Siphonoecetes (Centraloecetes) bulborostrum, De-La-Ossa-Carretero, Jose Antonio & Martí, Amparo, 2014

De-La-Ossa-Carretero, Jose Antonio & Martí, Amparo, 2014, A new species of Siphonoecetes Krøyer, 1845 Siphonoecetes (Centraloecetes) bulborostrum sp. nov. (Crustacea, Amphipoda, Ischyroceridae) from the western Mediterranean, coast of Iberian Peninsula, Zootaxa 3765 (1), pp. 69-76 : 71-74

Siphonoecetes (Centraloecetes) bulborostrum sp. n.

Siphonoecetes (Centraloecetes) sp. n. Marti (1996) p.111

Diagnosis. Body length up to 4,8 mm. Rostrum angular, apically rounded, moderately produced and reaching eye lobes, with a bulbous projection easily recognizable in a frontal view. Antenna 1 reaching antenna 2 peduncle article 5. Antenna 1 flagellum with four well-developed articles and terminal rudimentary article. Article 4 of peduncle on antenna 2 longer than article 5, flagellum with 4 articles, with two spines on article 3. Gnathopod 1 bearing 3 spines on posterior margin of propodus and 1 posterodistal spine on carpus. Gnathopod 2 propodus with 5 posterior spines; carpus with 1 spine. Uropod 1 and 2 rami unequal in length, inner shorter, 3/5 or more the length of outer ramus. Males with bulbous ventroapical projection on peduncle of uropod 1. Uropod 3 peduncle with 3–4 plumose setae and 1 spine.

Material examined. Holotype, male, 3.76 mm ( MNCN 20.04/9253). Paratype female, 3.26 mm ( MNCN 20.04/9254). Four specimens ( MNCN 20.04/9255), and ten specimens in personal collection of the authors for a total of 15 paratypes.

Type locality. Alicante coast (Alicante, East of Spain), 38º18.570´N 0º30.468´W, depth 10 m, (Station 1, Table 1 and Fig. 1 ).

Etymology. Named after the rostral projection.

Description. Based on holotype male, 3.76 mm. Except mouthparts that corresponded to other male of similar size.

HEAD as long as pereonite 1 and 1/2 of pereonite 2 combined along dorsal midline. Rostrum angular, apically rounded, in dorsal view reaching apices of eye lobes, with a bulbous subdorsal projection easily recognizable in a frontal view that seems to be covered by papilla. Eye lobes rounded. Eyes well-defined ( Fig. 2 ).

Antenna 1 as long as head, pereonites 1–5 and half of pereonite 6 combined, reaching to antenna 2 peduncle article 5, flagellum with four well-developed articles and terminal rudimentary article. Antenna 2 approximately as long as head, pereonites 1–6 and half of pereonite 7 combined; ventral projection of article 2 with two pairs of setae, article 4 little longer than 5, flagellum with 4 articles, with two spines in article 3.

Mouthparts normal, similar to other species of same subgenera ( Fig. 3 ). Maxilliped, inner and outer plate with 3–7 apical spines, with setae on distal margins. Long palp 4-segmented; articles 2–4 with setae. Second maxillae with setae; outer plate longer than inner. First maxillae with outer plate bearing 5–7 apical spines; palp 2- segmented with setae in distal margin. Mandibles left and right identical, mandibular palp developed, with long and pectinate setae; incisor and molar process well-developed. Lower lip, outer and inner lobes with setae on apical and medial margins; mandibular lobe developed.

PEREON. Coxal plates (1–4) longer than broad, rounded corners anteriorly prolonged, especially coxae 1 and 3, and with setae on anterior margin; plates 5–7 rounded, as long as broad, with setae. Gnathopod 1, basis with anterior margin straight, posterior margin convex with long setae; carpus 2.5 longer than wider with groups of setae in posterior margin and 1 posterodistal spine; propodus slender, 3 times longer than wider, bearing 2–3 spines on posterior margin, with setae in anterior and posterior margin; dactylus with 4 teeth and setae on posterior margin. Gnathopod 2, basis with anterior margin almost straight, posterior margin convex, with scattered long setae; carpus with a posteriodistal spine; propodus with groups of setae on anterior and posterior margins, palm with 5 spines increasing in length and with a slight excavation at middistal margin that end in a tooth; dactylus with 4 teeth and setae. Pereopods 3-4 basis with convex anterior margin and with scattered long and short setae, straight posterior margin with scattered setae; merus with 2 groups of setae on mid anterior margin, a tuft of long short setae on apex of anterior projection, 4–5 groups of setae on posterior margin, anterior and posterior merus lobes extending beyond carpus; propodus shorter than dactylus and with setae on palm. Pereopods 5–6 basis anterior margin with groups of long setae, posterior margin straight with scattered short setae; merus with a group of pectinate setae in posterior distal corner; propodus posterior margin with a spine and a long distal seta; dactylus bifurcate. Pereopod 7, basis anterior and posterior margin densely setose; propodus anterior margin with 3 groups of long setae; dactylus bifurcate.

UROSOME. Urosome smooth. Epimeral plates 1 and 2 as long as broad, rounded and with 3−4 long setae; epimeral plate 3 longer than broad, rounded and with shorter setae. Pleopods 1−3 ( Fig. 4 d) identical, peduncle with 2 retinaculae, 8−10 segmented rami with plumose setae on each segment. Uropod 1 with outer ramus approximately 2/3 length of peduncle, distal margin of peduncle serrate, bulbous ventroapical projection on peduncle, lateral margins of rami microserrate, apex with one long and 1–3 short spines; inner ramus 2/3 length outer ramus. Uropod 2 with outer ramus approximately 2/3 length of peduncle, distal margin of peduncle serrate; inner ramus more than 3/5 length outer ramus, lateral margins of rami microserrate, apex with one long and 1–4 short spines. Uropod 3 ramus with 1 short spine and with 3−5 longer setae; peduncle with a distal spine, subequal to ramus length, with 3−4 pectinate setae between spine and ramus. Telson approximately 40 percent wider than long, convex with apex slightly straight.

Size. ♂, max.= 4.8 mm; min.=1.4, mean= 3.2; ♀, max.= 4.2 mm; min.=1.2, mean= 2.9

Female: Similar to male, uropod 1 peduncle without bulbous projection.

Biology. Living in fine sand and mud sediment with high coverage of dead Posidonia oceanica rhizomes. This new species coexists with Siphonoecetes (Siphonoecetes) sabatieri de Rouville, 1894 in studied area, though they were never found in the same station. While S. bulborostrum sp. n. was found from 10 to 15 m, S. sabatieri was only found at 10 m depth and in shallower stations (4 m depth) over fine sand.

Color. Body yellow-brown with black spots on gnathopod 1–2 propodus and anteroventral margin of head and coxa1–3.

Distribution. So far known only form the type locality: Mediterranean coast near Alicante and Chafarinas Island.

Remarks. S. bulborostrum sp. n. is easily distinguishable of the other Siphonoecetes reported on Iberian Mediterranean coast due to the bulbous subrostral projection.

With respect to Siphonoecetes (Siphonoecetes) sabatieri de Rouville, 1894, this new species differs also in bulbous ventroapical projection on peduncle of uropod 1 of males, since it is characteristic of Centroloecetes subgenus. Regarding to the other species, Siphonoecetes (Centraloecetes) dellavallei Stebbing, 1899 , Siphonoecetes (Centraloecetes) kroyeranus Bate, 1856 , and Siphonoecetes (Centraloecetes) neapolitanus Schiecke, 1979 , rostrum in all of them is spine-like being longer than eyes’ lobes, while in S. bulborostrum sp. n. the rostrum is rounded and about as long as eyes’ lobes.

Figures

FIGURE 1. Stations where Siphonoecetes (Centraloecetes) bulborostrum sp. n. was found.

FIGURE 2. Siphonoecetes (Centraloecetes) bulborostrum sp. n. Holotype. Male., 3.76 mm. Body, head lateral view, head dorsolateral view, head dorsal view. Scale bar— 0.5 mm.

FIGURE 3. Siphonoecetes Krøyer, 1845, Siphonoecetes (Centraloecetes) bulborostrum sp. n. Male, 3.7 mm. Mouthparts, Mxp. maxiliped, Mx 1. maxila 1, Mx 2. maxila 2, Md., r., mandible right, Md., l., mandible left, L., lip. Scale bar— 0.05 mm.

FIGURE 4. Siphonoecetes Krøyer, 1845, Siphonoecetes (Centraloecetes) bulborostrum sp. n. Holotype. Male, 3.76 mm. Gn 1 – 2. gnathopod 1 – 2, Gn 2. P 3 – 4. pereopod 3 – 4. Scale bar— 0.25 mm.