Liropus gurui, Guerra-García, José M., Chatterjee, Tapas & Schizas, Nikolaos V., 2015

Guerra-García, José M., Chatterjee, Tapas & Schizas, Nikolaos V., 2015, New genus and new species of Caprellidae (Crustacea: Peracarida: Amphipoda) from the mesophotic coral ecosystems of Puerto Rico and St. Croix, Caribbean Sea, Zootaxa 4018 (1) : -

Liropus gurui sp. nov.

( Figs. 7–10 )

Type material. Holotype, male 4.4 mm (used for drawings of lateral view, antennae, gnathopods, pereopods 3–5 and abdomen) (vial and one slide, mouthparts dissected) (vial: MNCN 20.04/10080, slide: MNCN 20.04/10081), Abrir la Sierra, GPS coordinates N 18.76197, W -67.15696, W Puerto Rico, Caribbean Sea, 70 meters depth, 26 April 2012. All specimens, except those from La Parguera, SW Puerto Rico were collected during the 2012 mesophotic cruise organized by the CCRI-DMS-UPRM team ( Sherman et al. 2013).

Paratype “a”, female 3.5 mm (used for drawings of lateral view, gnathopod 2, pereopods 3–4 and abdomen) (vial and one slide, mouthparts not dissected) (vial: MNCN 20.04/10082, slide: MNCN 20.04/10083), Salt River Canyon, St. Croix. U.S. Virgin Islands, GPS coordinates N 17.78689, W -64.75856, Caribbean Sea, 70 meters depth, 4 May 2012.

Paratype “b”, male 2.3 mm (used for drawings of mouthparts) (vial and one slide, mouthparts dissected) (vial: MNCN 20.04/10084, slide: MNCN 20.04/10085), Bajo de Sico, GPS coordinates N 18.23075, W -67.43177, W Puerto Rico, Caribbean Sea, 50 meters depth, 28 April 2012.

Paratype “c”, male 2.1 mm (used for drawings of pereopods 6–7) (vial and one slide, mouthparts not dissected) (vial: MNCN 20.04/10086, slide: MNCN 20.04/10087), Precipicio, La Parguera, GPS coordinates N 17.87516, W -67.04882, SW Puerto Rico, Caribbean Sea, 50–55 meters depth, 24 February 2011.

Paratype “d”, female 2.5 mm (vial and one slide, mouthparts dissected) (vial: MNCN 20.04/10088, slide: MNCN 20.04/10089), Bajo de Sico, GPS coordinates N 18.23075, W -67.43177, W Puerto Rico, Caribbean Sea, 50 meters depth, 28 April 2012.

Paratype “e”, female 1.9 mm (vial, mouthparts not dissected) (vial: MNCN 20.04/10090), Bajo de Sico, GPS coordinates N 18.23075, W -67.43177, W Puerto Rico, Caribbean Sea, 50 meters depth, 28 April 2012.

Additional material examined. 1 mature male and 2 mature females collected from Tourmaline, GPS coordinates N 18.17530, W -67.32730, W Puerto Rico, Caribbean Sea, 54 meters depth, 29 April 2012; 1 mature female collected from Weinberg, La Parguera, GPS coordinates N 17.890440 W -66.989020, SW Puerto Rico, Caribbean Sea, 45 meters depth, 13 March 2008; 1 premature female collected from Precipicio, La Parguera, GPS coordinates N 17.87516, W -67.04882, SW Puerto Rico, Caribbean Sea, 50–55 meters depth, 24 February 2011.

Diagnosis. Eyes present, but with few ommatidia. Body dorsally smooth except for a dorsal acute projection located distally on pereonite 4. Anterolateral projections absent. Flagellum of antenna 1 two-articulate. Basis of gnathopod 2 shorter than pereonite 2. Pereopods 3 and 4 one-articulate. Pereopods 5 two-articulate. Abdomen with a pair of very short appendages in males, reduced to strong setae in females.

Etymology. The species is dedicated in honour of Prof. B. C. Guru, Utkal University, Bhubaneswar, Orissa, India, D. Sc. Thesis advisor of the second author (TC).

Description. Holotype male (4.8 mm)

Lateral view ( Fig. 7 ). Body dorsally smooth except for a dorsal acute projection located distally on pereonite 4. Head rounded, lacking any projections, eyes present but with few ommatidia. Pereonite 1 fused with head, suture indistinct. Pereonites 2, 3 and 4 without anterolateral projections. Pereonite 5 the longest. Pereonite 7 the shortest.

Gills ( Fig. 7 ). Present at middle of pereonites 3–4, small and oval, length about 1.5 times width.

Mouthparts ( Fig. 8 , figured and described from the male paratype “b”). Mouthparts remarkably small (ca. 0.05 mm). Mandibles with trituritive molar, moderately developed and dentate marginally. Three-articulate palp; distal article of palp the longest, with a setal formula 1-x- 1, being x=4; left mandible with incisor and lacinia mobilis five-dentate, followed by two accessory blades; incisor of right mandible five-dentate, lacinia mobilis looking like a blade, followed by two more blades; no sign of molar flake. Lower lip without setae; inner lobes small and globose, almost fused. Maxilla 1 outer lobe carrying six spines, palp two-articulate, distal article with three apical spines and one medial seta. Maxilla 2 inner lobe small, shorter than outer lobe, both with two apical setae. Maxilliped inner plate small, about 1/5 of outer plate in length, carrying two setae; outer plate oval, with five setae; palp four-articulate, third article the longest, with four setae and lacking distal projection; dactylus with two setulae distally.

Antennae ( Figs. 7 and 9 ). Antenna 1 ca. 1/5 of body length; peduncular article 1 with lateral bulge at distal end bearing several setae; peduncular articles 2 and 3 swollen distally; flagellum 2-articulate, longer than peduncular article 3, provided with long setae. Antenna 2 shorter than peduncle of antenna 1; peduncular articles 3–4 slightly swollen distally, proximal peduncular article with a well developed acute gland cone distally; swimming setae absent; flagellum two-articulate.

Gnathopods ( Figs. 7 and 9 ). Gnathopod 1 basis of the same length than the combination of ischium, merus and carpus; grasping margin of propodus smooth with several setae; two proximal grasping spines, dactylus bifid distally. Gnathopod 2 inserted on the anterior half of pereonite 2; basis shorter than pereonite 2; ischium rectangular; merus rounded; carpus short and triangular; propodus elongated, palm long and convex, slightly setose, with proximal projection provided with one large grasping spine; dactylus smooth and not narrowed medially or distally.

Pereopods ( Figs. 7 and 10 ). Pereopod 3 and 4 one-articulate, with two setae distally. Pereopod 3 larger than pereopod 4 and slightly curved upward ( Fig. 7 ). Pereopod 5 two-articulate, inserted on the middle of pereonite 5, with 3 setae distally. Pereopod 6 and 7 figured from the male paratype “c”, attached to the posterior end of the pereonites, six-articulate, basis without carina, ischium short and rectangular, merus, carpus and propodus palm carrying row of robust setae, dactylus curved. Pereopod 7 slightly larger than pereopod 6.

Penes ( Fig. 10 ) large, situated medially, distinctive, oval, length ca 2 times width.

Abdomen ( Fig. 10 ) with a pair of very short appendages, provided with three setae, a pair of lobes, and a single dorsal lobe.

Paratype female “a” (3.5 mm) ( Figs. 7 , 9 , 10 )

Similar to the male, except for the following characteristics: presence of oostegites on pereonites 3 and 4, oostegites setose on pereonite 3 ( Fig. 7 ). Pereopod 3 smaller than in male and not curved upward ( Fig. 10 ). Abdominal appendages reduced to strong setae ( Fig. 10 ).

Intraspecific variation. The morphological characteristics of the species are rather constant in the specimens examined. Mouthparts were similar in the three specimens dissected, except for the number of setae in the mandibular palp 1-x- 1 with x varying between 3 and 5. The flagellum of antenna 1 was always provided with two articles. Pereopods 3 in immature males were morphologically similar to pereopod 4 and not enlarged and curved upward as in the holotype male.

Remarks. The genus Liropus was established by Mayer (1890) and presently includes eleven species: Liropus africanus Mayer, 1920 ; L. azorensis Guerra-García, 2004 ; L. cachuchoensis Guerra-García, Sorbe & Frutos., 2008 ; L. elongatus Mayer, 1890 (type species); L. gracilis Chevreux, 1927 ; L. gurui sp. nov.; L. isabelensis Sánchez- Moyano, García-Asencio & Guerra-García, 2015; L. japonicus Mori, 1995 ; L. minimus Mayer, 1890 ; L. minusculus Guerra-García & Hendrycks, 2013 ; and L. nelsonae Guerra-García, 2003b . A morphological comparison among Liropus species and an illustrated key of the genus is provided by Guerra-García & Hendrycks (2013) and Sánchez-Moyano et al. (2015). The new species Liropus gurui is closely related to L. japonicus . These two species are the only ones in the genus with 2-articulated flagellum of antenna 1, peduncular article 1 of antenna 1 with lateral bulge on distal end and peduncular articles 2–3 swollen distally. These characteristics of the antennae are shared with the genus Pedoculina , as pointed out by Mori (1995), but both genera clearly differ in that Pedoculina is lacking mandibular palp. On the basis of these characters of antennae 1, and differences in the morphology of the mouthparts of P. gu r u i and P. japonicus in comparison with the remaining species of Liropus , a further phylogenetic analysis in the genus Liropus should be necessary to explore if these two species could be assigned to a new genus or not. At the moment, taking into account that the remaining morphological characters are in agreement with the diagnosis of the genus Liropus , and that we can find variation in some features within the genus such as the number of articles of pereopods and abdominal appendages (see Table 1, pp. 473 in Guerra- García & Hendrycks, 2013), it is proposed to maintain these two species in the genus Liropus .

The most important differences between Liropus gurui and L. japonicus are: (1) pereonite 3 in L. japonicus has an anteroventral margin extended forward, which is lacking in L. gurui ; (2) gnathopod 2 propodus in males of L. japonicus has a medial deep triangular cleft and is roughly serrate distally (see Fig. 3 a, pp. 333 in Mori, 1995), while it is smooth and lacks the cleft in L. gurui ; (3) pereopod 3 is twice as long in males of L. gurui than in males of L. japonicus ; (4) inner lobes of lower lip are slightly bilobated at the middle section in L. japonicus and not bilobated in L. gurui ; (5) abdominal appendages are vestigial in L. japonicus and slightly developed in L. gurui .

Most of the Liropus species have been collected from Atlantic or Mediterranean waters, except for L. isabelensis , L. japonicus and L. minusculus which have been found in the Pacific. All the species, apart from L. nelsonae , are distributed in the Northern Hemisphere, being more abundant in the border areas of temperate and tropical zones (see Guerra-García & Hendrycks, 2013).

Figures

FIGURE 3. Borikenella spinosa gen. nov., sp. nov. Antennae, gnathopod 1 and 2 of holotype male, 4.2 mm. Gnathopod 2 of paratype female “ a ”, 4.1 mm.

FIGURE 7. Liropus gurui sp. nov. Lateral view of holotype male, 4.4 mm, and paratype female “ a ”, 3.5 mm.

FIGURE 8. Liropus gurui sp. nov. Mouthparts of paratype male “ b ”, 2.3 mm.

FIGURE 9. Liropus gurui sp. nov. Antennae, gnathopod 1 and 2 of holotype male, 4.4 mm. Gnathopod 2 of paratype female “ a ”, 3.5 mm.

FIGURE 10. Liropus gurui sp. nov. Pereopods 3, 4 and 5, and abdomen (lateral and ventral view) of holotype male, 4.4 mm. Pereopods 3 and 4 and abdomen of paratype female “ a ”, 3.5 mm. Pereopods 6 and 7 of paratype male “ c ”, 2.1 mm.