Michaelcallianassa persica Sepahvand & Momtazi & Tudge 2020, sp. nov.

Michaelcallianassa persica sp. nov.

(Fig. 1)

Type material. Holotype: female (tl 23.6 mm, cl 6.7 mm), Persian Gulf, 25.5747848ºN, 53.7012269ºE, 38 m, INIOC1-221. Allotype: 1 damaged male (tl 26.4 mm, cl 7.8 mm), collected with holotype, INIOC1-222.

Diagnosis. Abdominal terga 3–5 each with a pair of longitudinal, anteriorly convergent grooves, with a transverse row of setae. Telson longer than wide, with two pairs of lateral movable spines as well as two spines dorsally in the center of the telson. Eyestalks tapering distally with well pigmented corneas. Maxilliped 3 propodus and carpus bearing dense setal pad on inner face. Major cheliped with ischium 4 times as long as wide, merus shorter than ischium, carpus 1.2 times as long as wide and chela 4 times as long as wide. Minor cheliped with ischium 4 times as long as wide, merus shorter than ischium and 2.4 times as long as wide, carpus 2.5 times as long as wide, chela 4 times as long as wide, and dactylus as long as length of palm.

Description. Female holotype. Carapace with triangular rostrum (Fig. 1C, D), reaching anteriorly to approximately two-third length of eyestalks, reaching corneas; carapace length about one quarter of total length; linea thalassinica extending to posterolateral margin of carapace; dorsal oval clearly demarcated by cervical groove (Fig. 1A, B, D). Length ratio of pleomeres 1–6 to telson measured anterior to posterior along midline 0.8: 1.8: 1.2: 1.0: 1.0: 1.6 (Fig. 1A, E). Pleomere 1 well-calcified; pleomere 2 glabrous dorsally (Fig. 1A); pleonal terga 3–5 (Fig. 1E) each with a pair of longitudinal, anteriorly convergent grooves, with large lateral round patches of setae; pleomeres 4–5 each with transverse row of setae; pleomere 6 about as long as wide, laterally excavate in posterior third.

Telson (Fig. 1F) rectangular in dorsal view, longer than wide; lateral margins concave proximally, then with 2 blunt triangular lobes more posteriorly, finally attenuating slightly to broadly rounded posterior angles; dorsal surface with 2 strong submedial spiniform setae. Posterior margin concave, bilobed, with 2 pairs of lateral spiniform setae. Uropodal endopod longer than telson, broadly triangular, 1.5 times as long as wide; posterior margin slightly convex; Exopod larger than endopod, 1.6 times as long as broad, anterior margin concave, posterior and distal margins continuous, strongly convex, dorsal plate with distal row of spiniform setae distinctly separated from setal row on posterior margin.

Eyestalks elongate and triangular with sharp distomedial tips (Fig. 1C, D); cornea located in distal third, with blackish pigments. Antennular peduncle (Fig. 1D) longer than antennal peduncle; article 1 much extended beyond eyestalk; article 3 longer than article 2. Antennal peduncle with rudimentary scaphocerite; article 5 about as long as article 4.

Third maxilliped (Fig. 1G) without exopod. Ischium rectangular, 2.1 times as long as wide; crista dentata of 8 sharp denticles; merus wider than long, combined length of ischium-merus about 4.2 times width. Carpus subovate, 2 times as long as broad bearing dense setal pad distally on the inner face, propodus sub-ovate, lower margin convex, smooth on upper margin, about as long as wide and slightly shorter than carpus with medial dense setal pad on the inner face. Dactylus digitiform, with stiff setae terminally.

First pereopods (chelipeds) unequal, dissimilar. Major cheliped (Fig. 1H) with ischium slender (3.0 times as long as broad), upper and lower margins unarmed. Merus about 1.5 times as long as wide; upper margin convex, smoothly rounded; lower margin almost straight. Carpus 1.2 times as long as wide, almost as long as merus, shorter than palm; upper margin almost straight, and lower margin weakly convex. Propodus about 1.6 times as long as wide (including fixed finger); upper and lower margins carinate. Palm sub-rectangular; dactylus hooked distally, about 0.8 times as long as palm, with dense setae on dorsal margin; fixed finger curved distally, cutting edge with six acute teeth, upper and lower margins bearing rows of long setae; narrow hiatus between fingers (Fig. 1H).

Minor cheliped (Fig. 1I) shorter, more slender and about 0.8 times length of larger cheliped. Ischium about 3.0 times as long as wide; upper and lower margins nearly straight, unarmed. Merus about twice as long as wide; upper and lower margins slightly convex, unarmed. Carpus about 2.3 times as long as wide, 1.2 times as long as merus, widened distally. Propodus lower margin straight with numerous setae; margins carinate; dactylus curved, almost as long as palm, unarmed on cutting edge; narrow hiatus between fingers (Fig. 1I).

Second pereopod (Fig. 1J) chelate. Ischium short, lower margin gently convex. Merus 3.0 times as long as ischium, about 3.0 times as long as greatest width. Carpus subtriangular, twice as long as wide. Propodus suboval with dense setae on lower margin, fixed finger margin smooth. Dactylus with dense setae on upper margin; cutting edge straight, smooth, terminating in corneous tip.

Third pereopod (Fig. 1K) hammer-shaped. Ischium broad, square. Merus subrectangular twice as long as broad. Carpus as long as merus, narrower than merus, widest subdistally, 2.5 times as long as wide. Propodus subquadrate, lower margin with prominent swollen proximal lobe overlapping carpus, upper margin straight, exterior surface scattered with short setae/setal clumps, upper and lower margins densely setose. Dactylus subtriangular, external margin densely setose.

Fourth pereopod (Fig. 1L) ischium rectangular, 2.2 times as long as wide; merus subrectangular, longer than ischium, unarmed; carpus shorter than merus, widest distally; propodus rectangular, as long as carpus, distolateral margin setose, lower distal corner forming weak subchela with dactylus; dactylus subtriangular, upper and lower margins slightly concave.

Fifth pereopod (Fig. 1M) chelate. Merus elongate; carpus shorter than merus, upper margin convex distally; propodus shorter than carpus, lower distal corner projecting to form a chela with dactylus, lateral margin distally with dense setae; dactylus hooked toward external side of fixed finger. Tips of dactylus and fixed finger obtuse.

Male pleopod 1 (Fig. 1N) uniramous, 2-articled; distal article concave distally, with 3 long distal setae. Male pleopod 2 (Fig. 1O) uniramous, 2-articled, article 2 about as long as elongate-ovate article 1, without setae.

Female pleopod 1 (Fig. 1P) uniramous, 2-articled; distal article long and straight. Female pleopod 2 (Fig. 1Q) uniramous, 2-articled; article 2 longer than article 1. Female pleopod 3 (Fig. 1R) biramous, foliaceous, and endopod bearing small, fused, narrow appendix interna on mesial margin.

Etymology: The new species is named after an older name for the country of origin, Persia.

Remarks: The new species brings to 25 the number of species of burrowing shrimps documented in the Persian Gulf and Gulf of Oman (Sepahvand & Tudge 2019). The new species is in possession of 6 spines on the cutting edge of large cheliped, the telson with 2 pairs of lateral spines as well as 2 spines in the mid-dorsal region, and the exopod has 4 movable spines on the distal margin. The present species agrees well with M. indica Sakai, 2002 and M. sinica Liu & Liu, 2009 in many diagnostic aspects, including body shape, the relative size and shape of pereopods 2–4, maxilliped 3, and the rostrum. However, they differ from Michaelcallianassa persica sp. nov as shown in the table 1.

Pleopod 1 and Pleopod 2 of Michaelcallianssa indica Sakai 2002 and M. sinica Liu & Liu 2009 are composed of three segments, while in the present study, and in Sepahvand et al., (2013), and Sepahvand & Sari (2010), these pleopods are composed of two segments. It seems that in callianassoids the second article of pleopod 1 or 2 has a shoulder which gives the appearance of a narrower distal section which could be misinterpreted as an articulation.

Using Sakai (2011), M. persica sp. nov. keys to Michaelcallianassa Sakai, 2002 but on the other hand using the key of Poore et al., (2019), the present new species assigns to Balsscallianassa Sakai, 2011. The keys of Sakai 2011 use the ornamentation of abdominal somites 3–5 for recognizing the genus Michaelcallianassa, while B. masoomi (Tirmizi 1970) and B. foresti (Le Loeuff & Intès, 1974) both in Balsscallianassa also have this type of ornamentation. Poore et al. (2019) emphasized the male major cheliped merus with a lower margin that is almost straight and male pleopod 2 being uniramous in defining the genus Michaelcallianassa, but these characters are also present in B. foresti (Le Loeuff & Intès 1974). It seems that the most reliable character state for delineation of these two genera is maxilliped 3.

It is also noted here that there can be differences in morphology between different size (and age) individuals, and it is possible that these smaller specimens of the new species, M. persica sp. nov. may be exhibiting some minor differences because of this. Further collection of more, and larger specimens of this species, will be useful to investigate this idea.

Among the known Cheramus -like species, Balsscallichirus masoomi (Tirmizi 1970) appears closest to the present new species in sharing the shape of the body, rostrum, pleomeres 2–5 and pereopods 2–4. However, B. masoomi (Tirmizi 1970) is readily distinguished from the present new species by its very narrow maxilliped 3, and armed ischium and merus of the large cheliped.