Articullichirus articulatus ( Rathbun, 1906 ) Poore & Dworschak & Schnabel, 2022

Poore, Gary C. B., Dworschak, Peter C. & Schnabel, Kareen E., 2022, Articullichirus, a new genus of ghost shrimp (Crustacea: Axiidea: Callichiridae) with one new species, Memoirs of Museum Victoria 81, pp. 123-133 : 124-127

Articullichirus articulatus ( Rathbun, 1906) comb. nov.

Figures 1 , 2

Callianassa articulata Rathbun, 1906: 892 , fig. 47.— Manning,

1987: 396. Callianassa (Callichirus) articulata .— De Man, 1928: 28, 94,

108.— Edmondson, 1944: 54, fig. 9. Corallianassa articulata .— Dworschak, 1992: 210, fig. 14.—

Tudge et al., 2000: 144.— Komai et al., 2015: 54.— Poore et al., 2019:

136, 144. Corallianassa collaroy .— Sakai, 1992: 212, fig. 1. Glypturus articulatus .— Sakai, 2011: 433 (part). Cheramus articulatus .— Poupin, 1998: 31. Not Callianassa articulata .— Chilton, 1911: 551–552 =

Articullichirus chiltoni sp. nov.

Material examined. Hawaii, Oahu, Honolulu, Harbour Entrance, coll. V. Pietschmann, 1927, NHMW 6621 (ovigerous female, 7.5 mm). French Polynesia, Tuamotu, Mataiva, Hoa Papino platier, coll. Mario Monteforte, 1982, MNHN IU-2013-19994 (=Th1232) (female, 7.3 mm).

Material not examined. Hawaii, Oahu, Kahala, coll. C.H. Edmondson, 1930–1933, BPBM S4669 , S4670 , S4671 , S4672 , S4673 , S4674 (6 specimens); Kawailoa, coll. C.H. Edmondson, 1921, BPBM S4668 ; Hanauma, coll. C.H. Edmondson, 1933, BPBM S4675 , S4676 (2) ; coll. Banner, 1938, S4677 (1); Waikiki, coll. Simon, 1941, BPBM S4678 (1) . Nihoa Island , RV Albatross , 48–60 m, USNM 30532 (female, holotype) ; Nihoa Island , RV Albatross , 42–48 m, USNM 30995 (female) . Oahu Island, Waikiki , coll. C.H. Edmondson, 1921 USNM 78119 (1).

Size. Cl. to 7.5 mm.

Type locality. USA, Hawaii, 42–60 m.

Diagnosis. Maxilliped 3 basis without mesial tooth or with 2 small mesial teeth; merus with or without small tooth on distal margin. Pereopod 1 coxa with small mesiodistal process with terminal setae. Uropodal endopod midlength about 1.3–1.4 times as long as wide, with tapering apex, with 2 dorsal clusters of setae, with 2 proximal dorsal teeth. Telson 1.4–1.7 times as wide as long, with sinuous posterior margin; with transverse dorsal row of 2 pairs of spiniform setae.

Description of female from Tuamotu (MNHN IU-2013-19994). Carapace length 0.28 of total length; cervical groove at 0.8 length of carapace; dorsal oval well defined; hepatic region with weakly sclerified line between dorsal oval and linea thalassinica.Rostrum and anterolateral carapace spines with unsclerified basal region; rostrum an anteriorly directed, acute spine as long as eyestalk; anterolateral spines set well back from rostrum, acute, one third as long as rostrum. Anterolateral branchiostegal margin extending dorsal to linea thalassinica, with small separate sclerified plate near beginning of linea thalassinica. Pleomere 1 with weak transverse groove, with dorsolateral longitudinal setal row; pleomere 2 about 1.4 times as long as pleomere 1 tergite; pleomeres 3–5 scarcely expanded laterally, with dense setose areas; pleomere 6 1.2 times as long as pleomere 5, pleomere 6 with posterolateral notch, with pair of lobes on posterior margin.

Eyestalks shorter than first article of antenna 1; with rounded mesiodistal lobe not visible in dorsal view; cornea globular, distally placed. Antennular peduncle reaching two thirds along antennal peduncle article 5. Antennal peduncle with acute scaphocerite. Right maxilliped 3 (left missing) basis with 2 small mesial teeth; ischium with crista dentata of 13 teeth, larger distally; merus width about 0.7 as long as ischium and merus together; merus shorter than ischium, with tooth on free distal margin; carpus articulating distolaterally on merus; propodus as wide as long, expanded as asymmetrical lobe; dactylus one third as wide as propodus, 0.7 times as long.

Pereopods 1 unequal, dissimilar; coxae with small mesiodistal process with terminal setae. Major pereopod 1 (right cheliped) carpus-propodus upper margin 0.8 times carapace length; ischium lower margin with row of 6 spines, larger distally; merus lower margin with 2 proximal teeth followed by irregularly toothed blade, upper margin evenly convex; carpus twice as wide as long, with blunt tooth at end of upper and lower margins; propodus upper margin smooth, with submarginal carina on mesial face, most visible distally, palm 1.1 times as long as wide, distomesial edge straight; fixed finger 0.45 times upper margin, cutting edge with broad tooth at midlength; dactylus stout, slightly longer than fixed finger, with terminal tooth, cutting edge with blunt tooth at midlength; ratio of dorsal lengths, merus: carpus: propodus – 1: 0.5: 1.45.

Minor pereopod 1 (left cheliped) about as long as major; ischium lower margin with 7 similar spines; merus lower margin with 3 proximal spines followed by irregularly toothed blade; carpus 1.1 times as wide as long, with tooth at end of upper and lower margins; propodus upper margin 1.2 times as long as greatest width; fixed finger 0.8 times upper margin, cutting edge lateral, crenellate over distal third; dactylus overreaching fixed finger, cutting edge smooth; ratio of dorsal lengths, merus: carpus: propodus – 1: 0.7: 1.0.

Uropod endopod 1.5 times as long as wide, anterior margin convex, without setae; posterior margin slightly concave, tapering to a narrowly rounded apex; marginal setae confined to distal and posterodistal margins; upper face with cluster of setae close to posterior margin, few scattered setae near anterior margin, with 2 proximal teeth and another at midlength. Exopod subtriangular, anterior margin straight, posterior margin concave, width 0.7 times anterior margin, upper face with proximal tooth; dorsal plate oblique, well separate from distal margin, armed with imbricating robust setae, posterodistal angle rounded, armed with imbricating robust setae, diminishing along posterior margin.

Telson 1.4 times as wide as long, lateral margins strongly evenly convex, posterior margin concave; with dorsal transverse row of 2 pairs of spiniform setae separated medially by cluster of fine setae; posterolateral margin with row of setae.

Distribution. Eastern Indo-Pacific (Hawaii, French Polynesia); upper shelf.

Remarks. We were unable to examine the holotype at the USNM but have illustrated others. Articullichirus articulatus is distinguished from the other two species by its tapering uropodal endopod, narrower in published figures ( Rathbun, 1906; Edmondson, 1944) than in our figures. Rathbun (1906) and Edmondson (1944: fig. 9d) noted a meral tooth on maxilliped 3 of specimens from Hawaii, also present on the female from French Polynesia examined by GCBP, but the tooth is absent on NHMW 6621 from Hawaii examined by PCD. Both specimens examined have a submarginal mesial crest on the major cheliped propodus, two pairs of short spiniform setae on the telson and a sharp scaphocerite. The mesial hook on the pereopod 1 coxa (present in A. collaroy and A. chiltoni ) is absent or replaced in the French Polynesian female by a short fingerlike process.

The description above is based on the specimen reported by Poupin (1998). We have not examined the individual from Moorea now in the Senckenburg Museum, Frankfurt, illustrated by Sakai (1992), which we assume to belong to this species.

Figures

Figure 1. Articullichirus articulatus (Rathbun, 1906). Hawaii, NHMW 6621 (ovigerous female, 7.5 mm). a, anterior carapace, eyestalks, antennular peduncle, antennal peduncle; b, c, telson, uropods (depressed); d, left uropod, telson; e, right uropod, telson. Scale bar = 1 mm.

Figure 2. Articullichirus articulatus (Rathbun, 1906). French Polynesia, MNHN IU-2013-19994 (female, 7.3 mm). a, carapace, eyestalks, pleomeres 1, 2; b, pleomeres 5, 6, telson (depressed); c, d, anterior carapace, eyestalks, antennular peduncle, antennal peduncle; e, pleomere 6, telson, lateral view; f, telson, dorsal view; g, uropodal endopod, dorsal view; h, uropodal exopod, dorsal view; i, maxilliped 3, outer view; j, right maxilliped 3, coxa to merus, mesial view (palp removed); k, proximal articles of left maxilliped 3 and cheliped in situ, ventral oblique view; l, left cheliped coxa, ventral view; m, right cheliped, mesial view; n, right cheliped fingers, lateral view; o, right cheliped propodus, dactylus, upper view; p, left cheliped; q, pereopod 2; r, pereopod 4. Scale bars = 1 mm. c1, b1, coxa, basis of right cheliped; cm, bm, im, coxa, basis, ischium of maxilliped 3. Scale bars = 1 mm.