Parapenaeopsis incisa Wang & Liu

Parapenaeopsis incisa Wang & Liu in Liu & Wang, 1987 Figs 1 d, 2 d, 3 d, 4 d, 5 d Parapenaeopsis incisa Liu and Wang 1986: 214 (nomen nudum); 1987: 525, fig. 3. (type locality: Wailuo, Guangdong, China); Liu and Zhong 1988: 210, fig. 130. Kishinouyepenaeopsis incisa – De Grave and Fransen 2011: 216. Material examined. Southern China • [MBM 155054]: Guangdong, Zhanjiang, Naozhou Island, 29 Jul. 1976, 1 ♀, cl 14.6 mm • [MBM 155041]: Hainan, Yinngehai, 55 - K 444, 7 Dec. 1955, 3 ♂♂, cl 14.5–14.8 mm, 3 ♀♀, cl 16.3–18.2 mm • [MBM 155057]: Hainan, Yinngehai, 57 - K 275, 26 Jun. 1957, 2 ♂♂, cl 12.9–14.4 mm, 2 ♀♀, cl 16.5–17.6 mm • [MBM 155044]: Hainan, Sanya, fish market, 90 C- 324, 25 Nov. 1990, 3 ♂♂, cl 13.2–14.9 mm, 3 ♀♀, cl 14.9–17.6 mm. Diagnosis. Rostrum more or less horizontal, straight, and with tip recurved upwards, bearing 6–8 (avg. 7.0, n = 14, excluding epigastric tooth) teeth along dorsal border except near tip, extending to distal antennular segment or just overreaching antennular peduncle. Postrostral carina with posterior 1 / 4 broadened and obscure, sometimes with weak median pit, extending posteriorly to 0.77–0.89 (avg. 0.84, n = 17) of carapace length. Longitudinal suture short, extending posteriorly to about level of epigastric tooth. Pereiopods I and II with basial spines and epipods, pereiopod III without basial spine. Abdominal somites I and II with dorsal carina absent. Telson lacking movable lateral spinules. Males with endopod of pleopod II strongly modified and boot-like; medial part of distal margin protruded and convex, but concealed by tuft of dense long stiff setae arising from anterodistal part of endopod; petasma horn-like with distolateral projections strongly elongated, tip of horn more or less bifurcated and without lateral protuberances on both sides. Female thelycum with anterior plate elongated rectangular and lateral margins more or less concave, 0.99–1.17 (avg. 1.09, n = 9) as long as wide, surface slightly sunken; posterior plate with median part completely flattened, lateral parts semicircular; tuft of setae behind posterior plate long and thick. Coloration. Not known, but likely similar to P. cornuta and P. amicus. The photograph of a fresh specimen from the Strait of Malacca, Malaysia, probably belongs to P. incisa (Fakhruddin et al. 2024: fig. 1; see Discussion); it has a color pattern very similar to P. cornuta and P. amicus, except with the body having more yellowish and greenish taints. Distribution. Known with certainty from around Hainan Island in the South China Sea, intertidal to about 30 m deep (Liu and Wang 1987; Liu and Zhong 1988). Probably also distributed to the Strait of Malacca off Malaysia and Bangladesh (Fakhruddin et al. 2024; see Discussion). Remarks. Parapenaeopsis incisa closely resembles P. cornuta and mainly differs in the shape of the genitalia. In males, the boot-like endopod of pleopod II has the median part of the distal margin protruded in P. incisa (Fig. 4 d) but is straight or concave in P. cornuta (Fig. 4 a). The tip of the horn-like petasma lacks a lateral protrusion in P. incisa (Fig. 3 d) but is distinctly protruded on the outer side in P. cornuta (Fig. 3 a). The thelycum of P. incisa has the anterior plate more or less rectangular and relatively long (0.99–1.17, avg. 1.09 as long as wide), while the median part of the posterior plate is completely flattened without any sign of elevation (Fig. 5 d). In P. cornuta, the thelycum has the anterior plate semi-quadrate and relatively short (0.74–0.95, avg. 0.85 as long as wide), and the posterior plate bears a weak median ovate boss (Fig. 5 a). These unique shapes of the genitalia are also useful in separating P. incisa from the other two species of the “ P. cornuta ” group (Table 2, Figs 3 – 5). Similar to the situation in P. amicus, other differences previously proposed to separate P. incisa from the other species of the “ P. cornuta ” group (Liu and Wang 1987; Liu and Zhong 1988) actually have many overlaps. Although morphologically P. incisa is most similar to P. cornuta, the high genetic differences (COI sequence divergence 15.0–17.5 %, Table 1) of P. incisa from the other species of the “ P. cornuta ” group well support its specific status. As P. incisa can only be satisfactorily distinguished from the other species of the “ P. cornuta ” group mainly by subtle differences in genitalia (Table 2), careful examination of the material reported as “ P. cornuta ” from various localities is necessary to determine the exact distribution of P. incisa.