Monoliropus leeae, Hong, Soon-Sang, Heo, Jun-Haeng & Kim, Young-Hyo, 2015

Hong, Soon-Sang, Heo, Jun-Haeng & Kim, Young-Hyo, 2015, A new species of Monoliropus Mayer, 1903 (Crustacea, Amphipoda, Caprellidae) from Korean waters, ZooKeys 517, pp. 111-121 : 112-117

Taxon classification Animalia Amphipoda Caprellidae

Monoliropus leeae sp. n. Figures 1, 2, 3, 4, 5

Type material.

Holotype: male, 9.3 mm, NIBRIV0000309619, Bukhang Port, Jukgyo-dong, Mokpo-si, Jeollanam-do, Korea, 34°48'00"N, 126°21'56"E, S.S. Hong and S.H. Kim, by light trap from 6-8 m depth, 11 July 2012. Paratypes: female, 11.7 mm, NIBRIV0000309620, 27 July 2012, same station data as holotype; 6 males, 5.3-6.7 mm, DKUAMP201501, 11 July 2012, same station data as holotype; 2 immature males and 5 immature females, 5.3-7.1 mm, DKUAMP201502, 27 July 2012, same station data as holotype.

Description.

Holotype, male, NIBRIV0000309619.

Body (Fig. 3A) 9.3 mm long, slender and long, surface smooth. Head round and smooth without projection. Eye small, round. Head and pereonite 1 fused, suture present. Pereonite 1 nearly smooth, with 1 small bump anterodorsally and a pair of minute blunt processes posterodorsally. Pereonite 2 with acute triangular process anterolaterally. Pereonites 3-4 subequal in length, with small uniarticulate pereopods and rounded gills ventrally, and tiny triangular process on both lateral sides. Pereonite 5 subrectangular, width 0.30 × length, with 6-articulate pereopod. Pereonite 6 smooth without process. Length ratio of pereonites 1-7 = 1.00: 1.52: 2.12: 2.23: 2.53: 1.40: 0.49.

Antenna 1 (Fig. 3B) 0.35 × body; length ratio of peduncular articles 1-3 = 1.00: 3.46: 0.84; flagellum 9-articulate, 0.76 × peduncular articles, each article with 1 or 2 aesthetascs ventrodistally.

Antenna 2 (Fig. 3C) slightly shorter than antenna 1; length ratio of peduncular articles 3-5 = 1.00: 2.75: 3.45; peduncular articles 4-5 with unequal simple setae ventrally; flagellum biarticulate, 0.30 × peduncular articles, proximal article elongate, 1.95 × distal article.

Upper lip (Fig. 3D) rounded, notched midventrally with pubescence apically.

Lower lip (Fig. 3E) well developed, inner and outer lobes with patch of pubescence apically.

Left mandible (Fig. 3F) incisor and lacinia mobilis 5-teethed; setal row with 3 pectinated setae; molar well developed, truncate; mandibular palp slender, triarticulate, length ratio of articles 1-3 = 1.00: 1.92: 1.85, article 2 with 6 simple setae, distal article acute apically, with 4 simple setae.

Right mandible (Fig. 3G) similar to left except setal row with 2 pectinated setae and molar flake present.

Maxilla 1 (Fig. 3H) inner plate absent; outer plate with 6 stout setal teeth (3 simple, 2 bifid and 1 denticulate) apically; palp biarticulate, distal article with 5 apical spines and 4 subapical setae.

Maxilla 2 (Fig. 3I) inner plate with dense pubescence medially and 8 simple setae on apical and subapical margins; outer plate longer than inner, with 12 simple setae apically.

Maxilliped (Fig. 3J) inner plate subrectangular, with 1 forked and 3 penicillate setae apically; outer plate much larger than inner plate, distomedial portion with rounded groove, distal margin rounded with 1 simple seta; palp 4-articulate, article 3 with subacute process apically, distal article falcate, with a row of setules along inner margin, length ratio of articles 1-4 = 1.00: 1.75: 1.70: 1.17.

Gnathopod 1 (Fig. 3K) propodus subrectangular, narrowing distally, width 0.45 × length, palm serrated with 1 proximal grasping spine; dactylus falcate, with irregular serrations on inner margin; length ratio of 6 articles = 1.00: 0.26: 0.38: 0.34: 1.02: 0.77.

Gnathopod 2 (Fig. 4A) anterior margin of carpus very short; propodus massive, width 0.44 × length, anterior margin convex, with rounded angle, palmar margin straight with proximal blunt process bearing grasping spine and acute poison tooth followed by rounded notch subdistally; dactylus elongate, falcate; length ratio of 6 articles = 1.00: 0.25: 0.27: 0.18: 1.34: 1.10.

Gill 3 (Fig. 4B) elongate, elliptical, 0.63 × pereonite 3.

Pereopod 3 (Fig. 4B) vestigial, uniarticulate, 0.07 × gill, with 4 simple and 2 penicillate setae.

Pereopod 4 (Fig. 4C) similar to pereopod 3, but slightly longer.

Pereopod 5 (Fig. 4D) well developed, slender, setose, 6-articulate, 1.21 × pereonite 5, inserted about 7/10 from the anterior end of pereonite 5; length ratio of 6 articles = 1.00: 0.21: 0.74: 0.87: 0.94: 0.68.

Pereopod 6 (Fig. 4E) well developed, setose, 6-articulate, 2.49 × pereonite 6, 1.20 × pereopod 5, attached to the posterodistal end of the pereonite 6; propodus subrectangular, palm defined by posterodistal blunt bump with grasping spine and seta; length ratio of 6 articles = 1.00: 0.28: 0.76: 0.84: 1.40: 1.00.

Pereopod 7 (Fig. 4F) similar and subequal to pereopod 6, length ratio of 6 articles = 1.00: 0.26: 0.78: 0.90: 1.50: 1.10.

Penes (Fig. 4G) cylindrical in shape, situated medially, width 0.50 × length.

Abdomen (Fig. 4G, H) with a pair of appendages, a pair of lateral and single dorsal lobes; appendage uniarticulate, with 3 lateral, 1 apical setae, distal portion covered with patch of fine setules; lateral lobe with 4 simple setae apically; dorsal lobe rounded, with 7 simple setae dorsally.

Paratype, female (sexually dimorphic characters), NIBRIV0000309620.

Body (Fig. 5A) 11.7 mm long. Body form generally as in male including antennae 1-2, but pereonites 3-4 with rounded brood pouches. Gnathopod 2 (Fig. 5B) palm slightly curved convexly. Pereopods 3-7 (Fig. 5 C–F) more setose than male. Abdomen (Fig. 5G) lacking appendages, lateral lobe wider than that of male.

Remarks.

The genus Monoliropus belongs to the family Caprellidae , which has close affinities with Metaprotella Mayer, 1890 and Triprotella Arimoto, 1970 as it possesses the following characters: 1) antenna 2, peduncles without swimming seta, flagellum biarticulate; 2) mandibular palp bi- or triarticulate; 3) pereopods 3-4 reduced, uniarticulate; 4) in male, abdomen with uni- or biarticulate appendages. However, Metaprotella is distinguished from Monoliropus by setal formula 1 –x–y– 1 of the distal article of mandibular palp and fused pereonites 6-7. Triprotella is very similar to the genus Monoliropus ; however, is discernible from Monoliropus by setal formula 1-1-1 of the distal article of the mandibular palp, uniarticulate pereopods 3-4, morphology of the gnathopod 2, and form of abdomen ( Sivaprakasam 1977; Laubitz 1991; Guerra-García 2002). The species Monoliropus agilis has been redescribed by Guerra-García (2004), showing a setal formula of mandibular palp of 1-1-1, and the abdomen very similar to that of the genus Triprotella . Therefore both genera could be re-established or synonymized in the future. The new species Monoliropus leeae sp. n. is similar to Monoliropus agilis Mayer, 1903, Monoliropus kazemii Momtazi & Sari, 2013, and Triprotella amica Arimoto, 1970, however, is distinguished from its congeners based on the characters listed in Table 1 and the combination of the following features: 1) body medium sized, 9-11 mm (vs. small sized, 4 mm in Monoliropus agilis , 5-7 mm in Triprotella amica ); 2) maxilla 1, outer plate with six stout setal teeth (vs. five in Triprotella amica , seven in Monoliropus agilis and Monoliropus kazemii ); 3) mandibular palp, distal article with four simple setae (vs. three simple setae in Monoliropus agilis and Triprotella amica ); 4) gnathopod 1, propodus subrectangular (vs. subtriangular in Monoliropus agilis , Monoliropus kazemii , and Triprotella amica ); 5) gnathopod 1, dactylus with serrations on inner margin (vs. with serrations both margins in Triprotella amica ); 6) pereonites 2-3 with acute triangular processes anterolaterally (vs. without triangular processes in Monoliropus agilis , Monoliropus kazemii , and Triprotella amica ); 7) pereopods 3-4 short (vs. elongate in Monoliropus agilis , Monoliropus kazemii , and Triprotella amica ); 8) abdominal appendage uniarticulate (vs. biarticulate in Monoliropus kazemii ).

Etymology.

The specific name leeae is in honor of Dr. Kyung-Sook Lee, who has contributed to knowledge of Korean caprellid Amphipoda .

Distribution.

Bukhang Port, Jukgyo-dong, Mokpo-si, Jeollanam-do, Korea.