Pilumnopeus indicus ( De Man, 1887 ) Patel & Trivedi & Mitra & Ng, 2024

Patel, Krupal, Trivedi, Jigneshkumar, Mitra, Santanu & Ng, Peter K. L., 2024, The taxonomy of Heteropanope indica De Man, 1887 from the Indian Ocean, with a note on Pilumnopeus pearsei (Rathbun, 1932) (Crustacea: Decapoda: Brachyura: Pilumnidae), Zootaxa 5437 (3), pp. 384-396 : 386-393

Pilumnopeus indicus ( De Man, 1887) comb. nov.

( Figs. 1–5 )

Heteropanope indica De Man, 1887: 53 , pl. 3, figs. 1, 2.— Alcock 1898: 208.— Kemp 1915: 242.

Pilumnopeus indica — Balss 1933: 33.

Heteropanope (Pilumnopeus) indica — Serène 1968: 87.

Benthopanope indica — Davie 1989: 144 (list).— Ng & Davie 2002: 377 (list).— Ng et al. 2008: 140 (list).— Dev Roy & Nandi 2008: 204 (list).— Trivedi et al. 2018: 58 (list).

Material examined. Type material: Lectotype (herein selected), female ( CW 14.7 mm, CL 10.2 mm) ZSI.3209/6, Mergui Archipelago, coll. J. Anderson. Other material: 1 male (CW 22.4 mm, CL 15.8 mm), 1 ovig. female (CW 20.9 mm, CL 14.3 mm), LFSC.ZRC-70, Ekkakula mangroves (20°71’51”N 86°86’37”E), Gahirmatha National Park, Odisha state, India, coll. J. Trivedi, 15 August 2019 ; 2 juvs. (CW 4.3 mm CL 3.2 mm, CW 3.8 mm CL 2.6 mm), ZRC 2019.1092 , intertidal rocky area with algae, just outside School of Marine Sciences , Cochin University, Cochin India, Kerala, India, coll. students, February 2019 ; ZRC 2021.0683 , probably Chennai coast, India, coll. M. Prema, 2018 ; 1 young female (CW 8.5 mm CL 5.6 mm), ZRC 2018.0097 , Jeram Polychaete Reef, intertidal muddy shore and intermittent sabellariid reefs, lower shore, Jeram , Kuala Selangor, Peninsular Malaysia, 3º13’ 27”N 101º18’13”E, coll. J.J. Eeo, 6 October 2013 ; 1 female (CW 16.8 mm CL 12.1 mm), ZRC 2021.0682 , 1 female (CW 18.1 mm CL 11.8 mm), 1 ovig. female (CW 1.4 mm CL 11.5 mm), ZRC 2017.1217 , Jeram Polychaete Reef , intertidal muddy shore and intermittent sabellariid reefs, lower shore, Jeram , Kuala Selangor, Peninsular Malaysia, 3º13’ 27”N 101º18’13”E, coll. J.J. Eeo, 14 December 2012 .

Comparative material. Pilumnopeus serratifrons ( Kinahan, 1856) : 1 male ( CW 19.9 mm, CL 14.8 mm), 1 female ( CW 13.9 mm, CL 10.4 mm), ZRC 1995.0972, Cudgera Creek, Hastings Point, New South Wales, Australia, coll. P.J.F. Davie, 15 May 1988; 1 female ( CW 7.4 mm CL 5.6 mm), ZRC 2023.0378, near mouth of Brisbane River, Brisbane, Queensland, Australia, coll. Queensland University Zoology Department; 1 female ( CW 13.1 mm CL 9.1 mm), ZRC 2008.0114, under boulders, low tide, near lighthouse, Lowly Point, Whyalla, South Australia, coll. S. & B. Ahyong, 9 May 2005. Pilumnopeus pearsei ( Rathbun, 1932) : Lectotype: male ( CW 9.2 mm CL 7.2 mm), USNM 62910a, Misaki, Japan, coll. A.S. Pearse, 5 August 1929; 1 paralectotype ovigerous female ( CW 8.2 mm CL 6.1 mm), USNM 62910b, same data as lectotype; 2 males ( CW 10.3 mm CL 8.2 mm, 10.5 X 8.0 mm), ZRC 2023.0377, Korea, coll. S.Y. Hong, ca. 2002. Pilumnopeus granulatus Balss, 1933: 2 males ( CW 8.3 mm CL 5.8 mm, CW 15.0 mm CL 11.2 mm), 1 ovigerous female ( CW 16.6 mm CL 11.6 mm), ZRC 2023.0379, Korea, coll. S.Y. Hong, ca. 2002. Pilumnopeus makianus (Rathbun, 1931) : 2 males (larger CW 16.0 mm CL 11.5 mm), 1 female (not measured), ZRC 1997.677, San-Tao-Lun, Yunlin County, Taiwan, coll. 1996; 1 male (not measured), ZRC 2016.0716, mudflat, Youkaku Bay, Amasuka, Kumamoto Prefecture, Japan, coll. Amasuka Marine Laboratory, no date. Pilumnopeus marginatus (Stimpson, 1858) : 1 female (not measured), ZRC 2023.0380, Ohura River, Okinawa Island, Ryukyus, Japan, coll. M. Irei, 16 November 1990; 1 female (not measured), ZRC 2013.0160, Naha City, Okinawa Island, Ryukyus, Japan, coll. T. Maenosono, 9 April 2007. Pilumnopeus vauquelini (Audouin, 1826) : 1 male (not measured), ZRC 2013.1795, around Qeslim Island, west of Homorzgan, Dargahan, Iran, 14–15 fathoms, in shrimp trawl, coll. M. Safaei, 2 February 2013.

Description (based on the morphology of male (CW 22.4 mm CL 15.8 mm): Carapace transversely hexagonal, broader than long (1.4–1.5 times) ( Figs. 1A , 2A , 3A , 4A ). Front distinctly bilobed, margin of each almost straight in dorsal view, separated by deep triangular notch, bearing small outer angle; inner supraorbital tooth small but distinct, supraorbital margin with 2 fissures on external half ( Figs. 1A , 2A , 3A , 4A ). Dorsal surface covered with scattered plumose setae barely visible with naked eyes. Frontal region with slightly arcuate, transverse row of small granules; epigastric and protogastric region with 5 transverse, minutely granulated low ridges, pubescent ( Figs. 1A , 2A , 3A , 4A ). Anterolateral margin with 3 teeth behind exorbital angle; first anterolateral tooth blunt, second and third teeth acute but not spine-tipped, third and fourth teeth subequal in size, or with third tooth slightly smaller; fourth tooth directed almost laterally or obliquely laterally ( Figs. 1A , 2A , 3A , 4A ). Epistome nearly smooth, median lobe broadly triangular, protruding anteriorly.

Third maxilliped with merus broader than long, much shorter than ischium, anterior and outer lateral margins slightly concave; ischium with oblique longitudinal depression, exopod not reaching anterior margin of merus, large rounded triangular subdistal tooth on inner margin, internal edge adjacent to merus and ischium granulated; flagellum long ( Figs. 1E , 3E ).

Chelipeds unequal; surface of larger chela gently rugose to almost smooth; smaller chela covered with scattered small granules and scattered short setae; carpus with blunt, inner subdistal tooth, inner distal margin of carpus granulated; fingers shorter than palm, cutting edges of fingers toothed, dentition stronger in larger chela ( Figs. 1C, D , 2C, D , 3C, D , 4D, E ).

Ambulatory legs relatively short; coxa, merus, carpus and propodus unarmed; covered with scattered long and short setae that partially obscure surface; dactylus terminating in acute chitinous tip ( Figs. 1A, B , 2A, B , 3A, B ).

Thoracic sternites 1 and 2 completely fused; sternites 2 and 3 separated by broad V-shaped suture, sternites 3 and 4 relatively long, transversely narrow, distance between tip of sternopleonal cavity and median point of suture between thoracic sternites 3 and 4 long, longer than distance between the sutures of sternites 3 and 4, and sternites 2 and 3; sternite 8 visible adjacent to male pleonal somite 3 ( Figs. 1F , 2F , 3F ). Pleon with 6 free somites and telson, covered with fine setae; telson triangular with rounded tip ( Fig. 2B, G ).

G1 slender, sinuous; distal part distinctly recurved from ventral view, with several large subdistal spines, stout setae along the inside edge near tip ( Fig. 4A, B ). G2 short, sigmoid, tip margin armed with spinules ( Fig. 4C ).

Ecological observations. Pilumnopeus indicus ( De Man, 1887) comb. nov. inhabits the intertidal zone in muddy or mangrove habitats. Individuals of the species are mostly found under dead logs or rock boulders in India; and the Malaysian specimens were from an unstable muddy polychaete reef subjected to strong tides.

Distribution. The species was originally described from the Mergui Archipelago ( De Man 1887) and is now known from various localities in India (Deb 1995; Trivedi et al. 2018, present study) and the western coast of Peninsular Malaysia (present record). Records of the species from East Asia, including Japan (e.g., Rathbun 1932; T. Sakai 1939, 1965, 1976; Miyake 1983; Wada 1995), Korea (e.g., Kamita 1941; Kim 1973; Kim & Chang 1985; Ko & Lee 2012), as well as Taiwan and mainland China (e.g., Dai et al. 1986; Dai & Yang 1991; Jeng et al. 1997; Ho et al. 2000; Ng et al. 2001, 1017) are here referred to P. pearsei (see discussion later).

Remarks. De Man (1887) described Heteropanope indica from one male and one female collected from the Mergui Archipelago and figured the overall dorsal habitus of the male and its right chela ( De Man 1887: pl. 3 figs. 1, 2). As no type was designated, both his specimens are syntypes. Only the female specimen could be found in ZSI, the whereabouts of the male is not known. De Man’s (1887) types from the John Anderson expedition are known to be also deposited in the Natural History Museum, London, but the male could not be found there. Hence, the female ZSI specimen on hand is designated as the lectotype of H. indica . In the present study, the lectotype and fresh specimens of B. indica are redescribed and illustrated. Balss (1933) transferred H. indica to Pilumnopeus A. Milne-Edwards, 1873 , in his reappraisal of pilumnid genera. On comparing the Japanese material identified as Pilumnopeus indicus with the type of H. pearsei, T. Sakai (1965: 160) argued that the two species appeared similar, and hence the latter was considered a junior synonym. This classification has since been followed by most later workers, including subsequent workers who reported it from Japan, Korea, China and Taiwan (T. Sakai, 1939, 1965, 1976; Kim 1973; Miyake 1983; Dai et al. 1986; Dai & Yang 1991; Jeng et al. 1997; Ho et al. 2000; Ko & Lee 2012). Davie (1989) did not treat or discuss H. pearsei . As for H. pearsei, Ng et al. (2001: 30) made a brief note on the inclusion of which as “ B. indica ” among the fauna of Taiwan, stating B. indica and Heteropanope pearsei represent distinct species (repeated by Ng et al. 2017). Both species, listed under Benthopanope , have been kept distinct by Ng et al. (2008).

The last author of the present study has examined the types of H. pearsei and it is a Pilumnopeus species as indicated by Ng et al. (2008) and as defined by Davie (1989). In the type lot (USNM 62910), the label indicates there are “2 cotypes and 10 paratypes ”. Rathbun (1932: 35–36) described the species from one “Type” male measuring “9.4 X 7.0 mm” from Misaki, Japan, with the catalogue number of USNM 62910, and this is considered to be the male examined here, differing only slightly in measurements. This specimen, following Article 73.1.2 and Recommendation 73F of the current zoological code ( ICZN 1999), should be regarded as the lectotype of the species as Rathbun (1932) did not state if she had more specimens in the original paper. There are in fact 11 more specimens as the present data shows, all of which are in the same container with the same data and under the same catalogue number. They should now be regarded as paralectotypes ( ICZN 1999: Articles 72.4.1, 72.4.1.1).

Comparisons show that H. indica De Man, 1887 , and H. pearsei Rathbun, 1932 , are distinct species, and both belong to Pilumnopeus . Pilumnopeus indicus differs in having the third and fourth anterolateral teeth clearly dentiform and subequal in size ( Figs. 1A , 2A , 3A , 4A ) (versus fourth tooth much smaller and lower than the third tooth in P. pearsei ; Fig. 6A–C; T . Sakai 1976: pl. 178 fig. 1); the fourth anterolateral tooth is directed obliquely laterally to almost laterally ( Figs. 1A , 2A , 3A , 4A ) (versus fourth tooth directed more anteriorly; Fig. 6A–C; T . Sakai 1976: pl. 178 fig. 1); the median lobe of the posterior margin of epistome is low ( Fig. 2F ) (versus median lobe triangular and pronounced; Fig. 6D ); the tooth at the inner angle of the carpus of the cheliped is prominent and sharp ( Figs. 1A , 2A , 3A , 4A, C ) (versus lower and generally more rounded; Fig. 6A–C; T . Sakai 1976: pl. 178 fig. 1); the lateral margin of the male pleonal somite 2 is gently convex ( Fig. 2E ) (versus margin distinctly convex; Fig. 6H ); and most significantly the G1 is relatively more longer, with the distal part strongly recurved with the tip overlapping with the main stem ( Fig. 5A, B ) (versus G1 relatively shorter, with the distal part more gently curved; Fig. 7A–C ; Takeda & Miyake 1969: fig. 12a, b; Dai et al. 1986: text-fig. 182(1); Dai & Yang 1991: text-fig. 182(1)).

With regard to distribution, the East Asian records of “ Pilumnopeus indica ” (T. Sakai 1939: 542, pl. 62, fig. 4; Kamita 1941: 133, fig. 72; T. Sakai 1965: 159, pl. 79, fig. 4; Kim 1970: 16; T. Sakai 1976: 500, pl. 178, fig. 2; Dai et al. 1986: 348, text-fig. 182, pl. 50(4); Dai & Yang 1991: 374, text-fig. 182, pl. 50(4); Wada 1995: 403, pl. 112, fig. 4; Muraoka 1998: 45); “ Pilumnopeus indicus ” ( Takeda & Miyake 1969: 125, fig. 12a, b; Miyake 1983: 138, pl. 46, fig. 5; Jeng et al. 1997: 118; Kim & Chang 1985: 54); “ Heteropanope (Pilumnopeus) indica ” ( Kim 1973: 400, 634, fig. 158, pl. 84, fig. 120a-d.); and “ Benthopanope indica ” ( Ho et al. 2000: 116; Ng et al. 2001: 30; K. Sakai 2004: no page number; Ko & Lee 2012: 24, pl. 5; Ng et al. 2017: 62) should now all be referred to P. pearsei . The G1 structure of the Japanese lectotype of P. pearsei ( Fig. 7A–C ) generally agrees with those specimens from China ( Dai et al. 1986; Dai & Yang 1991).

Pilumnopeus indicus is similar to P. convexus , however, they can be differentiated on the basis of the following characters: front comparatively less projecting in P. indicus ( Figs. 1A , 2A , 3A , 4A ) (versus front comparatively more projecting in P. convexus ; Ghory et al. 2013: figs. 1A, 2A, B); dorsal surface with regions well defined in P. indicus ( Figs. 1A , 2A , 3A , 4A ) (versus dorsal surface with regions not well defined in P. convexus ; Ghory et al. 2013: figs. 1A, 2A, B); distal region of G1 with less numerous spines in P. indicus ( Fig. 4B ) (versus distal region of G1 with more numerous spines in P. convexus ; Ghory et al. 2013: figs. 4G, 5F); the curved distal part of G1 is more elongated in P. indicus ( Fig. 4B ) (versus the curved distal part of G1 less elongated; Ghory et al. 2013: fig. 4G); no spines present on the outer boarder of the distal part of G1 ( Fig. 4B ) (versus numerous spines present on the outer boarder of the distal part of G1; Ghory et al. 2013: fig. 4G); distal part of G1 inner margin with long and more numerous spines ( Fig. 4B ) (versus distal part of G1 inner margin with short and less numerous spines; Ghory et al. 2013: fig. 4G); and G2 is less prominently bilobed in P. indicus ( Fig. 4C ) (versus G2 more prominently bilobed in P. convexus ; Ghory et al. 2013: fig. 4H). Ghory et al. (2013) and Wong et al. (2020) have noted that the record of “ P. indica ” from South Africa by Barnard (1955) is almost certainly P. convexus , and that Pilumnopeus salomonensis Ward, 1942 , from the Chagos Archipelago is a junior synonym of this species (see also Takeda & Miyake 1969: 127; Davie 1989: 143).

Pilumnopeus indicus is also similar to P. serratifrons , but it can be differentiated from the latter in the following characters: carapace comparatively broader than long (1.4–1.5 times) in P. indicus ( Figs. 1A , 2A , 3A , 4A ) (versus carapace comparatively less broader than long (1.3–1.4 times) in P. serratifrons ; Davie 1989: fig. 6); dorsal surface with five minutely granulated, pubescent, elevated lines on each side in P. indicus ( Figs. 1A , 2A , 3A , 4A ) (versus dorsal surface with small, rounded granules laterally, behind the epibranchial teeth and posterolaterally in P. serratifrons ; Davie 1989: fig. 6); front comparatively less projecting in P. indicus ( Figs. 1A , 2A, F , 3A , 4A ) (versus front comparatively more projecting in P. serratifrons ; Davie 1989: fig. 6) and distal part of the G1 is comparatively less curved in P. indicus ( Fig. 4A, B ) (versus distal part of G1 comparatively more curved in P. serratifrons ; Davie 1989: fig. 5F).

Pilumnopeus indicus resembles P. vauquelini but can be differentiated on the basis of the following characters: carapace comparatively more broader than long (1.4–1.5 times) in P. indicus ( Figs. 1A , 2A , 3A , 4A ) (versus carapace comparatively squarish (1.35 times) in P. vauquelini ; Audouin 1826: pl. 5 fig. 3; Guinot & Cleva 2009: 98, pl. 5); fingers of chelae not bent downwards in P. indicus ( Figs. 1C, D , 2C, D , 3 C, D , 4C, D ) (versus fingers of chelae sharply bent downwards, forming sharp angle with palm in P. vauquelini ; De Man 1889: pl. 9, fig. 5); and the tip of G1 is recurved to form a distinct hook-like structure in P. indicus ( Fig. 4A, B ) (versus the tip is more strongly curved in P. vauquelini ; Audouin 1826: pl. 5 fig. 3; Guinot & Cleva 2009: 98, pl. 5).

Figures

FIGURE 1. Pilumnopeus indicus (De Man, 1887) comb. nov., lectotype female (CW 14.7 mm CL 10.2 mm), ZSI.3209/6, Mergui Archipelago. A. overall dorsal habitus; B. overall ventral view; C. right chela (outer view); D. left chela (outer view); E. left third maxilliped; F. male pleonal somites 1–3, thoracic sternum and coxa of last ambulatory leg, showing small part of sternite 8 adjacent to pleonal somites 2 and 3. Scale bars: A–D = 5.0 mm, E, F = 2.0 mm.

FIGURE 2. Pilumnopeus indicus (De Man, 1887) comb. nov., male (CW 22.4 mm CL 15.8 mm), LFSC.ZRC-70, Odisha, India. A. overall dorsal habitus; B. overall ventral view; C. right chela (outer view); D. left chela (outer view); E. pleonal somites 1–3, thoracic sternum and coxa of last ambulatory leg, showing small part of sternite 8 adjacent to pleonal somites 2 and 3; F. frontal view of cephalothorax; G. thoracic sternum and pleon. Scale bars: A–D, F = 5.0 mm, E, G = 2.0 mm.

FIGURE 3. Pilumnopeus indicus (De Man, 1887) comb. nov., ovigerous female (CW 20.9 mm CL 14.3 mm), LFSC.ZRC-70, Odisha, India. A. overall dorsal habitus; B. overall ventral view; C. right chela (outer view); D. left chela (outer view); E. left third maxilliped; F. female pleonal somites 1–3, thoracic sternum and coxa of last ambulatory leg, showing small part of sternite 8 adjacent to pleonal somites 2 and 3. Scale bars: A–D = 5.0 mm, E, F = 2.0 mm.

FIGURE 4. Pilumnopeus indicus (De Man, 1887) comb. nov., female (CW 18.1 mm CL 11.8 mm), ZRC 2017.1217, Peninsular Malaysia, A. overall dorsal habitus; B. dorsal view of carapace; C. frontal view of cephalothorax; D. right chela (outer view); E. left chela (outer view). Scale bars: A–D = 5.0 mm, E, F = 2.0 mm.

FIGURE 5. Pilumnopeus indicus (De Man, 1887) comb. nov., male (CW 22.4 mm CL 15.8 mm), LFSC.ZRC-70, Odisha, India. A. left G1 (dorsal view); B. distal part of left G1 (dorsal view); C. left G2. Scale bars: A = 1.0 mm; B, C = 0.5 mm.

FIGURE 6. Pilumnopeus pearsei Rathbun, 1932. A, D–H, topotype male (CW 9.2 mm CL 7.2 mm), USNM 62910, Korea; B, male (CW 10.5 mm CL 8.0 mm), ZRC 2023.0377, Korea; C, topotype ovigerous female (CW 8.2 mm CL 6.1 mm), USNM 62910, Korea.A–C. overall dorsal habitus; D. frontal view of cephalothorax; E. left chela (outer view); F, right third maxilliped; G. thoracic sternites 1–6 and pleonal somites 6 and telson; H. pleonal somites 1–4, thoracic sternum and coxa of last ambulatory leg, showing small part of sternite 8 adjacent to male pleonal somites 2 and 3.

FIGURE 7. Pilumnopeus pearsei Rathbun, 1932, topotype male (CW 9.2 mm CL 7.2 mm), USNM 62910, Korea. A. left G1 (ventral view); B. distal part of left G1 (ventral view); C. distal part of left G1 (dorsal view); D. left G2; E. distal part of left G2. Scale bars: A = 0.5 mm; B, C = 0.2 mm; D = 0.25 mm; E = 0.1 mm.