Metapenaeus affinis (H. Milne Edwards, 1837)

Hsu, Yen-Cheng, Chen, Chien-Lin & Chan, Tin-Yam, 2022, On the penaeid shrimps of the genus Metapenaeus Wood-Mason in Wood-Mason & Alcock, 1891 (Crustacea, Decapoda, Penaeidae) of Taiwan, Zootaxa 5169 (4), pp. 331-346 : 331-332

Metapenaeus affinis (H. Milne Edwards, 1837)

( Figs. 1 , 8a )

Penaeus affinis H. Milne Edwards 1837: 416 (type locality: India).

Metapenaeus affinis — Maki & Tsuchiya 1923: 38, pl. 2-fig. 3.— Lee & Yu 1977: 91, figs. 62-63.— Miquel 1982: 47, figs. 11- 12.— Yu & Chan 1986: 143, fig. 16B, 2 unnumbered figs.— Lee et al. 1999: 445.

Material examined. Taipei City, Taipei market, 7 May 1985, 1 male cl 18.5 mm ( NTOU M02305 ) . Yunlin County, Mailiao, Station 1, 1 female cl 14.4 mm ( NTOU M02428 ) . Chiayi County, Budai fishing port, 2 Jul 2002, 9 males cl 18.9-21.7 mm, 15 females cl 21.0- 28.4 mm ( NTOU M02306 ) ; 25 Feb 2021, 1 female cl 21.6 mm ( NTOU M02412 ).— Dongshi fishing port, 12 Dec 2021, 2 males cl 22.2, 23.8 mm ( NTOU M02403 ) . Kaohsiung City, Kaohsiung fishing port, Mar 1975, 4 males cl 16.0- 22.3 mm, 4 females cl 15.8-22.8 mm ( NTOUM02312 ) .— Neiwei market, 17 Oct 2019, 1 female cl 29.2 mm ( NTOU M02313 ) .— Singda fishing port, 24 Jul 1984, 1 male cl 17.9 mm ( NTOU M02314 ) .— Kaohsiung Port , 5 Jan 1995, 9 males cl 12.8-19.2 mm, 9 females cl 16.3-33.2 mm ( NTOU M02311 ) ; Station 1, 1 Mar 1994, 6 males cl 10.9-20.8 mm, 9 females cl 14.6-21.5 mm ( NTOU M02308 ) ; Station 2, 1 Mar 1994, 1 male cl 19.5 mm, 2 juveniles cl 8.6, 13.0 mm ( NTOU M02309 ) ; Station 3, 1 Mar 1994, 1 male cl 16.11 mm ( NTOU M02413 ) ; Station 6, 1 Mar 1994, 1 male cl 19.2 mm, 3 females cl 20.2-31.6 mm ( NTOU M02310 ) . Pingtung County, Donggang fishing port, 27 Dec 1974, 2 males cl 19.4, 22.8 mm, 1 female cl 23.3 mm ( NTOU M02315 ) ; 21 Oct 1995, 1 male cl 22.15 mm, 1 female cl 18.6 mm ( NTOU M02414 ) ; 14 Aug 2015, 1 male cl 23.5 mm ( NTOU M02316 ) ; 9 May 2019, 1 male cl 22.2 mm, 4 females cl 23.9-28.3 mm ( NTOU M02317 ) ; 5 Mar 2021, 1 male cl 23.1 mm ( NTOU M02318 ) . No Specific data, 1 female cl 34.4 mm ( NTOU M02429 )

Diagnosis. Rostrum with 6–9 (excluding epigastric tooth) teeth along entire dorsal border, generally straight and with tip curved upwards, more or less extending to tip of antennular peduncle. Pereiopod I with ischial spine absent to distinct. In males, basial spine of pereiopod III not particular elongated, merus of pereiopod V bearing basal notch accompanied with carinated and twisted tubercle. Telson with minute movable lateral spinules. Male petasma with distomedian projections very low and crescent shaped, reaching behind tips of distolateral projections. Female thelycum with anterior plate having posterior part much wider than anterior part; coxal projections of pereiopod IV round plate like and often concealing anterior plate but not extending to lateral plates, lateral plates as two overlapped rounded flaps without any sharp ridge and median longitudinal fissure.

Coloration. Body generally greyish green and densely covered with dark dots. Antennal flagella, distal parts of pereiopods and pleopods reddish. Uropods red margined with distal parts somewhat greenish yellow.

Distribution. Widely distributed in the Indo-West Pacific from the Persian Gulf to Japan and Papua New Guinea, intertidal to 92 m deep ( Miquel 1982; Pérez Farfante & Kensley 1997; Chan 1998).

Remarks. Metpenaeus affinis mainly occurs in southern Taiwan and rather common there. Amongst the species of this genus in Taiwan, M. affinis is most similar to M. ensis (De Haan, 1844) . These two species can be distinguished by the following characters. The petasma has the distomedian projections very low in M. affinis ( Fig. 1b ) but as huge protuberances in M. ensis ( Fig. 3b ). The lateral plate of the thelycum has the posterolateral margins strongly folded anteriorly in M. ensis ( Fig. 3c ) but not folded up at all in M. affinis ( Fig. 1b ). In mature females the coxal projection of pereiopod IV is normal and not expanded in M. ensis , but round plate like and often concealing the anterior plate of thelycum in M. affinis . In mature males, the basal protuberance at the merus of pereiopod V is rounded in M. affinis ( Fig. 1d ) but spiniform in M. ensis ( Fig. 3d ). Moreover, the ischial spine of the pereiopod I in males is often (but not always) indistinct or absent in M. affinis but distinct in M. ensis . The tip of the rostrum is somewhat curved upwards in M. affinis ( Fig. 1a ) but generally straight in M. ensis ( Fig. 3a ). The posterior parts of the uropods are often greenish yellow in M. affinis ( Fig. 8a ) instead of bluish purple in M. ensis ( Fig. 8c ). Moreover, in large specimens the pereiopods are somewhat banded with red and while in M. ensis ( Fig. 8c ) but non-banded in M. affinis ( Fig. 8a ). Nevertheless, juveniles of these two species with gentalia not fully developed are rather difficult to separate.

Figures

FIGURE 1.Metapenaeus affinis (H. Milne Edwards, 1837), a, c, female cl 26.0 mm (NTOU M02306); b, d, male cl 22.2 mm (NTOU M02317). a, cephalothorax, lateral. b, petasma, ventral. c, thelycum. d, merus of pereiopod V, lateral. Scales: 3 mm.

FIGURE 3. Metapenaeus ensis (De Haan, 1844), a, c, female cl 28.8 mm (NTOU M02326); b, d, males cl 24.1 mm (NTOU M02325). a, cephalothorax, lateral. b, petasma, ventral. c, thelycum. d, merus of pereiopod V, lateral. Scales: 5 mm.

FIGURE 8. a, Metapenaeus affinis (H. Milne Edwards, 1838), male cl 22.2 mm (NTOU M02403). b, M. elegans De Man, 1907, male cl 19.1 mm (NTOU M02319). c, M. ensis (De Haan, 1844), female cl 32.7 mm (NTOU M02327). d, M. intermedius (Kishinouye, 1900), female, specimen lost, Dasi fishing port, Yilan county, 26 May 1988. e, M. joyneri (Miers, 1880), female cl 18.4 mm (NTOU M02338). f, M. moyebi (Kishinouye, 1896), male cl 12.3 mm (NTOU M02350).