Orchestia xylino, Lowry, J. K. & Fanini, Lucia, 2013

Lowry, J. K. & Fanini, Lucia, 2013, Substrate dependent talitrid amphipods from fragmented beaches on the north coast of Crete (Crustacea, Amphipoda, Talitridae), including a redefinition of the genus Orchestia and descriptions of Orchestia xylino sp. nov. and Cryptorchestia gen. nov., Zootaxa 3709 (3), pp. 201-229 : 208-212

Orchestia xylino sp. nov.

( Figs 2–5 )

Type material. Holotype, male, 13.1 mm, AM P.89967, Gournes, Heraklion, Crete, Greece (35°20'1"N 25°16'82"E), mixed west beach, transect A-trap 3, L. Fanini, November 2011. Paratype, female, 10.6 mm, AM P.89968; male, 11.4 mm, AM P.89969, same collection data as holotype.

Additional material examined. 4 specimens, AM P.89339, Gouves, Heraklion, Crete, Greece (35°20'9"N 25°18'24"E), cobble beach, transect B - trap 4, L. Fanini, March 2012; 1 specimen, AM P.89340, Gouves, Heraklion, Crete, Greece, (35°20'9"N 25°18'24"E), cobble beach, transect B - trap 3, Fanini, February 2012; About 58 specimens, P.89338, Gournes, Heraklion, Crete, Greece (35°20'1"N 25°16'82"E), mixed west beach, transect B - trap 3, L. Fanini, November 2011; 85 specimens, AM P.89337, Gournes, Heraklion, Crete, Greece (35°20'1"N 25°16'82"E), mixed west beach, transect A - trap 3, L. Fanini, November 2011.

Type locality. Gournes, Heraklion, Crete, Greece (35°20'4"N 25°6'49"E).

Etymology. Named for the restaurant directly behind the type locality where the samples for this study were initially processed.

Diagnosis (based on adult male). Gnathopod 1 carpus with cup-shaped palmate lobe. Gnathopod 2 dactylus posterior margin with posteroproximal sinus. Pleopod 7 sexually dimorphic (merus and carpus slightly enlarged). Telson with 10+ apical and lateral robust setae per lobe.

Description. Based on holotype, male, 13.1 mm, AM P.89967.

Head with two groups of small setae on ventroproximal surface. Antenna 1 short, not reaching middle article 4 of antenna 2 peduncle. Antenna 2 shorter than head and first 3 pereonites; peduncular articles slender; peduncular article 3 without plate or process ventrally; article 5 slightly longer than article 4; peduncular articles rugose with sparse, small robust setae, final article cone-shaped, with apical cluster of 'imbricated' setae. Labrum with a few robust setae; epistome with many pores; with apical setal patch. Mandible left lacinia mobilis 5-dentate (fifth tiny). Maxilliped palp article 2 with well developed distomedial lobe; article 4 reduced, button-shaped.

Pereon. Gnathopod 1 sexually dimorphic; subchelate; coxa 1 smaller than coxa 2; posterior margin of carpus and propodus each with lobe covered in palmate setae (carpal lobe truncated, sunken to form a hollow cup-like structure covered in palmate setae), carpus 3 × as long as broad, 2 × as long as propodus; propodus subrectangular, anterior margin with 3 groups of robust setae, medial surface with 4 cuspidate setae, posteromedial surface with 3 serrate setae, posterior margin with 6 cuspidate setae; palm transverse, with about 14 serrate setae in two rows; dactylus subequal in length to palm. Gnathopod 2 sexually dimorphic; subchelate; basis slender; merus with distally rounded posterodistal lobe on medial surface; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; carpus triangular, reduced (enclosed by merus and propodus), posterior lobe absent, not projecting between merus and propodus; propodus subovate, 1.3 × as long as wide; palm acute, reaching 40% along posterior margin, palm with shallow distal sinus, lined with robust setae, without protuberance or shelf near dactylar hinge, without palmar protuberances; posteromedial surface of propodus with groove; with cuticular patch at corner of palm; dactylus subequal in length to palm, posterior margin with posteroproximal sinus, spatulate distally. Pereopods 2–4 coxae about as wide as deep. Pereopods 3–7 cuspidactylate. Pereopods 3–7 dactyli with anterodistal patch of many rows of tiny denticles. Pereopod 4 subequal or slightly shorter than pereopod 3; carpus significantly shorter than carpus of pereopod 3; dactylus thickened proximally with a notch midway along posterior margin; dactylus with anterodistal setal patch. Pereopod 5 propodus subequal to or slightly shorter than carpus. Pereopods 6–7 long (1/2 length of body). Pereopod 6 not sexually dimorphic; subequal in length to pereopod 7; posterior lobe inner view posteroventral corner rounded, coxa posterior margin perpendicular to ventral margin, posterior lobe without ridge, posterior lobe with 5 or more marginal setae. Pereopod 7 sexually dimorphic (merus and carpus slightly incrassate); basis lateral sulcus present, slightly pronounced, posterodistal lobe present, shallow, broadly rounded; carpus into subtriangular plate.

Pleon. Pleopods all well developed. Pleopod 1–3 biramous; rami longer than peduncles. Epimeron 2 longer than epimeron 3. Epimeron 3 posterior margin smooth, with minute setae, posteroventral corner with small subacute tooth, ventral margin without robust setae. Uropod 1 peduncle with about 16 robust setae, peduncle distolateral robust seta present, small (less than 1/4 length of outer ramus), with simple tip; inner ramus subequal in length to outer ramus, inner ramus with 6 marginal robust setae in 2 rows; outer ramus with how many marginal robust setae. Uropod 2 not sexually dimorphic; peduncle number of robust setae with 3–6 robust setae; inner ramus subequal in length to outer ramus, with 6 marginal robust setae; outer ramus with 1 marginal robust seta. Uropod 3 peduncle with 5 robust setae; ramus subequal in length to peduncle, ramus linear (narrowing), with 4–5 apical setae. Telson broader than long, apically incised, dorsal midline entire, with 10–11 marginal and apical robust setae per lobe.

Female (sexually dimorphic characters). Based on paratype, female, 10.6 mm, AM P.89968. Gnathopod 1 posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; posterior margin with 2 cuspidate setae; with about 3 serrate setae. Gnathopod 2 mitten-shaped; basis expanded anteroproximally; merus without distally rounded posterodistal lobe on medial surface; carpus well developed (not enclosed by merus and propodus), posterior lobe present, projecting between merus and propodus; palm extremely acute, smooth, not lined with robust setae, nearly straight; without cuticular patch at corner of palm; dactylus not modified distally, blunt.

Habitat. Marine supralittoral living on mixed sand, coarse gravel and boulder stone beaches.

Remarks. Orchestia xylino is similar to other Mediterranean species such as O. montagui and O. stephenseni . It is a distinctive species easily recognised by the tan to brown colouration of the posterior part of its body. In addition, it has a number of unique characters such as: a rugose cuticle on antenna 2; a set of setae on the side of the head; a cup-shaped palmate lobe on the carpus of male gnathopod 1, which makes the carpus appear not to have a lobe; and a slightly incrassate merus and carpus on male pereopod 7.

Orchestia xylino is currently known only from coarse gravel and boulder beaches on the north coast of Crete east of Heraklion.

Distribution. Kokkini Hani, Gournes and Gouves, Crete, Greece (this study).

Figures

FIGURE 2. Orchestia xylino sp. nov., holotype, male, 13.1 mm, AM P. 89967, habitus, A 1, A 2, U 1 – 3, paratype, male, 11.4 mm, AMP. 89968, UR, T, Gournes, Heraklion, Crete, Greece. Scale lines represent 0.1 mm, except UR, U 1 represent 0.2 mm.

FIGURE 3. Orchestia xylino sp. nov., holotype, male, 13.1 mm, AM P. 89967, Gournes, Heraklion, Crete, Greece. Scale lines represent 0.1 mm, except MX 1 OP represents 0.05 mm.

FIGURE 4. Orchestia xylino sp. nov., holotype, male, 13.1 mm, AM P. 89967, all parts except, paratype, male, 11.4 mm, AM P. 89968, * G 1, * G 2, female, paratype, 10.6 mm, AM P. 89969, Gournes, Heraklion, Crete, Greece. Scale lines represent 0.2 mm.

FIGURE 5. Orchestia xylino sp. nov., holotype, male, 13.1 mm, AM P. 89967, all parts except, female, paratype, 10.6 mm, AM P. 89969, Gournes, Heraklion, Crete, Greece. Scale lines for P 5 – 7 represent 1.0 mm, remainder represent 0.2 mm.