Atarbolana makranensis, a new species of Cirolanidae (Crustacea, Isopoda) from Makran, Iranian coast of the Gulf of Oman

Abstract Atarbolana makranensis sp. n. is described from the intertidal zone of Makran along the Iranian coast of the Gulf of Oman. Atarbolana makranensis sp. n. can be recognized by the presence of a tuft of long setae on the antennal flagellum of males, elongate pleotelson with 12 robust marginal setae, pleotelson with narrowly rounded apex extending well beyond the uropodal endopod, uropodal endopod half as long as exopod with 14 robust marginal setae, and appendix masculina with an acute apex and extending beyond endopod distal margin. A key is provided for the four known species of Atarbolana Bruce & Javed, 1987.


Introduction
The isopod fauna of the Gulf of Oman is poorly studied; in particular, there is no record of this group from the northern coast of the Gulf of Oman. Among the different families, the family Cirolanidae has received little attention in the southern coastlines of Iran. Recently, Khalaji-Pirbalouty and Wägele (2011) described two cirolanid isopods, Baharilana kiabii and Cirolana tarahomii, from the Qeshm and Kish islands along Iranian coast of the Persian Gulf.
The genus Atarbolana Bruce & Javed, 1987, was established with the description of A. exoconta from the rocky intertidal coast of Manora Island, Pakistan. Atarbolana setosa Yasmeen, 1989, andA. dasycolus Yasmeen, 2004, have been subsequently described from the same coast (Karachi, Pakistan). Atarbolana makranensis sp. n. constitutes the fourth species of the genus from the northwestern Indian Ocean and is the first species of the order Isopoda recorded from the Iranian coast of the Gulf of Oman (Fig. 1).

Materials and methods
Specimens for this study were collected by turning over rocks and washing algae and sea grasses. The material was preserved in 96% ethanol and has been deposited in the Zoological Museum Hamburg, Hamburg, Germany (ZMH), and the Zoological Museum, University of Tehran, Iran (ZUTC). Appendages were dissected and fixed in stained antibacterial glycerine-gelatine (Merck). Drawings were made with the aid of a camera lucida attached to Olympus BX 51 and were then processed using Corel Draw (version X5) and Adobe Photoshop (version CS5). Terminology of the morphological characters follows that of Khalaji-Pirbalouty and Bruce (2014).   Javed and Yasmeen (1989), and A. dasycolus Yasmeen, 2004. Diagnosis. Diagnoses to the genus are to be found in Bruce and Javed (1987) and Javed and Yasmeen (1989).
Remarks. In addition to the generic diagnosis given by the above authors, pereopod 7 has a flattened merus and carpus with numerous long plumose setae. Female is similar to male but smaller on average. As stated by Bruce and Javed (1987), females differ from males (apart from primary sexual characteristics) by having a shorter and less setose antennal flagellum. Pleotelson elongation is less than that in males and in most cases number of robust setae are less than in those of males. In contrast to the diagnosis given by Bruce and Javed (1987), uropod rami of females are smaller than that of males; they are subequal and extending almost to the level of pleotelson apex or slightly extending beyond. Brood pouch composed of five pairs of oostegites arising on sternites 1-5.
There are several characters that exclude the species of this genus from Cirolana Leach, 1818, and other cirolanid genera. These characters are a cylindrical uropod exopod, an oval uropod endopod, the uropod peduncle with a row of robust setae along the ventral margin, and in having a reduced pleon.
The genera Eurylana Jansen, 1981, andPseudolana Bruce, 1979, with appendix masculina inserted medially, and short penes, appear to be most similar to Atarbolana.
However, Eurylana has no secondary unguis on the dactylus and is readily separated from congers by the morphology of the clypeal region and pleopods. Pseudolana differs in having a linear frontal lamina, five visible pleonites and a wide pleotelson (Bruce 1986). In addition, Atarbolana has endopods of pleopods 3-5 entirely without marginal setae. Only few genera like Anopsilana Paulian & Deboutteville, 1956 have such character, but with appendix masculine arising basally and absence of penes.
Diagnosis. Body 2.3 times as long as greatest width; pereonites 5-7, pleon and pleotelson bearing scattered small tubercles; flagellar articles 1-10 in male bearing a tuft of long serrate and simple setae; pleotelson elongated, with narrowly rounded apex, posterior margin with 12 marginal RS; uropod peduncle ventro-mesial surface with a row of 8 RS, uropodal endopod not reaching to pleotelson apex, with 14-15 (left/right) marginal RS, lateral margin proximally lacking RS, exopod about two times as long as endopod; appendix masculina with an acute apex, arising above mid-point of endopod medial margin, and extending slightly beyond endopod distal margin.
Antenna (Fig. 2D) peduncle articles 2-4 subequal in length, all articles each with a group of long simple setae on antero-distal corner, article 3 with 5-6 very long simple setae on ventral margin; flagellum with 17 articles, extending to posterior margin of pereonite 1, articles 1-10 bearing a tuft of long setae (some serrated), distoventral corner with a single long simple seta.
Pereopod 1 (Fig. 4A) basis 3.4 times as long as wide, superior margin with 3 long simple and 2 SPS, posterodistal angle with 3-5 long finely plumose setae; ischium inferior margin with 2 long simple setae, mediodistal margin with 3 long simple setae; merus inferior margin with 3 RS and 1 long simple setae, medio-distal margin with 1 long simple setae, superior margin with 3 long simple setae; carpus triangular, inferior margin with 2 RS and 4 long simple setae; propodus inferior margin with 10 RS and 3 sets of sub-marginal slender simple seta, superior margin with a single simple seta, superodistal angle with 2 simple and 1 plumose setae; dactylus with minute secondary unguis, bearing a transverse row of 8 simple setae at base.
Pereopod 2 (Fig. 4B) basis 2.5 times as long as wide, superior margin with 5 long simple and 3 SPS, posterodistal angle with 5 long finely plumose or simple setae; ischium inferior margin with 6 long simple setae, mediodistal margin with 3 long simple setae, superior margin with 3 long simple setae; merus inferior margin with 4 RS and 4 long simple setae, superodistal angle with 5 long setae, mediodistal margin with 2 long simple setae; carpus triangular, inferior margin with 2 RS and 3 long simple setae; propodus inferior margin with 7 robust and 2 sets of sub-marginal slender simple setae, superior margin with a single simple seta, supero-distal angle with a SPS and 3 simple setae; dactylus with minute secondary unguis, bearing a transverse row of several simple setae at base.
Pereopod 3 (Fig. 4C) similar to pereopod 2. Pereopod 4 (Fig. 4D) basis 2.3 times as long as wide, with 5 long simple submarginal and 2 SPS, postero-distal angle with 3 long simple setae and 2 long finely biserrate setae; ischium supero-distal angle with 2 long RS, supero-medial surface with 4 long simple setae, inferior margin with 2 sets of RS and 2 sets of long simple sub-marginal setae; merus inferior margin with 2 sets of RS (1 + 7), superior distal angle with 3 RS and 1 long simple seta; carpus inferior distal margin with 6 simple or serrated RS, superior distal angle with 2 RS; propodus inferior margin with 3 RS, superior distal angle with 1 SPS and 2 simple setae; dactylus with minute secondary unguis, sub-marginal row of 3 simple setae.
Pereopod 7 (Fig. 5C) basis 2.5 times as long as wide, postero-distal angle with 1 serrated RS and 4 long simple setae; ischium superior distal angle with 5 biserrate or simple RS, medial surface with 3 rows of long simple setae, inferior margin with 3 sets RS and 2 sets long simple sub-marginal setae; merus and carpus superior and inferior margins fringed with numerous long plumose setae; propodus inferior margin with 2 sets robust setae, superior distal angle with 1 RS, I simple and 1 SPS; dactylus with minute secondary unguis.
Female. Apart from sexual characters differs from male by having an antenna without tuft of long setae on flagellum articles; uropod rami smaller than in male and extending just beyond the pleotelsonic apex, endopod with 12 marginal RS (rather than 14 in male); pleotelson with 8 marginal RS (rather than 12 in male), elongation less than in male.