Parapenaeopsis amicus V. C. Nguyen 1971
Creators: name: Chan, Tin-Yam
name: Yang, Chien-Hui
name: Kumar, Appukttannair Biju
name: Hurzaid, Amirah
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Penaeidae
Parapenaeopsis
Parapenaeopsis amicus

description: Parapenaeopsis amicus V. C. Nguyên, 1971
Figs 1 c, 2 c, 3 c, 4 c, 5 c, 7 d
Parapenaeopsis amicus V. C. Nguyên 1971: 46, fig. 1 (type locality: West Tonkin Gulf); Hsu and Chan 2023: 222, figs 1, 6 a.
Parapenaeopsis sinica Liu and Wang 1986: 214 (nomen nudum), 1987: 527, fig. 4. (type locality: Wailuo, Guangdong, China); Liu and Zhong 1988: 212, fig. 131, pl. 3: 4, 5: 6.
Kishinouyepenaeopsis amicus – De Grave and Fransen 2011: 215.
Material examined.
Taiwan • [NTOU M 02365]: Yilan County, Dasi fishing port, commercial trawler, 17 Jul. 1984, 1 ♀, cl 26.6 mm • [NTOU M 02366]: Hsinchu City, Nanliao fishing port, commercial trawler, 4 Jul. 1984, 1 ♀, cl 31.1 mm • [NTOU M 02367]: Changhua County, Wenzi fishing port, commercial trawler, 5 Aug. 2021, 16 ♂♂, cl 17.5–22.3 mm, 18 ♀♀, cl 18.4–25.0 mm • [NTOU M 02368]: Yunlin County, Mailiao, Jul. 2009, 12 ♂♂, cl 11.4–17.6 mm, 18 ♀♀, cl 13.0– 22.5 mm • [NTOU M 02369]: Yunlin County, Mailiao, 18 May 2010, 2 ♂♂, cl 23.0– 24.3 mm, 1 ♀, cl 28.4 mm • [NTOU M 02418]: Chiayi County, Budai fishing port, commercial trawler, 26 May 1974, 3 ♂♂, cl 15.6–26.9 mm, 1 ♀, cl 30.5 mm • [NTOU M 02370]: Chiayi County, Budai fishing port, commercial trawler, 20 Jan. 1995, 4 ♂♂, cl 18.1–21.5 mm, 2 ♀♀, cl 18.4–20.1 mm • [NTOU M 02371]: Chiayi County, Budai fishing port, commercial trawler, 5 Feb. 2000, 20 ♂♂, cl 15.1–22.7 mm, 20 ♀♀, cl 15.3–23.4 mm • [NTOU M 00762]: Chiayi County, Budai fishing port, commercial trawler, 2 Jul. 2002, 8 ♂♂, cl 26.5–29.2 mm, 10 ♀♀, cl 22.5–33.2 mm • [NTOU M 02372]: Chiayi County, Budai fishing port, commercial trawler, 8 Feb. 2021, 21 ♂♂, cl 22.2–26.0 mm, 21 ♀♀, cl 23.1–31.1 mm • [NTOU M 02417]: Chiayi County, Budai fishing port, commercial trawler, 12 Dec. 2021, 2 ♀♀, cl 26.3–29.5 mm • [NTOU M 02373]: Kaohsiung City; 10 Mar. 1975, 1 ♂, cl 24.4 mm, 1 ♀, cl 29.2 mm • [NTOU M 02374]: Pingtung County, Donggang fishing port, commercial trawler, 5 Mar. 2021, 2 ♂♂, cl 24.5–25.0 mm, 1 ♀, cl 28.4 mm • [NTOU M 02375]: Penghu County, Third fishing port, commercial trawler, Jun. – Aug. 2013, 3 ♀♀, cl 24.1–36.6 mm.
Diagnosis.
Rostrum horizontal straight with tip recurved upwards, armed with 7–9 (avg. 7.8, n = 20, excluding epigastric tooth) teeth along dorsal border except near tip, extending to around tip of second segment of antennular peduncle. Postrostral carina with posterior 1 / 4 broadened and obscure, often with weak median pit, extending posteriorly to 0.77–0.89 (avg. 0.85, n = 20) of carapace length. Longitudinal suture short, extending posteriorly to about level of epigastric tooth. Pereiopods I and II bearing basial spines and epipods, pereiopod III lacking basial spine. Abdominal somites I and II without dorsal carina. Telson lacking movable lateral spinules. Males with endopod of pleopod II normal in shape, sword-like as exopod; petasma with distolateral projections elongated and horn-like, tip of horn distinctly protruded on both sides (outer protrusion often larger) and hammer-like. Female thelycum with anterior plate shovel-like to semicircular (more often), 0.59–0.73 (avg. 0.65, n = 10) as long as wide, surface sunken with distinct median longitudinal furrow extending to posterior plate; posterior plate with median part also sunken, lateral parts as 2 large semicircular processes; tuft of setae behind posterior plate short and thin.
Coloration.
(Fig. 7 c) Similar to P. cornuta except tuft of short setae behind thelycum colorless. Color photograph of this species given in Hsu and Chan (2023).
Distribution.
Known with certainty from Vietnam to southern China and Taiwan, intertidal to about 50 m deep (Liu and Wang 1987; Liu and Zhong 1988).
Remarks.
Although the general appearance of P. amicus is very similar to the other members of the “ P. cornuta ” species group, it can be readily distinguished by the shape of genitalia. For males, P. amicus is unique in having a normal pleopod II endopod (Fig. 4 c; v. s. greatly modified and boot-like, Figs 4 a, b, d). In females, the tuft of setae behind the thelycum is thin and short (Fig. 5 c; v. s. thick and long, Figs 5 a, b, d). Efforts to locate the types of P. amicus were unsuccessful (personal communication from Tran Anh Duc). As both P. amicus, described from Vietnam (V. C. Nguyên 1971: fig. 1 B), and P. sinica Liu & Wang, 1987, described from southern China (Liu and Wang 1987: fig. 4 e; Liu and Zhong 1988: fig. 131–5), have the characteristic short and thin setae behind the thelycum, they are determined to be synonyms.
Besides the pleopod II endopod in males and tuft of setae behind the thelycum in females, P. amicus can also be separated from the other species of the group by some subtle differences in the genitalia (Table 2). The tip of the horn-like petasma has both sides distinctly protruded and hammer-like in P. amicus (Fig. 3 c), but only with the outer side protruded in P. cornuta (Fig. 3 a) and P. maxillipedo (Fig. 3 b) or both sides not protruded in P. incisa (Fig. 3 d). In P. amicus, the thelycum has a median longitudinal furrow, the anterior plate is relatively short (0.59–0.73, avg. 0.65 as long as wide), and the posterior plate medially sunken (Fig. 5 c). For the other species of the “ P. cornuta ” group, the thelycum (Figs 5 a, b, d) generally lacks a median longitudinal furrow (but is occasionally present in P. cornuta), the anterior plates are usually longer (0.74–1.17 as long as wide), and the median parts of the posterior plates are flattened (in P. incisa, Fig. 5 d) to more or less protruding into a boss [low in P. cornuta (Fig. 5 a) and high in P. maxillipedo (Fig. 5 b)]. However, the characteristic shape of the genitalia is generally less developed in juveniles and young specimens. These subtle differences in genitalia are hence sometimes not useful to separate small individuals of this species group.
It is also found that the rostrum is relatively shorter, not reaching the tip of the antennular peduncle, in P. amicus (Fig. 1 c) and P. maxillipedo (fig. 1 b). In P. cornuta (Fig. 1 a) and P. incisa (Fig. 1 d), the rostrum is often extending to or even overreaching the tip of the antennular peduncle. Other differences previously proposed to distinguish P. amicus from the other species of the “ P. cornuta ” group [such as the number of rostral teeth, postrostral carina length, the presence of a median pit on postrostral carina, and setae on the branchiocardiac groove (Liu and Wang 1987; Liu and Zhong 1988; V. C. Nguyên 1971)] are found to be rather variable, with many overlappings.
Molecular analysis also indicates that P. amicus is more distant from the other species of the “ P. cornuta ” group (Figs 8, 9, Table 1). However, the body color of P. amicus (Fig. 7 d) is very similar to P. cornuta (Figs 7 a, b) and very likely also with P. incisa (see Hsu and Chan 2023; Liu and Zhong 1988), rendering it difficult to determine its exact distribution from literature. At present, it can only be confirmed that P. amicus is distributed from Vietnam to eastern Guangdong in southern China and Taiwan (Hsu and Chan 2023; Liu and Wang 1987; Liu and Zhong 1988). Whether P. amicus has a wider geographical distribution will need re-examination of the material reported as “ P. cornuta ” in the various localities from India to Australia. For example, a recent study found that P. amicus is actually much more abundant than P. cornuta in Taiwan (Hsu and Chan 2023).
description: Published as part of Chan, Tin-Yam, Yang, Chien-Hui, Kumar, Appukttannair Biju & Hurzaid, Amirah, 2025, On the commercial shrimps of the " Parapenaeopsis cornuta (Kishinouye, 1900) " species group (Crustacea, Decapoda, Penaeidae), pp. 609-625 in Zoosystematics and Evolution 101 (2) on pages 609-625, DOI: 10.3897/zse.101.145722