Liropus vitucoi, Guerra-García & Tato & Moreira, 2018

Guerra-García, José M., Tato, Ramiro & Moreira, Juan, 2018, Caprellidae (Crustacea: Peracarida: Amphipoda) from deep-sea waters off Galicia (NW Iberian Peninsula) with the description of a new genus and three new species, Zootaxa 4532 (2), pp. 151-202 : 155-161

publication ID	https://doi.org/ 10.11646/zootaxa.4532.2.1
publication LSID	lsid:zoobank.org:pub:A0A5340C-76C7-4EF7-939E-A9C3C6AC568B
DOI	https://doi.org/10.5281/zenodo.5959252
persistent identifier	https://treatment.plazi.org/id/03BE87AC-FFC8-FF8E-FF10-FEFFFCD5F9C5
treatment provided by	Plazi
scientific name	Liropus vitucoi
status	sp. nov.

Treatment

Liropus vitucoi View in CoL sp. nov.

( Figs. 2–6 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Type material. Holotype male, 3.9 mm (used for drawings of lateral and dorsal view, antennae, gnathopods, pereopods 3–5, abdomen, maxilliped, maxilla 1, upper lip and lower lip) (vial with 70% ethanol and one slide, mouthparts dissected) ( MHNUSC 10092 ); DIVA-Artabria I 2002, EBS-200, 8 September 2002, 43°40.192’N, 008°43.760’W, 212 m, muddy sand. GoogleMaps

Paratype “a” female, 2.9 mm (used for drawings of lateral view, gnathopod 2, pereopods 6 and 7, and abdomen, not dissected) ( MHNUSC 10093 ); DIVA-Artabria I 2003, EBS-200, 12 September 2003, 43°40.250’N, 008°43.755’W, 207 m, muddy medium sand GoogleMaps .

Paratypes collected together with the holotype: 4 males, 3 females, 5 juveniles (from them, 1 male “b” ( MHNUSC 10094 ) and 2 females “c” ( MHNUSC 10095 ) and “d” dissected ( MHNUSC 10096 ), 3 slides) (male “b” used for drawings of maxilla 2 and mandibles); DIVA-Artabria I 2002, EBS-200, 8 September 2002, 43°40.192’N, 008°43.760’W, 212 m, muddy sand GoogleMaps .

Other paratypes colleted together with paratype “a” (5 females, 5 juveniles, not dissected), (MHNUSC 10097); DIVA-Artabria I 2003, EBS-200, 12 September 2003, 43°40.250’N, 008°43.755’W, 207 m, muddy medium sand.

Additional material examined. 1 male, 1 juvenile, DIVA-Artabria I 2003, EBS-150, 14 September 2003, 43°34.127’N, 008°36.562’W, 152 m, muddy sand; 1 female, VERTIDOS 2004, CA-EBS-150-04, 18 September 2004, 42°50.507’N, 009°25.773’W, 151 m, muddy sand; 1 male, 1 juvenile, VERTIDOS 2004, AG-EBS-150-04, 17 September 2004, 42°30.391’N, 009°19.517’W, 148 m, muddy sand; 8 males, 3 females, 6 juveniles (1 inmature male used for lateral view figure), VERTIDOS 2004, AG-EBS-250-04, 19 September 2004, 42°31.176’N, 009°23.380’W, 248 m, muddy sand. Specimens kept in first author’s personal collection.

Diagnosis. Eyes present. Body dorsally smooth, apart from tiny dorsal tubercles anterolaterally on the head, near the eyes. Anterolateral projections present in pereonites 2, 3 and 4 in males, more developed on pereonite 2 than 3 and 4. Flagellum of antenna 1 four or five-articulate. Third article of the maxilliped palp with distal projection. Mandibular palp with setal formula 0-x-y-1 (from proximal to distal end). Basis of gnathopod 2 slightly shorter than pereonite 2. Pereopods 3 and 4 one-articulate. Pereopods 5 three-articulate. Abdomen without appendages, with a pair of lobes.

Etymology. The species is dedicated to our friend Prof. Dr. Victoriano Urgorri (“Vituco”) from Universidad de Santiago de Compostela for his great contribution to the field of Marine Biology. He was the leader of the cruise “Diva Artabria I” where the caprellid specimens of this new species were collected.

Description. Holotype male (3.9 mm)

Lateral view ( Fig. 2 View FIGURE 2 ). Body dorsally smooth except for two tiny dorsal tubercles on the head, near the eyes (see also dorsal view Fig. 2 View FIGURE 2 ). Eyes present. Pereonite 1 fused with head, suture present. Pereonites 2, 3 and 4 with anterolateral projections, especially developed in pereonite 2. Pereonite 5 the longest. Pereonite 7 the shortest.

Gills ( Fig. 2 View FIGURE 2 ). Present at middle of pereonites 3–4, small and elongate, length about 2 times width.

Mouthparts ( Fig. 3 View FIGURE 3 , maxilliped, maxilla 1, upper lip and lower lip figured from holotype male; mandibles and maxilla 2 figured and described from male “b”). Mouthparts remarkably small (ca. 0.05 mm). Mandibles with triturative molar, moderately developed and dentate marginally. Three-articulate palp; distal article of palp the longest, with a setal formula 0-x-y-1, being x=3 and y=4; left mandible with incisor and lacinia mobilis fivedentate, followed by three accessory blades; incisor of right mandible five-dentate, lacinia mobilis looking like a blade, followed by two more blades; no sign of molar flake. Upper lip without setae. Lower lip without setae; inner lobes small and globose. Maxilla 1 outer lobe carrying seven spines, palp two-articulate, distal article with three apical spines and two medial seta. Maxilla 2 inner lobe small, shorter than outer lobe, with four apical setae; outer lobe with five apical setae. Maxilliped inner plate small, about 1/4 of outer plate in length, carrying four-five apical setae; outer plate elongate, with five setae; palp four-articulate, second article the longest, third article provided with a distal acute projection.

Antennae ( Figs. 2 View FIGURE 2 and 4 View FIGURE 4 ). Antenna 1 ca. 1/3 of body length; flagellum 5-articulate. Antenna 2 slightly shorter than antenna 1; proximal peduncular article with an acute gland cone distally; swimming setae absent; flagellum two-articulate.

Gnathopods ( Figs. 2 View FIGURE 2 and 4 View FIGURE 4 ). Gnathopod 1 basis as long as ischium, merus and carpus combined; grasping margin of propodus smooth with several setae; two proximal grasping spines, dactylus bifid distally. Gnathopod 2 inserted on anterior half of pereonite 2; coxa provided with a distal projection (see lateral and dorsal view in figure 2); basis slightly shorter than pereonite 2; ischium rectangular; basis and ischium provided with a distal projection laterally; merus rounded; carpus short and triangular; propodus oval, palm ventrally setose, with proximal projection provided with one large grasping spine, and distal projection followed by U-notch; dactylus smooth and elongate.

Pereopods ( Figs. 2 View FIGURE 2 and 5 View FIGURE 5 ). Pereopod 3 and 4 tiny, one-articulate, with two setae distally. Pereopod 5 threearticulate, inserted on middle of pereonite 5, medial article provided with four setae; distal article very small, provided with a seta. Pereopod 6 and 7 lacking in holotype, figured and described from paratype female “a” (see below)

Penes ( Fig. 6 View FIGURE 6 ) large, situated medially, distinctive, oval, length ca. 2 times width.

Abdomen ( Fig. 6 View FIGURE 6 ) lacking appendages, provided with setae, a pair of lobes, and a single dorsal lobe with two plumose setae.

Paratype female “a” (2.9 mm) ( Figs. 2 View FIGURE 2 , 4 View FIGURE 4 and 6 View FIGURE 6 )

Similar to male except for following characteristics: head and body smooth lacking dorsal or anterolateral projections; presence of oostegites on pereonites 3 and 4, oostegites setose on pereonite 3 ( Fig. 2 View FIGURE 2 ); flagellum of antenna 1 with 4 articles; gnathopod 2 basis and ischium lacking distal projection, palm of propodus less setose than in male; pereopods 6 and 7 six-articulate, merus, carpus and propodus with a row of ventral setae, propodus with a proximal grasping spine, dactylus curved.

Intraspecific variation. The morphological characteristics of the species are rather constant in the specimens examined. Mouthparts were similar in the four specimens dissected, except for the number of setae in the mandibular palp 0-x-y-1 with possibilities 0-3-3-1, 0-3-4-1 or 0-4-4-1. Maxilla 1 outer lobe is always provided with seven spines in all specimens. The number of apical setae on the lobes of maxilla 2 also varies between 4 and 6. Regarding the ontogenetic development, the immature males are lacking dorsal tubercles on head and anterolateral projections on pereonites 3 and 4, and only the anterolateral projections on pereonite 2 are present (see figure 2)

Remarks. The genus Liropus was established by Mayer (1890) and, so far, included twelve 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. guerragarciai Mauro & Serejo, 2015 ; L. gurui Guerra-García, Chatterjee & Schizas, 2015 ; 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, 2003 . A morphological comparison among Liropus species is provided by Guerra- García & Hendrycks (2013), Mauro & Serejo (2015) and Sánchez-Moyano et al. (2015), and an illustrated key of the genus can be found in Guerra-García & Hendrycks (2013). Liropus vitucoi sp. nov. can be distinguished from the remaining species of Liropus by the combination simultaneously of the following characters: (1) tiny dorsal tubercles anterolaterally on the head, near the eyes, (2) presence of anterolateral projections in pereonites 2, 3 and 4 in males, (3) third article of the maxilliped palp with distal projection, (4) mandibular palp with setal formula 0-xy-1 (from proximal to distal end) (which is unique within the genus Liropus ), (5) pereopods 3 and 4 one-articulate and pereopod 5 three-articulate, (6) abdomen without appendages. Although most of the Liropus species are characterised by the presence of one pair of uniarticulate appendages in male abdomen, some species, such as L. minusculus , are provided by two pairs (one of the pairs vestigial), and in other species such as L. cachuchoensis , L. gurui , L. isabelensis , L. japonicus . L. nelsonae and L. vitucoi sp. nov. the single pair is vestigial or absent. Although the number of abdominal appendages could be considered a valid character to separate genera (see McCain, 1968), the gradual degree of variation in the abdomen of Liropus prevents a clear delimitation among different genera. On the other hand, the setal formula of the mandibular palp also shows a high variability within this genus, ranging from a single seta, a formula 1-x- 1 or 1-x-y-1, being in the new species 0-x-y-1. Something similar can be reported for the article 3 of the maxilliped palp since in some species there is a distal projection ( L. elongatus , L. isabelensis , L. minusculus and L. vitucoi sp. nov.) and other species lack this projection. Furthermore, the number of spines in the outer lobe of maxilla 1, although six in the majority of species, can be 7 (as in L. minusculus or L. vitucoi sp. nov.) or even 5 (as in L. guerragarciai or L. isabelensis ). Differences in these mouthparts characters could be also considered at genus level ( Mayer, 1903, McCain, 1968). Therefore, a detailed revision of the genus, with redescriptions of the poorly known species, such as L. africanus , L. gracilis , L. minimus and specially L. elongatus , which is the type species of the genus, is mandatory. An exhaustive phylogenetic analysis using morphological and molecular characters would be also necessary to explore the possibility of split the genus Liropus into several different genera, according to this variation in mouthparts and abdomen. At the moment, taking into account that all Liropus species share antennae and body features, reduction of pereopods 3-5, structure of gnathopods 1, 2 and pereopods 6 and 7, we have maintained the new species in the same genus until further studies could reveal evidences to split the genus.