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Association among ascidians: Facilitation of recruitment in Pyura spinifera

Journal Article


Abstract


  • Subtidal benthic communities on hard substrata are usually characterised by intense competition for space; neighbouring organisms are generally viewed as a threat to the maintenance of this limited resource. Here, I describe an association between two species of subtidal ascidians where the abundance of one appears to be wholly determined by the abundance of the other. Pyura spinifera is a large subtidal stalked ascidian that is common in south-eastern Australia and usually occurs in clumps. At the base of these clumps the unstalked ascidian Cnemidocarpa pedata is often present. Between February and May 1992, I used a removal experiment to test the prediction that the recruitment of P. spinifera was dependent on the presence of C. pedata. There were three treatments at two sites: (i) C. pedata were totally removed, (ii) C. pedata densities were reduced by half, and (iii) ascidians were left untouched (control). The removal of C. pedata significantly reduced P. spinifera recruitment relative to controls: recruitment of P. spinifera was only observed on C. pedata. Results were consistent between sites. Furthermore, laboratory settlement trials indicated that P. spinifera settle preferentially in response to cues with which recruits are normally associated, while settlement is poor or does not occur in the absence of such cues. Laboratory trials also indicate that these responses are mediated by water-borne compounds.

Publication Date


  • 1996

Citation


  • Davis, A. R. (1996). Association among ascidians: Facilitation of recruitment in Pyura spinifera. Marine Biology, 126(1), 35-41. doi:10.1007/BF00571375

Scopus Eid


  • 2-s2.0-0029660332

Start Page


  • 35

End Page


  • 41

Volume


  • 126

Issue


  • 1

Abstract


  • Subtidal benthic communities on hard substrata are usually characterised by intense competition for space; neighbouring organisms are generally viewed as a threat to the maintenance of this limited resource. Here, I describe an association between two species of subtidal ascidians where the abundance of one appears to be wholly determined by the abundance of the other. Pyura spinifera is a large subtidal stalked ascidian that is common in south-eastern Australia and usually occurs in clumps. At the base of these clumps the unstalked ascidian Cnemidocarpa pedata is often present. Between February and May 1992, I used a removal experiment to test the prediction that the recruitment of P. spinifera was dependent on the presence of C. pedata. There were three treatments at two sites: (i) C. pedata were totally removed, (ii) C. pedata densities were reduced by half, and (iii) ascidians were left untouched (control). The removal of C. pedata significantly reduced P. spinifera recruitment relative to controls: recruitment of P. spinifera was only observed on C. pedata. Results were consistent between sites. Furthermore, laboratory settlement trials indicated that P. spinifera settle preferentially in response to cues with which recruits are normally associated, while settlement is poor or does not occur in the absence of such cues. Laboratory trials also indicate that these responses are mediated by water-borne compounds.

Publication Date


  • 1996

Citation


  • Davis, A. R. (1996). Association among ascidians: Facilitation of recruitment in Pyura spinifera. Marine Biology, 126(1), 35-41. doi:10.1007/BF00571375

Scopus Eid


  • 2-s2.0-0029660332

Start Page


  • 35

End Page


  • 41

Volume


  • 126

Issue


  • 1