Cymodoce lirella, Schotte & Kensley, 2005

Schotte, Marilyn & Kensley, Brian, 2005, New species and records of Flabellifera from the Indian Ocean (Crustacea: Peracarida: Isopoda), Journal of Natural History 39 (16), pp. 1211-1282 : 1248-1252

Cymodoce lirella sp. nov. ( Figures 21 , 22 ) Material examined

Holotype: USNM 280294 , one male (7.0 mm), sta J-SEY-1, rubble and algal turf, Mahé Island, Seychelles, 0.5 m, 29 April 1984 . Paratypes: USNM 280295 , 19 male, 29 females, eight juveniles, from four stations, rubble and algal turf, 0.5–1.0 m .

Description

Male. Dorsal surface of cephalon and pereonites 1–4 smooth, bearing few marginal setae. Pereonites 5–7 each with two transverse rows of very small tubercles. Pleon with many small tubercles, some in transverse rows. Pleotelson very granulose with two large bosses, apically bifid and setose, posterior to two ridges of tubercles also bearing setae; two irregular, longitudinal rows of small tubercles between bosses; smaller bifid tubercle posterolateral to each boss. Posterior half of pleotelson with medial, large smooth domed boss; posterior margin tridentate, medial tooth raised and subtruncate, apically bifid, extending beyond lateral teeth.

Antennal flagellum with 19 articles. Antennule, article 1 with single lateral plumose seta; article 2 with one simple and four plumose setae; flagellum of about 17 articles, proximal 13 of which each bearing single aesthetasc. Epistome broad with pointed apex. Maxilliped as figured. Pereopod 1, propodus, carpus and merus with fringed, stubby setae on posterior margins. Pereopod 2, short fringe of setules with few interspersed setae on posterior margin of propodus, carpus and merus; two very stout setae, one tridentate, at posterodistal margin of carpus. Pereopod 7, several strong simple setae of varying lengths on posterior margin of propodus, carpus and merus; longer setae at anterodistal margins of carpus, merus and ischium. Penes separate at base, length six times width, parallel-sided, angled at apex, with sparse setules on medial margin in proximal half; apex appearing to twist apically. Pleopod 1, peduncle with four coupling hooks; exopod subelliptical, endopod triangular in shape. Pleopod 2, peduncle with four coupling hooks; appendix masculina slender, tapering to fine tip, 1.6 times length of endopod, curving in distal one-fourth toward midline of animal; bearing short fringe of short marginal setae in proximal half. Pleopod 4, endopod pleated with notch in medial margin near apex; exopod with subterminal articulation and many simple setae along outer margin and at apex. Pleopod 5, endopod rounded apically with fringe of short setae; exopod with complete articulation distally and four spinulose bosses. Uropodal endopod parallel-sided, concave in ventral view, subtruncate apically, dorsally granular with long marginal setae; exopod tuberculate with long dorsal and marginal setae, inner margin convex with acute tip, outer margin straight. Uropodal rami subequal in length, both extending beyond median tooth of pleotelsonic apex.

Ovigerous female. Dorsum smooth; two low bosses on pleotelson, median notch of pleotelsonic apex truncate.

Remarks

The males of this species seem to be somewhat variable in the degree of setation especially of the posterior body. The present species is very similar to C. zanzibarensis Stebbing, 1910a but distinct due to the former’s longer appendix masculina and smaller and much more slender body size. The median lobe of the pleotelsonic apex also extends farther relative to the lateral lobes in the new species. It is separated from C. tribullis Harrison and Holdich, 1984 , which has ‘‘hemispheric domes’’ at the ends of the pleotelsonic ridges instead of notched tubercles and possesses pads of setae on the merus and carpus. It resembles also C. longistylis Miers, 1884 , which differs in having subequal teeth at the pleotelsonic apex, lacking the prominent, dentate tubercules on either side of the pleotelson midline and having relatively longer uropods, the endopod of which is curved. Similar also to C. pelsarti Tattersall, 1922 , C. lirella has relatively shorter uropodal rami but much larger dentate tubercles on the pleotelson. The presence of a hemispherical dome anterior to the pleotelsonic notch is, according to Bruce, 1997, a possible apomorphy for Cymodoce s. str. Cymodoce lirella shares this character with all the four above-mentioned species.

Etymology

The specific name, from the Latin for ‘‘small ridge’’, used as a noun in apposition, refers to the two low ridges of the pleotelson.

Genus Dynamenella Hansen, 1905

Restricted synonymy. Dynamenella Hansen 1905, p 107 ; Harrison and Holdich 1982, p 89; Javed and Ahmed 1988, p 234.

Diagnosis

Eubranchiate with antennular peduncle article 1 not extended anteriorly as plate. Both sexes with pereon and pleon lacking dorsal processes, and with both uropodal rami lamellar, endopod greater than half length of exopod. Pereopod 1 markedly more robust than other pereopods. All pereopods with simple, not bifid secondary unguis. Exopod of pleopod 3 with or without articulation. Sexual dimorphism obvious.

Adult male. Penes long, tapering, fused at base. Appendix masculina arising from proximomedial angle of endopod of pleopod 2 and extending to or beyond apex of endopod; usually broad proximally and tapering to acute tip. Apex of pleotelson with dorsally directed foramen connected to apex by narrow slit. Ventral margins various. Uropods broader than those of female and immatures.

Ovigerous female. Mouthparts not metamorphosed. Apex of pleotelson various; bearing slight notch, simple groove, or foramen connected to apex by narrow slit. Uropods narrower than those of male. Brood pouch, lacking oostegites, formed by two opposing ventral pockets and opening in midline at sternite 4.

Key to species of Dynamenella from the Indian Ocean region

1. Pleotelson of adult male with dorsal, subapical foramen........ 2

– Apex of pleotelson in adult male folded to form posteriorly directed groove; pleotelson with four longitudinal carinae... D. scaptocephala Messana, 1990 [ Somalia]

2. Subapical foramen elliptical or transverse............ 3 – Subapical foramen neither elliptical nor transverse......... 4

3. Pleotelson having two identical bosses, each covered with several small tubercles; pleon without surface ornamentation...... D. quilonensis Pillai, 1954 [ India]

– Pleotelson granulose with irregular tubercles; pleon with two small, granular, transverse ridges............. D. alveolata sp. nov. [Off Sumatra]

4. Pleotelson smooth and unornamented, without obvious tubercles.....

......... D. mossambicus Ortiz, Berze-Freire and Wasikete, 1992 [ Mozambique]

– Pleotelson rugose or with tubercles.............. 5

5. Subapical foramen on pleotelson of male ‘‘key-hole’’-shaped, subcircular, extending anteriorly into smaller half circle; appendix masculina more than twice length of endopod........ D. granulata Javed and Ahmed, 1988 [ Pakistan]

– Subapical foramen on pleotelson of male circular; appendix masculina less than twice length of endopod................. 6

6. Pleotelson triangular with relatively straight sides; appendix masculina barely longer than endopod............. D. remex , sp. nov [ Madagascar]

– Lateral margins of pleotelson sinuous; appendix masculina extending well beyond endopodite..................... 7

7. Subapical foramen open posteriorly; lateral tubercles on pleotelson oblique; appendix masculina widening toward apex. D. bullejiensis Javed and Ahmed, 1988 [ Pakistan]

– Subapical foramen closed posteriorly; all tubercles on pleotelson round; appendix masculina tapering to acute apex... D. savigny (H. Milne Edwards, 1840) [ Egypt; Gulf of Aqaba; South Africa]

Note: Dynamenella yomsii Storey, 2002 , recorded from Phuket, Thailand, seems nearly identical to D. savignyi , known thus far only in the western Indian Ocean. Further investigation is needed to establish the division between these two species.

Figures

Figure 21. Cymodoce lirella sp. nov. (A) Male, dorsal view; (B) male, lateral view; (C) frontal lamina; (D) antenna; (E) antennule; (F) left mandible; (G) ventral pleon; (H) female, pleon; (I) pleopod 1; (J) male pleopod 2; (K) maxilliped.

Figure 22. Cymodoce lirella sp. nov. (A) Pereopod 1; (B) pereopod 1, fringed seta enlarged; (C) pleopod 4; (D) penes; (E) pleopod 3; (F) pleopod 5; (G) pereopod 2; (H) pereopod 2 carpal seta, enlarged; (I) pereopod 7.