Neocrangon orientalis, Han, Qingxi & Li, Xinzheng, 2009

Han, Qingxi & Li, Xinzheng, 2009, Neocrangon orientalis, a new caridean shrimp species (Crustacea, Decapoda, Crangonidae) from the East China Sea, Zootaxa 2050, pp. 65-68 : 65-68

Neocrangon orientalis sp. nov.

(Figs 1–2)

Material examined. East China Sea. MBM228966, holotype, female (cl 7.71mm), CN V580B-50, 30°31.0ʹN, 127°56.5ʹE, 365–395 m, muddy sand, Agassiz trawl, collectors: ZC Tang & JS Xu, 1 Jul 1978; MBM228967, paratypes, 2 females (cl 7.09, 8.85 mm), same data as holotype; MBM228968, paratypes, 1 male (posterior carapace and proximal pleon damaged), 4 females (cl 7.88–9.81 mm), CN V580B-55, same data as holotype.

Dignosis. Eyes moderate in size. Rostrum compressed laterally, slightly up-curved, tapered, dorsal carina faint, distinctly exceeding beyond end of cornea. Antennal scale about 0.94 (0.89–0.96) times of carapace length, about 4.13 (3.98–4.27) times longer than broad. Area among antennal, branchiostegal and hepatic spines deeply depressed, with grooves. First five pleomeres smooth, without dorsal carina, pleuron of fifth pleomere with posterolateral spine, sixth pleomere bearing pair of submedian carinae separated by median sulcus.

Description. Body slender, slightly compressed laterally. Integument very thin, with sparse long setae.

Eyes kidney-like, moderate in size ( Fig. 2 A). Corneal width about 0.27 (0.25–0.29) times of carapace length.

Rostrum ( Fig. 2 A) compressed laterally, slightly up-curved, tapered, about 0.38 (0.36–0.41) times of carapace length, distinctly exceeding beyond end of cornea. Anterodorsal tip acute. Dorsal carina of rostrum faint.

Carapace (Fig. 1) about 1.24 (1.18–1.28) times longer than wide. Dorsal surface armed with two teeth, posterior one stronger and larger, at about midlength of carapace, continued posteriorly with carina extending 0.6 of distance between posterior tooth and posterior margin of carapace, anterior dorsal tooth minute, nearly at level of posterior orbital margin, continued with an unconspicuous carina. Dorsolateral surface with unconspicuous carina paralleled with dorsal carina. Sulcus started from hepatic groove extending posteriorly beyond level of posterior dorsal tooth. Orbital, antennal, branchiostegal and pterygostomian spines present. Orbital spine larger than antennal spine, almost same as hepatic spine in size, continued posteriorly with short ridge; antennal spine acute, continued posteriorly with deep groove, combined with hepatic groove at posterior end; branchiostegal spine large, continued posterodorsally with low carina extending to basis of hepatic spine; pterygostomian spine minute. Orbital margin with deep, distinct cleft. Area among antennal, branchiostegal and hepatic spines deeply depressed, with grooves.

Fifth to eighth thoracic sternites armed with high, distinct plate respectively, anteriorly protruded into large spine, plates of fifth and sixth thoracic sternites located closely.

FIGURE Neocrangon orientalis Holotype female (cl 7.71 mm), MBM228966, lateral view. Scale bar: 1 mm.

Anterior five pleomeres smooth, without dorsal carina. Pleura of pleomeres ventrally broad rounded, fifth pleomere armed with posterolateral spine. Sixth pleomere about 0.87 (0.85–0.89) times of carapace length, bearing pair of submedian carinae separated by median sulcus ( Fig. 2 B). Sternites of anterior four pleomeres armed with large, acute median spines, sixth pleomere elevated into high blunt tubercle. Telson tapered posteriorly, with median longitudinal groove extending almost whole telsonal length, with four pairs of dorsolateral spines, anterior pair at midlength of telson, posterior pair at about posterior 0.25 of telsonal length, tip of telson armed with two pairs of long setae.

Antennal scale about 0.94 (0.89–0.96) times of carapace length, about 4.13 (3.98–4.27) times longer than wide, distolateral spine far exceeding distal margin of lamella.

Third maxilliped overreaching distal margin of lamella of antennal scale with ultimate segment. First pereiopod robust, exceeding antennal scale with dactylus; merus armed with strong spine on distal end of dorsal surface and two small spines respectively on outer and inner distal margins of ventral surface ( Fig. 2 C, D). Second pereiopod slender, dactylus about 0.2 of palmar length ( Fig. 2 E, F); Third pereiopod very slender, overreaching distal margin of lamella of antennal scale with dactylus and distal 0.67 of propodus ( Fig. 2 G). Fourth and fifth pereiopods with dactyli curved ventrally ( Fig. 2 H, I); Second, fourth, fifth pereiopods failing to reach distal margin of lamella of antennal scale.

Uropods overreaching telson ( Fig. 2 B).

Coloration in life. Unknown.

Size. All females non-ovigerous, 7.09–9.81 mm in cl; male unknown.

Variations. One paratype female (MBM228968, cl 8.06 mm) has its rostrum strongly ascended as much as 45°; one paratype female (MBM228967, cl 7.09) and two paratype females (MBM228968, cl 8.06, 8.07 mm) have a small and inconspicuous tubercle posterior to the anterior dorsal spine.

Distribution. So far only known from the type locality in the East China Sea, at the depths of 365–395 meters. Etymology. Drived from the Latin orientalis , referring to the type locality of the new species.

Remarks. The new species closely resembles Neocrangon resima ( Rathbun, 1902) in the situations of the dorsal teeth, smooth tergites of the first five pleomeres, and the long rostrum overreaching anterior margin of the cornea. It differs from N. resima by the following characters: 1) the rostrum in the new species arms with faint dorsal carina and cute anterior apex, and distinctly exceeds the end of the cornea (vs. the rostrum in N. resima arms with pronounced dorsal sulcus and blunt apex and varies in length); 2) the antennal scale in the new species is 0.94 (0.89–0.96) times as carapace length and is about 4.13 (3.98–4.27) times as long as broad (vs. the antennal scale in N. resima is four fifths of the carapace length, and 3.5 times as long as broad); 3) the posteroventral spine of the pleuron of fourth pleomere is absent, the posterolateral spine on the fifth is present (vs. the fourth pleuron in N. resima arms with minute posteroventral spine, the fifth pleuron has posterolateral point); 4) the first and second pleomeres have smooth posterior portions (vs. the posterior portions of the first and second pleomeres in N. resima elevate and are preceded by broad, shallow transverse sulci).

Including the new species, there have been five species in the genus Neocrangon Zarenkov, 1965 . The species can be distinguished by the following key.

Figures

FIGURE 2. Neocrangon orientalis sp. nov. A – I, holotype female (cl 7.71 mm), MBM 228966; J, paratype male, MBM 228968. A. rostrum and eyes, dorsal view; B. sixth pleomere and telson, dorsal view; C. first pereiopod, ventral view; D. palm of first pereiopod, ventral view; E. second pereiopod, ventral view; F. chela of second pereiopod, ventral view; G. third pereiopod, lateral view; H. fourth pereiopod, lateral view; I. fifth pereiopod, lateral view; J. second male pleopod, ventral view. Scale bars: 1 mm (A – E, G – J); 0.2 mm (F).