Microcosmus exasperatus Heller, 1878

Lambert, Gretchen, Lee, Serina Siew-Chen & Teo, Serena Lay-Ming, 2021, Ascidians collected during the 2013 Singapore Strait International Marine Biodiversity Workshop, Zootaxa 4933 (1), pp. 1-38 : 29

Microcosmus exasperatus Heller, 1878

Figure 11A, B

Individuals may reach 5 cm across, usually somewhat wider than tall, with a thick ridge of tunic between the widely spaced siphons especially when contracted. Siphonal spines small, dense, curved and sharply pointed, usually up to about 30 µm in length but may be slightly longer in large specimens. Tunic lining purple, siphonal lining red striped and mottled. Dorsal tubercle inrolled. Gonad in three parts on each side, left gonad crosses gut.

#0154A, nine branchial folds per side. One gammarid amphipod in branchial sac.

#3799C, juvenile 1.7 cm long. Creamy white tunic with red striping; resembles Polycarpa papillata externally. Oral siphon terminal, atrial siphon far back; siphons with red striping. Gonads not well developed but in the typical three parts.

#3827D, one small, on Polycarpa argentata .

#4614, small; 1.2 cm anteroposteriorly. Siphonal spines up to 44 µm long including embedded basal part. Eight branchial folds on the right side, seven on the left.

Distribution: China, Formosa, Indonesia, Philippines, Singapore, Vietnam, Australia, Hawaii, Guam, Fiji, Truk, New Caledonia, French Polynesia, Galápagos, E. and W. Africa, Suez and eastern Mediterranean, SE. U.S., Caribbean, Martinique, Brazil.

Detailed references: Van Name (1918 as Pyura exasperatus ; 1945); Millar (1975), Kott (1981, 1985); Monniot C. & Monniot F. (1987), Cole & Vorontsova (1998), Monniot C. (2002), Monniot F. (2010, 2018c), Lee et al. (2013). Other references: Millar (1965), Monniot C. (1983c), Nishikawa (1984), Monniot C. et al. (1985), Millar (1988), Monniot C. & Monniot F. (1994), Zheng (1995), Abbott et al. (1997), Rocha & Nasser (1998), Rocha & Costa (2005), Rocha et al. (2005), Shenkar & Loya (2009), Lee et al. (2016), Lambert (2003, 2019).

Figures

FIGURE 11. A, B: Microcosmus exasperatus. A: whole animal right side, 1.2 cm in height; B: siphonal spines, largest 44 um long; C: Microcosmus helleri in tunic, 2 cm in width, showing opened edges of embedded bivalve (arrow); D: bivalve removed from host tunic; E: anterior end of small Pyura curvigona (2 cm total length) partially embedded in Polyandrocarpa rollandi colony; F: P. curvigona siphonal spines, longest 211 µm.