Sphaeroma silvai, Khalaji-Pirbalouty, Valiallah & Wägele, Johann-Wolfgang, 2010

Khalaji-Pirbalouty, Valiallah & Wägele, Johann-Wolfgang, 2010, A new record of Sphaeroma annandalei Stebbing, 1911 (Crustacea: Isopoda: Sphaeromatidae) from the Persian Gulf, and description of a new related species (Sphaeroma silvai nov. sp.) from the South Atlantic Ocean, Zootaxa 2508, pp. 30-44 : 37-43

Sphaeroma silvai sp. nov.

( Figs 7–11 )

Sphaeroma annandalei . — Loyola e Silva, 1960: 28.

Material examined. Holotype: male (9.5 mm), Krofajapasi, west von WiaWia bank, Suriname, north coast, Boomstam, 27 September 1980 ( RMNH 6215). Allotype: 1 female (10 mm).

Paratypes: 24 males (5.5 to 10 mm); 12 juveniles (up to 4mm); 32 females (5.5 to 8.5 mm), same data as holotype; Krofajapasi, Suriname, 19 September 1980, ( RMNH 6214), 4 male (5.5 to 7.5 mm); 6 females (5.5 to 8.5 mm); Suriname, north coast, Mafappica, Kreek Kanaal, 6 April 1975, ( RMNH 6519), 1 male (8 mm); 2 non-ovigerous females (6.5 and 7 mm); 2 ovigerous females (7 and 8 mm); Harde modder bank, 2 Km Oost van Mdtapica, Getijzone, Suriname, 21 September, ( RMNH 6213), 1 female (7.5 mm); Cananéia-SP, São Paulo, Brazil, July 1952 ( ZMH –42310), 3 males (7.5, 9.5, 10 mm), 1 ovigerous female (9.5 mm).

Diagnosis. Cephalon dorsally with a pair of small tubercles on either side anteriorly. Pereopod 5 basis bearing extended sub-rectangular medial lobe. Pereonites 4 and 5 with continuous transverse ridges, flanked on either side by some small round tubercles; pereonites 6 and 7 with prominent elongated and entirely separate tubercles, the middle tubercles higher than the lateral ones. Pleon first segment not visible, laterally two caudally two curved sutures, dorsal surface with 4 tubercles in transverse row, the middle tubercles larger than lateral tubercles. Pleotelson dorsal surface with 5 prominent tubercles in middle side, and a longitudinal raw of 4 tubercles laterally; pleotelsonic apex is broadly rounded. Maxilliped endite elongate, with narrow apex, bearing 2 terminal circumplumose robust setae; distal margin with about 6 plumose setae, set between fine simple setae; palp articles 2–3 bearing dense fringes of long simple setae on superior margin.

Description of male. Body 1.85 times as long as greatest width, widest at pereonite 6 ( Fig. 7 A). Cephalon with a pair of weak tubercles on either side anteriorly, rostral process developed, barely visible in dorsal view. Pereonites 1–7 posterior margin with fringe of fine setae, pereonite 7 setae being longest; pereonites 2–7 with coxal plate sutures ( Fig. 7 B), coxal plates 2–3 subtruncate and lateral margin narrower than others, more rounded laterally in pereonites 4–7; pereonite 4–5 with continuous transverse ridges, flanked on either side by some weak tubercles; on pereonite 6–7 the ridges tend to break up in to a series of prominent elongated and entirely separate tubercles.

Pleon ( Fig. 7 A) without separate segment, posterior margin bearing two separate sutures on either side; dorsal surface with transverse row of 4 prominent tubercles, middle ones bigger than the others.

Pleotelson ( Fig. 7 A, 12E) dorsal surface with two separate pairs of prominent tubercles which followed by a single median prominent tubercle and flanked on either side by a longitudinal row of 4 tubercles; posterior margin with an upturned rim and broadly rounded apex.

Antennule ( Fig. 7 C) peduncle articles 1–2 with some small sensory palmate setae on ventral and dorsal margins, article 3 elongate, slender, with some short simple setae on middle surface; flagellum 13–articled, articles 4–12 each bearing aesthetascs, final article with 3 simple and 1 small sensory palmate setae.

Antenna ( Fig. 7 D) peduncle articles 3–5 superior margins and article 4 inferior margin fringed with long fine dense setae; flagellum 15-articled, each article with an apical tuft of simple setae.

Epistome ( Fig. 11 D) with triangular apex and concave lateral margins.

Right mandible ( Fig. 8 D, E) incisor with 2 cusps; spine row of 7 curved, serrate spines; palp article 2 as long as 1, article 2 and 3 distolateral margins with 24 and 25 biserrate setae.

Maxillule ( Fig. 8 A) lateral endite with simple setae on most of surface, apical margin with 12 robust, serrate or biserrate and a single simple robust setae, dorsal surface with 1 long, slender, serrate seta; mesial endite with simple setae on inner margin, apical margin with 3 long, terminal plumose robust setae (each of them with some spines, particularly on apical part), 2 short plumose setae and 1 simple seta.

Maxilla ( Fig. 8 B) lateral and middle endites oval, with about 28 finely pectinate robust setae; mesial lobe sub-quadrangular, with about 27 plumose setae.

Maxilliped ( Fig. 8 C) endite elongate, with narrow medially directed apical protrusion, bearing 2 terminal circumplumose robust setae; distal margin with about 6 plumose setae, set between fine simple setae and a single long circumplumose seta on distomedial corner; mesial margin concave with single coupling hook, inner surface with a row of about 20 long circumplumose setae; palp articles 2–3 bearing dense fringes of long simple setae on superior margin, articles 3–5 with several long simple setae on inferodistal angle; articles 4 and 5 slender, longer than wide.

Pereopod 1 ( Fig. 9 A) basis as long as ischium, superior margin fringed with simple setae and 2 small sensory palmate setae; ischium 4.0 times as long as greatest width, ischium and merus superior margins fringed with numerous long simple setae; merus and carpus inferior margins fringed with short setae; carpus triangular; propodus inferodistal angle with 1 biserrate and 1 nodular robust setae; rostral surface with transverse row of several long simple setae; dactylus secondary unguis simple, straight, with 3 simple setae at base. Pereopod 2 ( Fig. 9 B) ischium and merus with dense fringes of long stiff setae on inferior margins, carpus with 2 robust biserrate setae on inferodistal corner; merus, carpus and propodus inferior margins fringed with short setae. Pereopod 3 similar to pereopod 2. Pereopod 4 ( Fig. 10 A) very robust, basis with dense fine submarginal setae on inferior margin, superior margin extended, bearing dense, long, simple setae; ischium bearing inferior fringe of long, fine, simple setae, superior margin with 3 long robust setae; merus, carpus and propodus short, inferior margins with fringes of dense short setae. Pereopod 5 ( Fig. 10 B) basis with well extended sub-rectangular medial lobe, dorsally with some acute, stout sub-marginal setae ( Fig. 10 D), bearing superior long, simple, fine setae; ischium bearing inferior long, simple dense marginal setae, superior margin with 2 long robust setae, merus, carpus and propodus short, inferior margins with fringes of short simple setae. Pereopod 6 ( Fig. 10 C) basis and ischium with fringes of dense, long simple setae on inferior and superior margins, carpus with about 13 biserrate robust setae on superodistal corner, propodus elongated with fringe of short dense setae on inferior margin. Pereopod 7 ( Fig. 9 C) with inferior and superior margins of ischium to carpus bearing dense long simple fine setae; ischium superior margin convex, carpus distal margin with about 22 biserrate setae, propodus curved and elongate.

Pleopod 1 ( Fig. 11 A) exopod and endopod with approximately 47 and 18 plumose marginal setae; endopod nearly triangular, exopod distally wider than proximally, with a single long simple seta on proximal lateral corner and 3 long simple setae on superodistal margin lower than marginal setae; sympodite mesial margin with 3 coupling hooks. Pleopod 2 ( Fig. 11 B) exopod and endopod with approximately 45 and 26 plumose marginal setae; appendix masculina arising sub-basally, extending beyond endopod, with setules on most of surface except on distal parts; sympodite with 3 distomesial coupling hooks. Pleopod 3 ( Fig. 11 C) exopod and endopod with approximately 43 and 20 plumose marginal setae; sympodite with 3 distomesial coupling hooks, lateral margin with fringe of thin setae and 4 long simple setae on distolateral corner. Pleopod 4 ( Fig. 11 D) endopod with a pronounced and medially curved apical lobe with a single stout seta on apex; exopod with about 15 slender setae on lateral margin; sympodite with about 8 long slender setae on distolateral corner and a single simple seta on mesial margin. Pleopod 5 ( Fig. 11 E) exopod with 5 scale patches (3 distally of and 2 under the transverse suture), lateral margin with approximately 35 slender marginal and sub-marginal setae.

Penes ( Fig. 10 E) mesial margins folded, covered with several setules.

Uropodal rami subequal, extending well beyond pleotelsonic apex; endopod margins fringed with dense simple marginal setae; exopod lateral margin clearly serrate, with 6 teeth.

Female apart from sexual characters similar to male, however pleotelson is shorter than in male.

Remarks. Sphaeroma silvai sp. nov. is at a first glance closely related to S. annandalei Stebbing, 1911 . It was identified as a S. annandalei by Loyola e Silva (1960) due to the similarity of the pereon, pleon and pleotelson tuberculation; shape of the antenna and antennule; mouth parts; pereopods and pleopods. However, examination of material from Cananéia, SP, Brazil, 1952 [the same material on which Loyola e Silva (1960) based his identification] show that the new species is clearly distinguished from S. annandalei by the basis of pereopod 5, having a well-extended inferior lobe. Moreover, pereonites, pleon and pleotelson have higher and entirely separated tubercles. The pleotelson of S. annandalei has an obtusely narrowed apex with a longitudinal row of three tubercles on either side whereas S. silvai has a broadly rounded pleotelsonic apex with a longitudinal row of four tubercles. Furthermore, the ventral view of their pleotelson is entirely different (as shown in SEM Fig. 12 C, F). Uropod exopod serration differs also (compare Figs. 1 A and 7A).

Etymology. We take pleasure in naming this species for Prof. Jayme de Loyola e Silva, to acknowledge many years of contribution to the isopod taxa.

Figures

FIGURE 1. Sphaeroma annandalei, male. A, dorsal view; B, lateral view; C, antennule; D, antenna.

FIGURE 7. Sphaeroma silvai, holotype (male). A, dorsal view; B, lateral view; C, antennule; D, antenna.

FIGURE 8. Sphaeroma silvai sp. nov., holotype (male). A, maxillule; B, maxilla; C, maxilliped; D, right mandible; E, palp of right mandible.

FIGURE 9. Sphaeroma silvai sp. nov., holotype (male). A, pereopod 1; B, pereopod 2; C, pereopod 7.

FIGURE 10. Sphaeroma silvai sp. nov., holotype (male). A – C, pereopods 4 – 6; D, basis of pereopod 5; E, penes.

FIGURE 12. SEM. A – C Sphaeroma annandalei; A, frons and anterior of head; B, dorsal view of pleotelson; C, ventral view of pleotelson; D – F, Sphaeroma silvai sp. nov., paratype (male).