Heterosignum behbehanii sp. nov.

Figs 1, 2, 3, 4, 5 A, B

Etymology.

The species is named in honour of Dr Abdulmanaf Behbehani, a respected figure who taught Marine Biology and Ecology at Kuwait University and researched Kuwait's marine environment and Kuwait's intertidal macrofauna for over four decades.

Type material.

Holotype: • ♂, 1.12 mm (ZMH-K-64934), KUWAIT, Al-Salam Beach; 29°21.631'N, 47°57.204'E; 28. X. 2014; V. Grintsov leg. Paratypes: • 1 ♀, 1.34 mm (ZMH-K-64935), same data as the holotype • 1 ♂ 1.1 mm; 4 ♀♀ up to 1.25 mm (ZMH-K-64936), Umm Al-Maradim Island; 28°40.778'N, 48°39.207'E; 11. XI. 2014; V. Grintsov leg.

Diagnosis.

Eyes with 3 ommatidia; eyestalks with medium length, reaching proximal half of peduncular article 2 of antenna 2. Pereonites 2–7 with a pair of relatively short single lateral spine-like processes. The pleotelson has a relatively short anterior neck, length about 0.1 pleotelson length, lateral margins with 6 denticles each. Male pleopod 2 with an elongate, downwardly curved and distally pointed apex endopodal stylet.

Description.

Male: Body (Fig. 1 B) length 1.28 mm; about 2 times as long as wide, widest at pereonite 3.

Head (Fig. 1 B) 0.36 times as long as wide (including eyestalks); frontal margin convex, having pair of weak preocular lobes. Eyestalks (Figs 1 B, 4 A) arising from posterior half of head, reaching proximal half of peduncular article 2 of antenna 2, 0.62 length of head, eyes with 3 ommatidia.

Pereon (Figs 1 B, 4 A, 5 A) dorsal surface smooth; pereonite 1 laterally rounded, without lateral spine-like processes; pereonites 2–7 with a pair of short single lateral spine-like processes; pereonites 1–3 increasing in width and pereonites 4–7 decreasing in width. Pleonite 1 small, 0.26 times as long as wide, with pair of fine dorsal setae.

Pleotelson (Fig. 1 B, J) about 1.3 times longer than wide, anterior part narrow, about 0.13 times of total length of pleotelson, posterior part bulbous, tapering posteriorly, lateral margins each with 6 denticles, posterior margin rounded, ventral margins with a raw of small submarginal simple setae. Uropod (Fig. 1 I) cylindrical, endopod with 2 lateral and 6 apical setae; exopod about 0.3 length of endopod, with 3 apical setae.

Antennula (Fig. 1 C) peduncular article 1 shorter than article 2; article 2 with 1 simple and 3 small sensory palmate setae distodorsally; article 3 about 0.5 length of article 2, with 1 simple seta distally; flagellum with three articles, article 1 shortest, with 1 distoventral seta; article 3 subequal to article 2, distally with 1 long, 2 short setae and 1 aesthetasc.

Antenna (Fig. 1 D) with peduncle articles 1 and 2 combined about 0.8 length of article 3; peduncle article 3 with convex proximal protrusion bearing single seta, with 1 simple seta medially and 1 simple seta distally; article 4 about half length of article 3, with 2 distolateral setae.

Mandible (Fig. 1 E) incisor process with 5 and lacinia mobilis with 4 cusps; spine row with 4 robust serrate setae.

Maxillula (Fig. 1 F): lateral lobe with 9 robust apical setae; medial lobe with 4 robust serrate setae on distal margin.

Maxilla (Fig. 1 G) lateral and mesial lobes, each with 4 pectinate robust apical setae; medial lobe with 9 robust setae along distal margin, some of them serrated.

Maxilliped (Fig. 1 H) endite distal margin with 1–2 fan-shaped setae, 3 serrate setae, and 1 sub marginal seta medially, mesial margin with 2 coupling hooks; palp article 1 with 1 short seta laterally; article 2 shorter than article 3 with 2 setae medially; article 3 with 3 setae medially and 1 seta laterally; article 4 subequal in length to article 3, with 3 setae distomedially; article 5 narrowest, with 5 setae distally.

Pereopod 1 (Fig. 2 A) shorter than pereopods 2 – 7: basis 3.6 times as long as greatest width, superior margin with 1 and inferior margin with 2 small setae; ischium 0.5 times as long as basis, with 2 long setae distally; merus shorter than carpus, superior margin with 1 robust seta medially, with 2 robust setae on inferodistal corner; carpus inferior margin with 4 denticles, 3 robust setae and 1 submarginal simple seta, superior margin with 1 simple seta on distal corner; propodus longer than carpus, with 3 robust setae on inferior margin; dactylus with 1 subapical simple seta, unguis subequal in length to dactylus, accessory claw length 0.6 unguis length.

Pereopod 2 (Fig. 2 B) basis about 3.5 times as long as greatest width; ischium about 0.9 times as long as basis, with 1 long seta on inferior margin; merus about 0.5 times as long as carpus, inferior margin with 2 and superior margin with 1 long simple setae; carpus and propodus subequal in length, carpus inferior margin with 3 robust setae, superior margin with 1 seta medially and 2 simple long setae on distal corner; propodus inferior margin with 3 robust setae and 1 long simple seta, superior margin with 3 long simple setae; dactylus with 2 subapical simple setae, a small accessory claw, unguis 1.5 times as long as dactylus.

Pereopod 5 (Fig. 2 C) basis about 3.8 times as long as greatest width; ischium about 0.92 times as long as basis, with 1 long seta on inferior margin and 2 long setae on superior margin; merus about 0.46 times as long as carpus, inferior and superior margin with 2 simple setae each; carpus shorter than propodus, with 2 robust setae on inferior margin and 1 simple seta on superior margin medially; propodus inferior margin with 3 robust setae, superior margin with 3 simple setae; dactylus with 2 subapical simple setae; unguis 1.4 times as long as dactylus.

Pereopod 7 (Fig. 2 D) basis about 3.8 times as long as greatest width; ischium about 0.85 times as long as basis, with 1 long seta on inferior margin; merus about 0.47 times as long as carpus, inferior and superior margins with 1 long simple seta; carpus shorter than propodus, with 2 robust setae on inferior margin; propodus inferior margin with 2 robust setae, superior margin with 3 simple setae; unguis 1.5 times as long as dactylus.

Pleopod 1 (Fig. 3 A) distally separate, with 2–4 apical setae; short lateral projections present, each projection with 1–2 setae.

Pleopod 2 (Fig. 3 B) protopod length 2.4 width, with 16 simple marginal setae; second article of endopod elongate, downwardly curved, proximally swollen, becoming narrower until distal pointed apex, about 2.4 as long as protopod, without any ornamentation.

Pleopod 3 (Fig. 3 C), endopod with 2 long plumose setae apically and 1 long plumose seta laterally; exopod composed of two articles, narrower than endopod; article 2 with 1 terminal seta.

Penes (Fig. 3 D) fused along basal part, well separated at distal part, tapering to narrowly rounded apices.

Female (Figs 1 A, 4 B, 5 A, B). Similar to males in the morphology of all pereonal appendages. Body broader than in males, about 1.8 times as long as wide; widest at pereonite 3. The largest female length is 1.34 mm. Operculum (Fig. 3 E) ovate, 1.2 times as long as broad, without any marginal setae.

Remarks.

Heterosignum behbehanii sp. nov. is most similar to H. elegans Shimomura & Mawatari, 2002 from Japan, as both of these species have lateral spine-like processes on pereonites 2–7, a pleotelson with 6 denticles on its lateral margins of the posterior part, and pleopod 2 with a slender very long, curved second article of the endopod. However, the new species is distinguished from H. elegans in having its notably shorter lateral spine-like processes on pereonites 2–7, a smaller anterior part of the pleotelson (about 0.1 vs. 0.4 times the total length of pleotelson), and the first pleopod being distally separate instead of distally connected.

The new species differs from Heterosignum unicornis (Kensley, 1976), the only species reported from the Indian Ocean (southern Indian Ocean, Amsterdam Island). Heterosignum unicornis has a stout mid-dorsal spine (horn) on the first pereonite, lacking lateral spine-like processes on pereonites 5–7, and a pleotelson with 4 denticles on its lateral margins.