Settlement gregarious

Jensen, R.A. and Morse, D.E., Intraspecific facilitation of larval recruitment gregarious settlement of the polychaete Phragmatopoma califomica (Fewkes), J. Exp. Mar. Biol. Ecol., 83, 107, 1984. 

Toonen, R.J. and Pawlik, J.R., Settlement of the tube worm Hydroides dianthus (Polychaeta Serpul-idae) cues for gregarious settlement, Mar. Biol., 126, 725, 1996. 

Pawlik, J.R., Butman, C.A., and Starczak, V.R., Hydrodynamic facihtation of gregarious settlement of a reef-building tube worm, Science, 251, 421, 1991. 

Many ascidians live gregariously, and for some of these species conspecific chemical cues may play an important role in gregarious settlement of the larvae. The extracts of conspecific adults, larvae, or their conditioned seawater have been shown to contain metamorphosis inducers which have never been characterized.74-75 Recently, Fusetani and co-workers elucidated the structure of the metamorphosis inducer for the solitary ascidian Halocynthia roretzi, which was isolated from seawater conditioned by ascidian larvae.10 The compound isolated from the medium was identical to lumichrome, a compound known to be a degradation product of riboflavin (Figure 13.1). The origin of lumichrome in //. roretzi is not known at present. 

Several other researchers have studied chemical cues influencing gregarious settlement and metamorphosis of polychaete larvae. An unidentified waterborne cue was responsible for gregarious settlement of Hydroides dianthus,89 The inducer was not associated with the tubes, but rather with the bodies of adult worms. Extractions of adult worms with organic solvents removed the inductive capacity of the tissue. The activity was found in both polar (methanol) and nonpolar (dichlo-romethane) fractions of an extraction series.89... 

Sand dollars, Dendraster excentricus, exhibit gregarious settlement, and larvae undergo settlement and metamorphosis in the presence of adult-associated sand.92 Adults produce a chemical cue that remains associated with the sand and is stable for at least 7 weeks. Thus, settlement occurs within or near existing sand dollar beds. Highsmith92 suggested that the cue was a small peptide. This was confirmed by Burke,20-21 who isolated an active peptide of 980 Da from extracts of sands from sand dollar beds. 

Dreanno C, Matsumura K, Dohmae N, Takio K, Hirota H, Kirby RR, Clare AS (2006) An alpha2-macroglobulin-like protein is the cue to gregarious settlement of the barnacle Balanus amphi-trite. Proc Natl Acad Sci USA 103 14396-14401... 

Abstract Many barnacle species are gregarious. This is an essential behavior for those species that can only reproduce by mating with a neighboring barnacle. Proximity of adult barnacles is achieved by gregarious settlement of the cypris larva. The chemical basis of this behavior was established 60 years ago, but attempts to characterize the cue to settlement met with limited success. This chapter presents evidence obtained in recent years that the cue is an a2-macroglobulin-like cuticular protein, detected by cyprids using a tactile chemical sense as they explore the substratum for a suitable settlement site. 

Fig. 22.1 Gregarious settlement of barnacle cypris larvae, (a) Cyprids approach the substratum, perhaps after encountering a waterborne cue released by adults (b) contact with substratum and onset of (c) searching behavior (d) cyprid contacts an adult conspecific and is stimulated to settle by a cuticular protein - the settlement-inducing protein complex (SIPC). The cyprid may return to the plankton at any stage of the sequence (b-d). Drawing by Jorge A. Varela Ramos...

Burke, R.D. 1986. Pheromones and the gregarious settlement of marine invertebrate larvae. Bull. Mar. Sci. 39 323-331. 

Scheltema, R.S., I.P. Williams, M.A. Shaw C. London. 1981. Gregarious settlement by larvae of Hydroides dianthus (Polychaeta Serpulidae). Mar. Ecol. Prog. Ser. 5 69-74. 

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