Richardina crosnieri, Goy, Joseph W., 2015

Goy, Joseph W., 2015, Stenopodidean shrimps (Crustacea: Decapoda) from New Caledonian waters, Zootaxa 4044 (3), pp. 301-344 : 331-335

Richardina crosnieri n. sp.

( Figs. 24 –26)

Type material. HOLOTYPE: New Caledonia. BIOCAL, stn CP26, 22°40’S, 166°27’E, 1618–1740 m, 28.VIII.1985, 1 female (MNHN-NA 11991).

Diagnosis. Small stenopodid shrimp with slender, compressed body; carapace with distinct cervical groove bearing 22 strong, curved spines; strong antennal and hepatic spines; rostrum short, not reaching to end of antennular peduncle, strongly compressed, terminating in blunt point with 9 dorsal spines between 2 blunt tubercles, without ventral or lateral spines; eyes with cornea small, degenerate, unpigmented, narrower than peduncle; abdomen generally glabrous, anterolateral margin of first pleomere fringed with long setae and tranverse carina dividing pleomere in two sections, fifth pleomere with dorsal carina and posteriorly directed median ventral spine, sixth pleomere with row of 3 spines laterally on pleura; telson long, lanceolate with 2 dorsal longitudinal carinae bearing row of 6 spines, last spine overlapping rounded posterior margin; carpus of fourth and fifth pereiopods distinctly divided into 6 segments with terminae marked by 6 movable spines on ventral margin; propodus of fifth pereiopod distinctly longer than fourth, each indistinctly divided into 3 segments with 9 movable spines on ventral margins.

Description. Rostrum ( Figs. 24 , 25 A) broad at base, strongly compressed anteriorly short, not reaching past first antennular peduncle segment; dorsal margin with 9 spines between 2 blunt tubercles, terminating in blunt point. Ventral and lateral margins without spines.

Carapace ( Figs. 24 , 25 A) with distinct cervical groove bearing 22 strong, curved spines; branchiostegal groove rather indistinct. Group of 5 strong spines behind rostral base, not along carina. Large antennal and hepatic spines present; smaller spine on anterolateral margin. Branchiostegal spine small, 4 small pterygostomial spines present; distinct hepatic groove present. Ventrolateral angle rounded, only slightly produced anteriorly; posterolateral angle of branchiostegite obtuse.

Abdomen ( Fig. 24 ) generally glabrous, more or less compressed, with first pleomere overlapping second and second overlapping third. Anterodorsal margin of first pleomere fringed with long setae, tranverse carina dividing pleomere into two sections, pleuron ending in weak forwardly curved tooth, rest of margin rounded. Fourth pleomere with short dorsal carina about midlength, minute spine in articular notch, pleuron ending in small tooth. Fifth pleomere with dorsal carina, additional short carina midlength of posteror margin between 2 small spines, pleuron ending in acute point. Sixth pleomere pleuron with row of 3 spines midlaterally, ending in acute point. Ventrally pleomeres unarmed, except for median posteriorly directed spine on fifth pleomere.

Eyes ( Figs. 24 , 25 A) unpigmented, facets barely discernible; cornea narrower than peduncle. Ophthalmic peduncle robust, dorsally and medially with 4 strong spines.

Telson ( Fig. 25 B) lance-shaped, with median groove flanked by 2 longitudinal carinae. Telsonal base with pairs of small outer and medial spines. Dorsal surface of carinae with row of 6 strong spines, last spine overlapping rounded posterior margin. Proximal pair of carinal spines with 2 long plumose setae, next 2 pairs of carinal spines with single long plumose seta. Lateral margins of telson with strong spine slightly past midlength, provided with plumose seta along posterior half.

Uropods ( Fig. 25 C) well developed but with rami not exceeding telsonal length. Basal segment with 2 dorsal, 2 ventral spinules. Exopodite quadrangular with 7 teeth on its outer margin, including slightly larger terminal tooth; dorsal surface bears 2 parallel longitudinal ridges that extend nearly to posterior margin. Endopodite elongate, lobate without teeth on margins, only one dorsal longitudinal ridge. Unarmed margins of exopods, endopods with long plumose setae.

Epistome ( Fig. 25 D) triangularly rounded anteriorly with 2 short submedian spines. Labrum normally developed, diamond-shaped. Paragnaths moderately bilobed with lobes separated by median fissure, bordered by setae. Thoracic sternites broad, unarmed.

Antennular peduncle ( Figs. 24 , 25 A) moderately long, extending slightly past proximal third of scaphocerite. Basal segment with distinct, curved stylocerite above small spine on outer margin, distodorsally with appressed rounded process with scalloped margin, 2 small spines on distodorsal inner margin. Middle segment about half length of basal segment with large distodorsal spine on outer margin. Distal segment unarmed. Upper and lower flagella well developed, first 5 articles of lower flagellum with thick, stiff setae ventrally, delicate short setae along entire lengths of both flagella.

Antenna ( Fig. 25 A) with stout basicerite bearing 2 distodorsal spines on outer margin. Carpocerite unarmed, short, not exceeding first antennular segment. Antennal flagellum missing. Scaphocerite well developed, elongate, outer margin slightly concave proximally, with 4 strong teeth separated to some extent from terminal tooth. Dorsal surface with distinct longitudinal carina bifurcating about midlength.

Mandibles ( Figs. 25 E, F) robust, with short, fused molar and incisor processes. Molar process nearly smooth with rounded medial tooth; incisor bearing 4 large, 5 smaller teeth along its outer margin. Palp 3-segmented, proximal segment shortest; middle segment with few setae medially, more setae distodorsally; distal segment longest, setose laterally and distally.

Maxillule ( Fig. 25 G) with slender undivided endopodite bearing 9 plumose setae along its margins. Proximal endite broad, truncated distally with few lateral setae, numerous compound spinose setae distally. Distal endite of equal size, rounded, with setae along its margins.

Maxilla ( Fig. 25 H) with numerous plumose setae on both lobes of coxal and basal endites, proximal coxal endite broadest. Endopodite long, slender, exceeding anterior margin of scaphognathite, with 22 plumose setae along margin. Scaphognathite long, narrow, about 5.0 times longer than maximum breath, with numerous plumose setae along margin, 6 setae noticeably longer at distal posterior extremity.

First maxilliped ( Fig. 25 I) with 3-segmented endopodite. Proximal segment longer than broad with 8 plumose setae along outer margin, inner margin with 8 simple setae. Middle segment about 0.33 times length of proximal one, bearing 11 long plumose on outer margin, 4 simple setae on inner margin. Distal segment tapering, about 0.55 times length of middle segment, with minute simple terminal seta. Basipodite large, rounded anteriorly and posteriorly, slightly concave near middle, with outer margin bearing dense fringe of setae. Coxopodite bilobed with numerous setae. Exopodite well developed, flagellum arising from unsegmented peduncle with 11 proximal and 22 distodorsal long plumose setae. Large epipod present with slender proximal and distal lobes approximately equal in length.

Second maxilliped ( Fig. 25 J) with 4-jointed endopodite. Dactylus suboval, longer than broad, with dense fringe of short setae along distodorsal margin. Propodus equal to dactylar length, densely setose on dorsal margin, ventral margin cristate. Carpus short, triangular, about 0.5 times length of propodus with numerous long simple setae at distodorsal angle. Merus more than 2.0 times dactylar length, 3.0 times longer than broad, dorsal margin with 4 proximal long plumose setae, 9 short simple setae distdorsally; ventral margin slightly convex with dense fringe of long simple setae. Ischium and basis fused, but distinguishable as densely setose lobes; coxa unarmed. Exopodite long, slender, undivided with 4 proximal, 16 distdorsal long plumose setae.

Third maxilliped ( Fig. 25 K) endopodite strongly developed, 5-segmented. Dactylus slender, tapering, about 3.0 times longer than basal width, 4 simple setae on outer margin, numerous long simple setae mesially along inner margin. Propodus equal to dactylar length, with numerous long simple setae at distodorsal angle; setiferous organ distally, numerous long simple setae along inner margin. Carpus slightly longer than propodus with numerous simple setae along inner margin. Merus long, slender, about 2.0 times carpal length, with 4 strong spines on outer margin, smaller spine distodorsally, numerous long simple setae along inner margin. Ischium long, slender, equal to meral length, with distal spine, 6 short simple setae on outer margin; inner margin with row of 6 spines covered by numerous long simple setae. Exopodite slender, almost as long as ischium, with 18 long plumose marginal setae; laterally small elongate epipod.

First pereiopod (Fig. 26A, B) small, slender, when stretched reaching just past scaphocerite. Palm of chela somewhat compressed, dactylus less than 0.5 times propodal length. Fingers slightly compressed, without hooked tips. Cutting edges distinct with 8 small, stout, peg-like teeth separated by rectangular chitnous lamellae (Fig. 26B). Dactylus and propodus with few simple setae. Fingers and distodorsal extremity of palm bearing small tufts of long setae arranged like brushes. Distoventral carpus and proximoventral propodus with setiferous organ. Carpus longest segment, about 2.0 times propodal length, with scattered short and long simple setae. Merus about equal to carpal length with scattered simple setae. Ischium 0.6 times meral length with 4 simple setae on ventral margin. Basis and coxa short, unarmed; with small elongate epipod laterally.

Second pereiopod (Figs. 26C, D) similar to first, but longer, stronger. Finger tips not hooked, cutting edges with flattened chitinous ridges. Finger and distodorsal extremity of palm with small tufts of long setae, not as setose as those on first pereiopod. Carpus longest segment, slightly more than 2.0 times propodal length, with dorsal spine about midlength, scattered simple setae. Merus about equal carpal length, with few scattered setae. Ischium less than 0.5 times meral length, with few setae. Basis and coxa short, unarmed; with small elongate epipod laterally. Third pereiopods missing in specimen.

Fourth and fifth pereiopods (Figs. 26E, F) very long, slender, similar. Each carpus distinctly divided into 6 segments, marked by 6 terminal movable spines on ventral margins. Propodus of fifth pereiopod distinctly longer than fourth, each propodi indistinctly divided into 3 segments with 9 movable spies on ventral margins. Dactyli long, slender, uniunguiculate, curving to acute point; that of fifth pereiopod with one dorsal, one ventral seta.

First pleopods uniramous, second to fifth biramous, all lacking appendices, bearing no spinules.

Maxillipeds Pereiopods

I II III I II III IV V Measurements (mm). PCL: 8.1; RCL: 9.8; TL: 27.4

Distribution. New Caledonia, in 1618–1740 m.

Etymology. This species is named in honor of Dr. Alain Crosnier who made this interesting collection available for the present study, and who, like the holotype is a unique individual.

Coloration. Unknown.

Type locality. New Caledonia, 22°40’S, 166°27’E, 1618 –1740 m.

Systematic position. Richardina crosnieri n. sp, closely follows the definition of the genus Richardina given by Holthuis (1946), even though the holotype lacks third pereiopods. The other five species known in the genus Richardina are R. spinicincta A. Milne-Edwards, 1881 , R. frederici Lo Bianco, 1903 , R. ohtsukai Saito & Komatsu, 2009 , R. parvioculata Saito & Komatsu, 2009 , and R. rupicola Komai, 2011 . The overall small number of known specimens for each species makes any attempt at relationships rather difficult. In some respects (carapacial spination, third maxilliped spination) R. crosnieri is similar to the Atlantic R. spinicincta , while in other respects (lateral spines on sixth pleomere) the new species resembles the Pacific R. ohtsukai and R. rupicola and (small eyes) similar to the Pacific R. parvioculata .

Figures

FIGURE 24. Richardina crosnieri sp. nov. Female holotype, MNHN Na- 11991. Scale bar = 1.0 mm.

FIGURE 25. Richardina crosnieri sp. nov. Female holotype, MNHN Na- 11991. A, carapace, dorsal view; B, sixth pleomere and telson; C, uropods; D, epistome and labrum; E, left mandible, dorsal view; F, left mandible, ventral view; G, maxillule; H, maxilla; I, first maxilliped; J, second maxilliped; K, third maxilliped. Scale bars = 1.0 mm.