Parapenaeopsis amicus V. C. Nguyên, 1971

Parapenaeopsis amicus V. C. Nguyên, 1971 View in CoL

( Figs. 1 View FIGURE 1 , 6a View FIGURE 6 )

Parapenaeopsis cornutus — Parisi 1919: 64, pl. 5-figs. 1, 12; Chang 1965: 15, 3 unnumbered figs. (not Kishinouye, 1900)

? Parapenaeopsis cornutus — Maki & Tsuchiya 1923: 43, pl. 4-1. (not Kishinouye, 1900)

Parapenaeopsis amicus V. C. Nguyên, 1971: 46 View in CoL , fig. 1 (type locality: West Tonkin Gulf).

Parapenaeopsis cornuta View in CoL — Lee & Yu 1977: 87 (in part), figs. 58(?), 59D; Ma et al 2009: table 1. (not Kishinouye, 1900)

? Parapenaeopsis cornuta View in CoL — Yu & Chan 1986: 121 (in part), fig. 19B. (not Kishinouye, 1900)

Parapenaeopsis sinica Liu & Wang 1986: 214 View in CoL (nomen nudum); 1987: 527, fig. 4. (type locality: Guangdong, China); Liu & Zhong 1988: 212, fig. 131; Lee et al. 1999: 445; Perez Farfante & Kensley 1997:121.

Kishinouyepenaeopsis amica — Sakai & Shinomiya 2011: 499.

Kishinouyepenaeopsis amicus View in CoL — De Grave & Fransen 2011: 215; Hurzaid et al. 2020: fig. 3, table S2.

Material examined. Yilan County, Dasi fishing port, 17 Jul 1984, 1 female cl 26.6 mm ( NTOU M02365 View Materials ) . Hsinchu City, Nanliao fishing port, 4 Jul 1984, 1 female cl 31.1 mm ( NTOU M02366 View Materials ) . Changhua County, Wenzi fishing port, 5 Aug 2021, 16 males cl 17.5–22.3 mm, 18 females cl 18.4–25.0 mm ( NTOU M02367 View Materials ) . Yunlin County, Mailiao , Jul 2009, 12 males cl 11.4–17.6 mm, 18 females cl 13.0– 22.5 mm ( NTOU M02368 View Materials ) ; 18 May 2010, 2 males cl 23.0– 24.3 mm, 1 female cl 28.4 mm ( NTOU M02369 View Materials ) . Chiayi County, Budai fishing port, 26 May 1974, 3 males cl 15.6–26.9 mm, 1 female cl 30.5 mm ( NTOU M02418 View Materials ) ; 20 Jan 1995, 4 males cl 18.1–21.5 mm, 2 females cl 18.4–20.1 mm ( NTOU M02370 View Materials ) ; 5 Feb 2000, 20 males cl 15.1–22.7 mm, 20 females cl 15.3–23.4 mm ( NTOU M02371 View Materials ) ; 2 Jul 2002, 8 males cl 26.5–29.2 mm, 10 females cl 22.5–33.2 mm ( NTOU M00762 View Materials ) ; 8 Feb 2021, 21 males cl 22.2–25.1 mm, 21 females cl 23.1–31.1 mm ( NTOU M02372 View Materials ) ; 12 Dec 2021, 2 females cl 26.3–29.7 mm ( NTOU M02417 View Materials ) . Kaohsiung City, 10 Mar 1975, 1 male cl 24.4 mm, 1 female cl 29.2 mm ( NTOU M02373 View Materials ) . Pingtung County, Donggang fishing port, 5 Mar 2021, 2 males cl 24.5–25.0 mm, 1 female cl 28.4 mm ( NTOU M02374 View Materials ) . Penghu County, Third fishing port, Jun–Aug 2013, 3 females cl 24.1–36.6 mm ( NTOU M02375 View Materials ) .

Diagnosis. Rostrum with 7–9 (excluding epigastric tooth) teeth along dorsal border except near tip, horizontal straight with tip curved upwards, usually extending to tip of second segment of antennular peduncle. Longitudinal suture short and extending to about level of epigastric tooth. Pereiopods I and II with basial spines and epipods, pereiopod III lacking basial spine. Abdominal somites I and II without dorsal carina. Telson without movable lateral spinules. Males with endopod of pleopod II normal in shape, sword like as exopod; petasma without distomedian projection but with distolateral projections elongated and horn-like, tip of horn protruded at both sides (more distinct at outer side). Female thelycum with anterior plate shovel-like to semicircular, anterior margin convex, surface somewhat sunken and with distinct median longitudinal furrow; posterior plate without median boss, lateral parts as 2 large semicircular processes; tuft of setae behind posterior plate short and thin.

Coloration. Body generally greenish to bluish gray and densely covered with dark green dots, with antennal flagella and abdomen somewhat banded. Tip of rostrum dark brown to reddish brown. Eyes black gray. Uropods of tailfan dark green to dark red and with yellowish margins. Thoracic appendages pinkish white. Pleopods with rami reddish. Short setae behind thelycum colorless.

Distribution. Known with certainties in Vietnam to southern China and Taiwan, intertidal to about 50 m deep ( Nguyên 1971; Liu & Wang 1987; Liu & Zhong 1988).

Remarks. Liu & Wang (1987) split the Chinese material of P. cornuta ( Kishinouye, 1900) into three species with the erections of P. sinica Liu & Wang, 1987 and P. incisa Wang & Liu in Liu and Wang, 1987, without knowing that V.C. Nguyên (1971) had already named P. amicus from the “ P. cornuta Kishinouye, 1900 ” species complex. The molecular analysis of Hurzaid et al. (2020) indicated that there may be as many as eight species in the “ P. cornuta ” species complex, not including that P. maxillipedo Alcock, 1905 may often been confused with P. cornuta (see Chan 1998 and “Remarks” under P. cornuta ). Although members of the so called “ Kishinouyepenaeopsis ” group (containing the “ P. cornuta ” species complex and P. maxillipedo , with four species currently recognized; see Sakai & Shinomiya 2011; De Grave & Fransen 2011) have their petasma and thelycum very difficult to distinguish (see Chan, 1998; Hurzaid et al., 2020), P. amicus is unique in having a normal pleopod II endopod in males and the tuft of setae behind the thelycum thin and short (v.s. pleopod II endopod in males sock-like and tuft of seta behind thelycum thick and long). Thus, there is little doubt that P. sinica Liu & Wang, 1987 is a junior synonym of P. amicus V. C. Nguyên, 1971 as they both have the tuft of setae behind the thelycum thin and short (V. C. Nguyên 1971: fig. 1B; Liu & Wang 1987:fig. 4e; Liu & Zhong 1988: fig. 131–5).

Examination of the “ P. cornuta ” species complex material in Taiwan revealed the presence of two species. One of them has normal endopod at the pleopod II in males and the tuft of setae behind the thelycum thin and short, characteristics of P. amicus ( Fig. 1c, d View FIGURE 1 ). Moreover, the barcoding COI sequences of P. amicus from Taiwan and Shantou, Guangdong in southern China are considered as belonging to the same species by two different species delimitation analyses ( Li et al. 2014 as P sinica ; Hurzaid et al. 2020). The other species is identified here as P. cornuta . These two species are extremely similar even for body coloration. Nevertheless, the tuft of seta behind the thelycum is colorless in P. amicus but bluish in P. cornuta . Other than the endopod of the pleopod II are very different in males, the shapes of the petasma and thelycum differs in these two species. The tips of the distolateral horns in the petasma is protruded on both sides but only at the outer side in P. amicus ( Fig. 1b View FIGURE 1 ) and P. cornuta ( Fig. 2b View FIGURE 2 ), respectively. The thelycum has a median longitudinal furrow at the anterior plate and there is no median boss in the posterior plate in P. amicus ( Fig. 1c View FIGURE 1 ). On the other hand, the thelycum usually lacks a median furrow in the anterior plate while the posterior plate bears a median boss in P. cornuta ( Fig. 2c View FIGURE 2 ). Other characters previously suggested for separating P. amicus and P. cornuta (V. C. Nguyên 1971; Liu & Wang 1987; Liu & Zhong 1988) are found to have large overlaps and variations. Nevertheless, in the Taiwanese material it appears that P. amicus has a relatively shorter rostrum which generally only reaches the tip of the second segment of antennular peduncle. In P. cornuta , the rostrum is longer and often extends to the tip of the antennular peduncle.

Although both P. cornuta and P. amicus are now known in Taiwan, P. amicus is considerably more abundant. The Taiwanese material of P. cornuta illustrated in Parisi (1919: pl 5-fig. 1 a thelycum, fig. 12 a dorsal view of tail-fan) was argued by Kubo (1949) as not representing P. cornuta . Although it is true that the telson in Parapenaeopsis never has a dorsal carina but bearing a dorsal longitudinal furrow instead, the thelycum of Parisi (1919: pl.5-fig. 1) is typical of P. amicus in bearing a median longitudinal furrow at the posterior part of the anterior plate and lacking a median boss in the posterior plate. The absent of tuft of setae behind the thelycum in Parisi (1919: pl.5-fig. 1) may just be overlooked. The thelycum illustrated by Chang (1965) is almost identical with the one given by Parisi (1915), also lacking setae behind the thelycum. Moreover, the habitus drawing provided by Chang (1965) has the rostrum extending to the tip of the second segment of the antennular peduncle and fits better P. amicus than P. cornuta . The habitus and theylcum illustrated by Lee & Yu (1977: figs. 58, 59D) are also similar to those of Chang (1965) except for the presence of a turf of somewhat long setae behind the thelycum. Amongst the old collection in NTOU where part of Lee & Yu’s (1977) material are deposited, the lot NTOU M02418 has the same locality and date of their P 211 lot identified as P. cornuta . Lee & Yu’s (1977) P 211 lot has one female only while there are three males and one female in NTOU M02418. Nevertheless, the size and shape of the thelycum of the NTOU M02418 female is almost identical with the figure 59D of Lee & Yu (1977), only with the tuft of seta shorter. Therefore, it is highly likely that the female in NTOU M02418, which belongs to P. amicus , is the specimen used for the thelycum figure in Lee & Yu (1977: fig. 59D). The Taiwanese material of “ P. cornuta ” used in the molecular phylogenetic study of Ma et al. (2009: table 1—NTOU M00762) is actually P. amicus .

The Taiwan records of P. cornuta by Maki & Tsuchiya (1923) and Yu & Chan (1986) have the distinguishing characters discussed above not detailed enough for deciding if they are truly P. cornuta or represent P. amicus instead. Nevertheless, the photograph of Maki & Tsuchiya (1923: pl. 4-1) shows the rostrum reaches only the tip of second segment of the antennular peduncle and therefore may refer to P. amicus . On the other hand, the rostrum in the photograph of Yu & Chan (1986: 121, unnumbered photo) extends to the tip of antennular peduncle and likely represents the true P. cornuta . Even though P. amicus was listed as from Taiwan by Li et al. (1999, as P. sinica and see “Introduction”) and Hurzaid et al. (2020), no information of any sort was accompanied in these two reports. Therefore, it can be considered that P. amicus is formally recorded from Taiwan by the present work.