Oikopleura cophocerca ( Gegenbaur, 1855 )

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 : 356

Oikopleura cophocerca ( Gegenbaur, 1855)

Appendicularia cophocerca Gegenbaur 1855: 408 , Figs. 4 –5.

Oikopleura (Vexillaria) cophocerca: Tokioka 1960: 355 , Fig. 14.

Oikopleura cophocerca: Lohmann 1896: 66 , Pl. 11 Figs. 2 , 4 , Pl. 12 Figs. 1b , 2 , 3 . Smith et al. 1901: 104, Fig. 24. Bückmann 1969: 3, Fig. 6a–c. Fenaux 1993: 56, 71, 80; 1998: 300, 302. Aravena & Palma 2002: 312, 313, Fig. 4B .

Material examined. Twelve specimens ( MDAFWU 2020 /411–422), St.205, January 2020 .

Description. Trunk 1–1.5 mm long, moderately elongate. Mouth with a developed lower lip; oral glands large, rounded to rectangular. Left stomach lobe elongated, with a pocket-shaped caecum towards its posterior end. The rectum is horizontally oriented, and the anus is near the oral wall of the stomach. The endostyle is small and almost at an equal distance between the mouth and the anus. Gonads adjoining the gut hemispherically and protruding dorsally. Tail musculature broad, and five to eight oval subchordal cells in a line, disposed of in two groups.

Global distribution. The Atlantic Ocean, Indian Ocean, Pacific Ocean, the Mediterranean Sea and Red Sea ( Fenaux et al. 1998); Australian waters ( Thompson 1948). Type locality: Messina, Mediterranean Sea.

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 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

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.