Persianorchestia nirvana

Momtazi, Farzaneh, Lowry, Jim & Hekmatara, Maryam, 2017, Persianorchestia, a new talitrid genus (Crustacea: Amphipoda: Talitridae) from Gulf of Oman, Iran, Zootaxa 4238 (1), pp. 119-126 : 120-125

Persianorchestia nirvana gen. et sp. nov.

( Figs 1–4 )

Types. Holotype male, 10 mm, INIOC 2-1 S, Gulf of Oman , Iran (approx. 25°13’N 60°54’E) coll. M. Hekmatara, 2013 . Paratypes: 1 female, 7 mm, INIOC 2-2 S, same locality as holotype .

Other material examined. 245 females, 2 males and 5 juveniles, INIOC 2-3 S, same locality as types.

Type locality. Gulf of Oman , Iran, (approx. 25°13’N 60°54’E) supralittoral zone.

Etymology. The species is named for the new-born baby of the first author.

Ecological type Sand-hoppers. Specimens were found 10–12 cm below the sediment surface on a supralittoral sandy beach.

Description. Based on holotype, male, 10 mm, INIOC 1-2S.

Eyes present, well developed, about 2/3 of head length. Antenna 1 short almost reaching end of peduncular article 4 of antenna 2. Antenna 2 shorter than half body length; peduncular articles slender with many small robust setae, article 5 the longest; flagellum with 19 articles, final article large, cone-shaped, virgula divina present. Upper lip with apical setal patch; epistome with robust setae. Lower lip distolateral setal tuft absent, with vestigial inner plates. Mandible left lacinia mobilis 5-cuspidate. Maxilla 1 with small palp, 1-articulate; inner plate with two plumose setae; outer plate with 9 dentate setae. Maxilliped palp article 2 distomedial lobe well developed; article 4 small, button-shaped.

Pereon. Gnathopod 1 sexually dimorphic; parachelate; coxa smaller than coxa 2, anteriorly produced; posterior margin of carpus and propodus each with lobe covered in palmate setae, palmate lobes in male only; carpus longer than propodus, 1.6 × as long as propodus, 1.9 × as long as broad; propodus subrectangular, anterior margin with 5 groups of about 11 robust setae, medial surface with 9 cuspidate setae; palm with 3 serrate setae, palm obtuse, without spine patch on posterodistal corner; dactylus longer than palm, simplidactylate, without anterodistal denticular patch. Gnathopod 2 sexually dimorphic; subchelate; basis slender; ischium with weak rounded lobe on mid-anterior margin, without anterodistal lobe on medial surface; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; carpus triangular, posterior lobe absent, not projecting between merus and propodus; propodus subovate, 1.6 × as long as wide, palm acute, smooth, with proximally protuberance, covered with robust setae; dactylus shorter than palm, broadly curved, without anteroproximal bump, posterior margin without proximal sinus.

Pereopods 3–4 coxae as wide as deep. Pereopods 3–7 cuspidactylate; dactyli without anterodistal patch of many rows of tiny setae. Pereopod 4 as long as third pereopod. pereopod 5 propodus 1.1 × long as carpus. Pereopods 6–7 not sexually dimorphic. Pereopod 6 shorter than pereopod 7; coxa rounded, with 1 marginal seta. Pereopod 7 basis without lateral sulcus, posterodistal lobe present; merus and carpus slender and extended.

Pleon. Pleopods 1–3 biramous, all well developed. Pleopod 1 peduncle with 8 setae on outer margin and 1 medio-facial seta. Pleopod 2 with 10 setae on outer margin and 3 medio-facial setae. Pleopod 3 peduncle outer margin with 7 setae and 5 medio-facial setae. Epimera1 –3, without stridulating organs, posteroventral corner with small subacute spine, ventral margin smooth. Epimeron 2 subequal in length to epimeron 3. Uropod 1 peduncle with 10 robust setae; rami with apical spear-shaped setae, inner ramus slightly shorter than outer ramus, inner ramus with 6 marginal robust setae in a row; outer ramus slender, without marginal robust setae. Uropod 2 not sexually dimorphic; rami with apical spear-shaped setae, inner ramus slightly shorter than outer ramus, with 10 marginal robust setae; outer ramus with 2 marginal robust setae in 1 row, inner ramus with 4 marginal robust setae. Uropod 3 well developed; peduncle with 4 robust setae; ramus subequal in length to peduncle, with 3 marginal robust setae, and 4 apical setae. Telson apically incised, with 5–6 robust setae per lobe.

Female (sexually dimorphic characters). Based on paratype, female, 7 mm, INIOC 2-2S. Antenna 2 less than half body length; peduncular article 5 subequal to article 4 in length. Gnathopod 1 simple; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; carpus 2.5 × as long as broad; propodus anterior margin with 3groups of 6 robust setae. Gnathopod 2 mitten-shaped; basis not expanded; ischium without lobe on anterior margin; posterior margin of carpus and propodus each with lobe covered in palmate setae; carpus well developed (not enclosed by merus and propodus), posterior lobe present, projecting between merus and propodus; propodus 2.5 as long as wide, palm obtuse; dactylus shorter than palm, straight, posterior margin smooth, not modified distally, blunt. Oostegites longer than wide (length greater than 2 × width), weakly setose (14–18), setae with simple smooth tips.

Remarks. The sex ratio for our sample is extremely skewed towards females. We have no answer for this. Lucia Fanini (pers comm) suggested that since it is a one-off collecting event, it is possible even though there is a huge sex bias. It could be related to reproductive strategy or differential zonation of the species. In these cases if multiple sampling events were carried out during the year and systematically across the littoral, then the overall sex ratio should be more even.

Distribution. Iran. Gulf of Oman.

Figures

FIGURE 1. Persianorchestia nirvana gen. et sp. nov., holotype male, 10 mm, INIOC 2 - 1 S, and paratype, female, 7 mm, INIOC 2 - 2 S. Gulf of Oman, Iran. Scale 1 mm.

FIGURE 2. Persianorchestia nirvana gen. et sp. nov., holotype male, 10 mm, INIOC 2 - 1 S, Gulf of Oman, Iran. Scale 1 mm.

FIGURE 3. Persianorchestia nirvana gen. et sp. nov., holotype male, 10 mm, INIOC 2 - 1 S, Gulf of Oman, Iran. Scale 0.5 mm.

FIGURE 4. Persianorchestia nirvana gen. et sp. nov., holotype male, 10 mm, INIOC 2 - 1 S, and paratype, female, 7 mm, INIOC 2 - 2 S. Gulf of Oman, Iran. Scale 0.5 mm.