Penaeus (Ischiopeneaus), 2023

Chan, Tin-Yam, 2023, New subgeneric names for the most commercially important shrimp genus Penaeus Fabricius, 1798 (Crustacea, Decapoda, Penaeidae), ZooKeys 1141, pp. 29-40 : 29

Penaeus (Ischiopeneaus) subgen. nov.

Type species.

Penaeus longistylus Kubo, 1943.

Gender of subgenus.

Masculine.

Diagnosis.

Rostrum generally armed with 1 ventral tooth. Median sulcus at postrostral carina deep but distinctly shorter than half carapace length. Adrostral sulcus somewhat wider than postrostal carina and extending to near posterior margin of carapace. Gastrofrontal carina distinct and with posterior end turning anterodorsally. Cervical carina with dorsal end a distance from dorsal carapace. Hepatic carina distinct. First pereiopod with strong ischial spine. Fifth pereiopod bearing exopod. Sixth abdominal somite completely lacking dorsolateral sulcus. Telson with 3 pairs of lateral spines. Thelycum closed.

Etymology.

The name Ischiopenaeus alludes to the presence of a strong ischial spine at the first pereiopod in this subgenus of Penaeus .

Species included.

Penaeus (Ischiopenaeus) longistylus Kubo, 1943

Remarks.

This taxon corresponds to "gen. nov. 4" in the 11-genus scheme of fig. 3 in Yang et al. (2023). This subgenus differs from almost all the non-American “grooved” species in the first pereiopod bearing a strong ischial spine (vs. small to absent). Another non-American “grooved” species with a strong ischial spine at the first pereiopod is P. (Altiopeneaus) marginatus , which lacks a median sulcus on the postrostral carina and generally has two ventral rostral teeth. Thus, the enigmatic Melicertus similis Chanda & Bhattacharya, 2002 described from the Andaman Sea likely represents juveniles of P. (Ischiopenaeus) longistylus as its original description and figures ( Chanda and Bhattacharya 2002: figs 1, 6) indicated the presence of postrostral sulcus, only one ventral rostral tooth and the first pereiopod bearing a strong ischial spine. The “absence” of lateral spines on the telson in Melicertus similis is likely evidence that Chanda and Bhattacharya’s (2002) material are juveniles (total length including rostrum less than 80 mm) as juveniles of Penaeus generally have the lateral spines on the telson rather small and can be easily detached or overlooked.