Odysseylana Malyutina, 1995

Sidabalok, Conni M. & Bruce, Niel L., 2015, Revision of the cirolanid isopod genus Odysseylana Malyutina, 1995 (Crustacea) with description of two new species from Singapore, Zootaxa 4021 (2), pp. 351-367 : 352-354

Genus Odysseylana Malyutina, 1995

Odysseylana Malyutina, 1995: 101 –109. Parilcirolana Yu & Li, 2001: 59 –64.

Type species. Odysseylana sirenkoi Malyutina, 1995 ; by monotypy. Type locality, 10°46’N, 109°43’E, off southern Vietnam, east of Phu Quy Island ( Malyutina 1995).

Species included. Odysseylana setosa ( Yu & Li 2001) comb. nov., Beibu Gulf ( Tonkin Gulf) to northern South China Sea; Odysseylana sakijang sp. nov. and Odysseylana temasek sp. nov., both known only from Singapore.

Diagnosis (male). Body elongate, 2.9–3.5 as long as wide. Pereonites smooth, with or without fine tubercles on posterior margins of pleonites 4 and 5 and proximal surface of pleotelson. Cephalon anterior margin rounded or weakly produced, without rostral point, not medially indented. Pleonite 3 posterolateral margin acute, not extending posteriorly to posterior of pleonite 5; pleonite 4 rounded, encompassing and extending posterior to pleonite 5. Antennula peduncle articles 1 and 2 shortest, article 3 longest; flagellum equal or shorter than peduncle. Antenna peduncle article 3 about half as long as 4, article 4 longest, with row of long plumose setae (except Odysseylana sakijang sp. nov.); flagellum longer than peduncle. All pereopods with secondary unguis on dactylus. Pereopods 1–3 with superodistal margins of ischium and merus moderately produced; pereopod 1 merus inferior margin with single row of acute and blunt RS; pereopods 2 and 3 with single row of tubercular RS; carpus with a cluster of slender and acute setae on inferodistal; propodal palm with evenly-spaced row of stout acute RS. Pereopod 6 basis broader in inferior distal half; ischium and merus flat and widest distally; superodistal ischium– carpus with clusters of long acute RS and long simple setae; inferior margin of ischium–carpus with rows of long acute RS and long simple setae. Pereopod 7 similar with pereopod 6 but more slender. Penial processes present on sternite 7 as two papillae or small lobes. Pleopod 1 peduncle quadrate; endopod narrow, about 70% as long as wide. Pleopod 2 appendix masculina inserted basally.

Description (male). Body about 2.9–3.5 times as long as greatest width. Head wide, approximately 66–71% as wide as pereonite 1, anterior margin evenly rounded, without rostral point. Body surfaces unornamented or ornamented; pereonite 1 between 0.9–1.5 times as long as pereonite 2 in dorsal view. Pleon unornamented or ornamented, about 11–18% BL, with 4–5 visible unfused segments, pleonite 1 usually not concealed by pereonite 7; pleonite 2 epimera not posteriorly produced. Pleotelson without longitudinal carinae, or with 2 rows of small tubercles; posterior margin with PMS and 4–9 RS.

Antennula peduncle articles collinear, articles 1 and 2 not fused or partly fused with weak suture; peduncular article 2 not at right angles to article 1; article 3 well developed, about 0.6–0.9 as long as combined lengths of articles 1 and 2; flagellum between 0.8–1.0 as long as peduncle; without callynophore. Antenna peduncular articles 1–3 shortest, articles 4 and 5 longest, 4 longer than 5; flagellum about 1.3 as long as peduncle.

Frontal lamina pentagonal, lateral margins parallel or weakly concave; ventrally flat, with lateral angles, anteriorly acute; posteriorly abutting clypeus; approximately 1.25–2.0 times as long as basal width, not projecting anteroventrally from posterior. Clypeus ventral surface not projecting relative to frontal lamina. Mandible incisor wide, right incisor tricuspidate; spine row with 8–11 RS. Maxillula mesial lobe with 3 CP RS. Maxilliped palp article 2 mesial margin with 6–7 slender setae, lateral margin with 1 slender seta; article 3 mesial margin with 13– 18 slender setae, lateral margin with 11 slender setae; article 4 mesial margin with 9–13 slender setae, lateral margin with 5 slender setae; articles 3 and 4 distal margin width greater than proximal margin of article 4 and 5 respectively; endite with 2–3 coupling hooks.

Pereopods 1–7 dactylus with small secondary unguis present. Pereopod 1 dactylus longer than propodus palm; simple RS opposing dactylus. Pereopod 7 basis not noticeably broader in distal half compared to proximal half; margins with few discontinuous setae; ischium and merus flattened, distal margin between weakly and moderately expanded, inferior margins with few setae.

Pleopod 1 rami lamellar; endopod narrow, 0.6–0.7 as wide as exopod, 2.3–2.7 times as long as wide. Pleopod 2 appendix masculina 0.8–1.1 longer than endopod. Pleopods 1–5 with PMS present on all rami except endopod 5; pleopod 5 endopod shorter (0.8) than exopod. Uropod peduncle mesial margin produced; exopod lateral margin not excised.

Female. No ovigerous females present in material examined. Non-ovigerous females are similar to males but for the sexual characters; body size is slightly larger.

Remarks. Odysseylana Malyutina, 1995 can be identified by the following characters: elongate body shape (2.9–3.5 long as greatest width), the absence of rostral point; frontal lamina pentagonal; antenna peduncle articles 4 and 5 subequal in length with 4 the longest; pereopods 1–3 with the superodistal margin of ischium and merus moderately produced; pleopod 1 peduncle quadrate, and pleopod 1 endopod slender, 48–65% width of exopod. Malyutina (1995) included the highly distinctive shape and setation of the uropods and pleotelson in the generic diagnosis, but we consider those to be species-level characters.

Malyutina (1995) placed Odysseylana in the Conilera group of Bruce (1986) [= Conilerinae of Kensley & Schotte (1989)], sharing characters such as the short antennula , quadrate pleopod 1 peduncle, superodistal angles of pereopod 1–3 ischium and merus strongly produced and setose, and pereopods 5–7 with the ischium to carpus generally flattened and setose, sometimes the distal margin of the article also being expanded. In contrast Odysseylana differs significantly from that group in several critical characters, notably the antennal peduncle has articles 4 and 5 longest, the frontal lamina is pentagonal and relatively wide, with distinct anterolateral angles, pereopods 1–3 have the superodistal angles of the ischium and merus only moderately produced, and have a distinct secondary unguis on the dactylus; all these characters are in strong contrast to genera such Politolana Bruce, 1981 ( Riseman & Brusca 2002) , Natatolana Bruce, 1981 ( Keable 2006) and Dolicholana Bruce, 1981 ( Keable 1999) . In conclusion we do not consider that Odysseylana belongs with the Conilera group of genera.

Odysseylana shares several diagnostic characters with the Indo-Pacific genera Aatolana Bruce, 1993 , Baharilana Bruce & Svavarsson, 2003 and Plakolana Bruce, 1993 . These characters include the anterior margin of the head lacking a rostral point, being rounded or weakly medially protruded, the superodistal angles of the ischium and merus of pereopods 1–3 being moderately produced, quadrate pleopod 1 peduncle and the presence of lateral setae on uropod peduncle. Odysseylana differs from both Aatolana and Plakolana in lacking prominent and flattened penial processes, and also in having a pentagonal frontal lamina (linear in Plakolana , anteriorly rounded and posteriorly narrowed in Aatolana ), pereopods 1–3 have a small, blunt secondary unguis (absent or seta-like in Aatolana and Plakolana ) and relatively elongate pleopod 1 rami (exopod broadly rounded, endopod narrow in Plakolana ; pleopod 1 endopod in Aatolana has strongly convex lateral margin, and pleopod peduncles are complex). Odysseylana is most similar to Baharilana but differs in having two coupling hooks on the maxilliped endite rather than one, pleopod 2 appendix masculina is basal (vs. sub-basal) and straight (vs curved at tip).

The genus Parilcirolana Yu & Li, 2001 was described from the northern Gulf of Tonkin, Hainan Island and northern South China Sea near Macau. Yu & Li (2001) were apparently unaware of Malyutina’s (1995) publication as they made no mention of Odysseylana Malyutina, 1995 in their discussion or remarks. At the generic level we can find no differentiating characters to support Parilcirolana , with the diagnostic antennal, pereopodal and pleopod morphology entirely consistent with that of Odysseylana .

Some generic characters that were identified as diagnostic by Malyutina (1995) are here considered to be species characters, such as the incised distal margin of the pleotelson and conical shape of uropod exopod. Similarly, the dense setae on the pereopod 7 of O. setosa ( Yu & Li 2001) is also regarded as a species-level character.

Distribution. Odysseylana has a distribution centred on the tropical and subtropical western Pacific ( Fig. 1 ), from Singapore in the south to Macau in the north-east. The genus is absent from the relatively well-documented regions of Australia, South Africa and also the tropical western Indian Ocean.

Figures

FIGURE 1. Map showing distribution of Odysseylana species, ˔ Odysseylana setosa; ⋅ Odsseylana sirenkoi; • Odysseylana sakijang and O. temasek.