Pandalopsis houyuu, Komai & Hibino, 2019

Komai, Tomoyuki & Hibino, Mai, 2019, Three new species of the pandalid shrimp genus Pandalopsis Spence Bate, 1888 (Crustacea: Decapoda: Caridea) from the southwestern Sea of Okhotsk, with supplemental note on P. glabra Kobjakova, 1936, Zootaxa 4545 (1), pp. 1-31 : 11-17

Pandalopsis houyuu n. sp.

[New Japanese name: Shiretoko-morotoge-ebi]

Figs. 6–9 , 14

Material examined. Holotype: CBM-ZC 14617, female (cl 39.5 mm), Nemuro Strait, off Rausu, Shiretoko Peninsula , Hokkaido, 44°02.43’N, 145°21.15’E, 750 m, 8 September 2015, FB “Houyuu-maru”, shrimp trap, coll. K. Matsuzaki.

Paratypes: CBM-ZC 14618, 1 transitional male (cl 38.3 mm), same data as holotype; CBM-ZC 14619, 2 males (cl 30.7, 33.5 mm), 2 transitional males (cl 35.3, 37.6 mm), 1 female (cl 45.8 mm), 1 ovigerous female (cl 41.2 mm), off Rausu, 44°12.13’N, 145°23.31’E, 420 m, 9 September 2015, FB “Houyuu-maru”, shrimp trap, coll. K. Matsuzaki ; CBM-ZC 14620, 1 female (cl 44.1 mm), similar locality, 44°18.27’N, 145°23.50’E, 750 m, 13 May 2016, gill net, coll. K. Matsuzaki; CBM-ZC 14621, 1 transitional male (cl 37.6 mm), similar locality, depth and date not recorded, reared in aquarium until 11 December 2017, coll. K. Matsuzaki; CBM-ZC 14622, 1 transitional male (cl 43.0 mm), similar locality, depth not recorded, 2017, FB “Houyuu-maru”, shrimp trap, coll. K. Matsuzaki, reared in aquarium until 5 January 2018; CBM-ZC 14623, 1 male (cl 36.4 mm), similar locality, depth and date not recorded, coll. K. Matsuzaki, reared in aquarium until 14 October 2017; CBM-ZC 15180, 1 transitional male (cl 36.4 mm), same data as CBM-ZC 14619; CBM-ZC 15181, 1 transitional male (cl 37.7 mm), same data as holotype; AMF-ZC0023, 1 female (cl 40.9 mm), same data as CBM-ZC 15620; AMF-ZC0029, 4 males (cl 24.2– 33.5 mm), 2 transitional males (cl 33.5, 35.7 mm), 1 female (cl 41.6 mm), 1 ovigerous female (cl 38.2 mm), same data as holotype; AMF-ZC0030, 2 transitional males (cl 33.3, 36.2 mm), same data as CBM-ZC 14619; AMF- ZC0031 , 1 transitional male (cl 33.5 mm), off Rausu, depth not recorded, 7 September 2016, FB “Houyuu-maru”, shrimp trap, coll. K. Matsuzaki.

Description. Body ( Fig. 6A, B ) moderately robust; no tegmental scales.

Rostrum ( Fig. 7A, B ) reaching to overreaching distal margin of antennal scale, 0.8–1.4 times as long as carapace, gently curving dorsally; dorsal margin armed with 16–24 movable spines (those spines becoming more widely spaced toward distal), including 8–14 on rostrum proper and 7–11 postorbital, and 1 or 2 small fixed spines near apex, subdistal 0.2–0.3 leaving unarmed, posteriormost postrostral spine located at about midlength of carapace (0.49–0.53 of carapace length); ventral margin armed with 11–17 spines gradually increasing in size proximally (posteriormost spine subequal or slightly larger than preceding); lateral carina distinct in proximal half, becoming obsolescent toward distal.

Carapace ( Fig. 7A, B ) with postrostral carina moderately high, crested, extending to posterior 0.4 of carapace length; dorsal margin gently convex in lateral view with peak at posteriormost postrostral spine; antennal spine moderately large; branchiostegal spine distinctly smaller than antennal spine; pterygostomial margin broadly rounded; no conspicuous ridges or carinae on lateral surface; carapace surface almost glabrous, but with transverse patch of short setae near posterodorsal margin.

Pleon ( Figs. 6A ; 7C ) dorsally smooth, glabrous. Pleura 1–3 rounded, pleura 4 with small, ventrally curved posteroventral spine, pleuron 5 terminating posteriorly in moderately large spine. Pleomere 6 0.5–0.6 times as long carapace, 2.1–2.3 times as long as high, with small posteroventral spine; posterolateral process terminating in small spine. Telson ( Fig. 7D ) 1.3–1.5 times as long as pleomere 6, armed with 7–10 dorsolateral spiniform setae on either side; dorsal surface nearly flat, glabrous, with median tuft of stiff setae proximally; posterior margin terminating in small blunt triangular projection, bearing 3 or 4 small spiniform setae flanked by 1 pair of much longer spiniform setae.

Eye ( Fig. 7A, E ) broadly subpyriform, maximal diameter of cornea 0.2 or slightly less of carapace length; ocellar sinous present, but ocellus absent.

Antennular peduncle ( Fig. 7A, E ) reaching midlength of antennal scale. Article 1 subequal in length to articles 2 and 3 combined, with cluster of stiff or long spiniform setae on dorsodistal margin; stylocerite short, not reaching midlength of peduncular article 1, rounded. Articles 2 with few minute spiniform setae on dorsodistal margin. Outer flagellum 1.3–1.5 length of carapace, with aesthetasc-bearing portion subequal in length to carapace.

Antenna ( Fig. 7A, E ) with stout basicerite bearing moderately strong ventrolateral spine. Carpocerite not reaching midlength of antennal scale, reaching as far as article 1 of antennular peduncle. Antennal scale 0.8–1.0 times as long as carapace and 3.8–4.4 times longer than broad, lateral margin almost straight; distolateral spine ( Fig. 7F ) moderately slender, reaching as far as rounded lamella.

Maxilliped 3 ( Fig. 8A ) falling slightly short of or reaching distal margin of antennal scale. Ultimate article 1.1– 1.2 times as long as penultimate article (= carpus), terminating in small spiniform seta flanked by shorter spiniform setae ( Fig. 9A ). Distal two articles setose with several tufts of short stiff setae on extensor surface and obliquely transverse rows of long bristle-like setae on lateral or flexor lateral surfaces. Antepenultimate article (merusischium-basis fused article) longer than distal two articles combined, dorsomesially with prominent, rounded crest at midlength, dorsal surface proximal to crest forming shallow concavity; ventral margin keeled, with closely spaced short to long stiff setae; small, low protuberance present basally on dorsal surface. Exopod absent.

Pereopod 1 ( Fig. 8B ) shorter than maxilliped 3, minutely chelate, reaching midlength of antennal scale. Propodus slightly compressed laterally, gradually tapering, 0.6–0.8 times as long as carpus; mesial surface with field of dense stiff setae, composing grooming apparatus, on proximal 0.7. Carpus with row of tufts of short to long bristle-like setae on extensor and flexor margins, extensor margin with shallow concavity subterminally. Merus dorsal margin with few low protuberances distally and sparse stiff setae; ventral margin slightly expanded proximal to midlength, with row of low protuberances and short to long stiff setae. Ischium ventrally with prominent laminar expansion, fringed with closely set short to long stiff setae; terminal margin of lamina subacutely pointed or with few minute denticles.

Pereopods 2 ( Fig. 8C ) subequal, overreaching antennal scale by length of chela. Chela 0.4 times as long as carpus; dactylus 0.7–0.8 times as long as palm. Carpus subdivided into 15–18 articles. Merus 0.5 times as long as ischium, without annulation. Ischium faintly sinuous, with ventral margin slightly expanded in proximal half to accommodate chela when carried flexed, margin of expansion fringed with short, curved, stiff setae.

Pereopods 3–5 generally similar, decreasing slightly in length toward posterior. Pereopod 3 ( Fig. 8D ) overreaching antennal scale by 0.5–0.6 length of propodus. Dactylus ( Fig. 9B ) approximately 0.2 times as long as propodus, slightly curving, terminating in acute unguis not clearly demarcated basally; flexor margin with 6–9 (rarely 10; 8 on average) small accessory spiniform setae over entire length, becoming longer and more widely spaced distally, and 1 subterminal slender spiniform setae contiguous to unguis. Propodus ( Fig. 9C ) extensor surface with widely spaced tufts of or individual short setae and minute spiniform setae; lateral surface with sparse very short setae and scattered minute spiniform setae on flexor side; mesial surface with numerous, scattered minute spiniform setae on flexor side ( Fig. 9D ); flexor surface with slender spiniform setae increasing in size distally and arranged in irregular 2 or 3 rows, distal margin with 2 long spiniform setae. Carpus 0.5–0.7 times as long as propodus; extensor surface with numerous minute spiniform setae extending onto lateral and mesial faces; lateral surface with 2–4 (rarely 5 or 6) robust spiniform setae adjacent to flexor margin; mesial surface with numerous minute spiniform setae ( Fig. 9E ). Merus 0.9–1.0 times as long as carapace, armed with 7–14 lateral and 7–11 ventral robust spiniform setae. Ischium with 1 ventrolateral robust spiniform seta.

Pereopod 4 ( Fig. 8E ) overreaching antennal scale by 0.4 length of propodus, generally similar to pereopod 3. Dactylus ( Fig. 9F, G ) approximately 0.2 times as long as propodus, armed with 7–9 (rarely 10 or 11) accessory spiniform setae + 1 subapical spiniform seta. Carpus 0.6 times as long as propodus, with 2 or 3 (rarely 1 or 4) robust spiniform setae on lateral surface. Merus 0.9–1.0 times as long as carapace, with 5–10 lateral and 6–9 ventral robust spiniform setae. Ischium with 1 robust spiniform seta.

Pereopod 5 ( Fig. 8F ) overreaching antennal scale by 0.2 length of propodus. Dactylus ( Fig. 9H, I ) slightly shorter than those of pereopods 3 and 4, less than 0.2 times as long as propodus; flexor margin with 8–11 (rarely 13) accessory spiniform setae + 1 subapical spiniform seta contiguous to unguis. Propodus ( Fig. 9I ) slightly widened distally, with several prominent tufts of stiff setae, forming grooming apparatus, in distal 0.3; flexor margin with single row of widely spaced, minute spiniform setae, distal margin with cluster of 3 or 4 longer spiniform setae reaching proximal 0.3–0.4 of dactylus. Carpus 0.5–0.6 times as long as propodus, with 0–1 robust spiniform setae on lateral surface; extensor margin with sparse tufts of short setae; mesial surface with sparse tufts or individual short setae. Merus 0.8–0.9 times as long as carapace, with 6–9 lateral and 0–7 ventral robust spiniform setae. Ischium with 1 robust spiniform seta.

Endopod of pleopod 1 and appendix masculina on pleopod 2 showing sequential change with growth, suggesting protandrous hermaphroditism. Endopod of pleopod 1 in functional males ( Fig. 7G ) moderately broad, with relatively short and stout appendix interna and distinct lobule lateral to base of appendix interna; in transitional males ( Fig. 7H ), appendix interna subterminal in position; in females ( Fig. 7I ), endopod becoming broader, tapering to simple, bluntly pointed terminus. Appendix masculina of functional males ( Fig. 7J ) slightly shorter than appendix interna, bearing several long spiniform setae on terminus to distal half of upper surface; in functional males ( Fig. 7K ), appendix masculina reduced to half or less than half length of appendix interna, bearing very short setae terminally; in females, appendix masculina completely reduced.

Uropod ( Fig. 6A ) with rami subequal in length, reaching tip of telson.

Eggs large, 3.1–3.6× 2.5–2.7 mm (eyed stage).

Size. Largest functional male cl 36.4 mm; transitional males cl 33.3–43.0 mm; females cl 38.2–45.8 mm, ovigerous females cl 38.2–41.2 mm.

Colouration in life. Rostrum red in distal half, paler or semi-translucent in proximal half. Carapace generally red. Pleon mottled red, ventral parts of pleura darker. Telson red. Antennular peduncle reddish translucent; flagella reddish, without conspicuous markings. Antennal basicerite red; scaphocerite and carpocerite reddish translucent, but former distally red; flagellum reddish translucent proximally, but greater portion red. Maxilliped 3, pereopods 1–5, pleopods and uropod crimson.

Variation. The sequential change with growth seen in the pleopods 1 and 2 strongly suggests that Pandalopsis houyuu n. sp. is also a protandrous hermaphrodite as in other species of Pandalopsis . Like other congeneric species ( Komai 1994; this study), the rostrum of P. houyuu n. sp. tends to become proportionally shorter with increase of size ( Fig. 14 ); the ratio of the rostral length against the carapace length is 0.8–1.1 in the female stage.

Distribution. So far known only from Nemuro Strait, at depths of 420– 750 m.

Remarks. Pandalopsis houyuu n. sp. is morphologically similar to P. japonica and P. ochotensis in having dorsal spines on the distal half of the rostrum and a setal patch near the posterodorsal margin of the carapace. The new species differs from P. japonica in the following particulars: (1) ventral spines of the rostrum are generally relatively weaker in P. houyuu n. sp. than in P. japonica ( Fig. 7B versus Komai 1994: fig. 3B); (2) the lateral carina of the rostrum becomes obsolete distally in P. houyuu n. sp., rather than sharply delimited over the entire length in P. japonica ; (3) the dorsum of the carapace is more strongly elevated in P. houyuu n. sp. than in P. japonica ; (5) P. houyuu n. sp. attains larger size than P. japonica does (females 38.2–45.8 mm in cl versus 23.2–31.0 mm). In addition, the rostrum is generally proportionally shorter in P. houyuu n. sp. than in P. japonica , although variable (see Fig. 14 ). When females are compared, the rostrum is 0.8–1.1 times as long as the carapace in P. houyuu n. sp., whereas it is 1.4–1.8 times as long in P. japonica . The colouration in life is quite different between the two species. In P. houyuu n. sp., the body is generally red with mottled pattern on the pleon. In contrast, in P. japonica , the body is longitudinally striped with red and white (cf. Miyake 1982: pl. 22, fig. 1; Kim 2012: pl. 15).

Pandalopsis houyuu n. sp. is distinguished from P. ochotensis by the different armature of the dactyli of the pereopods 3 and 4. In P. houyuu n. sp., those dactyli are armed with six to ten small accessory spiniform setae almost over the entire length of the flexor margin, but in contrast, in P. ochotensis , there are only four or five very small accessory spiniform setae restricted to the proximal half of the flexor margin of these dactyli ( Komai & Amaoka 1989: fig. 2m). The posteriormost ventral spine of the rostrum is subequal or slightly larger than the preceding spines in P. houyuu n. sp., rather than smaller in P. ochotensis ( Komai & Amaoka 1989: fig. 2a). The carapace dorsum is more strongly elevated in P. houyuu n. sp. ( Fig. 7A ) than in P. ochotensis ( Komai & Amaoka 1989: fig. 2a) when females are compared.

Pandalopsis punctata Kobjakova, 1936 , represented only by the type material from the Sea of Okhotsk (depths 65–182 m) (Kobjakova 1936, 1937), also resembles P. houyuu n. sp. No modern description is available for P. punctata . Nevertheless, Kobjakova (1936) specifically mentioned that there were scattered small pits on the carapace surface in P. punctata , which are not present in P. houyuu n. sp. Furthermore, P. punctata occurs at much shallower depths than P. houyuu n. sp. does. It is unlikely that the two taxa are conspecific.

Etymology. The specific name of this new species is dedicated to the fishing boat “Houyuu-maru”, which has greatly contributed to document the high diversity of the deep-sea fauna of the Nemuro Strait.

Figures

FIGURE 6. Pandalopsis houyuu n. sp., A, holotype, female (cl 39.5 mm), CBM-ZC 14617, habitus in lateral view; B, individual reared in aquarium (not preserved), showing colour in life.

FIGURE 7. Pandalopsis houyuu n. sp., A–F, I, holotype, female (cl 39.5 mm), CBM-ZC 14617; H, K, paratype, transitional male (cl 35.3 mm), CBM-ZC 14619; G, J, paratype, male (cl 24.2 mm), AMF-ZC 0029. A, carapace and cephalic appendages, lateral view; B, rostrum and anterior part of carapace, lateral view (setae omitted); C, pleomeres 3–6, lateral view (setae omitted); D, telson, dorsal view; E, left eye, antennule and antenna, dorsal view (antennular flagella partially omitted); F, distal part of antennal scale, dorsal view; G, endopod of left pleopod 1 in male, ventral view (marginal setae omitted); H, same in transitional male, ventral view (marginal setae omitted); I, same in female, ventral view (marginal setae omitted); J, appendices interna and masculina of left pleopod 2 in male, mesial view; K, same in transitional male, mesial view. Scale bars: 10 mm for A–E; 2 mm for F; 1 mm for G–I; 0.5 mm for J, K.

FIGURE 8. Pandalopsis houyuu n. sp., A–F, holotype, female (cl 39.5 mm), CBM-ZC 14617, left thoracic appendages in lateral view. A, maxilliped 3; B, pereopod 1; C, pereopod 2; D, pereopod 3; E, pereopod 4; F, pereopod 5. Scale bars: 10 mm.

FIGURE 9. Pandalopsis houyuu n. sp., A–I, holotype, female (cl 39.5 mm), CBM-ZC 14617. Left thoracic appendages. A, distal part of ultimate segment of maxilliped 3, ventral view (setae omitted); B, dactylus of pereopod 3, lateral view; C, dactylus and propodus of pereopod 3, lateral view; D, proximal part of propodus of pereopod 3, mesial view; E, carpus of pereopod 3, mesial view; F, dactylus of pereopod 4, lateral view; G, dactylus and propodus of pereopod 4, lateral view; H, dactylus of pereopod 5, lateral view; I, dactylus and propodus of pereopod 5, lateral view. Scale bars: 5 mm for C, G, I; 2 mm for D, E; 1 mm for A, B, F, H.

FIGURE 14. Variation in the proportional length of the rostrum (against the carapace length) in Pandalopsis capillus n. sp., P. houyuu n. sp., and P. princeps n. sp.