Pseudocerceis cf. seleneides Messana, 1988

Castelló, José, 2017, New and little-known species of isopods (Crustacea, Isopoda) from the eastern Mediterranean, Zootaxa 4311 (2), pp. 151-182 : 177-180

Pseudocerceis cf. seleneides Messana, 1988

( Figs 18–19 )

Diagnosis: Messana, 1988: 306–312.

Material examined. Ovigerous female, 6.0 mm, sample 2M12, station 8: Beirut inside harbor, 1–2 m, G. Bitar & H. Zibrowius coll., 2 June 2000 ( MZB2016-3566, 24 slides).

Descriptive note of ovigerous female [ MZB 2016-3566]. Body oval in shape, strongly convex, provided with tufts of setae mainly around perimeter of body and dorsum of cephalon, pleon, and pleotelson. Integument slightly rough, finely dotted, milky-white in color (observed with a stereoscopic microscope), forming a reticle generally with pentagonal or hexagonal figures (observed under optical microscope). In dorsal view, appendages entirely hidden with exception of uropods. Cephalon three times wider than long. Eyes triangular, with more than 120 small ommatidia, placed in posterolateral angles of cephalon inserted in pereonite 1. Pereonite 1 longest and pereonite 7 shortest; this last segment approximately half of length of each pereonite 2–6. Pleon with 2 lateral sutures, not covered by pereonite 7. Pleotelson twice as long as pleon, with 2 longitudinal ridges preceded by tuft of setae; end of pleotelson with tube, open in ventral view.

Antenna 1 reaching pereopod 1, with 3 basal articles and flagellum with 11 articles; first flagellar article shortest, with 3 sensory setae and 2 simple setae; articles 4–8 and 10 bearing one aesthetasc; simple setae present on all articles. Antenna 2 slender and slightly longer than preceding one, also reaching pereonite 1; with 5 peduncular articles and flagellum with 9 articles; peduncle and flagellum of same length.

Mouthparts metamorphosed. Mandible as a simple lobe; palp unmodified, with 3 articles; article 2 with 8 pectinated setae, and apical article with 12 pectinated setae. Maxilla 1 outer lobe without setae, inner lobe lost during dissection. Maxilla 2 with 3 rounded lobes without setae. Maxilliped with palp reduced of 5 articles, curved inwards, without setae, slightly longer than endite. Apparent setae on margins of mouthparts due to scaly tegument.

Pereopod 1 stoutest, with carpus triangular and 3, 1, and 3 serrated setae on inner margin of merus, carpus and propodus respectively. Pereopod 2 with 2, 2, and 3 serrated setae on inner margin of merus, carpus and propodus respectively. Pereopod 3 similar to preceding one, with only serrated seta on merus and additional serrated seta on carpus. Pereopod 4 with merus flattened; 1, 2, and 2 serrated setae on inner margin of merus, carpus and propodus respectively. Pereopod 5 slightly more stylized but similar to pereopods 2–3; 2, 3, and 3 serrated setae on inner margin of merus, carpus and propodus respectively. Pereopod 6 thin; 2, 4, and 3 serrated setae on inner margin of merus, carpus and propodus respectively. Pereopod 7 longest, similar to preceding one; crown of serrated setae around distal margin of carpus. All pereopods with brush of short setae on inner margin of ischium (distal section), merus, carpus, and propodus. Length progressively increasing from pereopod 1 to pereopod 7. Oostegites oval; pereopod 6 extracted together with oostegite; relative length of oostegite:basis is 1.3.

Pleopod 1 sympod with 3 retinaculae; endopod subtriangular, much shorter than exopod; 2 teeth on externodistal angle of exopod; endopod with 16, and exopod with 30 long plumose setae; sensory serrated seta near start of outer margin of exopod. Pleopod 2 with sympod biarticulate, with 3 retinaculae; endopod subtriangular, shorter than exopod; 10 teeth on distal section of outer margin of exopod; endopod with 21, and exopod with 26 long plumose setae. Pleopod 3 sympod with 2 retinaculae; endopod subtriangular, similar in length to exopod; endopod with 16 and exopod with 39 long plumose setae. Pleopod 4 with single plumose seta on sympod; two rami subtriangular of similar length; exopod with 2 small lateral incisions in outer margin; inner margin of endopod with proximal, internal, triangular, toothed boss, and about 40 simple setae. Pleopod 5 with two rami subelliptical at end; inner margin of endopod lobed on proximal section; exopod with 2 terminal, toothed papillae, and internal, subterminal toothed papilla; subterminal articulation not observed, only lateral suture at same level of papilla; simple setae surrounding outer margin of each ramus.

Uropodal rami with smooth margins, not serrated; apices truncated, with concave margins, slightly oblique in exopodite; exopod shorter than endopod; long stout simple setae surrounding margins of two rami, absent only in inner margin of endopod.

Remarks. Messana (1988) described P. seleneides from 4 males from Gesira (coast of Somalia), the only record existing so far. The similar features of the appendages of the ovigerous female examined in this study and those of the males studied by Messana (1988) suggests that it may be the female of the same species. For this reason, a descriptive note is included in this study. The female of P. cf. seleneides was located in Beirut harbor ( Lebanon), which is the first recording for the Mediterranean Sea; presumably, it may have been introduced via the Suez Canal (Lessepsian species).

Figures

FIGURE 18. Pseudocerceis cf. seleneides Messana, 1988. OVigerous female 6.0 mm [MZB 2016 - 3566]: A, body, dorsal View; B, body, lateral View; C, antenna 1; D, antenna 2; E, detail of tegument reticle; F, anterior section of body, Ventrolateral View; G, pleotelsonic tube, Ventrolateral View (setae of margin, omitted); H, left mandible; I, right mandible; J, maxilla 1; K, maxilla 2; L, maxilliped. Scale bars: A – B, F – G = 1 mm; C – D = 0.5 mm; E = 0.05 mm; H – L = 0.25 mm.

FIGURE 19. Pseudocerceis cf. seleneides Messana, 1988. OVigerous female 6.0 mm [MZB 2016 – 3566]: A, pereopod 1; B, pereopod 3; C, pereopod 5; D, pereopod 7; E, oostegite of pereopod 6; F, uropod; G – K, pleopods 1 – 5. Scale bar: A – K = 0.5 mm.