The Seasonal Succession of Appendicularians (Tunicata: Appendicularia) off Plymouth

Abstract

Earlier descriptions showed that the community of appendicularians off the British coast was mainly composed of Oikopleura dioica (Appendicularia; Müller, 1846) and Fritillaria borealis (Appendicularia; Lohmann, 1896), rarely by Oikopleura fusiformis (Appendicularia; Fol, 1872) and Fritillaria pellucida (Appendicularia; Quoy & Gaimard, 1833) and exceptionally by Oikopleura longicauda (Appendicularia; Vogt, 1854). Based on weekly samples collected during 1989 at a single station off the coast of Plymouth, we describe the first complete seasonal cycle of appendicularians in this area. The results suggest that rather than being occasional visitors, O. fusiformis, F. pellucida and O. longicauda are consistently present and abundant from mid to late summer. Moreover, the seasonal shifts in structure of the community of appendicularians in the area, as depicted by multivariate analysis, are consistent with those of the more southerly central Cantabrian coast (Spain). This suggests that they are viable populations rather than occasional expatriates from other areas.