Calcium Dependence of Settlement and Nematocyst Discharge in Actinulae of the Hydroid Tubularia mesembryanthemum

Abstract

The influence of Ca2+ and Mg2+ ions on both atrichous isorhiza (AI) discharge and settlement of actinular larvae of the hydroid Tubularia mesembryanthemum was investigated. Mg2+-supplemented artificial seawater (ASW) completely inhibited both events at a concentration of 206 mM, whereas lowered Mg2+ concentrations enhanced them. Ca2+ ions in the bathing solution highly regulated AI discharge and settlement, and Mg2+ ions may down-regulate these events. The effect of inorganic Ca2+-channel blockers, including Gd3+ and La3+, was also examined. Larval settlement was inhibited by Co2+, Ni2+, Cd2+, La3+, and Gd3+, with half inhibitory concentrations (IC50) of 5800, 260, 53, 45, and 7 {mu}M, respectively; AI discharge was also inhibited by these ions, with IC50 values of 6600, 500, 78, 41, and 5 {mu}M, respectively. These results suggest possible involvement of stretch-activated Ca2+ channels in the signal transmission of both AI discharge and larval settlement.

Role of Protein Kinase C, G-Protein Coupled Receptors, and Calcium Flux During Metamorphosis of the Sea UrchinStrongylocentrotus purpuratus

“…MR, membrane receptor; GP, G protein; SERCA pump, smooth endoplasmic reticulum calcium ATPase. documented for several species (see Ilan et al, 1993;Clare et al, 1995;Clare, 1996;McCauley, 1997;Kawaii et al, 1999). In addition, the role of calcium could be related to the transduction pathways in which GPCRs and PKC participate.…”

“…In Balanus amphitrite, calcium concentrations 5 mM above those of normal seawater activate metamorphosis, whereas concentrations 10 mM above the normal levels inhibit metamorphosis (Clare, 1996). On the other hand, reducing the concentration of calcium in seawater inhibits metamorphosis in the hydroid Tubularia mesembryanthemum (Kawaii et al, 1999). In larvae of the sea urchin Lytechinus variegatus, excess calcium in seawater stimulates metamorphosis, and the number of metamorphosed larvae tends to decrease as calcium concentration increases (Cameron et al, 1989).…”

“…In some species, activation of the morphogenetic changes can be triggered, in the absence of natural cues, by several organic and inorganic compounds, which have been used as artificial inducers. These include neuroactive substances such as ␥-aminobutyric acid (GABA), 3,4-dihydroxyphenylalanine (DOPA), catecholamines, and choline derivatives, organic and inorganic compounds, and the inorganic ions Mg 2ϩ , Li ϩ , NH 4 ϩ , Cs ϩ , and K ϩ (Pearce and Scheibling, 1994;Avila et al, 1996;Fleck, 1998;Kawaii et al, 1999;Carpizo-Ituarte et al, 2002).…”

“…The role of calcium as a second messenger during metamorphosis has been partially documented in different phyla, including the gastropod Haliotis rufescens (Baxter and Morse, 1987), the polychaete Phragmatopoma californica (Ilan et al, 1993), the brachiopod Terebratalia (Freeman, 1993), the crustacean Balanus amphitrite (Clare et al, 1995;Clare, 1996), the hydrozoan Phialidium gregarium (McCauley, 1997), and the hydroid Tubularia mesembryanthemum (Kawaii et al, 1999). In all of these organisms, the compounds applied affected transduction pathways dependent on cAMP, the participation of the IP 3 /DAG system, and calcium channels.…”

Effect of different ions on larval metamorphosis of the musselMytilus galloprovincialis

“…It indicated that these four ions can be used as low or non‐toxic inducers of M. galloprovincialis larval metamorphosis for the application in the studies of aquaculture. Many researchers have tested the effects of the ions on larval settlement and metamorphosis of marine invertebrates for the purpose of explaining the mechanism of larval settlement (Pawlik ; Clare ; Carpizo‐Ituarte & Hadfield ; Kawaii, Yamashita, Nakai, Takahashi & Fusetani ; Hadfield et al . ; Pechenik, Li & Cochrane ; Amador‐Cano, Carpizo‐Ituarte & Cristino‐Jorge ; Seipp et al .…”