Plesionika persica ( Kemp, 1925 )

Chan, Tin-Yam, Chakraborty, Rekha Devi, Purushothaman, P., Kuberan, G. & Yang, Chien-Hui, 2018, On Plesionika persica (Kemp, 1925) and P. reflexa Chace, 1985 (Crustacea: Decapoda: Pandalidae) from India, Zootaxa 4382 (3), pp. 583-591 : 584-586

Plesionika persica ( Kemp, 1925)

( Fig. 1 )

Parapandalus persicus Kemp, 1925: 273 , fig. 8. (type locality: Gulf of Oman)

Parapandalus filipes Calman, 1939 ; 202, fig. 2. (type locality: Gulf of Oman, see Remarks) Plesionika filipes — Chace 1985: 46.

Plesionika persica — Chace, 1985: 46; Tiefenbacher 1992: 120; Fransen 2006: 73, fig. 21; De Grave & Fransen 2011: 450.

Material examined. India, Kalamuku, Cochin, 250-300 m, April 2017, 1 male cl 11.8 mm, 1 specimen sex undetermined cl 10.5 mm ( NTOU) ; Kerala, Cochin, 250-300 m, April 2017, 4 males cl 10.0–12.0 mm, 5 females cl 10.0–12.0 mm ( CMFRI ED.2.4.3.5).

Diagnosis. Rostrum slightly shorter than carapace, curving downwards at basal region, slightly recurved upwards and nearly straight after passing antennular peduncle; with low rostral crest and bearing 6–8 dorsal teeth (including 3 teeth posterior to orbital margin and posteriormost tooth sometimes with incomplete basal suture) restricted to proximal half of rostrum and none with barbed tip; ventral margin armed with 5–7, rarely 3 teeth. Postrostral ridge blunt but strong, extending to about middle of carapace and not highly elevated. Carapace with fainted hepatic and branchial grooves; antennal and pterygostomian spines present and distinct, similar sized; orbital margin with upper part straight and dorsally inclined forwards, lower part slightly convex. Eyes without distinct ocellus. Stylocerite tapered anteriorly and not markedly folded upwards laterally, extending to about middle of second segment of antennular peduncle. Scaphocerite slender, 4.6–4.8 times as long as maximum width, distolateral tooth just exceeding distal margin of lamina, basicerite spine moderately long and just exceeding proximal end of lateral margin of scaphocerite. Maxilliped III and pereiopods all lacking epipods. Pereiopod I overreaching scaphocerite by dactylus and half propodus, propodus about 0.41–0.43 times as long as carpus. Pereiopod II subequal, extending to tip of scaphocerite and bearing 14–20 carpal articles. Posterior 3 pereiopods very long, with pereiopods IV and V even thread like (see Remarks). Abdomen with tergite III without any spine, dorsal ridge or groove; pleuron IV posteroventrally rounded, while pleuron V with posteroventral angle somewhat pointed; somite VI 2.2–2.5 times longer than maximum height; telson as long as somite VI and bearing 3 pairs of dorsolateral spines (excluding pair adjacent to posterior margin of telson).

Distribution. Arabian Sea and Red Sea, mesopelagic, at depths of 0–2500 m (see Tiefenbacher 1992; Fransen 2006).

Remarks. Plesionika persica is characterized in having extremely long thread- like pereiopods IV and V. Only three described species in genus Plesionika have such overlong posterior pereiopods: P. persica ( Kemp, 1925) , P. filipes ( Calman, 1939) and P. taiwanica Chan & Yu, 2000 ( Chan & Yu 2000). Plesionika persica and P. filipes are very similar ( Chace 1985) and have their type localities nearby. Although Calman (1939) mentioned that the holotype of P. filipes was collected from the “South Arabian Coast”, the exact position of the station (i.e., St. 76B) for the holotype is 24o13’54”–24o16’42’N/ 59o16’42”E / 59o03’30”E – 59o06’30”E (see Tiefenbacher 1992), which is actually at the entrance of Gulf of Oman and very near to the type locality of P. filipes (23o44’30”N, 58o52’15”E; Kemp 1925). Therefore, these two species are treated as synonyms by Tiefenbacher (1992) and followed in recent works (e.g., Fransen 2006; De Grave & Fransen 2011). Plesionika taiwanica is endemic to Taiwan and superficially rather similar to P. persica except for having a much longer rostrum that bearing numerous ventral rostral teeth. Nevertheless, detailed comparisons revealed many more differences between these two species. There are strap-like epipods on the maxilliped III and anterior four pereiopods in P. taiwanica but all these appendages lack epipods in P. persica . In P. taiwanica , there is no rostral crest (versus a low rostral crest in P. persica ) and the upper part of the orbital margin is slightly convex (versus straight in P. persica ). The stylocerite is obtuse and distinctly folded upwards laterally in P. taiwanica but tapered anteriorly and not particularly folded upwards laterally in P. persica . Moreover, the lateral carapace is smooth in P. taiwanica but bearing fainted hepatic and branchial grooves in P. persica . Therefore, more studies are necessary to determine if these two species with overlong pereiopods are really closely related and can be grouped together. For example, the presence or absence of epipods on the maxilliped III and anterior pereiopods have been considered by many workers as of generic importance (see Chace 1985; Holthuis 1993).

The “Diagnosis” provided above is based on the Indian material except for the posterior three pereiopods that are all missing or very incomplete in the specimens examined. Nevertheless, the present material can still be satisfactorily identified as P. persica by the remaining characters especially by the shape of the rostrum (short and with low rostral crest, bearing few teeth on both dorsal and ventral borders and with dorsal teeth restricted to proximal half of rostrum), smooth abdominal tergite III and telson having 3 pairs of dorsolateral spines (see Kemp 1925; Calman 1939; Tiefenbacher 1992; Fransen 2006). Moreover, the male specimen deposited at NTOU has fewer ventral rostral teeth (only three) than other specimens reported for the species.

Plesionika persica is recorded for the first time from India (off the Arabian coast), though this species appears to be rather common in the other parts of the Arabian Sea and the Red Sea ( Calman 1939; Tiefenbacher 1992; Fransen 2006). Nevertheless, the coloration of this species is still unknown and with all known material preserved in formalin we are unable to work for genetic sequencing.

Figures

FIGURE 1. Plesionika persica (Kemp, 1925), Kalamuku, 250–300 m, sex undetermined cl 10.5 mm (NTOU). A, lateral carapace; B, anterior carapace, lateral; C, right antennular peduncle and stylocerite, lateral; D, abdominal somites II to VI and tail fan, lateral.Scales = 2 mm.