Prachynella shijiki, Lowry & Stoddart, 2012

Lowry, J. K. & Stoddart, H. E., 2012, The Pachynidae fam. nov. (Crustacea: Amphipoda: Lysianassoidea) 3246, Zootaxa 3246 (1), pp. 1-69 : 52-53

Prachynella shijiki sp. nov.

( Fig. 36 )

Prachynella lado (sic). ― Hirayama, 1985: 182, figs 175–178.

Prachynella lodo . ― Ishimaru, 1994: 59.

Type material. HOLOTYPE, female, 6.5 mm, AMBL-Amph. 26, specimen no. 1, Shijiki Bay , Hirado Island , West Kyushu, Japan, western North Pacific Ocean, [approx. 33°15’N 129°24’E], 0–40 m, July 1977, M. Azuna. PARA- TYPE, male, AMBL-Amph. 26, specimen no. 2, same locality. [material described and illustrated by Hirayama, 1985, as Prachynella lado ; the third specimen recorded by Hirayama is now lost, according to Professor Kikuchi, Director of Amakusa Marine Biological Laboratory, 1991].

Etymology. Named for the type locality; used as a noun in apposition.

Type locality. Shijiki Bay , Hirado Island , West Kyushu, Japan, western North Pacific Ocean, approx. 33°15’N 129°24’E, 0–40 m depth .

Diagnostic description. Head lateral cephalic lobe large, broadly rounded; ventral margin curved. Antenna 1 peduncular article 1 with posterodistal spine; accessory flagellum 2-articulate, article 1 short; flagellum with strong 1-field callynophore in female and male. Mandible lacinia mobilis a simple robust seta; lamina dentata absent; accessory setal row present, on raised setose ridge; molar a nonsetose flap; palp attached distally; palp article 2 broad, shorter than article 3; article 3 with subparallel margins. Maxilla 1 outer plate with 10 setal-teeth in 7/3 arrangement, outer row setal-teeth with medial cusps; palp vestigial, 1-articulate, apical setae absent. Maxilliped inner plate small; outer plate large; palp 3-articulate (articles 1 and 2 fused). Gnathopod 1 chelate; ischium smaller than propodus, not swollen posteroproximally; carpus extremely compressed; propodus length about 2.2 × breadth, posterior margin well developed, palm with produced corner (pollex length about 1.2 × breadth), corner of palm with complex robust seta; dactylus reaching to corner of palm. Gnathopod 2 palm minute, obtuse. Pereonite 4 with 1 dorsal spine. Pereonite 5 without dorsal spines. Pereopod 5 merus with posteroproximal shoulder. Pereopod 6 basis with posteroventral lobe weakly produced; merus longer than broad, with posteroproximal shoulder. Pereopod 7 basis subquadrate with posterior margin weakly dentate. Oostegites from gnathopod 2 to pereopod 5. Epimeron 3 posterior margin without projections, posteroventral corner broadly rounded. Uropod 3 biramous, inner ramus extending more than halfway along outer ramus but not reaching base of article 2. Telson shorter than broad, entire, slightly emarginate.

Remarks. Hirayama (1985) identified these specimens as P. lodo (mis-spelled as lado ), but clearly illustrated a dorsal spine on pereonite 4, not pereonite 5. We have examined the material and confirm that this is true. Prachynella shijiki is further distinguished from P. lodo and P. oculata by the relative lengths of gnathopod 1 propodus: in P. shijiki the length of the main part of the propodus (from mid-proximal point to articulation of the dactylus) is about 5 times the length of the dactylus; in P. lodo it is about 3 times the length and in P. oculata about 2 times.

Distribution. Japan, western North Pacific Ocean; 0–40 m depth.

Figures

FIGURE 36. Prachynella shijiki, sp. nov. Holotype female, 6.5 mm, AMBL-Amph. 26, Shijiki Bay, Hirado Island, Japan. Scales represent 0.1 mm.