Calcinus shawi, Lemaitre, 2022

Calcinus shawi View in CoL sp. nov.

( Figs. 1A–H View Figure 1 , 4 View Figure 4 )

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Calcinus aff. sirius View in CoL . — Poupin and Lemaitre, 2003: 17, fig. 1d, 4, 5b [MNHN Pg 6395, Rapa I., 100 m]. — Malay and Paulay, 2010: 640, tab. 1 [same specimen, MNHN Pg 6395, molecular analysis, specimen n° H93b]. — Malay et al., 2012: 166, tab. 1 [same specimen, MNHN-IU-2011-5105 (ex-MNHN Pg 6395), Genbank n° FJ620251]. Not C. sirius Morgan, 1991 View in CoL .

Material examined. French Polynesia, Austral Is., BENTHAUS Expedition. Rapa I., stn DW1894, 27°40.13’S 144°21.51’W, 100 m, 8/11/2002: holotype, ovigerous female, SL 5.5 mm (MNHN-IU-2011-5105, ex-MNHN Pg 6395, Genbank n° FJ620251) GoogleMaps .

Diagnosis. Ocular acicles terminating in simple spine ( Fig. 1B View Figure 1 , B’). Left chela, largest ( Fig. 1A, C View Figure 1 ) with outer face regularly convex; upper margin of palm with 7 blunt spines; lower margin with few tubercles on distal half. Upper margin of right chela with 6 corneous-tipped spines ( Fig. 1A, D View Figure 1 ). Dactyl of P2 ( Fig. 1E, F View Figure 1 ) slightly shorter than propodus, with 10 movable spines on ventral margin. Dactyl of P3 ( Fig. 1G View Figure 1 ) slightly shorter than propodus, with 7 movable spines on ventral margin. Ventrodistal pilosity of P3 weak, slightly denser than that of P2 ( Fig. 1F, G View Figure 1 ). Telson with posterior lobes each armed with single terminal spine ( Fig. 1H View Figure 1 ). Overall live color orange, paler on ocular peduncles, without colored stripes or spots; eggs bright red.

Description. Shield 0.85 times as broad as long. Rostrum ( Fig. 1B View Figure 1 , B’) triangular, slightly overreaching level of broadly subtriangular lateral projections; anterior margins between rostrum and lateral projections concave. Anterodorsal plate of branchiostegite with dorsal margin nearly smooth, with few spinules on proximal half.

Ocular peduncles ( Fig. 1B View Figure 1 ) 1.14 times (right) or 0.70 times (left, probably regenerating) as long as shield, slightly constricted medially; cornea weakly dilated, diameter approximately one-sixth length of ocular peduncle. Ocular acicles ( Fig. 1B View Figure 1 , B’) well developed, subtriangular, terminating in simple spine.

Antennular peduncles reaching to distal 0.25–0.30 of right ocular peduncle. Ultimate segment 0.38 times as long as shield. Antennal peduncles shorter than antennular peduncles, reaching between midpoint and distal one-third of right ocular peduncle. First segment with ventrolateral angle produced, bearing 2 or 3 spines. Second segment with laterodistal angle produced, terminating in bifid spine; distomesial angle with minute spine. Third segment with strong spine at ventrodistal angle. Fourth segment with dorsodistal spine. Fifth segment unarmed. Antennal acicle reaching beyond proximal margin of fifth antennal segment, terminating in strong spine; dorsolateral margin with spine distally, dorsomesial margin with row of spines.

Left chela larger than the right, ( Fig. 1C View Figure 1 ), 0.74 times as high as long. Dactyl 0.55 times palm length; cutting edge with 2 subtriangular calcareous teeth on proximal half; dorsal margin granulated. Fixed finger with 3 triangular teeth on proximal half of cutting edge; outer and lower faces with granules. Palm with outer face regularly convex, without depressions, coarsely granular; inner face smooth; upper margin of palm with a row of 7 blunt spines and a few accessory tubercles in between. Carpus with prominent submedian tubercle on outer face; upper margin with 1 or 2 small indentations and 1 strong spine at dorsodistal angle. Merus stout, triangular in cross-section; ventromesial margin with few spines distally; ventrolateral margin with 2 spines distally; upper margin unarmed.

Right chela smaller than left ( Fig. 1D View Figure 1 ), with 6 corneous spines on upper margin of palm.Dactyl about as long as palm; cutting edge with 3 triangular teeth on proximal half; dorsal surface with 2 subparallel rows each of 5 or 6 spines; fixed finger with 1 large triangular tooth on cutting edge, proximally, outer face with tubercles, those near tip bearing setae. Palm with outer face weakly convex, smooth on proximal two-thirds, tuberculated distally, near base of fingers; inner face flat, smooth. Upper margin of carpus with 2 or 3 spines increasing in size distally. Merus similar to that of left cheliped.

Ambulatory legs similar from left to right. P2 ( Fig. 1E, F View Figure 1 ) exceeding left cheliped by length of dactyl when fully extended; dactyl 0.81 times as long as propodus; ventral margin with widely-spaced, sparse tufts of setae and 10 minute spines;propodus with few long setae, and minute movable spine at ventrodistal angle; carpus 0.60 times as long as propodus, with strong dorsodistal spine; merus slightly longer (1.06 times) than propodus, with lateroventral spine distally. P3 ( Fig. 1G View Figure 1 ) shorter than P2, overreaching tip of left cheliped by distal half of dactyl when fully extended; ventrodistal pilosity not brush-like and only slightly denser than that of P2; dactyl shorter (0.85) than propodus, ventral margin armed with 7 minute spines; propodus unarmed on ventral and dorsal distal angles; carpus 0.68 times as long as propodus, with dorsodistal spine; merus slightly shorter (0.96 times) than propodus, with indistinct lateroventral spine, distally. Fourth pereopod semichelate; dactyl terminating in corneous claw, ventrolateral margin with row of spinules; propodus with broad rasp consisting of several rows of corneous scales; carpus with dorsodistal spine; merus unarmed, ventral margin with long setae. Fifth pereopod chelate, with rasp on propodus and dactyl; carpus and merus unarmed, subovate in cross-section.

Abdomen with 4 unpaired biramous left pleopods. Sixth abdominal tergite calcified, with dorsal face divided into 4 subequal areas by longitudinal and transverse furrows. Telson with posterior lobes asymmetrical ( Fig. 1H View Figure 1 ), left more elongated than right; lobes with long setae marginally, each with 1 posterior spine slightly curved ventrally.

Live color ( Fig. 1A View Figure 1 ). Shield and posterior carapace orange. Ocular peduncles pale orange on proximal third, fading gradually to white on distal two-thirds. Antennular peduncles orange, becoming pale on distal fourth of terminal segment; flagella orange. Antennal peduncles orange, with white-tipped spines; f lagella orange. Chelipeds bright orange. Ambulatory legs orange, a little darker at setal pores. Abdomen redbrown; eggs bright red.

Distribution and habitat ( Fig. 4 View Figure 4 ).So far known only from Rapa Island, Austral Islands, French Polynesia; dredged at 100 m on hard bottom of rocks and corals.

Etymology. Named in honor of Ian Shaw, who took the first color photographs of Australian specimens of C. sirius , which made possible the determination of the characters that distinguish that species from this new one.

Remarks. Calcinus shawi sp. nov. and three other IWP species, C. albengai , C. dapsiles , and C. sirius , share the following characters: 1) ocular acicle with a single terminal spine; 2) spinose upper margin of right chela; 3) regularly convex outer face of left chela, lacking depressions; 4) single posterior spine on left lobe of telson; 5) without distinct brush of setae on ventral margin of P3. The latter three species were included in Malay and Paulay’s (2010,fig.14) Clade X along with the ESU C. aff. albengai , the shallow water (<50 m)color variant of the deep water (50–280 m) C. albengai , and two species having a distal brush of setae on the ventral margin of P3, Calcinus argus Wooster, 1984 , and Calcinus anani Poupin and McLaughlin, 1998 . Subsequently, Malay et al. (2012) have found that Poupin and McLaughlin’s (1998) C. anani is restricted to French Polynesia, and described C. fuscus from Japan and western Pacific. The photograph of C. anani from Japan in Malay and Paulay (2010, fig 14) and their sequences of C. anani from Bismarck archipelago, Papua New Guinea (UF4808), actually represent C. fuscus .

Calcinus shawi View in CoL can be easily separated from all species of Malay and Paulay’s (2010) Clade X by their color patterns. Live colors of C. anani View in CoL and C. fuscus View in CoL are illustrated in Malay et al. (2012, fig. 2) and that of C. albengai View in CoL , C. aff. albengai View in CoL , and C. argus View in CoL in Poupin and Lemaitre (2003, fig. 1) and Hoover (1999: 253). Additional photographs can be found in the Internet databases of Legall and Poupin (2021) and Myorin (2021). In C. shawi View in CoL the ambulatory legs are overall uniformly orange (a little darker at setal pores), while most other species of Clade X have a pattern of spots or lines on the ambulatory legs. Calcinus albengai View in CoL , C. aff. albengai View in CoL , and C. argus View in CoL have the ambulatory legs punctuated with white spots. Calcinus fuscus View in CoL and C. anani View in CoL have a pattern of reticulated lines forming elongated oval patches on propodi and dactyls.

Calcinus shawi View in CoL sp. nov. cannot be confused with any other Calcinus species that are not in clade X. All of them are different by their color pattern and/ or by morphological characters presented in the key of Poupin and McLaughlin (1998) including: several distal spines on the ocular acicle and/or lobes of telson; external face of the right palm not regularly convex; dorsal margin of the right chela smooth; and distal setation of P3 more pronounced than that of P2, sometimes forming a brush of setae.

Calcinus shawi View in CoL sp. nov. is closely related to two Australian species also in Malay and Paulay’s (2010) Clade X and reported from similar latitudes in the southern hemisphere, C. dapsiles View in CoL from WA and C. sirius View in CoL from EA. The live coloration of the C. dapsiles View in CoL was previously known by the color photograph in Jones and Morgan (2002: 116), whereas that of C. sirius View in CoL has only now been discovered by the first author in the ‘Hermit crab visual dictionary’ managed by Myorin (2021). The differences in coloration of these three species, which can be useful in their identification, are contrasted below under the discussion of C. dapsiles View in CoL and C. sirius View in CoL .