Cymodoce truncata Leach, 1814

Khalaji-Pirbalouty, Valiallah, Bruce, Niel L. & Wägele, Johann-Wolfgang, 2013, The genus Cymodoce Leach, 1814 (Crustacea: Isopoda: Sphaeromatidae) in the Persian Gulf with description of a new species, Zootaxa 3686 (5), pp. 501-533 : 506-512

Cymodoce truncata Leach, 1814

( Figs 3–7 )

Cymodoce truncata Leach, 1814: 433 .— Leach, 1818: 342, 343.— Tattersall, 1905: 6.— Norman & Scott, 1906: 44, pl. IV.— Torelli, 1929: 61, 1930: 307, pl. 9, fig. 8.— Monod, 1931: 53, 54, figs. 47–49; 1937: 14.— Omer-Cooper & Rawson, 1934: 39 –41, pls. 2–4.— Dumay, 1972b: 642 –651, pl I, II.— Ellis, 1981: 126.— Harrison & Holdich, 1984: 301.— Castelló, 1986: 63.— Schotte & Kensley, 2005:1243.

? Sphaeroma inerme Tattersall, 1906: 601 .

Not Cymodoce truncata .— Glynn, 1972: 286 –289, figs 6–7 (misidentification, = C. richardsonae ).

Material examined. Lectotype (here designated), 3 (10.5 mm), in two parts, Devon, England, coll. W. E. Leach ( BMNH, 1979. 439.1). Paralectotype: 1 Ƥ (6.5 mm), same data as lectotype ( BMNH, 1979: 418.1). Non-type: 1 male (11.0 mm), 1 ovigerous Ƥ (9.0 mm), Ballynaniu Harb., Galway, ( BMNH 1911. 11. 8.8406–8407).

Diagnosis. Head and pereonites 1–4 smooth, lacking tubercles, pereonites 5–7 with two transverse rows of small tubercles. Pleon posterior margin with two weak extensions bearing two tufts of long setae on either side. Pleotelson with 2 longitudinal and 1 semilunar tuberculate ridges on either side dorsally; posterior half of the pleotelson with medial hemispheric dome, bearing a process on top and a tuft of long setae arranged on it radially; posterior margin trilobed, medial lobe extending just beyond lateral lobes. Appendix masculina extending slightly beyond endopod, tapering evenly to a rounded apex. Uropod rami extending just beyond pleotelsonic medial lobe apex.

Description of male. Body about 2.2 times as long as greatest width (pereonite 6). Head and pereonites 1–4 dorsal surfaces smooth; pereonites 5–7 with two transverse rows of small, and increasingly more prominent tubercles. Pereonites 2–7 coxal plates with evident sutures, and bearing some long setae on distal surface.

Pleon with a row of tubercles over two, long, straight, separate and parallel sutures at each side, dorsally bearing scattered uneven tubercles of various sizes; posterior margin with two weak extensions and two pronounced tufts of simple long setae on each side.

Pleotelson dorsal surface densely setose, bearing scattered small tubercles over most of surface, these tubercles arranged in 4 longitudinal ridges dorsally, each pair followed by large prominent boss; dorsolateral surfaces bearing semilunar tuberculate ridge, densely setose apically; posterior region with domed boss bearing process on top and tuft of long setae arranged it radially. Apex of pleotelson lateral lobes blunt; medial lobe extending slightly beyond the level of lateral lobes, bearing two apical conical tubercles and tuft of long setae, dorsally tuberculate. ( Figs. 3 A, B; 7A, C, D, 21A)

Antennule ( Fig. 3 C) peduncle article 1 bearing scattered weak tubercles; article 2 short with some small sensory palmate setae on ventral and dorsal margins, article 3 about 1.7 times as long as article 2; flagellum with 16 articles, articles 4–15 each bearing a pair of aesthetascs.

Antenna ( Fig. 3 D) peduncle article 1 setose; articles 2–5 each bearing long setae on posterior angle; article 5 about 1.2 times as long as article 4; flagellum with 18 articles.

Epistome ( Fig. 3 E, 7B) granulose, with acute apex, lateral margins concave.

Left mandible ( Fig. 4 C) incisor with 3 cusps, lacinia mobilis bluntly dentate, spine row of 5–6 serrate spines.

Maxillule ( Fig. 4 A) lateral endite with long fine setae on mesial margin, outer margin bearing small stout setae, apical margin with 10 simple or serrate RS and 1 short RS; mesial endite with 4 long, robust, comb and 1 short simple seta.

Maxilla ( Fig. 4 B) lateral and middle endites each with 10 curved pectinate RS; mesial endite with 2 long rarely plumose, 2 long robust comb, 9 long or short robust proximally plumose and distally biserrate setae, and some slender simple setae.

Maxilliped ( Fig. 4 D) endite lateral margin sinuate, mesial margin with single coupling hook, distal margin with 5 blunt rarely plumose RS and 7 long circumplumose RS, inner surface with 3 long circumplumose RS; palp article 2 with single long seta on superiodistal angle.

Pereopod 1 ( Fig. 4 E) basis 2.7 times as long as greatest width, ischium superior margin with 1 curved, acute RS on proximal corner and 1 long RS on medial angle; merus superodistal angle with 3 RS, inferior margin with 4 biserrate RS and single long apically palmate seta; carpus inferior margin with 4 biserrate RS; propodus inferior margin with 4 biserrate RS set in amongst acute scales; dactylus inferior margin with serrate cuticular scale.

Pereopod 2 ( Fig. 4 F) basis about 3 times as long as greatest width, with 3 small sensory palmate seta; ischium superior margin with 1 long RS on medial angle; merus superodistal angle with 3 RS, inferior margin with 5 robust biserrate setae and single long apically palmate seta; merus, carpus and propodus inferior margin fringed with short setae; carpus inferior margin with 4 biserrate RS, and long apically palmate seta, superodistal angle with 2 RS; propodus inferior margin with 6 RS, superodistal angle with 2 long simple setae and a single sensory palmate seta. Pereopod 3 ( Fig. 5 A) is similar to pereopod 2 as illustrated.

Pereopods 4 and 5 ( Fig. 3 B, Fig. 3 C) similar as illustrated.

Pereopod 6 ( Fig. 5 D) basis about 3.4 times as long as greatest width, superior margin with several simple and 4 sensory palmate seta; ischium superior margin with 3 RS; merus superior distal margin with 3 long setae, inferior margin with 4 robust biserrate setae and single long apically palmate seta; carpus subequal in length to merus, inferior margin 9 robust biserrate setae and a single long apically palmate seta, distal margin with 7 robust biserrate or simple setae; propodus superodistal corner with 2 slender and a single sensory palmate setae, inferior margin with 4 robust biserrate setae.

Pereopod 7 ( Fig. 5 E) similar to pereopod 6, except in some details such as number of setae on merus, carpus and propodus.

Penial processes ( Fig. 6 F) about 10.4 times as long as basal width, tapering to rounded apex; distal third covered with cuticular branched scales.

Pleopod 1 ( Fig. 4 A) exopod and endopod with approximately 43 and 32 plumose marginal setae; exopod proximally with a single biserrate RS on lateral angle; endopod nearly triangular, medial margin bearing a longitudinal fold fringed with fine setae; sympod mesial margin with 4 coupling hooks.

Pleopod 2 ( Fig. 6 B) exopod and endopod shape as for pleopod 1, with approximately 44 and 28 plumose marginal setae; appendix masculina slender, arising sub-basally, extending slightly beyond endopod (by about 0.16 its length), tapering evenly to a rounded apex, distally bearing cuticular branched scales on most of surface, proximally with single cuticular scales on medial marginal; sympod with 3 distomesial coupling hooks.

Pleopod 3 ( Fig. 6 C) exopod and endopod with approximately 51 and 18 plumose marginal setae; endopod distally truncate; exopod sub-elliptical, narrowing proximally, with transverse suture; sympod with 3 distomesial coupling hooks, lateral margin with fringe of thin setae and 1 long plumose setae on distolateral corner.

Pleopod 4 ( Fig. 6 D) endopod with pronounced and curved apical lobe; exopod bearing 1 apical plumose seta, lateral margin with approximately 33 slender simple setae and numerous short setae (7 distal and 26 proximal to the transverse suture); sympod with plumose setae on distolateral corner.

Pleopod 5 ( Fig. 6 E) exopod with 5 scale patches (3 distally of and 2 under transverse suture), lateral margin with approximately 19 slender simple marginal setae (2 distal and 17 proximal to the transverse suture); endopod distolateral margin fringed with fine setae on about one-third of length, several small setae medially.

Uropodal rami ( Fig. 3 A, 7A) extending just beyond pleotelsonic medial lobe apex; endopod distally oblique with scattered tubercles on dorsal surface, distal and lateral margins fringed with long setae; exopod wider than endopod, lateral margin with thick upturned rim, straight and tuberculate, medial margin rounded, distal half finely crenulate, apex with hardened point.

Female. Apart from sexual characters similar to sub-adult male, pleotelsonic medial lobe round and lateral lobes barely visible in dorsal view ( Fig. 3 F).

Remarks. Several species have been placed in synonymy with Cymodoce truncata: Norman and Scott (1906) synonymised C. emarginata Leach, 1818 with C. truncata . Cymodoce pilosa Milne Edwards, 1840 , C. robusta Nierstrasz, 1918 , and C. richardsoniae Nobili, 1906 were synonymised by Torelli (1930). The illustrations of C. hanseni Dumay, 1972d are very similar to her own illustrations of C. pilosa , thus suggesting that the two belonging to a single species. However, C. truncata is distinct, the species being recognized by the presence of four dorsal longitudinal tuberculate ridges on the pleotelson, flanked on either side by a semilunar tuberculate ridge. Furthermore, the posterior part of the pleotelson has a domed boss with a process on top, surrounded radially by a tuft of long setae.

Omer-Cooper and Rawson (1934), suggested that C. emarginata Leach, 1818 may prove to be a junior synonym of C. truncata . However, their drawings of the type species and a specimen from the Shetland Islands are significantly different and do not appear to represent the same species. Furthermore, there is also a clear difference between the drawings that they gave for C. truncata and for C. emarginata , suggesting that those two species are not the same.

Glynn (1972) reported C. truncata from the Red Sea. Based on the brief description and illustration by Glynn (1972) and on our own examination of Glynn’s material (USNM 138248/SLS) and other material from the Red Sea (SMF-3480), we do not accept that this is C. truncata . According to the original description and illustration of C. richardsoniae given by Nobili (1906) from the Red Sea, Glynn’s material is very similar to C. richardsoniae in having a pleotelson with two longitudinal, straight, prominent ridges dorsally, flanked on either side by 2–3 prominent tubercles. We agree with Monod (1937) and Harrison and Holdich (1984) that C. richardsoniae is a distinct species (see redescription herein, and conclude Glynn’s material and other material we examined from the Red Sea are C. richardsoniae .

Figures

FIGURE 3. Cymodoce truncata Leach, 1814. Lectotype (BMNH, 1979. 439. 1); A, dorsal view; B, lateral view; C, antennule; D, antenna; E, epistome; F, female (BMNH, 1979: 418.1).

FIGURE 4. Cymodoce truncata Leach, 1814. Lectotype (BMNH, 1979. 439. 1); A, maxillule; B, maxilla; C, left mandible; D, maxilliped; E, pereopod 1; F, pereopod 2.

FIGURE 5. Cymodoce truncata Leach, 1814. Lectotype (BMNH, 1979. 439. 1); A – E, pereopods 3 – 7.

FIGURE 6. Cymodoce truncata Leach, 1814. Lectotype (BMNH, 1979. 439. 1); A – E, pleopods 1 – 5; F, penes.

FIGURE 7. Cymodoce truncata Leach, 1814, Non-type (BMNH 1911. 11. 8. 8406 – 8407); SEM, dorsal view; B, frons and anterior of head; C, pleotelson dorsal view; D, pleotelson posterior part.