPTORS

1. Taurine sensitive receptors in the antennules of the spiny lobster, Panulirus argus, were identified electrophysiologically.2. Recordings from single receptors revealed a narrow and consistent specificity when tested with taurine, taurine analogs and derivatives, and structurally related compounds.3. Taurine was the most stimulatory compound tested. Threshold concentrations for 36 individual receptors ranged from 10-8 to 10-10 M.4. The taurine analogs, hypotaurine and β-alanine, were also very effective but the phosphonic acid analog of taurine was ineffective.5. Regarding receptor specificity, receptor stimulation was greatest with compounds having single terminal basic (amine) and acidic groups separated by two carbon atoms. Compounds having terminal basic and acidic groups separated by three to five carbon atoms were also active. However, activity decreased with the distance of separation of charged groups.6. Alpha-amino acids and compounds with terminal basic and acidic groups separated by only one...

Chemoreception in the pigfish, Orthopristis chrysopterus: The contribution of amino acids and betaine to stimulation of feeding behavior by various extracts

Abstract 1. 1. In extracts of crab, oyster, sea urchin and mullet, the major stimulants of feeding behavior in the pigfish, Orthopristis chrysopterus, were substances of less than ca. 1000 mol. wt. 2. 2. Quantitative analyses of betaine and the amino acids were conducted to permit the formulation of synthetic mixtures based on the composition of the four extracts. 3. 3. Synthetic mixtures of betaine and the amino acids could account for most of the stimulatory capacity of extracts of crab, oyster and mullet, but for only a small portion of that of sea urchin extract. 4. 4. Comparative tests of solutions containing betaine and/or the amino acids indicated that response elicitation by a particular extract could be due to one of four types of collaborative effects involving these (or other) substances.

Chemical stimulation of feeding behavior in the pinfish, Lagodon rhomboides: Characterization and identification of stimulatory substances extracted from shrimp☆

1. 1. Substances in shrimp extract that induce feeding behavior in the pinfish, Lagodon rhomboides, had amino acid-like properties as evidenced by molecular weights of less than ca. 1000, methanol solubility, stability to acid hydrolysis, retention on a cation exchange column and their non-volatile nature. 2. 2. A quantitative analysis of the 20 amino acids present in shrimp extract provided specific concentrations used to prepare artificial solutions whose potencies were compared in a quantitative manner to the extract itself. 3. 3. A mixture was resolved that contained five amino acids (aspartic acid, glycine, glutamine, isoleucine and phenylalanine) plus betaine which accounted for 20–25% of the activity of the extract. Of the individual substances in the mixture, only betaine had significant activity when tested alone yet it accounted for less than 10% of the activity of the mixture. Quantitative data on the combined effects of various of the six substances are provided.

Chemoreception in the shrimp, Palaemonetes pugio: The role of amino acids and betaine in elicitation of a feeding response by extracts

Abstract 1. 1. Substances of less than ca . 1000 molecular weight present in extracts of blue crab, oyster, sea urchin and mullet were the principal stimulants of a feeding response in the shrimp, Palaemonetes pugio . 2. 2. Synthetic mixtures of amino acids and betaine, formulated on the basis of the composition of the extracts, were found to account for 60–100% of the activity of extracts of crab, oyster and sea urchin but for only ca . 30% of the activity of mullet extract. 3. 3. When tested alone, betaine had only a modest stimulatory capacity; yet this substance made a very significant contribution to the activity of the mixtures. 4. 4. Assays of betaine alone, or of certain mixtures of amino acids, yielded unusual “bell-shaped” dose-response relationships.

CHEMORECEPTION IN THE MUD SNAIL, NASSARIUS OBSOLETUS. II. IDENTIFICATION OF STIMULATORY SUBSTANCES

1. A study was made of the compounds in shrimp extracts which induce the proboscis search reaction in Nassarius obsoletus.2. Compounds identified in shrimp extracts were as follows: alanine, asparagine, aspartic acid, betaine, glutamic acid, glycine, histidine, homarine, inosine, isoleucine, leucine, lactic acid, lysine, methionine, phenlyalanine, proline, serine, taurine, threonine, trimethylamine oxide, tryptophan, tyrosine, urea, and valine. Carnitine was tentatively identified. The amino acids and lactic acid were determined quantitatively; betaine was determined semi-quantitatively.3. Glycine (ca. 10-3 M) and lactate (ca. 5x 10-4 M) were the only compounds identified in the extracts which possessed marked stimulatory capacities when tested individually; betaine (ca. 10-3 M) was mildly stimulatory. However, quantitative analyses of these compounds in shrimp extracts showed that they were present in insufficient concentrations to account for the responses observed with the dilutions of extract which we...

Olfactory receptors of the spiny lobster: ATP-sensitive cells with similarities to P2-type purinoceptors of vertebrates

Summary1.A distinct population of ATP-sensitive cells, with response characteristics indicative of P2-type purinoceptors found in internal tissues of vertebrates, was identified among the antennular olfactory cells of the spiny lobster,Panulirus argus.2.Extracellular recordings from single cells showed that the ATP-sensitive cells had the following properties in common with P2 purinoceptors: a) potency sequence of ATP>ADP>AMP and adenosine; b) broad sensitivity to nucleotide triphosphates including those with modifications in both the purine and ribose moieties; c) stimulated by slowly degradable analogs of ATP, namely,β, γ-imido ATP (AMPPNP),β, γ-methylene ATP (AMPPCP), and α,β-methylene ATP (AMPCPP).3.The activity sequence of the ATP-sensitive cells for nucleotides and related substances was ATP≥2′-deoxyATP>GTP>CTP≥XTP≥ITP> 8-bromo-ATP=ADP, with pyrophosphate, AMP, and tripolyphosphate being virtually inactive.4.The potency sequence for the slowly degradable analogs was AMPPNP>ATP = AMPPCP> AMPCPP.5.Differences in structure-activity relationships, response duration, and response magnitude clearly distinguished the ATP-sensitive cells from another type of olfactory purinoceptor, the AMP-sensitive cells, also occurring in the antennules of the lobster.6.Comparisons between the ATP-sensitive chemoreceptors of the lobster and of certain insects revealed similarities in the activity sequence of ATP, ADP, AMP, and certain other nucleotides. However differences existed in the relative potencies of ATP, AMPPNP, and AMPPCP, and in the relative inactivity of inorganic pyrophosphate in the lobster.7.The findings of this study lend additional credence to the earlier hypothesis that receptors for transmitters and modulators existing in internal tissues may have evolved from external chemoreceptors of primitive unicellular organisms.

Adenosine 5′-monophosphate, an internal regulatory agent, is a potent chemoattractant for a marine shrimp

Summary1.The nucleotide adenosine 5′-monophosphate (AMP) is a potent chemoattractant for the marine shrimp,Palaemonetes pugio. Behavioral bioassays of AMP in the concentration range of 0.1 to 1000 μmol/l show that the dose-response curve is biphasic with the maximum response occurring at about 10 μmol/l.2.AMP is much more potent than ADP. ATP and adenosine are inactive as attractants.3.Bioassays of 28 substances structurally related to AMP show that the integrity of both the adenosine and the ribose phosphate moieties are required for maximal activity. However, the integrity of the ribose phosphate is of special importance since most of the substances having changes in this moiety are completely inactive as attractants.4.The response to AMP is antagonized by theophylline and adenosine.5.The behavioral results suggest that the shrimp possesses external chemoreceptors with marked similarities to the R-type, or P1-type, purine receptors that are present internally in vertebrate tissues.6.Comparisons are made of the structure-activity relationships of nucleotides stimulating behavioral responses in the shrimp and other lower organisms. Possible evolutionary relationships between external chemoreceptors in lower organisms and internal receptors for neurotransmitters and modulators are noted.