Pegea confoederata ( Forskål, 1775 ), Van Soest, 1974

Karunarathne, Krishan D. & Croos, M. D. S. T. De, 2021, Pelagic tunicates (Appendicularia and Thaliacea) of Sri Lanka: two first records with an annotated checklist, Zootaxa 5067 (3), pp. 352-376 : 360

Pegea confoederata ( Forskål, 1775)

Salpa confoederata Forskål 1775: 115 .

Salpa octofora Cuvier 1804: 579 , Fig. 7.

Salpa scutigera Cuvier 1804: 577 , Figs. 4 , 5.

Salpa quadrata Herdman 1888: 84 , Pl. 9 Figs. 1 –8.

Salpa dolium Quoy & Gaimard 1834: 575 , Pl. 90 Figs. 1 –8.

Pegea confoederata: Tokioka 1960: 396 . Van Soest 1974a: 171, Fig. 15a; 1998: 235, Table 14.1. Madin & Harbison 1978: 338, Fig. 3C, F . Godeaux 1998: 288, 290, Figs. 17.16d, 17.20a. Gershwin et al. 2014: 16. Kim et al. 2017: 455, Fig. 1C . Purushothaman et al. 2017. Ishak et al. 2018: 473, Table 1 .

Material examined. Nineteen aggregate zooids ( MDAFWU 2017 /479–496, 524), St.62, October to December 2017., 1 embryo and 5 aggregate zooids ( MDAFWU 2017 /473–478), St.81, July and September 2017., 1 aggregate zooid ( MDAFWU 2017 /472), St.133, June 2017., 8 solitary zooids and 19 aggregate zooids ( MDAFWU 2017 /497– 523), St.170, November 2017., 2 embryos and 13 aggregate zooids ( MDAFWU 2019 /120–134), St.205, December 2019 ( Fig. 3A–D ) .

Description. Solitary zooid: Transparent body 18–60 mm long, with the pear-shaped test, smaller posteriorly ( Fig. 3D ). Both anterior and posterior terminal regions are thinner than the stomach region. Anterior muscle pair (M I–II) slightly touch forming a cross; posterior pair (M III–IV) do not touch each other; 18–32 muscle fibres per single band. The nucleus (stomach + intestine) is flatly encircled by the developing stolon.

Aggregate zooid: Transparent body 19–55 mm long, with a cylindrical-shaped, thick, smooth test ( Fig. 3A, C ). The posterior terminal region is very thick, extended around the nucleus; no posterior projections or protuberances. Both muscle-band pairs (M I–II and M III–IV) are short because they are interrupted before reaching the mid-lateral region, and are linking (anterior pair slightly touching and posterior pair fused) in the mid-dorsally forming two crosses; 6–20 muscle fibres per single band. Nucleus (stomach + intestine) is spherical. Embryo 5–19 mm in length ( Fig. 3B ).

Global distribution. The Atlantic Ocean, Indian Ocean, Pacific Ocean, Australian waters, the Mediterranean Sea and Red Sea ( Van Soest 1998). Type locality: Eastern Mediterranean .

Figures

FIGURE 1. Sampling localities of pelagic tunicates within the three regions of Sri Lankan Exclusive Economic Zone (EEZ) denoted by BBR (Bay of Bengal Region), LSR (Laccadive Sea Region) and IOR (Indian Ocean Region). Source of the map: Maritime Boundaries Geodatabase, Flanders Marine Institute (https://www.marineregions.org/). Remarks of each sampling station (St.) indicated by open circles are in Table 1

FIGURE 3. Re-reported salp, Pegea confoederata, to Sri Lanka in “Waya-jel-Survey” in preserved form (A–D): a colony of zooids (A); embryo (B); aggregate zooid (C); solitary zooid (D). E—endostyle; G—gill; N—nucleus; S—stolon. Scales: B = 5 mm; C & D = 8 mm; A = 20 mm.

FIGURE 4. Schematic diagrams of Sri Lankan pelagic tunicates, showing the general morphology of their families (A–H): the lateral view of mature individuals of Fritillariidae (A) and Oikopleuridae (B); gonozooid (C) and degenerated oozooid / nurse (D) of Doliolidae; dorsal view of a solitary zooid (E) and aggregate zooid (F) of Salpidae; a blastozooid (G) and sagittal section of a colony (H) of Pyrosomatidae. Adapted from Claus (1883), Esnal (1981), Barnes et al. (1993) and Sri Lankan specimens. Note: The tails of appendicularian diagrams have been rotated through 90º for clarity.