Leviapseudes tethys, Gouillieux & Labrune & Esquete, 2023

Gouillieux, Benoit, Labrune, Céline & Esquete, Patricia, 2023, Leviapseudes tethys (Tanaidacea: Apseudidae), a new species from a submarine canyon of the French Mediterranean Sea, with remarks and a diagnosis for the genus, European Journal of Taxonomy 879, pp. 24-37 : 27-32

Leviapseudes tethys sp. nov.

urn:lsid:zoobank.org:act:6CC0E63B-44B8-41C5-8A3C-F499F0749EDF

Figs 2–4

Etymology

Tethys, noun in apposition; the species is named after the Tethys Sea that existed from the end of the Palaeozoic Era to the Mesozoic Era and from which the Mediterranean Sea is a present remnant; it also corresponds to the name of the research vessel used to sample the new species.

Material examined

Holotype FRANCE • ♂, BL = 8.39 mm, rostrum–telson, appendages damaged; Gulf of Lion , Lacaze-Duthiers Canyon; 42.53582° N, 3.43690° E; depth 600 m; 1 Jun. 2019; replica sample LDTH – site 2 – C1; van Veen grab; MNHN-IU-2016-3391.

Paratype FRANCE • 1 ♂, broken, BL = 8.06 mm, rostrum–pleonite 2, appendages damaged; Gulf of Lion , Lacaze-Duthiers Canyon; 42.53673° N, 3,43833° E; depth 600 m; 1 Jun. 2019; replica sample LDTH – site 2 – C5; van Veen grab; MNHN-IU-2016-3390 .

Description

BODY ( Fig. 2A–B ). 8.39 mm long; carapace 17% of total body length. Cephalothorax, including rostrum, longer than pereonites 1–2 combined. Ocular lobes well developed, spiniform, without pigmentation. Lateral spiniform apophyses slightly developed. Rostrum reaching half-length of first antennular article, triangular. Pereonites decreasing in width distally; pereonites 1–2 with posterolateral spiniform apophyses, pereonites 3–6 with anterolateral and posterolateral spiniform apophyses. Pereonite 1–3 wider than long, 4–6 longer than wide. All pereonites with ventral hyposphenia. Pleon 20% of total body length. Pleonites all wider than long, each of equal length, with posterolateral apophysis. Pleotelson shorter than last three pleonites combined.

ANTENNULE ( Fig. 2C ). Subequal to carapace and pereonite 1–2 combined. Peduncle article 1 about twice as long as two succeeding articles combined, with some simple setae of various lengths on both margins; article 2 longer than article 3, with a few scattered simple setae; article 3 with four distal simple setae; article 4 naked. Outer flagellum longer than peduncle, consisting of 20 segments. Inner flagellum reaches 0.62 length of outer flagellum, consists of 10 segments.

ANTENNA ( Fig. 2D ). Article 1 naked with ventral process, twice as wide as other articles, half as long as article 2. Article 2 with one inner and two distal short simple setae. Article 3 distinctly shorter than article 4. Article 5 longer than articles 3 and 4 combined, with three simple medial setae and three distal setae comprised of two simple and one pinnate seta distally; following articles (6–16) diminishing successively in length and width; each article with 1–4 simple setae. Squama longer than articles 3 and 4 combined, with 12 simple setae.

LABRUM ( Fig. 3K ). With lateral margins covered by a few simple setae and minute setation distally.

MANDIBLE ( Fig. 3A–B, G ). With very broad molar process with numerous minute distal setae. Palp article 1 less than half as long as article 3, with 10 simple setae; article 2 2.25 times as long as article 1, with 10 bipinnate setae decreasing in length distally (except first seta shorter than second) and 10 shorter simple setae; article 3 with a single, followed by 11 pairs of bipinnate setae increasing in length distally and two distal simple setae (longest). Left mandible incisor broad, with five blunt denticles. Lacinia mobilis slender, with blunt denticles and three small spines. Setal row consists of nine simple and multifurcated setae.

LABIUM ( Fig. 3F ). Lobe setulated on distal part of outer margin and on middle of inner side. Palp with numerous simple setae on both margins, tipped by three spines.

MAXILLULE ( Fig. 3H–I ). Outer endite tipped with 12 spines, two simple subdistal setae, setules on both margins. Inner endite with four setulated and one simple distal setae, setules on both margins. Palp with two articles; article 1 distinctly longer than article 2, naked; article 2 tipped by 12 distally finely serrated setae.

MAXILLA ( Fig. 3J ). Outer lobe of movable endite with six long setulated setae and two long setulated feathered setae on outer margin. Inner lobe of movable endite with row of nine setulated setae. Outer lobe of fixed endite with three setulated, two simple, and three multifurcate spines. Inner lobe of fixed endite with row of eight setulated setae distally and row of numerous (>30) simple setae subdistally.

MAXILLIPED ( Fig. 3C–E ). Endite with 13 distal setae, outer ones slender and long, inner ones larger and shorter; one subdistal inner pinnate seta and one outer long simple seta; inner margin with a row of 14 setulated setae and four coupling hooks. Palp article 1 with four inner simple distal setae and one outer seta. Article 2 inner margin with a row of numerous simple and pinnate setae of same size and five longer simple setae, outer margin with one distal simple seta. Article 3 with seven long simple and seven shorter pinnate setae, all increasing in length distally. Article 4 tipped with nine pinnate setae. Pinnate setae very difficult to distinguish from simple setae.

EPIGNATH. Not recovered.

CHELIPED ( Fig. 4A ). Basis shorter than carpus, with two ventral spines and a cluster of simple setae distoventrally; merus almost half as long as carpus, with many simple setae ventrally and no setae distodorsally; carpus with numerous long setae on ventral and dorsolateral margins; propodus with one short seta dorsally, near dactylus insertion of two long and three short dorsal setae, and two long and one short ventral setae. Fixed finger inner margin with a row of well calcified teeth and a row of short setae, outer margin with two long setae, distal part with many short setae. Dactylus narrow, longer than fixed finger, with three long simple setae. Exopod biarticulated, distal article with one median and three distal plumose setae.

PEREOPOD 1 ( Fig. 4B–C ). Basis longer than merus, with minute proximal setae and three ventral spines; ischium with a minute ventral seta; merus about 1.5 times as long as carpus, with numerous simple setae, and one ventrodistal and one dorsodistal spine; carpus subequal in length to propodus, with two ventral and one dorsodistal spine, six ventral simple setae, a row of dorsolateral simple long setae and multiple simple lateral setae; propodus with a row of eight spines ventrally, a row of simple long setae and two spines dorsolaterally; dactylus 0.6 times as long as propodus, with 2–5 ventral and one dorsal short seta; unguis 0.3 times as long as dactylus. Exopod biarticulated, distal article with one medial and three distal plumose setae.

PEREOPOD 2 ( Fig. 4D ). Basis long and slender, about 5.5 times as long as wide, marginally shorter than carpus and propodus combined, with two minute setae proximally and three simple distoventral setae. Ischium with two ventrodistal setae. Merus 0.5 times as long as carpus, with seven ventral, four dorsodistal and one distolateral simple setae. Carpus slightly smaller than propodus, with seven ventral setae and a medio-distal diagonal row of setae. Propodus with a medio-distal diagonal row of simple setae and many simple ventral setae. Dactylus longer than propodus, with one minute dorsal seta at midlength and one minute distal seta. Unguis smaller than dactylus.

PEREOPOD 3 ( Fig. 4E ). Similar to pereopod 2 except less setose and basis about 4 times as long as width.

PLEOPOD ( Fig. 4F ). Basal part divided into two articles, first article small and naked, second article longer with four outer and four inner plumose setae; endopod and exopod with many (>20) plumose setae, exopod longer than endopod and consisting of one article only.

UROPODS. Lost.

Ecological data

Leviapseudes tethys sp. nov. was sampled at 600 m depth on deep muddy sand (D50 = 9.3 µm and 88% of silt <63 µm). Sediment organic content at this location was about 6.5% AFDW (Ash Free Dry Weight). In total, three individuals were collected over five grabs (two in C1 grab and one in C5 grab). Unfortunately, a juvenile specimen was lost during the study (specimen collected in LDTH – Site 2 – C1). The new species was mainly collected with Polychaeta Grube, 1850 and represents the only Tanaidacea ( Table 1 ).

Figures

Fig. 2. Leviapseudes tethys sp. nov.A. Holotype, ♂ (MNHN-IU-2016-3391), dorsal view. B–D. Paratype, ♂ (MNHN-IU-2016-3390). B. Dorsal view. C. Antennule. D. Antenna. Scale bars = 0.5 mm.

Fig. 3. Leviapseudes tethys sp. nov. Paratype, ♂ (MNHN-IU-2016-3390). A. Mandibular palp, right. B. Mandible, left. C. Maxilliped. D. Maxilliped endite, left, with close-up of distal part. E. Maxilliped endite, right. F. Labium, left. G. Molar process distal part. H. Maxillule. I. Maxillule endite. J. Maxilla. K. Labrum. Scale bars = 0.1 mm.

Fig. 4. Leviapseudes tethys sp. nov. A–C, E. Paratype, ♂ (MNHN-IU-2016-3390). D, F. Holotype, ♂ (MNHN-IU-2016-3391). A. Cheliped, right. B. Pereopod 1, right. C. Pereopod 1, left, proximal part of basis. D. Pereopod 2, left. E. Pereopod 3, right. F. Pleopod 2. Scale bars = 0.5 mm.