Liropus azorensis, Guerra-García, 2004

Guerra-García, José M., 2004, Deep-sea Caprellidea (Crustacea, Amphipoda) from Azores with the description of three new species, Zoosystema 26 (2), pp. 235-262 : 237-243

Liropus azorensis n. sp.

( Figs 2-5 )

TYPE MATERIAL. — Holotype: stn 64, (MNHN- Am 5259). Allotype: stn 64, (MNHN-Am 5260). Paratypes: stn 64, 4, 2 (MNHN-Am 2949), and 5, 4, 4 juveniles (MNHN-Am 2956).

ETYMOLOGY. — Named azorensis alluding to Azores Islands, the place where the species was found.

DISTRIBUTION. — So far, only known from the Azores.

DESCRIPTION

Holotype, male (6.7 mm)

Lateral view ( Fig. 2A ). Body dorsally smooth. Head rounded; eyes without distinguishable ommatidia. Pereonite 1 fused with head, suture present. Pereonites 3 and 4 subequal. Pereonite 5 the longest. Pereonite 7 the shortest.

Gills ( Fig. 2A ). Present on pereonites 3-4, elongate, length about four times width.

Mouthparts. Upper lip ( Fig. 3A ) symmetrically bilobate, with minute setulae apically. Mandibles ( Fig. 3D, E ) with three-articulate palp; distal article of palp with a row of five plumose setae, and another two setae displaced from the row, a very small one distally and another longer one proximally, both smooth; mandibular molar present, bordered by teeth; left mandible ( Fig. 3E ) with incisor five-toothed, lacinia mobilis five-toothed followed by two plumose setae; incisor of right mandible ( Fig. 3D ) fivetoothed, lacinia mobilis deeply serrate, followed by two plumose setae; molar flake absent. Lower lip ( Fig. 3B ) inner and outer lobes well demarcat- ed, without setae; inner lobes rectangular, with a medial cleft. Maxilla 1 ( Fig. 3F ) outer lobe carrying six robust setae; distal article of the palp with four apical setae and a medial seta. Maxilla 2 ( Fig. 3G ) inner lobe rectangular, carrying five distal setae; outer lobe rectangular, 1.7 times as long as inner lobe, with five apical setae. Maxilliped ( Fig. 3C ) inner plate rectangular carrying four setae and a nodular seta; outer plate oval, 2.2 times as long as inner plate, with a seta apically and three smaller setae laterally; palp four-articulate, second article with three setae and third article with five setae.

Antennae. Antenna 1 ( Fig. 4A ) about two fifth of body length; proximal article of peduncle without projection; flagellum broken in holotype (nine-articulate in male paratype). Antenna 2 ( Fig. 4B ) about one half length of antenna 1; proximal peduncular article with acute projection distally; swimming setae absent; flagellum twoarticulate.

Gnathopods. Gnathopod 1 ( Fig. 4C ) basis 1.2 times longer than ischium to carpus combined; propodus palm with a pair of grasping spines proximally; grasping margin of propodus palm with small setulae. Gnathopod 2 ( Fig. 4D ) inserted on the anterior half of pereonite 2 ( Fig. 2A ); basis as long as pereonite 2; ischium rectangular; merus rounded; carpus short and triangular; propodus oval, as long as basis; palm with proximal projection provided with a single spine, followed by serrate margin and small U-notch; dactylus with smooth margin.

Pereopods. Pereopods 3 ( Fig. 5A ) and 4 ( Fig. 5B ) two-articulate; proximal article twice as long as distal one, provided with a distal seta; distal article with three setae. Pereopod 5 ( Fig. 5C ) twoarticulate, attached at the middle of pereonite 5; proximal article twice as long as distal one, with two distal setae; distal article with three setae. Pereopod 6 ( Fig. 5D ) attached to the posterior end of the pereonite 6, six-articulate, basis without carina, ischium short and rectangular, propodus palm carrying row of plumose setae, with two plumose setae on a proximal projection. Pereopod 7 ( Fig. 5E ) slightly larger than pereopod 6.

Penes. Penes ( Fig. 5F ) situated laterally, oval, length about 1.2 times width.

Abdomen. Abdomen ( Fig. 5F ) with a pair of appendages, a pair of lateral lobes and a single dorsal lobe. Appendages well developed, twoarticulate; proximal article rectangular with three setae; distal article almost tabicated into two articles, with two proximal setae and one seta and a strong spine distally. Dorsal lobe with two plumose setae.

Allotype, female (5.8 mm)

Oostegites setose on pereonite 3 and slightly setose on pereonite 4 ( Fig. 2B ). Genital papillae ( Fig. 2B ) setose. Abdomen ( Fig. 5G ) with appendages one-articulate provided with a lateral setae and a distal strong spine.

REMARKS

The specimens of Liropus azorensis n. sp. are in agreement with the diagnosis of the genus apart from the pereopods 3 and 4, which are twoarticulate instead of one-articulate. This characteristic enlarges the generic diagnosis and can be used to distinguish L. azorensis n. sp. from the remaining species in the genus. In the described species of the genus Liropus the abdominal appendages are small, being one-articulate or very reduced, even degenerated into setae. The abdomen of L. azorensis n. sp. differs from the abdomen of the remaining species mainly by the

A presence of large appendages which are twoarticulate (almost three-articulate) in males.

The body length measured for the males of L. azorensis n. sp. was 5.03 ± 0.77 mm (mean ± standard deviation) (range 4.13-6.70 mm). For the females it was 4.27 ± 0.78 mm (3.59- 5.80 mm). In connection with the intraspecific variation, most of the morphological characters are constant in all the specimens examined although small differences were found in the mouthparts. The number of setae following the lacinia mobilis varies, being two or three depending on the specimen. The cleft of the inner lobes is very marked in some specimens and almost absent in other specimens.

Regarding the geographic distribution, L. africanus Mayer, 1920 , L. gracilis Chevreux, 1927 , and L. azorensis n. sp. have been recorded in the North Atlantic ( McCain & Steinberg 1970) while L. nelsonae Guerra-García, 2003 was found in the South Atlantic (Guerra-García 2003). Liropus elongatus Mayer, 1890 and L. minimus Mayer, 1890 are, so far, Mediterranean endemics (Krapp-Schickel 1993) and L. japonicus Mori, 1995 extended the distribution of the genus to the Pacific Ocean (Mori 1995).

Figures

FIG. 2. — Liropus azorensis n. sp., lateral view; A, male; B, female showing a detail of genital papillae and pereopod 5. Scale bar: 1 mm.

FIG. 3. — Liropus azorensis n. sp., male mouthparts; A, upper lip; B, lower lip; C, maxilliped; D, right mandible; E, left mandible; F, maxilla 1; G, maxilla 2. Scale bars: 0.05 mm.

FIG. 4. — Liropus azorensis n. sp.; A-D, male; A, antenna 1 with detail of basal article; B, antenna 2 with detail of basal articles; C, gnathopod 1; D, gnathopod 2; E, female gnathopod 2. Scale bars: A, B, D, E, 0.5 mm; C, 0.1 mm.

FIG. 5. — Liropus azorensis n. sp.; A-F, male; A, pereopod 3; B, pereopod 4; C, pereopod 5; D, pereopod 6; E, pereopod 7; F, abdomen; G, female abdomen. Scale bars: A-C, F, G, 0.05 mm; D, E, 0.5 mm.