Ecology

Polycarpa papillata are only solitary, with no colonial forms existing and are considered a fouling organism that colonise new areas of substrate extremely quickly (Butler and Connolly, 1996; Rocha et.al 2012).  As such they can be quite problematic as pest species on the underside of boats and in fisheries where they can reduce the productivity of the farm (Aldred and Clare, 2014).  However while they are abundant when a patch of environment is first opened up or in new environments a study by Butler and Connolly (1996) showed that abundance reduced with time and over the six years that they ran the study P.papillata became rare towards the end.  This was thought to be primarily due to their solitary life history, they are not able to compete with the reproductive output of asexually reproducing species (Butler and Connolly, 1996).  This is supported by studies investigating competition between solitary and colonial ascidians; it was shown that when there were colonial and solitary species competing for the same space that the solitary species was overgrown most of the time (Dias et.al 2008).  The early communities of P.papillata were found to be highly modular seeming to rely on long adult lives and vegetative growth for community survival (Butler and Connolly, 1996).  This means that they rely on the individuals generating a highly organised community structure to increase the efficiency of feeding as well as overlap of generations and the ability to get larger after settlement for the success of their community. 

The overlap of generations may be important for larval settlement, as P.papillata does not asexually reproduce by budding for successful reproduction individual’s benefit from being in the company of other individuals (Rocha et.al 2012).  The adults that are already established may be letting off species conspecifics that larvae respond to and settle on.  This would not be unusual as it is seen in other tunicate species for example studies have shown that Herdmania curvata (a tropical ascidian) requires specific environmental and chemical signals to induce settlement and metamorphosis (Degnan, 2001).  Whether this is the case for P.papillata is undetermined as studies have not been undertaken that investigate this factor. 

P.papillata are filter feeders, filter feeders in general hold a very important role in the ecosystem as they work to filter the water in the system removing suspended matter, which they use as food (Carballo and Naranjo, 2002; Rocha et.al 2012).  The fact that P.papillata also has ashort lived pelagic larval stage makes a good indicator for bioinvasion (Rocha et.al2012).

One of the P.papillata specimens that was dissected was found to have an Amphipod living in its pharyngeal basket (Fig. 4).  This indicates that P.papillata also provides habitat for other organisms adding to its ecological importance.