Cheramus iranicus, Sepahvand, Vahid, Momtazi, Farzaneh & Tudge, Christopher, 2015

Sepahvand, Vahid, Momtazi, Farzaneh & Tudge, Christopher, 2015, Cheramus iranicus, a new species of ghost shrimp (Decapoda: Axiidea: Callianassidae) from the Persian Gulf, Iran, Zootaxa 4040 (2), pp. 215-224 : 216-223

publication ID	https://doi.org/ 10.11646/zootaxa.4040.2.7
publication LSID	lsid:zoobank.org:pub:7F0C06CE-53AA-4D31-A180-191909020328
DOI	https://doi.org/10.5281/zenodo.6106635
persistent identifier	https://treatment.plazi.org/id/038087A0-FFF8-FF8F-5BCB-B79FFB8AEE8A
treatment provided by	Plazi
scientific name	Cheramus iranicus
status	sp. nov.

Treatment

Cheramus iranicus View in CoL sp. nov.

( Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Material examined. Holotype: male (tl 20.7 mm, cl 5.18 mm), INIOC-1-15S.

Allotype: female (tl 15.26 mm, cl 3.65 mm), INIOC-1-16S, the Persian Gulf, west of Qeshm Island (26°35'12.87"N, 55°08'0.67"E).

Paratypes: 1 male (tl 21.18 mm, cl 5.51 mm), 1 female (tl 22.27 mm, cl 5.58 mm), INIOC-1-17S, the Persian Gulf, west of Qeshm Island (26°35'12.87"N 55°08'0.67"E), 5 February, 2014.

Type locality. Persian Gulf, west of the Qeshm Island, 26°35'12.87"N, 55°08'0.67"E; at depth of 40– 50 m.

Diagnosis. Rostrum reaching to one third length of eyestalks; eyestalks with prominent slender distal spine; thoracic shield (plate on thoracic sternite 7) ( Fig. 3 View FIGURE 3 D) pentagonal with strongly produced anteromedian margin; ventral surface with shallow groove posteriorly; third maxilliped with broad (suboperculiform) merus and ischium; larger cheliped with 7 denticles on ventral margin of ischium, merus oval with proximal ventral spine; telson as broad as long, broadest proximally, proximolateral margins convex, posterior margin strongly concave medially with median tooth or fixed spine and with 2 movable spines at each angle; uropodal exopod not particularly broad with truncate posterior margin.

Description. Carapace with frontal margin ( Fig. 3 View FIGURE 3 A) bearing short, spiniform rostrum not reaching to cornea, reaching approximately one third length of eyestalks and obtuse rounded projection lateral to rostrum; carapace length about one quarter of total length; orbital margins evenly concave; linea thalassinica distinct, extending to posterolateral margin of carapace; dorsal oval clearly demarcated with deep cervical groove and shallow anterior and transverse grooves behind rostral base ( Figs. 2 View FIGURE 2 A, 3A, D). Anterior branchiostegal lobe (pterygostomial angle) triangular, extending to anterior margin of first segment of antennal peduncle ( Fig. 3 View FIGURE 3 D).

Length ratio of pleomeres to telson measured along midline 1.0: 1.6: 1.2: 1.0: 1.2: 1.6 (anterior to posterior) ( Fig. 3 View FIGURE 3 D). First pleomere ( Fig. 3 View FIGURE 3 D) narrowing anteriorly in dorsal view; pleuron with defined ventral margin. Second pleomere ( Figs. 2 View FIGURE 2 A, 3D) approximately as long as wide; pleuron having posterolateral margin slightly expanded, with few setae on ventro-distal margin. Third to fifth pleura each with posterior tuft of long setae and few dorsal setae; posterolateral margins slightly expanded. Sixth pleomere ( Figs. 2 View FIGURE 2 A, 3D, E) 1.2 times longer than wide, subquadrate, with parallel lateral margins and a row of setae ( Fig. 2 View FIGURE 2 A); without conspicuous notch on lateral margins.

Telson ( Fig. 3 View FIGURE 3 D, E) subtrapezoidal, slightly narrowing posteriorly, width approximately equal to length (1.2 times wider than long), lateral margins each with low convexity proximally and 2 pairs of movable spines near posterolateral angle; posterior margin deeply concave and bilobed, with small medial tooth and some spines and long spiniform setae. Dorsal surface slightly convex, armed with 1 pair of movable spines, proximomedian tuft of long setae and 2 tufts of long setae on each side of mid-line.

Uropodal protopod bearing bilobed posterodorsal margin. Endopod elongate, sub-semicircular, with distinctly convex inner margin and nearly straight outer margin ( Fig. 3 View FIGURE 3 D, E), about twice as long as broad, and distinctly longer than telson, lateral margin unarmed; mesial margin fringed with setae, distal margin with cluster of 4 movable spines (spiniform setae) mixed with flexible setae; dorsal surface armed with 2 movable spines on either side of obtuse median ridge. Exopod larger than endopod, rounded oblong, 2.5 times as long as broad; dorsal surface slightly elevated along midline; dorsal plate with distal row of 4 spiniform setae distinctly separated from setal row of posterior margin; posterior margin roundly truncate with row of stiff setae of various lengths and stoutness.

Eyestalks ( Fig. 2 View FIGURE 2 B, 3A, 3D) mildly elongate, subtriangular, contiguous, armed each with prominent spine on distal margin, tip overreaching distal end of basal antennal article; cornea located subterminally and laterally, large and occupying more than half eyestalk width in dorsal view, darkly pigmented.

Antennule peduncle ( Fig. 3 View FIGURE 3 B) slightly shorter than antennal peduncle, ultimate segment 3 times as long as penultimate segment, with long setae, penultimate segment shorter than basal segment, with long setae ventrally; flagella unequal and dissimilar, upper flagellum composed of 14 articles and thicker and shorter than lower flagellum, lower flagellum with 19 articles, bearing short setae.

Antennal peduncle ( Fig. 3 View FIGURE 3 C) with third segment as long as second segment, fourth segment longest, about 2 times as long as fifth segment. Scaphocerite tiny, subovate, terminating in sharp, curved spine.

Small process on either side of epistome bearing setae ( Fig. 3 View FIGURE 3 A).

Mandible ( Fig. 4 View FIGURE 4 A) with smooth molar process. Incisor process with 7 small unequal teeth, with slightly concave inner surface. Mandibular palp 3-segmented, curved mesially, third segment larger than two proximal segments, bearing many stiff setae; basal article 0.8 times as long as second article. First maxilla ( Fig. 4 View FIGURE 4 B) with basal endite wide, bearing dense setation; distal endite proximally rounded; endopod long and slender, terminal part deflected. Second maxilla ( Fig. 4 View FIGURE 4 C) with exopod of broad distal lobe, 2 times as long as wide, endopod long and slender, tip digitiform; proximal and distal endites each longitudinally subdivided and with numerous setae on mesial margin. First maxilliped ( Fig. 4 View FIGURE 4 D) with exopod crest-shaped with setose external margins; endopod greatly reduced to bud-like process; distal endite elongate with curved lateral margins, minutely denticulate, covered with long setae. Second maxilliped with small epipod ( Fig. 4 View FIGURE 4 E). Dactylus short, about half as long as propodus, with dense setation on distal and dorsal margins. Propodus slightly arcuate, length 2 times width. Carpus short and triangular. Merus length exceeding 4 times width. Exopod unsegmented, short, reaching nearly to midlength of merus. Third maxilliped ( Fig. 4 View FIGURE 4 F, G) without exopod. Ischium rectangular,1.5 times as long as wide; crista dentata on mesial face composed of 15 sharp denticles; merus wider than long, combined length of ischium-merus about 3.2 times width. Carpus subovate, 2 times as long as broad. Dactylus narrow and digitiform, with stiff setae terminally.

First pereopods (chelipeds) unequal and dissimilar. Larger cheliped ( Fig. 2 View FIGURE 2 C) with ischium slender (about 3.0 times as long as broad), proximo-dorsal margin straight, disto-dorsal margin conspicuously convex (sinuous dorsal margin), with series of 7 acute spines on ventral margin slightly increasing in size distally. Merus about 1.5 times as long as wide; dorsal margin strongly convex, smoothly rounded; ventral margin also convex, with a small spine proximally, remainder of ventral margin with row of minute rounded denticles of similar size, and with row of setae. Carpus short, stout, 0.9 times as long as wide, with dense setation on ventral margin; disto-ventral angle rounded; mesial surface nearly flat; carinae present on dorsal and ventral margins. Propodus heavy, about 1.6 times as long as broad (including fixed finger); carinae present on dorsal and ventral margins. Palm sub-rectangular in lateral view; dactylus hooked distally, about 0.8 times as long as palm, with dense setae on dorsal margin and along cutting edge; fixed finger curved distally, cutting edge with hook-like tooth distally, remainder with row of small teeth, dorsal and ventral margins bearing row of long setae; narrow hiatus between fingers.

Smaller cheliped ( Fig. 2 View FIGURE 2 D) shorter and much more slender than larger cheliped. Ischium about 4.0 times as long as wide; dorsal margin nearly straight, unarmed; ventral margin with row of 8 subequal spines. Merus about 2 times as long as broad; dorsal margin slightly convex with minute spine proximally; ventral margin with small proximal spine preceded by row of rounded denticles or granules. Carpus about 2.5 times as long as broad and 1.3 times as long as merus, widened distally; carinae present on dorsal and ventral margins. Propodus straight ventrally with numerous setae; carinae present on dorsal and ventral margins; dactylus almost as long as palm, unarmed on cutting edge; distinct hiatus between fingers.

Second pereopod ( Fig. 2 View FIGURE 2 E) chelate. Ischium short, ventral margin gently concave. Merus 2.5 times as long as ischium, about 3.0 times as long as greatest width; ventral margin sinuous, with row of long setae. Carpus subtriangular, 1.8 times as long as wide, concave distally with dense setae proximoventrally. Propodus triangular with dense setae on ventral margin, fixed finger margin smooth. Dactylus with dense setae on dorsal margin; cutting edge straight, smooth.

Third pereopod ( Fig. 5 View FIGURE 5 A) strongly compressed laterally, non-chelate. Ischium 2 times as long as wide, ischium and merus with same width. Merus 1.7 times as long as ischium, 3.4 times as long as wide. Carpus, subtriangular, distal margin with two low lobes, and tufts of long setae at each angle. Propodus wider than carpus, subovate, with row of numerous setae, becoming longer proximally, on ventral margin. Dactylus much shorter than propodus.

Fourth pereopod missing.

Fifth pereopod ( Fig. 5 View FIGURE 5 B) slender, chelate, longer than second to fourth pereopods. Coxa 2 times as long as wide. Ischium about as long as coxa. Merus about 2 times as long as ischium. Carpus slightly shorter than propodus. Propodus with dense setae on distal part. Dactylus curved, partially obscured by dense setae.

Male first pleopod ( Fig. 5 View FIGURE 5 C) uniramus, two segmented, proximal segment thick at base, distal segment (ramus) tapered to blunt tip, with few setae distally.

Male second pleopod absent.

Appendix interna of third through fifth pleopods slender, finger–like; each exopod longer and broader than endopod ( Fig. 5 View FIGURE 5 D).

Female first pleopod ( Fig. 5 View FIGURE 5 E), uniramous, composed of three segments, proximal segment about 2.3 times longer than distal, with 5 long plumose setae. Female second pleopod ( Fig. 5 View FIGURE 5 F) biramous; endopod straight, with two terminal plumose setae, exopod longer than endopod, with 14 plumose setae.

Habitat. sandy-muddy bottom with shell fragments.

Remarks. The new species is unique in the possession of a sharp distal spine on the eyestalk and the telson with two pairs of lateral movable spines and a deep median concavity and a small but distinct median spine on the posterior margin. Among other Cheramus -like species, it is also characterized by a spiniform rostrum, suboperculiform merus-ischium of the third maxilliped and slender, digitiform appendices internae on the third to fifth pleopods. Among the known Cheramus -like species, Callianassa thorsoni Sakai, 2005 , transferred to Trypaea by Sakai (2011), appears closest to the present new species in sharing the sharp distal spine on the eyestalk and the general configuration of the telson. However, C. thorsoni is readily distinguished from the present new species by the only faintly concave posterior margin of the telson. In C. thorsoni , only the minor cheliped of the male paratype was preserved, in which there are only three tiny teeth on the ventral margin of the ischium. In the present new species, the ischium ventral margin is serrated by seven or eight small teeth on both chelipeds.

As previously mentioned, the composition of the genus Cheramus has not been consistent between taxonomists. In the present study, we accept the concept discussed by Komai et al. (2014) and provisionally assign our new species to Cheramus based on the following characters: 1) the long, slender body with a relatively small cephalothorax, 2) carapace with rostral spine, 3) corneas subterminal and lateral, 4) chelipeds unequal, major without distinct meral hook, 5) antennular peduncle not much longer or stouter than antennal peduncle, 6) distal margin of merus of third maxilliped not strongly produced, 7) plp1 slender and uniramous in both sexes; plp2 absent in male, slender and biramous in female; rami of plp3–5 relatively slender, with slender, finger-like appendix interna, 8) uropodal exopod elongate, length more than twice width.

Manning & Felder (1991) assigned the following species to Cheramus : Callianassa profunda Biffar, 1973 , Callianassa marginata Rathbun, 1901 , Cheramus orientalis Bate, 1888 , and Callianassa oblonga Le Loeuff & Intès, 1974 . Tudge et al. (2000) added Callianassa longicauda Sakai, 1967 , C. praedatrix de Man, 1905, C. propinqua de Man, 1905, C. rectangularis Ngoc-Ho, 1991, C. sibogae de Man, 1905, and C. spinophthalma Sakai, 1970 to Cheramus . Sakai (2011) later transferred Callianassa anoploura , C. longicauda , C. malaccaensis , C. nigroculata , C. contipes Sakai, 2002 , C. aqabaensis Dworschak, 2003 , C. lobetobensis de Man, 1905, C. modesta de Man, 1905, C. parvula Sakai, 1988, and Poti gaucho Rodrigues & Manning, 1992 to Cheramus . In more recent studies, Cheramus cavifrons Komai & Fujiwara, 2012 , C. spinicauda Komai, Maenosono & Fujita, 2014 and C. ohuranus Komai, Maenosono & Fujita, 2014 were all described from Japanese waters ( Komai & Fujiwara 2012; Komai et al. 2014). However, according to the on-line World Register of Marine Species ( Poore 2015), only 9 species referred to Cheramus are listed. Cheramus iranicus sp. nov. is easily distinguished from these species by the deeply bilobed telson with a prominent medial tooth in combination with the two pairs of lateral movable spines. This combination of telson armature is found only in Cheramus in the species, C. propinquus (De Man, 1905) ( Sakai 2011) and C. cavifrons ( Komai & Fujiwara, 2012) . Also, the additional characters of the major cheliped (7 ischial spines and a single proximal meral spine) and the distinctive post-corneal spine on each eyestalk are considered diagnostic.