Sea snakes (Elapidae, Hydrophiinae) in their westernmost extent: an updated and illustrated checklist and key to the species in the Persian Gulf and Gulf of Oman Author Rezaie-Atagholipour, Mohsen Author Ghezellou, Parviz Author Hesni, Majid Askari Author Dakhteh, Seyyed Mohammad Hashem Author Ahmadian, Hooman Author Vidal, Nicolas text ZooKeys 2016 622 129 164 http://dx.doi.org/10.3897/zookeys.622.9939 journal article http://dx.doi.org/10.3897/zookeys.622.9939 1313-2970-622-129 371E464E6EF34E649D98ABC99ED71A52 Taxon classification Animalia Squamata Elapidae Hydrophis schistosus Daudin, 1803 Figures 3a, 4e, 5, 6, 7 Hydrophis schistosus Daudin, 1803: 386. Enhydrina schistosa - Boulenger 1887 : 408. - Boulenger 1896 : 302. - Smith 1926 : 39. - Volsoe 1939 : 14. - Gasperetti 1988 : 306. - Leviton et al. 1992 : 120. - Carpenter et al. 1997 : 246. - Firouz 1999 : 191. - Latifi 2000 : 336. - Baldwin and Gardner 2005 : 248. - Firouz 2005 : 209. - Soorae et al. 2010 : 535. - Egan 2007 : 143. - Safaei and Esmaili 2009 : 45. - Rastegar-Pouyani et al. 2008 : 20. Hydrophis schistosus - Kamali 2013 : 242. - Safaei-Mahroo et al. 2015 : 282. Material examined. Persian Gulf: 1 specimen, Larak Island [(ZMSBUK.HD.58), TL 971, SVL 857, HL 29.6, HW 12.6, GL 18.4, SNL 5.3, NEL 3.1, ND 52, GBD 100, NSL 7, NSR 47, BSR 57, NV 301], February 2014, collector: M. Ghavasi. Gulf of Oman: 8 specimens, Jask and Ras-Meydani, depth 18-50m [(ZMSBUK.HD.14), TL 1147, SVL 1008, HL 29.4, HW 14.5, GL 20.8, SNL 5.3, NEL 3.7, ND 55, GBD 95, NSL 8, NSR 48, BSR 55, NV 315; (ZMSBUK.HD.21), TL 1180, SVL 1064, HL 31.2, HW 12.3, GL 22.4, SNL 5.4, NEL 3.4, ND 54, GBD 109, NSL 9, NSR 51, BSR 57, NV 303; (ZMSBUK.HD.25), juvenile, TL 508, SVL 451, HL 17.9, HW 7.7, GL 12, SNL 2.9, NEL 1.3, ND 26, GBD 39, NSL 8, NSR 51, BSR 59, NV 344; (ZMSBUK.HD.41), TL 1093, SVL 977, HL 30.5, ND 51, GBD 95, NSL 8, BSR 60; (ZMSBUK.HD.45), TL 1057, SVL 943, HL 31.3, HW 18, GL 20.5, SNL 4.4, NEL 3.9, ND 48, GBD 96, NSL 7, NSR 47, BSR 60, NV 323; (ZMSBUK.HD.50), TL 1172, SVL 1064, HL 36.7, HW 19.3, GL 23.7, SNL 5.5, NEL 4.6, ND 60, GBD 105, NSL 8, NSR 51, BSR 61, NV 316; (ZMSBUK.HD.51), TL 932, SVL 823, HL 28.4, HW 13.7, GL 17.7, SNL 5.6, NEL 3.4, ND 45, GBD 98, NSL 8, NSR 50, BSR 61, NV 325; (ZMSBUK.HD.52), TL 1230, SVL 1093, HL 35.2, HW 16.6, GL 23.5, SNL 4.8, NEL 4.4, ND 62, GBD 116, NSL 8, NSR 53, BSR 65, NV 340], October and November 2013, collector: M. Rezaie-Atagholipour; 3 specimens, Jask, mangrove swamps, depth 1-3m [(ZMSBUK.HD.27), TL 966, SVL 855, HL 28.3, HW12.3, GL 19.7, SNL 4.9, NEL 3.7, ND 44, GBD 90, NSL9, NSR 52, BSR 59, NV 327; (ZMSBUK.HD.29), TL 1080, SVL 947, HL 30.5, HW 18.1, GL 17, SNL 5.6, NEL 4.1, ND 50, GBD 80, NSL 9, NSR 40, BSR 58, NV 348; (ZMSBUK.HD.62), TL 1032, SVL 907, HL 28.5, HW 16, GL 20.1, SNL 5.2, NEL 4.5, ND 52, GBD 88, NSL 8, NSR 47, BSR 59, NV 327], December 2013, collector: M. Rezaie-Atagholipour; 2 specimens, Beris and Pasa-Bandar, depth 20-40m [(ZMSBUK.HD.49), TL 1044, SVL 928, HL 30.8, HW 12.7, GL 19.3, SNL 5, NEL 3.7, ND 50, GBD 105, NSL 7, NSR 51, BSR 64, NV 302; (ZMSBUK.HD.53), TL 1095, SVL 955, HL 31.9, HW 14.7, GL 19.4, SNL 2.5, NEL 4.2, ND 50, GBD 95, NSL 8, NSR, BSR, NV, NB], August 2013, collector: M. Rezaie-Atagholipour. Diagnosis. Head of medium size; rostral beaked-shaped, elongate with decurved and pointed tip (Figures 2a, 3a); mental elongate, slender and dagger-shaped, hidden in the groove between chin shields (Figures 3a, 6c); body slightly elongate, not markedly slender anteriorly (Figure 6 e-f ); 301-348 ventrals [340-354 ( Volsoe 1939 )], small and more or less indistinguishable from adjacent scales at mid-body (Figure 4e); 40-55 scale rows on neck and 53-65 on body [47-52 and 56-60 ( Volsoe 1939 )]. Coloration . Gray or dark olive dorsally, whitish ventrally; body rings developed in juveniles but paler or absent in adults (Figure 6e); exceptionally black dorsally (Figure 6f). Size. Mean TL 1036 mm, maximum 1230 mm (n = 14) [n = 3, maximum TL 1350 mm ( Volsoe 1939 )] General distribution. Indo- West Pacific, from the Persian Gulf to Australia ( David and Ineich 1999 ). IUCN Red List Category. Least concern ( IUCN 2016 ). Remarks. Hydrophis schistosus is distinct from other species in the Persian Gulf and Gulf of Oman due to its beaked-shaped rostral and dagger-shaped mental. Results of our field surveys showed that the species is more abundant in the Gulf of Oman rather than in the Persian Gulf. This is supported by other studies as eight specimens have been hitherto examined from the Gulf of Oman ( Boulenger 1887 , 1896 ; Smith 1926 ; Volsoe 1939 ) versus three specimens from the Persian Gulf ( Corkill 1932 ; Smith 1926 ; present study). Furthermore, during two months boat surveys in Hara (mangrove) Biosphere Reserve in the eastern Persian Gulf, only two specimens of the species were found ( Rezaie-Atagholipour et al. 2012 ). Nonetheless, two specimens collected by Rezaie-Atagholipour et al. (2012) and the only specimen collected in this study were from Strait of Hormoz in the boundary of the two gulfs. Therefore these three specimens may be vagrant, and can not be strictly allocated to a particular population in the Persian Gulf. Concerning the two remaining specimens reported from the Gulf by Corkill (1932) and Smith (1926) , no exact locality was mentioned. In conclusion, populations of Hydrophis schistosus in the Persian Gulf seem likely to be in low abundance. On the other hand, results of this study showed that the species is one of the most abundant sea snakes in the Gulf of Oman. In total, 26 % of all specimens examined here were Hydrophis schistosus , all but one collected from the Gulf of Oman. Approximately 71% (261 of 367 specimens) of sea snakes that Safaei and Esmaili (2009) collected from coastal waters of Hormozgan Province (eastern Persian Gulf and western Gulf of Oman) were Hydrophis schistosus . They mentioned that most of these specimens were collected from Gulf of Oman. They failed however to report the exact proportions. Mating behavior of the species was sighted during a boat survey through coastal waters of Jask (western Gulf of Oman) in December 2013, the two animals having been seen intertwined and floating on the surface (Figure 7). Hydrophis schistosus is an aggressive sea snake. This snake is prey-specific, mostly consuming spiny catfishes ( Glodek and Voris 1982 ; Voris and Moffett 1981 ). Recent morphological and molecular evidence revealed that this species consists of two convergent lineages through its geographical distribution range. Now, the Australian lineage is elevated to species status and provisionally referred as to Hydrophis zweifeli (see Ukuwela et al. 2013 ).