Metamorphosis of the marine gastropod Phestilla Sibogae Bergh (nudibranchia: aeolidacea). I. Light and electron microscopic analysis of larval and metamorphic stages

Bonar, Dale B.; Hadfield, Michael G.

doi:10.1016/0022-0981(74)90027-6

Cited by 117 publications

(109 citation statements)

References 25 publications

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“…When larvae of P. sibogae become competent, they develop a propodial mucus gland (Bonar 1974), and when settled larvae are being dislodged from a surface by flowing water, a layer of clear, deformable material that looks like mucus can be observed connecting the foot to the surface . The drag on a P. sibogae larva tending to push it downstream shears the mucus between the larva's foot and the substratum.…”

Section: Discussionmentioning

confidence: 99%

Hydrodynamic forces on larvae affect their settlement on coral reefs in turbulent, wave-driven flow

2009

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This study investigates a key aspect of how ambient flow affects the recruitment of water-dispersed marine larvae onto benthic substrata: the sweeping away of larvae that have landed on surfaces. Through a combination of field and laboratory measurements, we studied how waves interact with a complex substratum to affect hydrodynamic forces encountered by microscopic larvae sitting at different positions on the bottom terrain. We used larvae of the nudibranch Phestilla sibogae settling onto coral reefs as the system to address this question. Laser Doppler anemometry was utilized within a laboratory flume to measure water velocities encountered 200 mm from coral surfaces by microscopic larvae sitting at different locations within a reef of the branching coral Porites compressa. Comparing wave-driven flow, based on conditions measured over P. compressa reefs in Hawaii, with unidirectional flow of the same mean velocity, we found that peak shear stresses along coral surfaces were ,15 times greater and hydrodynamic forces on larvae were ,10 times higher in wave conditions. Peak forces on larvae sitting on the reef top were 3-10 times greater than on larvae 5-10 cm below the reef top. Intermittent bursts of high velocity, which occurred more often at the reef top than within it, determined the settlement probability for larvae in different reef microhabitats. The faster and more strongly a larva sticks to a surface, the higher the probability of successful settlement. Using values for P. sibogae adhesive strength, we predict they can settle only on sheltered surfaces within reefs.

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Section: Discussionmentioning

confidence: 99%

Hydrodynamic forces on larvae affect their settlement on coral reefs in turbulent, wave-driven flow

2009

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“…Phestilla ingests its velar ciliated cells and incorporates the remaining supportive cells into the cephalic epidermis (Bonar and Hadfield, 1974). Ilyanassa may lose the velum in toto (Scheltema, 1962), or ciliated cells may drop off individually or in clumps (Couper and Leise, 1994).…”

Section: Discussionmentioning

confidence: 99%

“…Ilyanassa may lose the velum in toto (Scheltema, 1962), or ciliated cells may drop off individually or in clumps (Couper and Leise, 1994). Like Phestilla, Ilyanassa metamorphoses a number of hours after initial exposure to an inducer (Bonar and Hadfield, 1974;Levantine and Bonar, 1986). The reason for this long delay is unknown.…”

Section: Discussionmentioning

confidence: 99%

Serotonin Injections Induce Metamorphosis in Larvae of the Gastropod Mollusc Ilyanassa obsoleta

Couper

Leise

1996

The Biological Bulletin

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Abstract:Bath-applied serotonin (5-HT) induces competent larvae of the marine snail Ilyanassa obsoleta to metamorphose. Previously, the mode of action of 5-HT, whether as an external ligand or as an internal neurotransmitter, was unknown. Larvae were injected with 10 -4 M 5-HT and other pharmacological agents to provide evidence that serotonergic neurons are necessary for metamorphosis in Ilyanassa larvae and that serotonin functions as a neurotransmitter or neuromodulator during this process. About 50% of 5-HT-injected animals metamorphose within 48 hours. Fluoxetine, a 5-HT re-uptake inhibitor, and alpha-methy1-5-hydroxytryptamine (αm5HT), a 5-HT agonist, were also effective inducers of metamorphosis. Gramine (3-[dimethyl-aminomethyl]indole), a 5-HT antagonist, inhibited the inductive activity of 5-HT, while the amino acid gamma-aminobutyric acid (GABA) resulted in rates of morphological restructuring similar to those of controls. Collectively, the results of our experiments support the idea that serotonergic neurons are active during larval metamorphosis of Ilyanassa and that 5-HT does not induce metamorphosis by binding to epidermal chemoreceptors.

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“…These are loss of the velum, a process common to all molluscan veliger larvae, and shell dehiscence, which occurs in many opisthobranchs (Bonar and Hadfield, 1974;Hadfield, 1978). These events, in addition to the chemosensory initiation of metamorphosis, could involve neuronal networks within the CNS that drive appropriate effector organs.…”

Section: Introductionmentioning

confidence: 99%

An inducer of molluscan metamorphosis transforms activity patterns in a larval nervous system

Leise

Hadfield

2000

The Biological Bulletin

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Abstract:Larvae of the nudibranch mollusc Phestilla sibogae metamorphose in response to a small organic com-pound released into seawater by their adult prey, the scleractinian coral Porites compressa. The transformations that occur during metamorphosis, including loss of the ciliated velum (swimming organ), evacuation of the shell, and bodily elongation, are thought to be controlled by a combination of neuronal and neuroendocrine activities. Activation of peripheral chemosensory neurons by the metamorphosis-inducing compound should therefore elicit changes within the central nervous system. We used extracellular recording techniques in an attempt to detect responses of neurons within the larval central ganglia to seawater conditioned by P. compressa, to seawater conditioned by the weakly inductive coral Pocillopora damicornis, and to non-inductive seawater controls. The activity patterns within the nervous systems of semi-intact larvae changed in response to both types of coral exudates. Changes took place in two size classes of action potentials, one of which is known to be associated with velar ciliary arrests. Article:Introduction For a number of molluscan larvae, specific chemical compounds from the juvenile environment can act as chemosensory cues and trigger metamorphosis. For example, inductive compounds may be given off by the adult prey (Hadfield and Karlson, 1969;Hadfield, 1977Hadfield, , 1978 Koss, 1978, 1988;Lambert and Todd, 1994;Avila et al., 1996;Lambert et al., 1997), by adult conspecifics (Pechenik, 1980;McGee and Targett, 1989;Pechenik and Gee, 1993), by bacteria associated with adult conspecifics (Fitt et al., 1990;Tamburri et al., 1992), and by the algal food of the juveniles (Scheltema, 1961;Kriegstein et al., 1974;Switzer-Dunlap and Hadfield, 1977; Morse et al., 1979;Levantine and Bonar, 1986;Morse, 1990;Boettcher and Targett, 1996;Leise et al., 1996). In gastropods, sensory neurons that may mediate the induction of settlement and metamorphosis occur on the head, between the ciliated velar lobes (Bonar, 1978; Koss, 1982, 1984;Wodicka and Morse, 1991;Baxter and Morse, 1992;Uthe, 1995;Marois and Carew, 1997;Kempf et al., 1997), and on the foot (Chia and Koss, 1989). Our understanding of how these neurons function is still limited. Observations of Morse and colleagues (Trapido-Rosenthal and Morse, 1985; Morse, 1987, 1992;Morse, 1990;Wodicka and Morse, 1991) strongly imply that receptors for lysine, an amino acid that modifies inducer reception, lie on chemosensory cilia in the apical sensory organ of larval abalone. If pre-competent nudibranch and abalone larvae are exposed to an inducer substance, they display habituation-that is, decreased rates of metamorphosis-when they reach competency (Hadfield, 1980;Hadfield and Scheuer, 1985; TrapidoRosenthal and Morse, 1986;Avila et al., 1996). Habituation is thus a phenomenon associated with the morphogenetic pathway that directly initiates metamorphosis.More recent studies are beginning to elucidate further internal mechanisms that are downstream fr...

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Metamorphosis of the marine gastropod Phestilla Sibogae Bergh (nudibranchia: aeolidacea). I. Light and electron microscopic analysis of larval and metamorphic stages

Cited by 117 publications

References 25 publications

Hydrodynamic forces on larvae affect their settlement on coral reefs in turbulent, wave-driven flow

Hydrodynamic forces on larvae affect their settlement on coral reefs in turbulent, wave-driven flow

Serotonin Injections Induce Metamorphosis in Larvae of the Gastropod Mollusc Ilyanassa obsoleta

An inducer of molluscan metamorphosis transforms activity patterns in a larval nervous system

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