Neurophysiological control of swimming behaviour, attachment and metamorphosis in black-footed abalone (Haliotis iris) larvae

Abstract

Neurophysiological control of swimming behavior, attachment and metamorphosis in black-footed abalone (Haliotis iris) larvae AbstractExperiments were conducted to test the effect of a range of chemicals on larval responses in swimming behavior, attachment, and metamorphosis of the black-footed abalone (Haliotis iris). The effect of antibiotics on larval survival was first tested within negative (filtered seawater) and positive (GABA at 10 -5 , 10 -4 , and 10 -3 mol L -1 ) control assays over 3days. This experiment corroborated the effectiveness of using antibiotics to improve survival of larvae without obvious synergistic interactions with the GABA inducer or confounding effects of potential bacterial interactions. Chemical treatments (acetylcholine, potassium chloride, dopamine, and glutamine) were then tested at various concentrations for their ability to modulate swimming behavior and induce larval attachment and metamorphosis over 14 days. Generally, larval state shifted from swimming to attached, and from attached to metamorphosed in the control and treatments over time. However, the peak percentage of attached and metamorphosed larvae varied in time among chemicals and concentrations.While overall percent metamorphosis was minimally enhanced after 14 days of exposure to some chemical treatments at certain concentrations, all treatments displayed significant capacities to down-regulate larval swimming and induce early attachment and metamorphosis. Mortality was recorded throughout the duration of the experiment, and was generally low (<20%) across controls and most treatments for exposures of less than 12 days.Interpretations of specific results from this study are used to elucidate neurophysiological control of larval activities for this abalone species. Comparisons with other marine 3 invertebrates highlight the specificities of chemical cues and endogenous regulatory mechanisms across relatively closely related taxa. IntroductionChemoreception is believed to facilitate larval settlement processes and metamorphosis of a great number of marine invertebrate taxa, including polychaetes ( algae where bacterial and diatom biofilms are in abundance. However, the involvement of biofilms in the facilitation of settlement and metamorphosis by crustose coralline algae is questionable for some abalone species (Huggett et al. 2005;Roberts et al. 2007.Furthermore, specific settlement-inducing compounds within these natural surfaces have rarely been identified (but see Morse et al. 1980;Suenaga et al. 2004).Another approach to investigate chemoreception and associated transduction mechanisms has been to test specific pharmacologically active compounds for their ability to induce settlement and metamorphosis. The amino acid and neurotransmitter γ-amino butyric acid (GABA) consistently has been shown to induce larval attachment and metamorphosis of several abalone species (Morse 1990;Roberts & Nicholson 1997; Bryan & Qian 1998; Moss 4 1999). While a pure-form of GABA is unlikely to be an environmental cue (Kaspar & M...

Neuroactive compounds induce larval settlement in the scleractinian coral Leptastrea purpurea

“…Due to the use of HCl solution for the epinephrine experiment, controls were conducted with both FSW as well as 0.005 M HCl. All chemicals were tested at 10 −3 M, 10 −4 M, 10 −5 M, 10 −6 M, 10 −7 M. These concentrations have been used in several other studies investigating neurotransmitters in marine invertebrates 39,40,90,91 . In case the highest concentration did not lead to 100% mortality of the exposed larvae, chemicals were tested in higher concentrations (10 −2 M, 10 −1 M).…”

The use of chemical and biological settlement cues in enhancing the larval settlement of abalone (Haliotis midae): Implications for hatcheries and ocean ranching

“…Liu et al (2006) reported that increased rearing density increases the possibility of collision among individuals causing an abrupt cessation of the beating of the preoral cirri, followed by rapid retraction of the velum. Abalone larvae swim with an extended velum which, if retracted, results in the larvae being unable to swim, therefore resulting in them sinking to the bottom of the aquarium (Alfaro et al, 2014). This reduces the chances of the larvae settling on the suspended settlement sheets.…”

“…Moss and Tong (1992) reported that inducers such as synthetic chemicals (KCl and GABA) arrest the movement of the cilia of the veliger, forcing the abalone larva to move downwards. Chemical cues such as potassium chloride, dopamine, and glutamine can down‐regulate larval swimming and induce early attachment and metamorphosis of Haliotis iris (Alfaro et al, 2014). Although the mechanism by which KCl induces settlement of abalone larvae is poorly understood, Baloun and Morse (1984) reported that an increase in the concentration of K + in a defined seawater medium induces settlement in larvae Haliotis rufrescens .…”

GABA is an inhibitory neurotransmitter in the neural circuit regulating metamorphosis in a marine snail

“…In the invertebrate phyla, and particularly among adult molluscs, GABA has important actions in multiple behaviors, including, but not limited to, feeding and hunting (Arshavsky et al, ; Díaz‐Ríos et al, ; Jing et al, ; Norekian and Malyshev, ; Kobayashi et al, ), olfaction and chemoreception (Nezlin and Voronezhskaya, ; Ito et al, , ), nociception (Kavaliers et al, ), vision and vestibular responses (Alkon et al, ; Rogers et al, ; Yamoah and Kuzirian, ; Jin et al, ), and the maintenance of posture (Deliagina et al, ). The actions of GABA have been less well studied in developing molluscs (Hatakeyama and Ito, ; Stewart et al, ; Alfaro et al, ), with the exception of its ability to induce larval settlement or metamorphosis in various species of gastropods and bivalves (Table ). Because of the number of molluscan species in which GABA can induce settlement, metamorphosis or both, we investigated the actions of this neurotransmitter during larval metamorphosis in the eastern mud snail Tritia (=Ilyanassa) obsoleta .…”