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Abstract
The hydroid Zyzzyzus warreni is usually found in shallow coastal waters forming aggregations of solitary polyps embedded in demosponges. Early life history transformations and settlement responses by the actinulae of this hydroid were studied in the laboratory using 13 species of sponges and 2 species of algae collected in the São Sebastião Channel (Brazil) as substrata. The absence of oral tentacles and mouth in the actinulae and early events of metamorphosis suggest that these larvae are unable to spend long periods in the plankton and attach quickly near conspecifics when a preferred substratum is encountered. The time required for settlement and the number of elicited settlings indicated four settlement responses: (a) frequent and short-time settlement, in actinulae exposed to Halichondria cebimarensis, Mycale angulosa, M. aff. americana, M. laxissima (skeleton) and Tedania ignis; (b) moderate and delayed settlement, in actinulae exposed to Aplysina caissara, A. fulva, Haliclona melana and M. microsigmatosa; (c) no settlement, in actinulae exposed to Suberites aurantiacus and to the algae Hypnea musciformis and Sargassum cymosum; and (d) lethal response, in actinulae exposed to Amphimedon viridis, Aplysilla rosea, Dragmacidon reticulatum and M. laxissima. These responses indicate a considerable degree of species discrimination by the actinulae and are consistent with substrata used by the hydroid in the natural environment.
Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark
Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark
Acknowledgements
We thank Márcio Custódio (IB – USP) for his constructive comments during this investigation, and to Stefania Puce and an anonymous referee for reviewing and improving an early version of the manuscript. A. E. Migotto and A. C. Marques received financial support from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq; 305608/2006-1, 481309/2007-1, 302596/2003-8, 304720/2009-7, and 562143/2010-6) and FAPESP (1998/07090-3, 2001/02626-7, 2003/02432-3, 2004/09961-4, 2006/05821-9, and 2011/50242-5). U. Pinheiro received financial support from Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco.
Notes
Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark