Leucon (Macrauloleucon) watlingi Brito & Serejo 2023, sp. nov.
Creators: name: Brito, Ayrton Do Ramo
name: Serejo, Cristiana Silveira
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Cumacea
Leuconidae
Leucon
Leucon watlingi

description: Leucon (Macrauloleucon) watlingi sp. nov.
(Figs. 1B, 8, 9 and 10)
Material examined. Holotype female, 3.6 mm, #SANSED7 D09- R1 (0–2), MNRJ 30544.
Paratypes: female 4.9 mm, #HAB7 H6, MNRJ 28904 (dissected, lost inthe fire); female, 3.7 mm, #SANSED4 H06- R3, (0–2) MNRJ 30543 (dissected); female, 1.9 mm, #SANSED1 C06- R3 (0–2), MNRJ 30545; female, 2.3 mm, #SANSED1 D06- R2 (0–2), MNRJ 30550; female, 4.2 mm, #SANSED2 E06- R3 (0–2), MNRJ 30546; female (broken), notmeasured, #SANSED7A06- R1 (5–10), MNRJ 30547; male (carapace), notmeasured, SANSED7 C07- R1 (0–2), MNRJ 30548; male, 1.6 mm, #SANSED7 D06- R3 (0–2), MNRJ 30549; female, 2.1 mm, #SANSED8 G06- R1 (0–2), MNRJ 30551.
Additional material (lost inthe fire): female, 2.6 mm, #HAB6 C7, MNRJ 28902; 3 females, 2.4–3.3 mm, male, 1, 8 mm, #HAB7 D6, MNRJ 28903; 2 females, 3.2 and 3.3 mm, #HAB8 A7, MNRJ 28906; 2 females, 3.1 mm, #HAB8 D6, MNRJ 28907; female, 3.3 mm, #HAB8 E6, MNRJ 28908; female, 1.5 mm, #HAB9 H7, MNRJ 28909; female, 1.8 mm, #HAB7 H6, MNRJ 28905; females, 1.8 mm, # AMB3 E5, MNRJ 28893; male, 3.5 mm, 2 females, 2.3 and 3.4 mm, # AMB3 F5, MNRJ 28894; 2 females, 1.4 and 1.5 mm, # AMB6 D5, MNRJ 28896; male, 2.9 mm, # AMB5 C5, MNRJ 28895; male, notmeasured, # AMB11 B5, MNRJ 28897; female, 2.9 mm, # AMB11 C6, MNRJ 28898; female, 3.4 mm, # AMB11 F10, MNRJ 28899; 2 females, 2 and 3.5 mm, # AMB12 D5, MNRJ 28900; female, 2.9 mm, # AMB12 F5, MNRJ 28901.
Development. Females: mature longer than 3.7 mm, preparatory 3.6 mm, immature between 2.1 and 2.3 mm, manca shorter than 2.1 mm. Males: mature and preparatory unknown, second immature 3.5 mm, first immature 2.9 mm, manca shorter than 1.8 mm.
Type locality. Santos Basin, SP, Brazil, 25°39’59’’S – 45°05’01’’W; 695 m.
Distribution. Brazil: Santos Basin (RJ, SP, SC), Campos Basin (RJ), Espírito Santo Basin (ES); 381–3001 m.
Etymology. The name watlingi is in honor of Dr. Les Watling (University of Hawaii), an esteemed researcher in Cumacea studies and a great reference in Leuconidae taxonomy.
Diagnosis. Pseudorostrum less than half carapace length, unarmed or with very small dorsal teeth and 2 ventral teeth. Frontal lobe with 2 teeth. Carapace ventral margin with serration of 4 teeth and small teeth laterally. Maxilliped 3 merus with 2 teeth on outer margin. Pereopod 2 ischium absent, carpus as long as propodus and dactylus together. Pereonite 2 and 3 unarmed. Uropodal endopod article 1, 3 times longer than article 2, article 2 with 3 teeth.
Description: Holotype preparatory female, MNRJ 30544.
Preparatory female, 3.6 mm. Carapace 1.5 times pereon length including pseudorostrum, with dorsal serrations of 2 small teeth on frontal lobe, frontal margin with serration of 4 teeth; pseudorostrum less than 0.5 times carapace length (measured from frontal lobe to posterior margin), 2 ventral teeth; branchial siphon extending 0.8 times carapace length; antennal notch small; anteroventral corner rounded with serration. Pereon with pereonites 2 and 3 unarmed. Pleon about 0.5 times total body length (Figs. 1B and 8).
Paratype. Mature female, 4.9 mm, MNRJ 28904 (lost inthe fire).
Antenna 1, not geniculate between articles 1 and 2; article 1, 0.7 times article 2 length, naked; article 2 as long as 3, with plumose setae; article 3 with plumose setae; main flagellum of 3 articles, article 1 naked, article 2 with 2 distal simple setae, article 3 with simple setae and 2 aesthetascs; accessory flagellum of 1 article, shorter than main flagellum article 1 (Fig. 9 a 1).
Antenna 2 rudimentary (Fig. 9 a 2).
Mandibles, basis truncate, incisor with 2 distal simple setae, lacinia mobilis with 4 cusps (Fig. 8 md).
Maxilla 1 with 2 endites, palp with one bristle (broken during dissection) (Fig. 9 mx1).
Maxilla 2 with 3 endites; broad endite with row of distal plumose setae; narrow endites with simple setae (Fig. 9 mx2).
Maxilliped 1, basis with long plumose seta; ischium absent; carpus with numerous setae on inner margin; propodus with 2 long plumose setae on outer margin and numerous simple setae on inner margin; dactylus with strong terminal and 2 subterminal plumose setae (Fig. 9 mxlp1).
Maxilliped 2, basis about 0.4 times length of remaining articles together, with plumose seta at inner distal corner; merus with plumose seta on distal inner margin; carpus with 10–11 plumose setae on inner margin; propodus with long plumose seta on outer margin and about 4–5 plumose setae on inner margin; dactylus with strong terminal and 3 subterminal simple setae (Fig. 9 mxlp2).
Maxilliped 3, basis 0.8 times length of remaining articles together, with plumose setae on inner margin, distolateral corner with 3 long plumose setae; ischium with cuspidate seta on inner margin; merus with 2 teeth and long plumose seta on outer margin and plumose setae on inner margin; carpus with plumose setae on inner margin and small simple seta at outer corner; dactylus with terminal simple seta and 3 subterminal simple setae; exopod, flagellum with 3 articles (Fig. 9 mxlp3).
Pereopod 1, basis 0.3 times length of remaining articles together, with plumose setae on inner margin, cuspidate setae at inner distal corner; ischium with tiny plumose seta; merus, carpus and propodus with simple and plumose setae; dactylus with long terminal simple setae and 3 pairs of subterminal simple setae; exopod, flagellum with 4 articles (Fig. 10 p 1).
Uropod, peduncle longer than pleonite 6 and shorter than rami with 4 setae on inner margin, last one cuspidate; endopod 2-articulate, article 1, 2.5 times article 2 length, with 5 cuspidate setae on inner margin, article 2 with 2 cuspidate setae and 3 teeth on inner margin, terminal cuspidate seta and subterminal plumose seta; exopod as long as endopod with 3 distal plumose setae (Fig. 10 u).
Paratypes, mature female, 3.7 mm, MNRJ 30543.
Mature female, 3.7 mm. Pereopod 2, basis about 0.6 times length of remaining articles together, with plumose setae; ischium absent; merus with plumose setae; carpus with 2 long plumose setae and cuspidate seta at outer distal corner; propodus naked; dactylus with 11 long plumose setae; exopod, flagellum with 4 articles (Fig. 10 p 2).
Pereopod 3, basis about 1.25 times length of remaining articles together, with plumose setae; ischium and merus with plumose setae; carpus and propodus with simple annulate setae; dactylus small with long simple annulate seta (Fig. 10 p 3).
Pereopod 4, basis about 1.1 times length of remaining articles together, with plumose setae; ischium and merus with plumose setae; carpus and propodus with simple annulate setae; dactylus small with long simple annulate seta (Fig. 10 p 4).
Pereopod 5, basis about 1.1 times length of remaining articles together, with plumose setae; ischium and merus with plumose setae; carpus and propodus with simple annulate setae; dactylus small with long simple annulate seta (Fig. 10 p 5).
Variation. Teeth on frontal lobe varies in size, may be very small or absent, some specimens may present very small dorsal teeth on pseudorostrum; branchial syphon may extend as long as carapace (Fig. 9 h).
Remarks. Leucon (M) watlingi sp. nov. is most similar to L. (M) weddelli Ledoyer, 1993 inthe presence of pseudorostrum shorter than half carapace length, frontal lobe with 2 teeth, small lateral teeth on carapace, maxilliped 3 merus with 2 teeth on outer margin, pereopod 2 ischium absent. However, L. (M) watlingi sp. nov. differs from L. (M) weddelli Ledoyer, 1993 in the presence of a serration of 4 teeth on the frontal margin of the carapace (versus 2 strong teeth on the frontal margin of the carapace), pereopod 2 carpus as long as the propodus and dactylus together (versus pereopod 2 carpus longer than the propodus and dactylus together), pereonites 2 and 3 unarmed (versus pereonites 2 and 3 with dorsolateral teeth), uropodal endopod article 1, 3 times longer than article 2 (versus uropodal endopod article 1, 2.6 times longer than article 2) (Ledoyer 1993; Mühlenhardt-Siegel 2011a; 2011b).
Furthermore, Leucon (M.) watlingi sp. nov. and L. (M) complexus Mühlenhardt-Siegel, 2011 have pereopod 2 carpus shorter than the propodus and dactylus together, a character that sets them apart from all other species of the subgenus. However, Leucon (M.) watlingi sp. nov. differs from L. (M) complexus in the presence of a frontal lobe with 2 teeth (versus 3 teeth), pereopod 2 lacks ischium (versus with ischium), uropodal endopod article 1, 3 times longer than article 2 (versus 2.5 times longer than article 2), article 2 with 3 teeth on the inner margin (versus article 2 with 1 shallow tooth on the inner margin) (Mühlenhardt-Siegel 2011b).
description: Published as part of Brito, Ayrton Do Ramo & Serejo, Cristiana Silveira, 2023, Leuconidae Sars, 1878 (Crustacea: Cumacea) from the southwestern Atlantic, filling the distribution gap along the Brazilian coast, pp. 101-134 in Zootaxa 5383 (2) on pages 117-120, DOI: 10.11646/zootaxa.5383.2.1, http://zenodo.org/record/10350586