Molgula manhattensis ( De Kay, 1843 )

Pyo, Jooyeon, Lee, Taekjun & Shin, Sook, 2012, Two newly recorded invasive alien ascidians (Chordata, Tunicata, Ascidiacea) based on morphological and molecular phylogenetic analysis in Korea *, Zootaxa 3368 (1), pp. 211-228 : 220-222

4. Molgula manhattensis ( De Kay, 1843)

( Figs. 2D , 5 , Table 3)

Ascidea manhattensis De Kay, 1843: 259 . Caesira manhattensis: Van Name, 1912: 471 , figs. 4, 5, pl. 45, figs. 11-15, pl.71, figs. 151, 152 Molgula manhattensis: Berrill, 1928: 163 ; Van Name, 1945: 385, figs. 271-273; Tokioka & Kado, 1972: 21; Lambert &

Lambert, 1998: 675; Stachowicz et al., 2002: 2576; Carman et al., 2007: 175; Hiscock, 2008: 3823; Carman & Grunden,

2010: 23; Haydar et al., 2011: 68; Sanamyan & Monniot, 2011c: 103788.

Materials examined. 35 inds., Mokpo , 26 June 2010, Lee T, fish trap at 2.5 m depth ; 47 inds., Gunsan , 27 June 2010, Shin S, under floating dock at 0.2 m depth ; 84 inds., Mokpo , 21 Oct. 2010, Pyo J, fish trap at 2.1 m depth ; 26 inds., Gunsan , 22 Oct. 2010, Shin S, under floating dock at 0.1 m depth ; 41 inds., Incheon, 22 Oct. 2010, Lee T, ropes at 3.2 m depth ; 12 inds., Gwangyang , 26 June 2011, Lee T, fish trap at 3.4 m depth ; 56 inds., Mokpo , 26 June 2011, Lee T, under floating dock at 0.2 m depth ; 33 inds., Incheon, 27 June 2011, Pyo J, ropes at 2.7 m depth ; 6 inds., Songjeong , 19 Oct. 2011, Pyo J, dock wall at 1.1 m depth ; 7 inds., Busan, 19 Oct. 2011, Pyo J, under floating dock at 0.2 m depth ; 12 inds., Dadaepo , 19 Oct. 2011, Shin S, ropes at 2.2 m depth ; 35 inds., Mokpo , 20 Oct. 2011, Lee T, under floating dock at 0.1 m depth ; 21 inds., Incheon, 21 Oct. 2011, Shin S, ropes at 3.8 m depth .

Description. Body commonly ovoid shaped ( Fig. 5A–C, L ). Tunic thick, grayish or greenish color, semitransparent, sometimes covered with debris and fibrils; visceral organs observed by naked eye on each side. Oral siphon 6 lobed, positioned at anterior part of body ( Fig. 5G ). Six to eight tentacles surround opening of oral siphon into pharynx ( Fig. 5H ), and each tentacle irregularly branched 7–16 ramification. Atrial siphon 4 lobed, positioned closed beside oral siphon less than 5 mm ( Fig. 5G ). Dorsal tubercle C-shaped or horseshoe-shaped groove ( Fig. 5I ). Branchial sac with six folds, on each side curved and spirally arranged stigmata ( Figs. 5J, K ). Muscles well developed around siphons. Endostyle extended from base of oral siphon to posterior of pharynx. Gut positioned on left side of branchial sac ( Fig. 5E ). Stomach narrow, small, completely hidden by large conspicuous pyloric gland, but not exactly marked off from rest of gut. Intestine tapering from end of stomach, gonad in second gut loop. Renal sac positioned beneath gonads on body wall of right side, slightly curved ( Fig. 5D ). Gonads located on each side, consist of testis and ovary surrounded by testis; right gonad deflected, positioned parallel with renal sac and at right angle with left gonad ( Figs. 5D, E ). Oviduct short, extends toward atrial siphon.

Size. Individuals measured up to 24 mm long and usually attached to ropes and hard substrates by posterior part; usual size is 15–20 mm.

Distribution. Native to Northeast America from Maine to Texas. Northeast Atlantic ( Norway to Portugal), Northeast Pacific (Puget Sound, San Juan Archipelago, Vancouver Island, California), South Australia, Tasmania, China, Japan, and Korea ( Korea Strait, Yellow Sea).

Remarks. Molgula manhattensis ( De Kay, 1843) was first described from New York harbor. Its distribution in Northwest Atlantic extends from Cape Cod to Southern Louisiana interrupted by the Florida peninsula ( Van Name 1945). Although its European distribution extends from Norway to Portugal, it is patchy ( Monniot 1969). The inferred anthropogenic vectors for these introductions were hull fouling and oyster translocations ( Tokioka & Kado 1972; Cohen & Carlton 1996), and possibly ballast water ( Hewitt et al. 2004). This species was first found in Mokpo, Gunsan and Incheon of Yellow Sea, Korea in June 2010 and was found spread out at Songjeong, Busan and Dadaepo of Korea Strait in 2011 ( Table 3).

Figures

FIGURE 2. Five invasive alien ascidians at four collection sites in Korea: A, C. lepadiformis attached to dock wall at 4.7 m depth in Busan port; B, A. aspersa attached to ropes at Tongyeong yacht marina; C, C. intestinalis attached on thick cloth at Gampo harbor; D, M. manhattensis attached on floating buoy at Mokpo yacht marina; E, S. plicata attached to rope at Tongyeong yacht marina. Scale bars: A–E. 10 cm.

FIGURE 5. Molgula manhattensis: A, C, Individuals densely aggregated on a rope; B, Individuals on a fish trap; D, Right side; E, Left side; F, Sagittal section of branchial sac; G, Oral and Atrial siphon; H, Tentacles; I, Dorsal tubercle; J, Six folds of branchial sac; K, Stigmata; L, Individuals attached to fish trap. 1—oral siphon, 2—atrial siphon, 3—tentacles, 4—dorsal tubercle, 5—folds of branchial sac, 6—stigmata, 7—intestine, 8—gonads, 9—renal sac, 10—tunic, 11—endostyle. Scale bars: A–B. 50 mm; C–F, L. 5 mm; G–K. 1 mm.