Parapontophilus cornutus, Komai, 2008

Komai, Tomoyuki, 2008, A world-wide review of species of the deepwater crangonid genus Parapontophilus Christoffersen, 1988 (Crustacea, Decapoda, Caridea), with descriptions of ten new species, Zoosystema 30 (2), pp. 261-332 : 292-295

Parapontophilus cornutus n. sp. ( Figs 10-12 ; 35 )

TYPE MATERIAL. — Holotype: Austral Islands . BENTHAUS, stn CP 1965, Tubuai Island, 23°21.3’S, 149°33.9’W, 500-1200 m, 19.XI.2002, ♀ 9.7 mm (MNHN-Na 16159).

Paratypes: BENTHAUS, same data as holotype, 1 ♂ 8.0 mm (MNHN-Na 16160). — Stn CP 1966, 23°21.3’S, 149°34’W, 636-1200 m, 19.XI.2002, 1 ♀ 7.6 mm (MNHN-Na 16161).

ETYMOLOGY. — From the Latin cornutus , meaning horn, in reference to the characteristic horn-like rostrum of the new species.

DISTRIBUTION. — So far known only from the Austral Islands in French Polynesia ( Fig. 35 ). Actual bathymetric range of this new species remains unclear, as the present specimens were collected from very steep slopes ranging from 500 to 1200 m.

DESCRIPTION

Rostrum( Figs 11C ; 12A, B )slender,elongate subconical, 0.25-0.40 of carapace length, somewhat directed upward, distinctly overreaching distal margins of corneas; lateral margins with 2 pairs of minute teeth closely appressed to rostrum.Carapace ( Figs10 ; 11A, B ; 12 ) about 1.50 times longer than wide; anterior epigastric tooth absent; posterior epigastric and cardiac teeth moderately small; postorbital tooth absent; postorbital ridge very low,obsolete;epibranchial ridge low, but well-marked; branchiostegal tooth relatively strong, reaching or slightly overreaching dorsodistal margin of antennal basicerite.

Third pleonal somite ( Fig. 10 ) with moderately convex tergum and with somewhat produced posterodorsal margin. Fifth somite ( Fig. 11D ) with low, posteriorly widened plateau on dorsal surface, median part of plateau shallowly sulcate. Sixth somite ( Figs 10 ; 11D ) about 4.10 times longer than wide, 3.20-3.30 times longer than deep; dorsal surface with low, blunt submedian ridges flanking shallow median sulcus.Telson ( Fig. 11E ) shorter than sixth pleonal somite.

Eye ( Fig. 11A, B ) generally bean-shaped; cornea pigmented with light brown or gray in preservative; corneal surface distinctly faceted with moderately small lenses as in P. junceus ; maximal diameter of cornea 0.17-0.20 of carapace length; eye-stalk slightly constricted near base; papillalike projection on mesial face small. Antennular peduncle ( Fig. 11A ) falling short of midlength of antennal scale. Antennal scale ( Fig. 11A ) about 0.70 of carapace length, 3.90-4.10 times long- er than wide; lateral margin noticeably concave, distolateral tooth overreaching distal margin of lamella.

Palm of first pereopod ( Fig. 11F ) about 4.20 times longer than wide; cutting edge moderately oblique; pollex relatively small, width of palm including tip of pollex about 1.25 of width proximal to base of pollex; merus with relatively weak dorsodistal tooth. Second pereopod short, reaching or falling short of midlength of merus of first pereopod. Fourth pereopod ( Fig. 11G ) overreaching distal margin of antennal scale by half to full length of dactylus; dactylus ( Fig. 1H) not flattened with rounded dorsal surface, 0.30-0.40 of propodal length; carpus 1.0-1.12 of propodal length. Fifth pereopod ( Fig. 11I ) similar to fourth, slightly falling short of distal margin of antennal scale. Appendix masculina of male second pleopod ( Fig. 11J ) about 0.70 length of appendix interna, bearing 7 long spiniform setae.

Coloration in life

Unknown.

Size

Male CL 8.0 mm; females CL 7.6-9.7 mm.

REMARKS

The length of the rostrum shows substantial variation, although only three specimens are available for study. In the male paratype, the rostrum slightly overreaches the corneas, whereas it far exceeds them in the female paratype.

This new species is distinctive in having a number of unique characters within the species group, including the elongate, conical rostrum, the tiny, appressed lateral teeth on the rostrum, the presence of a distinct, broad plateau on the tergum of the fifth pleonal somite, the distinct submedian ridges on the sixth pleonal somite, the short, subconical dactyli of the fourth and fifth pereopods being less than half length of the propodi, and the carpi of those pereopods being subequal or longer than the propodi. The well-developed distolateral tooth of the antennal scale, which distinctly overreaches the distal lamella, distinguished Parapontophilus cornutus from most other species of the group except for P. cyrton n. sp.

Figures

FIG. 10. — Parapontophilus cornutus n. sp., habitus (rostrum broken off, setae partially omitted), ♀, 9.7 mm, holotype, Tubuai Island, Austral Islands, French Polynesia (BENTHAUS, stn CP 1965) (MNHN-Na 16159). Scale bar: 5 mm.

FIG. 11. — Parapontophilus cornutus n. sp.: A, carapace and cephalic appendages, dorsal view; B, anterior part of carapace and eyes, dorsal view; C, rostrum, dorsal view; D, fifth and sixth pleonal somites, dorsal view; E, telson, dorsal view; F, subchela of left first pereopod, ventral view; G, left fourth pereopod, lateral view (setae omitted); H, same, dactylus and distal part of propodus, lateral view;I, dactylus, propodus and carpus of right fifth pereopod, lateral view; J, appendices masculina and interna of left second pleopod, mesial view; A, B, D-I, ♀ 9.7 mm, holotype, off Tubuai Island, Austral Islands, French Polynesia (BENTHAUS, stn CP 1965) (MNHN-Na 16159); C, ♀ 7.6 mm, paratype, same data as holotype (MNHN-Na 16161); J, ♂ 8.0 mm, paratype, same lot. Scale bars: A, D-G, I, 2 mm; B, C, 1 mm; H, J, 0.5 mm.

FIG. 12. — Parapontophilus cornutus n. sp.: anterior part of carapace and cephalic appendages, lateral view (setae partially omitted): A, ♂ 8.0 mm, paratype, Tubuai Island, Austral Islands, French Polynesia (BENTHAUS, stn CP 1965) (MNHN-Na 16160); B, ♀ 7.6 mm, paratype, same locality (BENTHAUS, stn CP 1966) (MNHN-Na 16161). Scale bar: 2 mm.

FIG. 35.— Geographic distribution of Parapontophilus abyssi (Smith,1884) (■), P.cornutus n. sp.(❖), P.cyrton n. sp.(✽), P.difficilis n. sp. (▼), P. geminus n. sp. (✖), P. junceus (Bate, 1888) (●), P. longirostris n. sp. (▲), P. occidentalis (◆) and P. profundus (Bate, 1888) (✚).