Leptochelia parasavignyi, Larsen, Kim, Nagaoka, Ryoko & Froufe, Elsa, 2012

Larsen, Kim, Nagaoka, Ryoko & Froufe, Elsa, 2012, Tanaidacea (Crustacea) from Macaronesia III. The shallow-water Tanaidomorpha from the Cape Verde archipelago, Zootaxa 3498, pp. 24-44 : 25-34

publication ID	https://doi.org/ 10.5281/zenodo.212695
DOI	https://doi.org/10.5281/zenodo.6178273
persistent identifier	https://treatment.plazi.org/id/36728B7A-FF86-FFE1-FF13-44DFFD756EB3
treatment provided by	Plazi
scientific name	Leptochelia parasavignyi
status	sp. nov.

Treatment

Leptochelia parasavignyi View in CoL n. sp. Larsen

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

Material examined. Holotype non-ovigerous female. Body length 2.3 mm. (Genbank # T327 JX402116 View Materials Reg # MMF 42308), Mindelo beach, St. Vicente, 0.5 m depth, hard bottom algae. Paratypes (Reg # MMF 42309): 50+ specimens of both genders and most developmental stages, same locality and Mindelo Marina, sandy bottom algae.

Diagnosis. Female. Pereonite 6 longer than pereonite 2. Antennule proximal article just over three times as long as wide, article 2 longer than article 3. Maxilliped basis with four to five long distal setae, palp article 2 with one outer and four inner setae. Cheliped basis only 1.5 times as long as wide, carpus 1.9 times as long as wide. Pereopod 1 basis 4.5 times as long as wide, carpus longest seta 0.45 times length of propodus, dactylus 1.5 times as long as unguis, combined longer than propodus; pereopods 2 and 3 carpus as long as merus and 0.6 to 0.7 times as long as propodus; Uropod endopod with five articles, exopod uniarticulate, 0.8 times as long as first endopod article.

Primary male. Body smaller than adult female. Antennule with eight articles (flagellum with only five articles). Antenna spiniform setae slimmer. Cheliped carpus longer and slimmer. Pereopod 1 dactylus and unguis much shorter than in female. Pereopod 6 basis without dorsal marginal flange. Uropodal exopod uniarticulate..

Etymology. Named after the morphological similarities with Leptochelia savignyi .

Description. Female. Body from non-ovigerous holotype, appendages from dissected ovigerous paratype.

Body ( Fig. 1 View FIGURE 1 A). Elongate, slender, 8.5 times as long as wide. Carapace subrectangular, almost twice as long as wide, longer than pereonites 1 and 2 combined, with slight rounded rostrum, naked. Pereonites, each bearing one short, simple anterolateral setae. Pereonite 1 shortest, pereonites 2, 3, 4, and 5 progressively longer; pereonite 6 longer than pereonite 2. Pleon slightly wider than pereon, about one-quarter of total length. Pleonites about three times as wide as long; anterior three pleonites with one- posterior two pleonites with three short, simple mediolateral setae. Pleotelson only marginally longer than pleonite 5, with one simple lateral and two pairs of terminal simple setae.

Antennule ( Fig. 1 View FIGURE 1 B). Article 1 just over three times as long as wide, with medial and distal setulose and simple setae of which one is longer than article 2. Article 2 longer than article 3, with two distal setae of which one is longer than article 3. Article 3 marginally longer than one quarter of article 1, with small ventrodistal process and two simple distal setae. Article 4 minute, with four simple distal setae and one aesthetasc.

Antenna ( Fig. 1 View FIGURE 1 C). Article 1 with small ventrodistal projection and one ventrodistal seta. Article 2 longer than article 1, with conspicuous single ventrodistal and dorsodistal spiniform setae arising from small projections. Article 3 shorter than article 2, with dorsodistal spiniform seta. Article 4 longest, less than twice as long as article 2, with two long simple and three setulated distal setae. Article 5 slender, less than half as long as article 4, with two simple distal setae. Article 6 minute with three long and one minute distal setae.

Mouthparts. Labrum ( Fig. 2 View FIGURE 2 A) with conspicuous lateral projections, setulose. Left mandible ( Fig. 2 View FIGURE 2 B) incisor with one distal and two apical denticles, lacinia mobilis with wide, crenulate distal edge and fine setulation/ serration on proximal edge, molar with strongly chitinized crushing surface with small pointy teeth. Right mandible ( Fig. 2 View FIGURE 2 C) incisor bifurcate, with small single dorsal crenulation, and fine setulation/serration on proximal edge, molar as in left mandible. Labium ( Fig. 2 View FIGURE 2 D) with two lobes, distal margin with multiple setae and setules. Maxillule ( Fig. 2 View FIGURE 2 E) endite with ten spiniform distal setae and distally setulose outer- and sparsely medial inner setulation; palp with two long distal setae. Maxilla ( Fig. 2 View FIGURE 2 F) simple, ovoid, naked. Maxilliped ( Fig. 2 View FIGURE 2 G) Basis with four right and five left long (exceeding distal margin of palp article 2) setae; endites distally with single outer seta and three flat spiniform setae, inner one shorter than outer two, lateral corners finely setulose; palp article 1 naked; article 2 with outer-distal seta and four inner distal setae, inner proximal margin finely setulose; article 3 with eight inner setae; article 4 with ten inner and one outer subdistal setae. Epignath ( Fig. 2 View FIGURE 2 H) apparently naked but the tip has broken off so this might be an artefact.

Cheliped ( Fig. 3 View FIGURE 3 A) attached to carapace via a large triangular sclerite. Basis only 1.5 times as long as wide, with sub-dorsodistal seta. Merus triangular, with four ventral setae. Carpus almost twice as long as wide, with two dorsoproximal and one dorsodistal setae and three ventrodistal setae. Propodus, inclusive fixed finger, almost twice as long as wide, with inner row of six pinnate setae of which the most ventral is longer than the others, with one setae at dactylus insertion. Fixed finger shorter than body of propodus, with chitinised ridge overlapping unguis, with three setae on cutting edge and four ventral setae. Dactylus with dorsoproximal seta, with process on cutting edge but without small spiniform setae.

Pereopod 1 ( Fig. 3 View FIGURE 3 B) longer than other pereopods. Coxa with seta. Basis slender, shorter than combined length of propodus, dactylus, and unguis, with one simple, and one setulose dorsoproximal setae. Ischium with one ventral seta. Merus longer than carpus, with three small distal setae. Carpus about one-third as long as basis, with three short and two longer distal setae. Propodus shorter than carpus and merus combined, with one ventral subdistal seta and three dorsal subdistal setae, with small dorsal spine just proximal to dorsal setae and distal spine. Dactylus with dorsoproximal seta, combined with unguis as long as propodus, longer than unguis.

Pereopod 2 ( Fig. 3 View FIGURE 3 C) shorter than pereopod 1. Coxa with seta. Basis wider than that of pereopod 1, with two setulose and one simple dorsoproximal setae. Ischium with two ventral setae. Merus as long as carpus, combined longer than propodus, with one simple and one spiniform ventrodistal setae. Carpus with one simple and one spiniform ventrodistal setae and scales, with additional two dorsodistal setae. Propodus longer than half of basis, with one small spiniform ventral subdistal seta and three dorsal/medial subdistal setae, with small dorsal spine just proximal to dorsal seta and small distal spine. Dactylus with proximal spines combined with unguis shorter than propodus, longer than unguis.

Pereopod 3 ( Fig. 3 View FIGURE 3 D) similar to pereopod 2 except: basis with just one dorsoproximal setulose seta and propodus with only two dorsal subdistal seta and large spine.

Pereopod 4 ( Fig. 3 View FIGURE 3 E) coxa fused with pereonite. Basis stout, more than twice as long as wide and longer than rest of pereopod, with one ventroproximal setulose seta. Ischium with two ventral setae. Merus as long as carpus, with paired ventrodistal spiniform setae. Carpus with two dorsodistal setae, one inner and two outer curved spiniform setae. Propodus about as long as merus, with three stout and one spiniform pinnate dorsodistal setae and small spine proximal from dorsal setae, with ventrodistal pair of spiniform setae. Dactylus curved and incompletely fused with unguis, distally with small spines. Unguis combined with dactylus about half as long as propodus.

Pereopod 5 ( Fig. 3 View FIGURE 3 F) similar to pereopod 4 except: basis with one simple and two setulose ventroproximal setae and propodus with several dorsal spines.

Pereopod 6 ( Fig. 3 View FIGURE 3 G) as pereopod 4 except: basis with one setulose dorsoproximal seta. Propodus with five stiff pinnate and two longer simple dorsodistal setae and several dorsal spines.

Pleopods ( Fig. 1 View FIGURE 1 D) all five pairs similar. Basal article with one circumplumose inner seta. Endopod with single inner plumose seta and 18 outer plumose setae, distal seta shorter and thicker and with curved serrated apex, gap between most proximal seta and other outer setae. Exopod with 25 outer plumose setae, most proximal seta circumplumose, seems to arise from a process and is separated by a gap from remaining setae.

Uropod ( Fig. 1 View FIGURE 1 E) basal article naked. Exopod uniarticulate, more than half as long as first endopod article, with one medial and one distal setae. Endopod with five articles, distal three articles each with a single seta.

Description. Primary male.

Body ( Fig. 4 View FIGURE 4 A) shorter than female with relative longer pleon and shorter pereon. Cephalothorax subrectangular, longer than wide, almost as long as pereonites 1 to 3 combined, eyes larger than those of female. Pereonites, bearing one short, simple lateral seta. Pereonite 1 shortest. Pereonites 2 and 3 each 1.3 times as long as pereonite 1. Pereonites 4 and 5 longest, almost twice as long as pereonite 1. Pereonite 6 only marginally longer than pereonite 1. Pleon wider than pereon. Pleonites about four times as wide as long, each with one short, simple mediolateral seta. Pleotelson ( Fig. 5 View FIGURE 5 H) short, 1.2 times as long as pleonite 5, twice as wide as long, with mediolateral simple seta and two pairs of simple apical setae of unequal length and one pair of sub apical setae.

Antennule ( Fig. 4 View FIGURE 4 B) consists of eight articles. Article 1 only about three times as long as wide, with one dorsodistal simple seta. Article 2 longer than half of article 1, with one ventrodistal simple seta. Article 3 about half as long as article 2, with three simple distal setae. Article 4–7 serially repeating, all with aesthestascs (many more than illustrated). Article minute, with three long and one tiny simple distal setae.

Antenna ( Fig. 4 View FIGURE 4 C,D) Article 1 square and with one tiny simple seta. Article 2 with ventro- and dorsodistal spiniform setae (thinner than in female). Article 3 about as long as article 2, with dorsodistal spiniform seta (thinner than in female). Article 4 twice as long as article 3, with three long simple and one setulose distal setae. Article 5 slender, shorter than article 4, with one long simple distal seta. Article 6 minute with four long and two shorter simple distal setae.

Mouthparts reduced. Labrum ( Fig. 5 View FIGURE 5 A) prominent but naked, fused to clypeus. Mandibles absent. Maxillule ( Fig. 5 View FIGURE 5 B) endite absent, basis naked, palp pseudo-uniarticulate. Maxilliped ( Fig. 5 View FIGURE 5 C) basis naked, endite absent, palp pseudoarticulate. Epignath ( Fig. 5 View FIGURE 5 D) fully developed with distal setulation.

Cheliped ( Fig. 5 View FIGURE 5 E,F) slender, about half as long as body, attached to body via triangular sclerite bearing a seta. Basis less than twice as long as wide, with single, outer sub-dorsodistal seta. Merus triangular, with three ventral setae. Carpus longer than propodus inclusive fixed finger, with two dorsoproximal and one dorsodistal setae, with two longer and one short ventro-subdistal setae. Propodus including fixed finger as long as basis, with one setae at dactyls insertion and inner row of six pinnate setae of which the most ventral is longer than others. Fixed finger with two small projections on cutting edge, not overlapping unguis, with three setae on cutting edge and four ventral setae. Dactylus with dorsoproximal seta and inner row of small spiniform setae.

Pereopod 1 ( Fig. 6 View FIGURE 6 A) as in female except: dactylus/unguis much shorter relative to propodus.

Pereopod 2 ( Fig. 6 View FIGURE 6 B) as in female except: carpus with two small spiniform setae. Dactylus ventral spine absent small spines present on dorsal margin.

Pereopod 3 ( Fig. 6 View FIGURE 6 C) similar to pereopod 2 except: merus with spiniform ventral setae. Propodus with only two dorsal subdistal setae.

Pereopod 4 ( Fig. 6 View FIGURE 6 D) as in female except: basis slimmer. Merus to dactylus with scales or minute spines.

Pereopod 5 ( Fig. 6 View FIGURE 6 E) as pereopod 4 except: basis with additional ventromedial simple seta

Pereopod 6 ( Fig. 6 View FIGURE 6 F) as pereopod 4 except: propodus with five pinnate and one simple dorsodistal setae. Dactylus with more demarcated spines at unguis insertion.

Pleopods ( Fig. 5 View FIGURE 5 G) all similar. As in female except: with fewer but longer plumose setae not separated by gap on endopod.

Uropod ( Fig. 5 View FIGURE 5 H) basal article with several distal and subdistal setae. Endopod with four articles, all with setae. Exopod uniarticulate, almost as long as first endopod article, with long medial seta and two unequally length distal setae.

Remarks. The genus Leptochelia is one of the genera in Tanaidomorpha with the most cryptic species and present serious obstacles for species identification ( Bamber 2010). At the same time it is one of the most commonly found genera in the world ( Larsen & Rayment 2002) and thus it seems a proper target for genetic studies ( Larsen 2001). Leptochelia parasavignyi is clearly closely related to L. savignyi but genetic comparison with L. savignyi from Gran Canarias and France showed 25% overall difference in the COI gene. This is more than L. dubia Krøyer differs from L. forresti Stebbing (Drumm 2010) and two to four times as much as between species of Zeuxo (Larsen et al. research in progress). Morphologically L. parasavignyi differs from L. savignyi primarily in the longer antennule article 2 and the longer pereonite 6. Additional characters separating the female L. parasavignyi from L. savignyi are: Antennule article 2 longer than article 3. Antenna article 1 with seta; article 2 longer than article 1; article 3 with spiniform seta arising from ventrodistal process. Cheliped basis only 1.5 times as long as wide, dactylus and unguis, combined longer than propodus. Pereopod 2 ischium with two setae. Uropod endopod with five articles (see below); exopod 0.8 times as long as first endopod articles. For the primary male the separating characters are: Antennule with a total of eight articles (‘flagellum’ with only four serially repeating articles); article 3 shorter. Cheliped propodus shorter. Pereopod 6 basis without dorsal marginal flange. The uropod endopod has four articles (see below).

Leptochelia parasavignyi View in CoL can be separated from another Macaronesian Leptochelia View in CoL , L. caldera View in CoL Bamber & Costa, 2009 from (Azores) by: Female; antennule article 2 longer than article 3. Maxilliped basis with four to five setae. Primary male; cheliped propodus much shorter.

The new species can be separated from all other species, except those of the ‘minuta’ group, by having four or five maxilliped basis setae. From the member of the ‘minuta’ group, the new species differ by the short male cheliped propodus.

It is interesting that the number of maxilliped basis setae differs between the left and right basis. The number of these setae is otherwise considered a stable diagnostic character on the species level, but Guţu & Iliffe 2011 also illustrate a variable number (three to four) of these setae in one specimen of Leptochelia View in CoL ( L. vatulelensis View in CoL ). This cave dwelling species can be separated from the new species by the lack of a spiniform eye-lobe and by aforementioned difference in maxilliped basis seta number.

The use of the uropodal article number as a diagnostic character, sparks some controversy. We are convinced that this character is not entirely stable, neither in this genus nor in many other taxa, while some authors are of the opposite view ( Bird & Bamber 2000, Bamber 2010). We therefore recommend caution regarding the use of this character until further data can be collected.