Portaratrum fascinatus, Guerrero-Kommritz, Jürgen, 2003

Guerrero-Kommritz, Jürgen, 2003, Portaratrum, a new genus of deep­sea Tanaidacea (Crustacea) with description of two new species, Zootaxa 282, pp. 1-14 : 9-13

Portaratrum fascinatus n. sp. ( Figs 3 , 4 )

Material examined: Holotype: ZMH K­ 40357, non­ovigerous female, 2.7 mm, Sonne station 105/574, 7°4.156´S, 088°27.786´W, 4179 m, 24.01.1996, BC.

Paratypes: ZMH K­ 40358, ovigerous female, 2.5 mm, Sonne station 105/574, 7°4.203´S, 088°27.94´W, 4166 m, 20.01.1996, BC. ZMH K­ 40359, non­ovigerous female, 1.6 mm, dissected, Sonne station 55/539, 7°4.37´S, 088°27.76´W, 4160 m, 16.01.1996, BC.

Diagnosis: Cheliped robust, chela wide and stout, exopod of uropod about half of the length of endopod first article. First article of maxilliped palp with stout simple seta. Propodus of pereopods 1–3 smooth.

Description: Non­ovigerous female. Body ( Fig. 3 a): long and slender, 6.5 times longer than wide.

Cephalothorax ( Fig. 3 a, b, c): of oval shape.

Pereon ( Fig. 3 a, b): pereonite 2 longest, pereonite 3 as long as pereonite 4, pereonite 5 shorter than 4 and longer than 6. Pereonite 1 shortest.

Pleon ( Fig. 3 a, b): pleonite 1 slightly larger than following pleonites. Pleonites 2–5 of equal length. Pleonite 5 with prominent ventral spiniform process, pleotelson pentameral, narrower than pereon, apex blunt.

Antennula ( Fig. 3 d): composed of four articles. First article longest, as long as following three articles together, with one simple seta. Second article with two distal simple setae. Third article with three simple setae in longitudinal row. Fourth article with six terminal simple setae and one aesthetasc.

Antenna ( Fig. 3 e): composed of six articles. First article short, naked. Second article wider than long with a ventral distal spine and four dorsal setules. Third article as long as wide, naked. Fourth article longest, with two long ventral and one simple dorsal setae. Fifth article longer than wide, with one simple long ventral seta. Sixth article shortest, with one short and four long simple terminal setae.

Labrum ( Fig. 3 f): hood­shaped with many setules on the distal margin.

Mandible ( Fig. 3 g): well calcified, lacinia mobilis pointed, pars molaris well developed and broad, ending in several spinules.

Maxillule ( Fig. 3 h): endite naked with four short and five long spines.

Maxilla ( Fig. 3 i): drop shaped (triangular) with pointed angle.

Labium ( Fig. 3 j): composed of two lobes, with row of fine setules on distal angle.

Maxilliped ( Fig. 3 k): basis oval, endites with lobe or ‘scale’ distally, without setae. Palp composed of four articles. First article with long stout external seta. Second article with two simple and one serrate stout inner setae. Third article with three simple stout setae. Fourth article with four stout simple terminal setae.

Epignath: not recovered.

Cheliped ( Fig. 4 a): basis fused to cephalothorax, as long as wide. Merus triangular, with one ventral simple seta. Carpus with irregular ventral margin with two ventral simple setae at midlength and one dorsal distal seta. Propodus stout, twice as long as wide, fixed finger half as long as propodus; two ventral simple setae and three short simple dorsal setae near cutting edge. Cutting edge with a cutting plate composed of six weak teeth. Dactylus as long as fixed finger, naked.

Pereopod 1 ( Fig. 4 b): basis 3.5 times longer than wide, naked. Ischium short with one simple seta. Merus with one stout simple distal seta. Carpus shorter than propodus and longer than merus, with one stout simple distal seta. Propodus naked, as long as dactylus and unguis together, with one small stout distal seta. Dactylus smooth. Unguis sharp and slender about as long as dactylus.

Pereopod 2 ( Fig. 4 c): as pereopod 1 except carpus with three stout simple distal setae.

Pereopod 3 ( Fig. 4 d): as pereopod 2 except basis three times as long as broad, with plumose seta at midlength and propodus with three stout simple terminal setae.

Pereopod 4 ( Fig. 4 e): basis about 4.75 times longer than broad, naked. Ischium short, with one simple seta. Merus shorter than carpus, with two stout simple distal setae. Carpus shorter than propodus, with two stout simple distal setae. Propodus with three stout simple terminal setae. Dactylus smooth. Unguis short and sharp, about one third the length of dactylus.

Pereopod 5 ( Fig. 4 f): as pereopod 4 except merus with one stout simple distal seta.

Pereopod 6 ( Fig. 4 g): as pereopod 4 except merus with three stout simple distal setae. Carpus with four stout simple distal setae. Propodus with four simple stout terminal setae.

Pleopods ( Fig. 3 l): biramous, basal article pentameral, endopod as exopod, with six simple terminal setae.

Uropods ( Fig. 3 m): biramous, basal article as long as first article of endopod. Exopod uniarticled, about half length of first endopod article, with two long terminal setae. Endopod biarticled, first article with two long distal setae, second article with four long simple distal setae.

Ovigerous female: As for non­ovigerous female, except pereonites compressed dorsoventrally and oostegites are formed on pereonites 1–4. Marsupium with 13 eggs.

Neuter: Not known.

Male: Not known.

Type locality: Abyssal plains of the tropical East Pacific. DISCOL, station 105/574, 7° 4.156´S 088° 27.786´W, 4179 m.

Etymology: The Latin fascinatus (enchanted); refering to the Enchanted Island (Islas Encantadas) the former Spanish name of the Galapagos Islands, located to the north of the sampling area; a part of the ‘Enchanted’ Sea.

Remarks: Portaratrum afer and P. f a s c i n a t u s differ in the form of the cheliped: in P. fascinatus the carpus is shorter and wider, the ventral setae are larger than in P. a f e r. The propodus of pereopods 1–3 is serrated in P. a f e r and smooth in P. fascinatus . The dactyli of pereopods 4–6 in P. a f e r have a ventral groove bordered by spinules; in P. fascinatus the dactyli of the pereopods 4–6 do not have a groove or spinules. The uropod exopod is about one­third of the length of the first article of the endopod in P. a f e r and is about the half of the length in P. fascinatus .

Distribution: Known only from the abyssal plains of the tropical East Pacific Ocean.

Figures

FIGURE 3. Portaratrum fascinatus n. sp., holotype ZMH K­ 40357, non­ovigerous female: a, body, dorsal view; b, body, lateral view; c, cephalothorax, ventral view. Scale bar 1 mm. Paratype ZMH K­ 40359, non­ovigerous female: d, antennula; e, antenna; f, labrum; g, mandibles; h,. maxillula; i, maxilla; j, labium; k, maxilliped; l, pleopod; m, uropod. Scale bar 0.1 mm.

FIGURE 4. Portaratrum fascinatus n. sp., paratype ZMH K­ 40359, non­ovigerous female: a, cheliped, external view; b, pereopod 1; c, pereopod 2; d, pereopod 3; e, pereopod 4; f, pereopod 5; g, pereopod 6. Scale bar 0.1 mm.