Pareurystheus vitucoi, Tato & Moreira, 2017

Tato, Ramiro & Moreira, Juan, 2017, Two new species of the Suborder Senticaudata (Crustacea: Amphipoda) from the upper continental slope off Galicia (NW Iberian Peninsula), Zootaxa 4300 (2), pp. 217-237 : 219-227

publication ID	https://doi.org/ 10.11646/zootaxa.4300.2.4
publication LSID	lsid:zoobank.org:pub:E46A4B57-13DE-43AC-8275-49DC40EEE5D8
DOI	https://doi.org/10.5281/zenodo.6010008
persistent identifier	https://treatment.plazi.org/id/DD0C87D5-FFA6-FFB9-FF07-FEB69FA7FEF8
treatment provided by	Plazi
scientific name	Pareurystheus vitucoi
status	sp. nov.

Treatment

Pareurystheus vitucoi sp. nov.

( Figs 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Material examined. Holotype: AdUlt male, 4.6 mm, ethanol in the mUseUm (MHNUSC 10065); “DIVA-Artabria I” crUise; sample DRN-03-1000, 2003/09/16; 43° 53.575’ N; 008° 56.868’ W; 1005 m depth; rocky bottoms). Allotype: AdUlt female, 3 mm long (MHNUSC 10066); “DIVA-Artabria I” crUise; sample AT-03-800, 2003/09/15; 43° 51.774’ N; 008° 53.640’ W; 800 m depth; rocky bottoms). Paratypes: 6 adUlt females, 1.6–2.9 mm long (MHNUSC 10067); “DIVA-Artabria I” crUise; sample AT-03-800, 2003/09/15; 43° 51.774’ N; 008° 53.640’ W; 800 m depth; rocky bottoms).

Additional non-type material: 28 jUvenile (“DIVA Artabria I”sample AT-03-800, 2003/09/15; 43° 51.774’ N; 008° 53.640’ W; 800 m depth; rocky bottoms) specimens kept in first aUthor’s personal collection.

Diagnosis. Head, lacking eyes and rostrUm. Antenna 1 longer than antenna 2, exceeding half of total body length; accessory flagellUm present, bi-articUlate, minUte distal article. Antenna 2 shorter than half body length. Coxal plate 1 redUced, coxal plates 2–4 well developed; coxal plate 2 bigger than 3 and 4. Pereopod 5 strongly modified in males, with well developed basis and merUs; basis posterior lobe overlapping ischiUm; carpUs, propodUs and dactylUs redUced. Pereopods 6–7 well developed and spinose. Epimeral plates with posterior small seta in a notch. Uropods spinose, Uropod 3 rami sUbeqUal in length.

Description of the holotype. Head ( Fig. 1 View FIGURE 1 A). Lacking eyes, with small roUnded cephalic lobe. Epistome anteriorly projected.

Antenna 1 ( Fig. 1 View FIGURE 1 B–D). Exceeding half of total body length; longer than antenna 2. PedUncle article 1 wider proximally than distally, distal margin of article with dorsal and ventral setae and 2 ventral stoUt setae ( Fig. 1 View FIGURE 1 D); article 2 aboUt twice as long as article 1, elongate and narrow, distal margin with short setae; pedUncle article 3 shorter than article 1, aboUt 1/3 of article 2; with a single short seta on ventral margin and naked dorsal margin. Accessory flagellUm small, composed by 2 articles, article 2 minUte ( Fig. 1 View FIGURE 1 C). FlagellUm with 17 articles with ventral short setae on some of them.

Antenna 2 ( Fig. 1 View FIGURE 1 A, E). AboUt half of length of antenna 1. PedUncle article 1 compressed, barely visible; article 2 short and wide with ventral gland cone; article 3 two times longer than wide with distal ventral setae; article 4 aboUt twice as long as article 3, long and narrow with ventral setae and a distal dorsal seta; article 5 slightly longer than article 4, long and narrow with ventral and dorsal setae. FlagellUm with 5 articles and short distal setae.

Mouthparts. Upper lip bilobed ( Fig. 2 View FIGURE 2 L). Mandible ( Fig. 2 View FIGURE 2 A, B) molar and incisor well developed; setal row present; mandibUlar palp with 3 articles and distal composite setae on article 3 ( Fig. 2 View FIGURE 2 C, D). Maxilla 1 ( Fig. 2 View FIGURE 2 G) inner plate redUced, withoUt seta; oUter plate with 6 distal denticled stoUt setae ( Fig. 2 View FIGURE 2 H); palp strongly developed, 2-articUlate, with 4 distal stoUt setae. Maxilla 2 ( Fig. 2 View FIGURE 2 I) inner plate lower than oUter plate, both with smooth setae on distal margin. Maxilliped ( Fig. 2 View FIGURE 2 J) inner plate redUced, sUbqUadrate in shape, with 3 sUbdistal setae; oUter plate roUnded, reaching 1/4 length of palp article 2, with 4 setae and 1 stoUt setae on inner margin; palp 4-articUlate; article 2 two times as long as article 1, with setae on inner margin and 1 mediofacial stoUt setae; article 3 with a bifid distal process near insertion of last article; with long sUbdistal setae on inner margin, close to bifid process and a distal seta on oUter margin; article 4 cUrved, with a row of minUte setae on inner margin ( Fig. 2 View FIGURE 2 K) and 2 distal setae. Lower lip ( Fig. 2 View FIGURE 2 E) bilobed, with row of short setae and 2 long setae at apex of each lobe ( Fig. 2 View FIGURE 2 F).

Coxal plates ( Fig. 1 View FIGURE 1 A). SUbqUadrangUlar; plate 2 bigger than plates 1, 3 and 4.

Gnathopod 1 ( Fig. 3 View FIGURE 3 A). Typical of genUs. Basis elongate, wider distally, with short setae on distal margin; ischiUm redUced, short and broad, with posterior long seta on distal margin; merUs short, redUced, with long setae on distal margin; carpUs inserted on merUs dorsal margin, ventral margin densely covered with long setae, with a sUbdistal row of setae and 1 stoUt setae on oUter face of merUs; dorsal margin mUch less setose, with single sUbdistal seta and 2 distal setae; propodUs ovate; ventral margin slightly concave near dactylUs inserction; dorsal margin with sUbdistal seta and distal seta; palmar margin serrate with setae of variable length, limited by 2–3 stoUt setae ( Fig. 3 View FIGURE 3 B); dactylUs cUrved, aboUt half length of propodUs; with small denticles on inner margin, withoUt nail ( Fig. 3 View FIGURE 3 C).

Gnathopod 2 ( Fig. 3 View FIGURE 3 D). Similar to gnathopod 1 bUt articles more developed. Basis elongate, wider distally, with a short median seta in a anterior ridge; ischiUm redUced, short and broad, with a short distal seta; merUs slightly longer than ischiUm, with posterior ventral setae; carpUs well developed, narrow on proximal margin and wide on distal margin, posterior margin with 4 groUps of setae; anterior margin with 2 distal setae; propodUs well developed, palmar margin straight with short and long setae and 2 proximal stoUt setae; with short setae on lateral face and 2 distal setae on anterior margin; dactylUs cUrved and well developed; aboUt half of length of propodUs with denticles and short setae on the posterior margin; anterior margin naked, withoUt visible nail.

Pereopod 3 ( Fig. 3 View FIGURE 3 E). Typical of genUs. Basis elongate and narrow with 3 anterior and 1 posterior setae; ischiUm short and broad; merUs 3 times longer than ischiUm, wide distally, with anterior and posterior setae; carpUs aboUt 2/3 length of merUs with 2 setae on posterior margin and distal seta on anterior margin; propodUs elongate and narrow, with 3 setae on posterior margin, 1 seta and 1 sUbdital stoUt seta on anterior margin; dactylUs slightly cUrved, simple; aboUt half of length of propodUs; withoUt setae and nail.

Pereopod 4 ( Fig. 3 View FIGURE 3 F). Similar in shape to pereopod 3. Basis elongate and narrow, with 2 short setae on anterior margin and 1 on posterior margin; ischiUm short and broad; merUs similar in shape to pereopod 3 merUs, with 2 anterior setae and 1 posterior seta; carpUs aboUt 2/3 length of merUs, with 3 posterior setae; propodUs elongate and narrow, with 4 short setae on posterior margin, 2 lateral setae and 1 distal stoUt seta; dactylUs slightly cUrved, naked and withoUt nail.

Pereopod 5 ( Fig. 4 View FIGURE 4 A). Basis well developed, broad and elongate with light serrations on anterior and posterior margins; distal margin with roUnded posterodistal lobe, overlapping ischiUm and merUs; anterior margin with 3 short stoUt setae and distal setae, posterior margin with 3 short setae; ischiUm redUced, short and broad, with distal setae on anterior margin; merUs well developed, almost as broad as long; distal margin with small lobes on each side of carpUs insertion, posterior margin with a pair of proximal stoUt setae more or less overlapped by basis lobe and a second pair of distal stoUt setae mixed with short setae; carpUs mUch less developed than merUs, long and narrow, distal end with 3 stoUt setae and some simple setae; propodUs long and narrow with 2 groUps of stoUt setae along lateral face,1 stoUt seta and simple seta on distal margin; dactylUs simple, aboUt half of length of propodUs, slightly cUrved, withoUt setae and nail.

Pereopod 6 ( Fig. 5 View FIGURE 5 A). Longer than pereopod 5. Basis elongate, broad proximally and narrow distally, with 4 stoUt setae on anterior margin and 2 setae on posterior margin; posterior margin serrate; ischiUm redUced, with 1 distal seta on anterior margin; merUs 3 times longer than broad, with 2 small lobes on insertion of carpUs, with 2 stoUt setae on posterior margin and 3 setae on anterior margin; carpUs shorter than merUs, with stoUt setae on both sides of propodUs insertion; propodUs long and narrow with 3 pairs of stoUt setae on lateral face and several distal long setae; dactylUs simple, aboUt half of length of propodUs, withoUt setae and nail.

Pereopod 7 ( Fig. 5 View FIGURE 5 B). Similar to pereopod 6 in shape and size; basis elongate, broad proximally and narrow distally, with 2 stoUt setae on anterior margin; posterior margin serrate; ischiUm redUced, short and broad; merUs similar to pereopod 6 merUs, 3 times longer than broad, with 2 stoUt setae on posterior margin and posterior and anterior stoUt setae on distal margin; carpUs shorter than merUs with distal stoUt and simple setae; propodUs elongate and narrow with 3 pairs of stoUt setae along lateral face; dactylUs slightly cUrved.

Pleon. Epimeral plates with roUnded distal margin ( Fig. 6 View FIGURE 6 A), with posterodistal corner notched; each notch with 1 short seta.

Uropod 1 ( Fig. 6 View FIGURE 6 B). PedUncle elongate with acUte distal interramal process, with 2 medial stoUt setae and 2 distal stoUt setae; oUter ramUs sUbeqUal in length to pedUncle with 1 dorsal median stoUt seta and 3 distal stoUt setae; inner ramUs slightly longer than oUter, with 2 stoUt setae along dorsal margin and 4 distal stoUt setae.

Uropod 2 ( Fig. 6 View FIGURE 6 C). PedUncle elongate, narrowing to distal apex, with 2 dorsal stoUt setae; oUter ramUs aboUt eqUal length of pedUncle, with 1 dorsal median stoUt seta and 4 distal stoUt setae; inner ramUs longer than oUter, with 3 dorsal stoUt setae and 3 distal stoUt setae.

Uropod 3 ( Fig. 6 View FIGURE 6 D). PedUncle elongate, narrow on distal margin, with 2 stoUt setae on dorsal margin; rami shorter than pedUncle; inner ramUs with 2 dorsal stoUt setae and 2 distal setae; oUter ramUs shorter than oUter, with distal simple setae.

Telson 3 ( Fig. 6 View FIGURE 6 E). With a pointed posterior apex and 2 lateral crests, each one with 1 apical stoUt seta.

Sexual dimorphism. Males and females are very alike in appearance in most of the characters bUt the fifth pereopod. This appendage is shorter in males than in females, with enlarged basis and merUs and redUced carpUs, propodUs and dactylUs. In females, pereopod 5 articles are similar in size and shape to pereopods 6–7 articles ( Fig. 4 View FIGURE 4 B). As in other Pareurystheus species, coxa 2 are more developed in males and gnathopods are less developed in females, the first pair being simple.

Intraspecific variation. The nUmber of stoUt and simple setae is related to the size and developmental stage of specimens, especially on the Uropods.

Type locality. Ferrol Canyon, (Galician continental margin, NW Iberian PeninsUla), 43°53.575’N, 008°56.868’W, 1005 m depth.

Distribution and habitat. Pareurystheus vitucoi sp. nov. was foUnd in rocky bottoms at 800 and 1005 m in the Ferrol Canyon, (off Galicia, NW Iberian PeninsUla).

Etymology. We are pleased to name this species after Prof. Victoriano Urgorri ("VitUco") (Universidade de Santiago de Compostela) in regard to his friendship and many contribUtions to the field of Marine Biology.

Remarks. The genUs Pareurystheus is composed by 7 valid species; all of them can be distingUished from P. vitucoi sp. nov. in the presence of eyes and smaller coxal plates. The closest species to P. vitucoi sp. nov. is P. anamae ( GUrjanova, 1952) ; the latter can be distingUished by the longer accessory flagellUm, the shape and size of pereopods 6–7 (less developed) and the presence of dorsal setae on the Urosomites. Pareurystheus vitucoi sp. nov. also differs from other species of the genUs according to several characters. Following Conlan (1983), P. tzvetkovae Conlan, 1983 and P. dentatus ( Holmes, 1908) are characterised by the shorter Uropod 3 rami. Pareurystheus latipes Tzvetkova, 1977 and P. sexdentatus ( Stephensen, 1944) differ from P. vitucoi sp. nov. by the absence of posterodistal stoUt setae on article 1 of antenna 1. Pareurystheus gurjanovae Tzvetkova, 1977 presents Uropod 3 with longer rami. Finally, P. amakusaensis Hirayama, 1984 presents smaller coxal plates, different shape and size of gnathopods 1–2 and pereopod 5, setose epimeral plate 2 and very redUced inner ramUs of Uropod 3.

P areurystheus vitucoi sp. nov. is UniqUe in genUs Pareurystheus dUe to its short and bi-articUlate accessory flagellUm (while described as mUltiarticUlate in other species of the genUs) and its well developed (mainly coxa 2 in males) and overlapping coxal plates (while weakly developed and slightly overlapping coxae in many other species of this genUs). However, P. vitucoi sp. nov. also shows the diagnostic characters of the genUs: shape and size of the head with weakly developed cephalic lobe; antenna 1 longer than antenna 2; pedUncle article 3 of antenna 1 shorter than article 1; gnathopod 2 larger than gnathopod 1; pereopod 5 strongly modified and shorter than pereopods 6–7.