Pseudolitochira integra ( Miers, 1884 )

Ng, Peter K. L., Clark, Paul F., Clark, Brett & Kamanli, Seyit A., 2021, Pseudolitochira integra (Miers, 1884) (Crustacea: Brachyura: Pilumnidae): redescribed and illustrated from micro-CT scanning the type female, Zootaxa 4969 (2), pp. 377-391 : 381-387

Pseudolitochira integra ( Miers, 1884)

( Figs. 2–5 )

Carcinoplax integra Miers, 1884: 543 , pl. 48, fig. C, c; 1886: 233 (list); Ward 1942: 101, pl. 6, fig. 5.

Litocheira integra — Tesch 1918: 165 (key, discussion).

Pseudolitochira integer — Serène 1968: 86 (list).

Pseudolitochira integra — Türkay 1975: 128, 12 (list); Ng 1987: 79, 97 (list); Ng & Tan 1988: 18 (discussion); Ng et al. 2008: 144 (list); Ng et al. 2018: 144 (discussion).

Carcinoplax subinteger Lanchester, 1900: 750 , pl. 46, fig. 9a (unnecessary replacement name for Carcinoplax integer Miers, 1884 ; see Ng & Tan 1988: 15, 17).

Not Carcinoplax integer —De Man 1887: 93 (= Heteropilumnus holthuisi Ng & Tan, 1988 ; see Ng & Tan 1988: 14).

Not Litochira integra — Alcock 1900: 314; De Man 1929: 9, 13 (= Heteropilumnus holthuisi Ng & Tan, 1988 ; see Ng & Tan 1988: 14).

Not Litocheira integra — Laurie 1915: 464, pl. 45, fig. 2 (= Heteropilumnus setosus (A. Milne-Edwards, 1873) ; see De Man 1929: 8).

Not Litocheira subintegra — Gordon 1931: 549, fig. 25b (= Heteropilumnus holthuisi Ng & Tan, 1988 ; see Ng & Tan 1988: 14).

Not Heteropilumnus subinteger — Balss 1933: 44, pl. 7, figs. 32, 33 (= Heteropilumnus holthuisi Ng & Tan, 1988 ; see Ng & Tan 1988: 14).

Not Pseudolitochira integra — Naruse 2010: 32 (part: RUMF-ZC-973) (= Pilumnus turgidulus Rathbun, 1911 ; see Maenosono 2019: 33, tab. 1).

Not Pseudolitochira integra — Machida 2017: 53, figs. 2, 3 (= Zehntneriana amakusae ( Takeda & Miyake, 1969) ; see Maenosono 2019: 33).

Not Pseudolitochira integra ( Miers, 1884) , identity uncertain:

Litochira subintegra — Tesch 1918: 175, pl. 16, fig. 1.

Litocheira integra — Borradaile 1903: 430; Bouvier 1915: 296, text-fig. 34; De Man 1929: 13, pl. 2, fig. 4; T. Sakai 1955: 108, fig. 3.

Heteropilumnus integra — Holthuis 1953: 22; T. Sakai 1976: 493, text-fig. 264a, 304; Miyake 1983: 233; Nagai & Nomura 1988: 112; Ito 1992: 46; Nomura et al. 1996: 17; Jeng 1997: 16, 22; K. Sakai 2003: 20.

Pseudolitochira integra — Takeda & Miyake 1976: 110; Ng et al. 2001: 31; Naruse 2010: 32 (part: RUMF-ZC-967); Komatsu 2011: 274; Hosie et al. 2015: 276; Ng et al. 2017: 63; Ng et al. 2018: 144.

Pseudolitochira integer — Paulay et al. 2003: 498.

Pseudolitocheira integra — Serène et al. 1974: 23; Marumura & Kosaka 2003: 61.

Incerta sedis:

Pseudolitochira integra — Dev Roy 2008: 60, 168; Dev Roy & Bhadra 2011: 113, 186; Dev Roy & Nandi 2012: 203; Trivedi et al. 2018: 60.

Pseudolitocheira integra — Dev Roy & Bhadra 2011: 221, 231, 256.

Heteropilumnas integra — Rao et al. 1989: 74.

Heteropilumnus integra — Venkataraman et al. 2004: 309; Rao 2010: 195; Trivedi et al. 2018: 59.

Pseudolithochira integra — Innocenti & Manzoni 2017: 47.

Material examined. Holotype: ♀ (4.9 × 3.4 mm) (NHM 1882.24), Seychelles, 7.3–22 m, coll. H.M.S. Alert. Species diagnosis. As for genus.

Description of female holotype. Carapace transversely subovate, width 1.6 times length; surface covered with short pubescence that partially obscures surface, never with long setae along margins; dorsal carapace surface mostly smooth except for small group of low granules behind anterolateral margin, regions almost undiscernible, with only shallow H-shaped gastric grooves barely visible; postfrontal lobes low, just visible. Frontal margin extremely wide, bilobed, margin gently convex, with a low postfrontal ridge; no lateral lobule present on frontal margin, smoothly confluent with supraorbital margin. Supraorbital margin finely granulated, with small submedian indentation, no fissure; infraorbital margin distinctly sinuous, without tooth or spine. Orbits wide; eyes large, ocular peduncle stout, cornea large, extending beyond external orbital tooth when retracted. External orbital tooth low; anterolateral margin relatively short, appears entire, with small granules, no clear indication of lobes, low concavities in parts; joining posterolateral margin as gently curve; posterolateral margin sharply converging towards gently sinuous posterior carapace margin. Suborbital, subhepatic and pterygostomial regions smooth. Antennules folding almost transversely; basal antennal article subrectangular; flagellum entering orbital hiatus. Epistome relatively narrow longitudinally; posterior margin entire, median lobe triangular with shallow median cleft, confluent with gently concave, entire lateral margins. Endostomial ridges distinct.

1 and 2; E, posterior thoracic sternum and pleon.

Third maxilliped completely covering buccal cavity when closed; ischium short, subrectangular with shallow submedian sulcus; merus quadrate, anteroexternal angle rounded, not auriculiform; exopod relatively stout, reaching to just before distal margin of merus, with long flagellum.

Chelipeds subequal, outer surfaces covered with long and short setae which obscures surfaces. Basis-ischium short, anterior margin granulated. Merus trigonal in cross-section, margins almost smooth or with low granules, not armed. Carpus relatively elongate, surface mostly smooth except for weakly granulose distal surfaces; inner distal angle formed by low, rounded obtuse tooth. Outer surface of chela covered with numerous small granules, reaching to half-length of fingers; fingers shorter than palm, with 2 rows of low ridges, proximal part with granules; cutting margins with low teeth.

Ambulatory legs proportionately slender, relatively long; second leg longest, fourth leg shortest; surfaces covered with short and long setae which obscures margins. Merus smooth with rounded margins, unarmed. Carpus with shallow subdorsal groove, unarmed. Propodus smooth. Dactylus relatively long, almost straight along proximal corneous part with tip gently curved; dactylo-propodal lock well developed.

Thoracic sternites 1 and 2 completely fused to form triangular plate; deep sinuous suture between sternite 2 and sternite 3; sternites 3 and 4 fused, with shallow broad median grooves demarcating them. Sutures between sternites 4 and 5, 5 and 6 medially interrupted; other sutures complete. Sternopleonal cavity shallow. Vulvae large, subovate, flat, without sternal vulvar covers; occupying anterior two-thirds of sternite 6, touching suture with sternite 5.

Pleon ovate, covering about half of thoracic sternum; somite 1 longitudinally narrow, reaching to coxae of last ambulatory legs, lateral edges gradually tapering; telson triangular.

Remarks. The description and figures (reproduced here as Fig. 2 ) of P. integra by Miers (1884) contain some inaccuracies. The anterolateral margin was described and figured as entire ( Miers 1884: pl. 8, fig. C) but the structure is lined with small granules ( Fig. 5A ). The exopod of the third maxilliped was figured as only reaching to just after the edge of the ischium ( Miers 1884: pl. 8, fig. c), but it is actually distinctly longer, reaching to just before the distal edge of the merus ( Fig. 5D ). The outer surface of the chela was figured as smooth ( Miers 1884: pl. 8, fig. c’), but is covered with numerous distinct rounded granules ( Fig. 5C ).

The nomenclature of Carcinoplax integra has also presented a number of taxonomic problems. Shortly after Miers (1884) described his species, the name C. integra became confused with another allied taxon. De Man (1887: 93) identified two males and a female from Elphinstone Island, Mergui Archipelago as C. integer , which he later referred to “ Litocheira subinteger Lanchester, 1900 ” (De Man 1929: 9). The latter name is problematical because De Man (1929) did not realise that Lanchester (1900) had merely changed the spelling of the species name, from “ integra ” to “ subinteger ” because he argued that original Miers (1884) name was inaccurate. Lanchester (1900) had specimens from Singapore or Malacca (exact location not stated) and believed them to be conspecific with Carcinoplax integer Miers, 1884 . Lanchester (1900) commented that since the anterolateral margin of his specimens were not entire and had low teeth, the name chosen by Miers was inappropriate and he therefore renamed the species “ Carcinoplax subinteger ”. This change of name, however, is not permitted under the zoological Code ( ICZN 1999: Article 72.7) especially since both names share the same type specimen (see Ng & Tan 1988: 15, 17). Consequently, the C. subinteger of Lanchester, 1900, must therefore be treated as an unnecessary replacement name for Carcinoplax integer Miers, 1884 . Ng & Tan (1988) also indicated that the Lanchester (1900) specimens were an undescribed species and named it Heteropilumnus holthuisi . Nevertheless, Carcinoplax integra and Carcinoplax subintegra have sometimes been treated as two separate taxa in the literature (e.g., Tesch 1918: 165). Ng & Tan (1988) also assigned the specimens of De Man (1887) from Mergui to H. holthuisi , but they did not examine the material. The present study re-examined specimens of De Man (1887) in NHM (2 ♂, 10.1 × 7.8 mm, 7.5 × 6.3 mm, NHM 1886.52, Mergui Archipelago, coll. Anderson) and confirm here that they are both H. holthuisi as proposed by Ng & Tan (1988; see Fig. 6 ).

Borradaile (1903: 430) reported a specimen from Male Atoll in the Maldives, but he noted his specimen (sex not specified) differed from the material of Lanchester (1900). He ( Borradaile 1903) considered it the same as what De Man (1887) reported as L. subinteger as his crab had three, and not two notches, on the anterolateral margin and possessed a relatively narrower front. Borradaile (1903), however, did not elaborate on these differences. Later, Bouvier (1915: 296, fig. 34) recorded and partly figured Litocheira integra based on a male 5 × 4 mm from Mauritius, but compared to the type, the anterolateral margin he figured was very spinose and the ocular peduncles were too short. This specimen of Bouvier (1915) almost certainly belongs to another species.

Ward (1942) reported on the brachyuran crabs from Mauritius and adjacent islands. He listed Litocheira decharmoyi Bouvier, 1915 , as belonging to Pseudolitochira , but did not provide an explanation ( Ward 1942: 52). He ( Ward 1942: 101, pl. 6, fig. 5) also stated that 2 female specimens (15 and 11 mm in carapace width) of P. integra were examined from Chagos Islands. From his figure, this material is probably conspecific with P. integra as recognised here.

Further clarification is required for the identity of a number of records assigned to P. integra . From the Indian Ocean, Innocenti & Maz (2017: 47) listed two specimens from Somalia, but they did not figure their material. Workers from India and its nearby islands have recorded and/or listed P. integra on several occasions ( Rao et al. 1989; Venkataraman et al. 2004; Dev Roy 2008; Rao 2010; Dev Roy et al. 2011, 2012; Trivedi et al. 2018), but their specimens will need to be re-examined to see if they are really this species. The specimens of Heteropilumnus or Pseudolitochira integra reported from the central Pacific and Marshall Islands by Holthuis (1953) and Paulay et al. (2003) will all need to re-examined. Considering the distribution, it seems unlikely that this material will be conspecific with P. integra s. str.

The first record of P. integra from the western Pacific was by T. Sakai (1955: 108, text-fig. 3) who listed the species (as Litocheira integra ) from the Bonin Islands (present day Ogasawara Islands) in Japan. Tune Sakai (1976: 493, text-fig. 264a) placed the species in Heteropilumnus (as Heteropilumnus integra ), commenting that his female specimen (5.5 × 3.5 mm) matched the original descriptions except that the anterolateral margin had two rudimentary indentations whereas in the type female, it was entire. Since then, the name (as a Heteropilumnus or Pseudolitochira ) has been used in various reports and lists from Japan and Taiwan ( Takeda & Miyake 1976; Miyake 1983; Ito 1992; Nomura et al. 1996; Jeng 1997; Ng et al. 2001, 2017; Motoh 2003; K. Sakai 2003; Marumura & Kosaka 2003; Komatsu 2011; Naruse 2010). Maenosono (2019) showed that the material listed as Naruse (2010) from Okinawa was mixed, containing both what he regarded as P. integra as well as Pilumnus turgidulus Rathbun, 1911 . The record of P. integra by Machida (2017) is incorrect and Maenosono (2019) referred it to Zehntneriana amakusae ( Takeda & Miyake, 1969) instead. Maenosono (2019: fig. 11A, B, C) described and figured a series of specimens from Okinawa at length and his material agrees well with that reported by T. Sakai (1955, 1976) as well as that figured in Nagai & Nomura (1988). His specimens compare well with the type of P. integra except that the carapace is proportionately much wider (width to length ratio 1.8), the frontal margin is not protruding, being only level with the orbits and the anterolateral margin is differently structured, with the lateral area armed with a low lobiform tooth. Despite these similarities, confirmation is required as to the identity of “ P. integra ” by Maenosono (2019). The structures of the posterior margin of the epistome and third maxillipeds are not clear from his figures ( Maenosono 2019: fig. 11C) but appear to agree; and the condition of the male pleon (particularly the transversely narrower somites 1 and 3) agrees more with what is known for Heteropilumnus s. str. (see Ng et al. 2018: figs. 7D, 8D). The male and female specimens of Maenosono (2019) will need to re-examined to see if material is congeneric with P. integra , but regardless, it is certainly not conspecific.

The material recorded from the Moluccas will also need re-examination. The material identified as L. subintegra by Tesch (1918: 175, pl. 16, fig. 1) is probably another species, its quadrate carapace, weakly marked anterolateral margin and long ambulatory legs are completely different from the type female of P. integra as well as Heteropilumnus holthuisi . Ng & Tan (1988) assigned it to H. holthuisi with doubt but this seems unlikely. The same is true for the record of P. integra by Serène et al. (1974) from this area.

The main issue with the identification of P. integra , however, is that to date this species has only been described from female specimens and consequently the morphology of the male pleopod remains unknown. Türkay (1975: 126) discussed this problem about the lack of male specimens. That being said, the Japanese male figured by Maenosono (2019) is probably shared by congeners and his specimens probably belong to Pseudolitochira , although it is probably not P. integra as redescribed here. The male pleon and male first gonopod he figured ( Maenosono 2019: figs. 13C, 14M, N) are typical for pilumnids, resemble those of Heteropilumnus satrai and are essentially of the Heteropilumnus type.

Figures

FIGURE 2. Pseudolitochira integra (Miers, 1884), holotype ♀ (4.9 × 3.4 mm), NHM 1882.24, Seychelles. A, overall dorsal view; B, buccal cavity and frontal regions; C, outer view of left chela. After Miers (1884: pl. 8 figs. C, c, c’).

FIGURE 3. Pseudolitochira integra (Miers, 1884), holotype female (4.9 × 3.4 mm) (NHM 1882.24), Seychelles. A, overall dorsal view; B, left fourth ambulatory leg; C, left ambulatory propodus and dactylus; D, sternopleonal cavity and vulvae.

FIGURE 4. Pseudolitochira integra (Miers, 1884), holotype ♀ (4.9 × 3.4 mm), NHM 1882.24, Seychelles. A, overall dorsal view; B, ventral view of cephalothorax.

FIGURE 5. Pseudolitochira integra (Miers, 1884), holotype ♀ (4.9 × 3.4 mm), NHM 1882.24, Seychelles. A, dorsal view of carapace; B, frontal view of cephalothorax; C, outer view of right chela; D, buccal cavity, third maxillipeds and thoracic sternites

FIGURE 6. Heteropilumnus holthuisi Ng & Tan, 1988. ♂ (10.1 × 7.8 mm) (NHM 1886.52), Mergui;A, dorsal view of carapace; B, frontal view of maxilliped; C, frontal view of cephalothorax; D, lateral view of cephalothorax; E, anterior thoracic sternum and pleon; F, posterior thoracic sternum and pleon; ♂ (7.5 × 6.3 mm) (NHM 1886.52), Mergui; G, overall dorsal view.