Metacirolana chemola, 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 : 1237-1240

Metacirolana chemola sp. nov.

( Figures 15 , 16 )

Material examined

Holotype: USNM 280287 , one ovigerous female (3.5 mm), IIOE sta 447, off Somalia, 10 ° 009N, 51 ° 159E, 59–61 m, 16 December 1964 . Paratypes: USNM 280288 , one male

4.0 mm, immature male 3.0 mm, four ovigerous females 3.1–4.0 mm, two females 2.9– 3.0 mm, same data as holotype.

Other material examined. USNM 280289 , one immature male, two ovigerous females , IIOE sta 445, off Somalia, 9 ° 419N, 51 ° 059E, 60–70 m, 16 December 1964 .

Description

Ovigerous female. Body length about 2.5 times width. Cephalon with slight mid-dorsal depression anteriorly, tiny rostral process present. Pigment variable, scattered chromatophores on all somites including pleotelson. Coxae 2–7 with distinct furrows. Pleotelson posterior margin coarsely serrate, apex flanked by two notches each containing a single short, spine-like seta, and bearing 12–13 short plumose setae.

Antennular flagellum with five to six articles and two aesthetascs on each of articles 3–5. Antennal flagellum reaching pereonite 3, bearing 11–12 articles. Frontal lamina columnar, pentagonal in head-on view; in ventral view appearing truncate distally, tapering basally, length 1.5 times greatest width. Mandibular palp, penultimate article bearing about six fringed and 11 simple setae; terminal article with four fringed and six simple setae. Maxilla 1 with 11 spine-like setae on the outer ramus; maxilla 2 as figured. Pereopods and pleopods 1, 3–5 as figured.

Uropods coarsely serrate, endopods subequal in length to pleotelson, exopods shorter. Exopod with two short, stout spine-like setae and simple setae on lateral margin, two such setae on mesial margin; endopod much wider, acute distally with one stout, spine-like seta and long, simple setae on lateral margin, two robust spine-like setae present on mesial margin.

Male. Pereon more slender than in female. In mature males, mid-dorsal depression on cephalon is flanked by low bosses. Appendix masculina on pleopod 2 parallel-sided, extending beyond endopod by less than one-quarter length, abruptly tapering to acute apex. Penes separate, flat, length about twice width with two simple setae between rami.

Remarks

This species closely resembles its congener from the Gulf of Aqaba, M. fishelsoni Bruce and Jones, 1978 , but differs in the shape of the apex of the pleotelson (being an obtuse median angle in M. fishelsoni and lacking the two prominent spine-like setae on the apex), as well as in the numbers of setae on the maxillule and mandibular palp, far fewer in the case of the latter species. The two notches on the pleotelsonic apex and lack of sculpturing thereon immediately separate it from all other congeners in the Red Sea and western Indian Ocean.

Etymology

The specific name, from the Greek ‘‘chemola’’, a notch, refers to this feature on the pleotelsonic apex.

Family SPHAEROMATIDAE H. Milne Edwards, 1840

Figures

Figure 15. Metacirolana chemola sp. nov. (A) Male, dorsal view; (B) male, lateral view; (C) antennule; (D) antenna; (E) frontal lamina; (F) apex of pleotelson; (G) maxilla 1; (H) maxilla 2; (I) mandible 3; (J) pleopod 1; (K) male pleopod 2; (L) maxilliped; (M) uropod.

Figure 16. Metacirolana chemola sp. nov. (A) Pleopod 4; (B) pleopod 5; (C) pereopod 7; (D) penes; (E) pereopod 1; (F) dactylus of pereopod 1; (G) pereopod 2; (H) pleopod 5.