Pelagic tunicates (Appendicularia and Thaliacea) of Sri Lanka: two first records with an annotated checklist Author Karunarathne, Krishan D. 0000-0003-1780-9749 Department of Aquaculture and Fisheries, Faculty of Livestock, Fisheries and Nutrition, Wayamba University of Sri Lanka, Makandura, Gonawila, 60170, Sri Lanka. & krishankarunarathne @ gmail. com; krishan. dk @ wyb. ac. lk; https: // orcid. org / 0000 - 0003 - 1780 - 9749 krishankarunarathne@gmail.com Author Croos, M. D. S. T. De 0000-0003-4449-6573 Department of Aquaculture and Fisheries, Faculty of Livestock, Fisheries and Nutrition, Wayamba University of Sri Lanka, Makandura, Gonawila, 60170, Sri Lanka. & dileepa _ dc @ yahoo. com; dileepad @ wyb. ac. lk; https: // orcid. org / 0000 - 0003 - 4449 - 6573 dileepa_dc@yahoo.com text Zootaxa 2021 2021-11-11 5067 3 352 376 journal article 3575 10.11646/zootaxa.5067.3.2 9b8d33b9-c9df-4f9d-abeb-de1c7b84f3e0 1175-5326 5681899 AF3DF45F-B248-4BDD-904F-F55D735DC867 Thalia sibogae Van Soest, 1973 Thalia sibogae Van Soest 1973: 204 , 205, Fig. 8; 1998: 235, Table 14.1. Kim et al . 2011: 147 , Fig. 5. Purushothaman et al . 2017 . Ishak et al . 2018: 454 , 459–465, Figs. 4a–e , 5. Material examined. One solitary zooid ( MDAFWU 2018 /85), St .133, January 2018 ( Fig. 2D–F ) . Description. Solitary zooid: Transparent body bulky rounded with a very thick, smooth test, with two long (about one third of body length), tapering processes on the posterior end ( Fig. 2D–F ); length without processes 7 mm . Atrial palps fairly small and bifurcate ( Fig. 2F ); lateral projections very small, simple and not bifurcated ( Fig. 2D, F ); medioventral projections are small and of unequal length, the anterior ones are the smallest ( Fig. 2E ). Six body muscles broad; M I narrowly interrupted dorsally, M II–IV converged mid-dorsally, M V and M VI near but do not touch dorsally; M II–V in complete rings, M VI interrupted ventrally ( Fig. 2D ). Totally (M I–VI) 60 muscle fibers. The nucleus (stomach + intestine) is close to the middle posterior projection ( Fig. 2D–F ). FIGURE 2. Firstly reported pelagic tunicates to Sri Lanka in “ Waya-jel -Survey” ( A–F ): a live colony of Pyrostremma spinosum near to the sea surface ( A & B ), and an illustration of its blastozooid ( C ); Thalia sibogae solitary zooid in preserved form ( D ), ventral view of medioventral projections ( E ), and an illustration of its posterior part ( F ). a —anus; ap —atrial palp; dmp — dorsal medioventral projection; e —endostyle; es —excurrent/buccal siphon; g —ganglion; is —incurrent/atrial siphon; lp —lateral projection; n —nucleus; o —ovary; pb —pharyngeal basket; pp —posterior projection; sl —stolon; sm —stomach; t —testis; vmp —ventral medioventral projection. Scales: E = 0.5 mm; C, D, F = 1 mm; A & B = 0.4 m. Images A & B by Franco Banfi from off Mirissa, Sri Lanka Aggregate zooid: Not collected. Global distribution. The Central Indo-Pacific ( Van Soest 1973 , 1998 ; van der Land 2008 ); Korean waters ( Kim et al . 2011 ); the east coast of Peninsular Malaysia ( Ishak et al . 2018 ). Type locality: Pulu Sanguisapio, Tawi-Tawi Island, Sulu archipelago ( Siboga -Expedition St . 93, 05°N , 120°E ). Remarks. Although Van Soest (1973) did not observe lateral projections on the type material of T. sibogae , tiny lateral projections may exist with solitary zooids of T. sibogae according to Kim et al . (2011) and Ishak et al . (2018) . Therefore, the Sri Lankan specimen resembles the specimens of Kim et al . (2011) and Ishak et al . (2018) . The total number of muscle fibres (M I–VI) in solitary zooids of Thalia democratica ( Forskål, 1775 ) shows a clinal variation, decreasing from higher to lower latitudes ( Van Soest 1975b ); and there is a possibility to be such a variation in T. sibogae , but data is not enough in the literature for comparison. Local name: Indi Gaduwa (in Sinhalese) [note: usually fishers use this term for tiny salps, while the Pegea -like larger salps are called ‘ Rata-indi Gadu ’ in Sinhalese and ‘ Pereechcham Katti ’ in Tamil]. Local importance: None [but, Pegea -like larger salps regularly clog into fishing nets (authors’ observations)].