Callianassa ehsani Sepahvand & Tudge & Momtazi 2018, sp. nov.
Creators: name: Sepahvand, Vahid
name: Tudge, Christopher
name: Momtazi, Farzaneh
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Callianassidae
Callianassa
Callianassa ehsani

description: Callianassa ehsani sp. nov.
(Figs. 1–4)
Type material. Holotype: female (tl 23.6 mm, cl 6.1 mm), Gulf of Oman, 26°48'12"N, 57°01'06"E, 10–13 m, INIOC-1-97S. Allotype: 1 damaged male (tl 26.4 mm, cl 7.8 mm), collected with holotype, INIOC-1-98S.
Description. Carapace with short, broad, triangular rostrum (Fig. 1A–D), acuminate, reaching anteriorly to approximately one-third length of eyestalks, not reaching cornea; 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 by deep cervical groove (Fig. 1A, B). Shallow groove originating immediately below linea thalassinica demarcating small triangular plate (branchiostegal sclerite) between linea thalassinica and branchiostegite, plate rounded anteriorly and with short setae (Fig. 1C, D).
Pleon with pleomere:telson length ratio measured along midline 1: 2: 1.2: 1.2: 1: 1.6 (anterior to posterior) (Fig. 1A, B). Pleomere 1 (Figs. 1A, B) narrowing anteriorly in dorsal view; pleuron with defined ventral margin.
Pleuron 2 (Figs. 1A, B) distinctly longer than other somites; posterolateral margin slightly expanded, bearing tuft of setae directed laterally adjacent to posterolateral margin (Fig. 1B). Pleura 3–5 each with posterolateral tuft of long setae and a few dorsal setae; posterolateral margins slightly expanded. Pleomere 6 (Figs. 1A, B) 1.2 times longer than wide, subquadrate, with parallel lateral margins and row of setae.
Telson (Figs. 1A, G) trapezoidal, slightly narrowing posteriorly, about 1.1 times as long as broad, low transverse ridge anteromedially, bearing row of setae; posterior corners with fringe of elongate setae and small lateral spine; posterior margin with small medial spine centrally.
Uropodal protopod bearing bilobed posterodorsal margin. Endopod of uropod elongate oval, sub-semicircular, with distinctly convex inner margin and nearly straight outer margin (Fig. 1A, G) twice as long as wide, extending more than 1.5 times length of telson beyond edge of telson, distal margin fringed with setae. Exopod of uropod 1.2 times length of endopod. Upper exopodal plate 0.8 times length of lower, distal margin convex, densely fringed with setae. Lower exopodal plate densely fringed with setae, median rib on dorsal surface well developed.
Eyestalks (Figs.1C, D) short, subtriangular, contiguous along midline, small, darkly pigmented cornea subterminal.
Antennular peduncle (Fig. 1C, E) slightly shorter than antennal peduncle, ultimate article 3 times as long as penultimate article, with long setae, penultimate article shorter than basal article, with long setae; flagella unequal and dissimilar, upper flagellum composed of 15 articles and thicker and shorter than lower flagellum, lower flagellum with 21 articles, bearing short setae.
Antennal peduncle (Fig. 1C, F) with article 3 shorter than article 2, article 4 longest, about 2 times as long as article 5.
Mandible (Fig. 2A) with smooth molar process. Incisor process with 5 small equal teeth, with slightly concave inner surface. Mandibular palp 3-articled, curved mesially, article 3 larger than two proximal articles, basal article 0.7 times as long as article 2.
Maxilla 1 (Fig. 2B) with basal endite wide; distal endite proximally triangular; endopod long and slender, terminal part deflected. Maxilla 2 (Fig. 2C) with exopod 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.
Maxilliped 1 (Fig. 2D) with endopod greatly reduced, minute; proximal endite narrow; distal endite elongate with straight mesial and curved outer margin, mesial half of external surface and margins heavily setose; exopod not noticeably broad, curved mesially, epipod softly bilobed with distal lobe smaller than proximal lobe, posterior end tapering to narrow terminal.
Maxilliped 2 (Fig. 2E) with long, narrow endopod; endopodal merus length exceeding 4 times width; carpus short; propodus slightly arcuate, length 2 times width; dactylus short, about half as long as propodus; exopod narrow, shorter than endopodal merus; epipod minor.
Maxilliped 3 (Fig. 2F, G) ischiomerus narrow; ischium subrectangular, 1.9 times as long as broad; crista dentata with a row of fine and slender denticles; merus subtriangular, two-thirds length of ischium, mesial margin broadly convex, distal margin entirely facing to carpus distally; carpus triangular, 1.5 times as long as broad; propodus subquadrate, longer than broad, with entirely convex ventral margin; dactylus digitiform, smaller than propodus. Exopod absent.
Major pereopod 1 (first cheliped) (Fig. 3A–B) with ischium slender (about 3.0 times as long as broad), proximo-dorsal margin straight, disto-dorsal margin conspicuously convex, with series of 6 or 7 acute spines on ventral margin. Merus about twice as long as wide; dorsal margin almost straight with two small spines proximally; ventral margin with arcuate proximal tooth (meral hook) bearing basal tooth; meral margin distal to proximal tooth straight and smooth. Carpus broadened, as high as long, slightly shorter than merus. Propodus heavy, about 1.5 times as long as broad (including fixed finger); fixed finger two-thirds length of upper margin of palm and smooth on prehensile margin; dactylus slightly longer than fixed finger, dorsal margin incurved downward distally, 1.5 times as long as broad; fixed finger curved distally, cutting edge with hook-like tooth medially, dorsal and ventral margins bearing row of long setae; narrow hiatus between fingers; dactylus hooked distally, about 0.9 times as long as palm, with dense setae on dorsal margin and cutting edge with 2 blunt teeth.
Minor pereopod 1 (first cheliped) (Fig. 3C) shorter and much slenderer than major cheliped. Ischium about 4.0 times as long as wide; dorsal margin nearly straight, unarmed; ventral margin with row of 4 subequal spines. Merus about 2 times as long as broad; dorsal margin slightly convex. Carpus about 2.5 times as long as broad and 1.3 times as long as merus, widened distally. Propodus straight, ventrally with numerous setae; dorsal and ventral margins carinate; dactylus almost as long as palm, unarmed on cutting edge; distinct hiatus between fingers.
Pereopod 2 (Fig. 3D) ischium short, ventral margin gently divergent, merus 3 times as long as ischium, broadened, slightly less than 3 times as long as wide; carpus triangular, almost half length of merus; propodus with dense setae on ventral margin, fixed finger margin smooth; dactylus with dense setae on dorsal margin; cutting edge straight, smooth.
Pereopod 3 (Fig. 3E) ischium short, ventral margin gently divergent distally, merus 2.8 times as long as broad; Carpus triangular in lateral view, 2 times as long as wide. Propodus with flexor margin produced into small lobe directed proximally, 1.3 times as wide as long; mesial surface with scattered tufts of short setae. Dactylus triangular, 0.8 times as long as propodus.
Pereopod 4 (Fig. 3F) merus 1.3 times as long as ischium; carpus 0.8 as long as merus; propodus rectangular in lateral view, 0.8 times as long as carpus, lateral surface scarcely setose, ventrodistal corner obtusely protruded; dactylus less than half length of propodus.
Pereopod 5 missing.
Pleopod 1 (Fig.4A) uniramous, 2-articled, proximal article thick at base, distal article tapered to blunt tip, with few setae distally. Pleopod 2 biramous, endopod composed of two articles, with few setae distally on both rami and laterally on exopod (Fig. 4B). Pleopods 3–5 (Fig. 4C–D) foliaceous, endopod bearing stubby, projecting appendix interna; exopod strongly arcuate; both endopod and exopod with setose margins.
Allotype: Damaged, but general shape of body similar to holotype. Ischium of large chelipeds with 7 acute spines and meral hook on merus consisting of 3 spines (Fig. 3G). Pleopod 1 uniramous, composed of 1 article (Fig. 4E). Pleopod 2 a minute medially lobed tapered papilla (Fig. 4F).
Remarks. Using Sakai (2011), Callianassa ehsani sp. nov. keys out to C. thailandica Sakai, 2005. The new species, however, can be easily distinguished from C. thailandica Sakai, 2005 by the following characters: 1) ischium of major cheliped armed with 6 or 7 acute spines on the ventral margin in C. ehsani, whereas such spines are absent in C. thailandica; 2) the telson in C. thailandica is square and slightly broader than long with a shallowly concave mid-posterior margin versus longer than broad telson with a broadly convex, medially spinulate posterior margin in C. ehsani.
The present species agrees well with C. persica Sakai, 2005 in many diagnostic aspects, including body shape, the relative size and shape of pereopods 2–4, maxilliped 3, the uropod and the rostrum. However, they differ as follows: the anterolateral projections of the carapace in C. persica are obtuse whereas those of C. ehsani are more acute; although the general form of maxilliped 3 is similar the ischium and merus are broader in relation to their length in C. persica; the uropodal endopod and exopod are more rounded in C. persica; and even though they share a median spine on the telson, C ehsani has an additional lateral spine on each side of the distal margin of the telson. It should be noted that pereopod 1 is not presently known in C. persica, so the comparison of this character in these two species is impossible. Also noteworthy is that a conspicuous meral hook is found on the large cheliped in many species currently assigned to the genus Callianassa (sometimes in both males and females) including C. aqabensis Dworschak, 2003, C. australis Kensley, 1974, C. chakratongae Sakai, 2002, C. coriolisae Ngoc-Ho, 2014, C. costaricensis Sakai, 2005, C. exilimaxilla Sakai, 2005 and C. thailandica (see Kensley 1974; Sakai 2002, 2005; Dworschak 2003; Ngoc-Ho 2014). Although often reported in the literature, the condition of the male and female pleopods 1 and 2 has limited potential for use as a taxonomic and systematic character. In fact, Dworschak (2003) noted that the presence or absence of pleopods 1 and 2 varied throughout the size range of individuals studied in C. aqabensis. The uniramous, single-articled male pleopod 1, a vestigial bud for male pleopod 2, a uniramous, 2- articled female pleopod 1 and a biramous, female pleopod 2 present in C. ehsani are also seen in C. aqabensis, although the exact morphology of the vestigial bud of male pleopod 2 does differ. Callianassa thailandica has a uniramous, weakly 2-articled male pleopod 1, male pleopod 2 is absent, the female pleopod 1 is uniramous but 3- articled and the female pleopod 2 is also absent. There are no data for the morphology of the female pleopods 1 and 2 in C. persica, and the male is recorded as having pleopods 1 and 2 absent.
The new species represents the only species of Callianassa (as currently understood) from the Gulf of Oman. Etymology. The new species is named in memory of University of Tehran biology student, Ehsan Entezari, for his enthusiasm to learn about nature.
description: Published as part of Sepahvand, Vahid, Tudge, Christopher & Momtazi, Farzaneh, 2018, Callianassa ehsani, a new species of Callianassidae (Crustacea, Decapoda, Axiidea) from Gulf of Oman, Iran, pp. 370-378 in Zootaxa 4410 (2) on pages 371-377, DOI: 10.11646/zootaxa.4410.2.6, http://zenodo.org/record/1221660