Leuconidae Sars, 1878 (Crustacea: Cumacea) from the southwestern Atlantic, filling the distribution gap along the Brazilian coast Author Brito, Ayrton Do Ramo Setor de Carcinologia, Museu Nacional / Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão s / n, 20940 - 040, Rio de Janeiro, Brazil & Programa de Pós-graduação em Ciências Biológicas (Zoologia), Museu Nacional / Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão s / n, 20940 - 040, Rio de Janeiro, Brazil Author Serejo, Cristiana Silveira Setor de Carcinologia, Museu Nacional / Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão s / n, 20940 - 040, Rio de Janeiro, Brazil & Programa de Pós-graduação em Ciências Biológicas (Zoologia), Museu Nacional / Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão s / n, 20940 - 040, Rio de Janeiro, Brazil text Zootaxa 2023 2023-12-11 5383 2 101 134 https://www.mapress.com/zt/article/download/zootaxa.5383.2.1/52444 journal article 10.11646/zootaxa.5383.2.1 1175-5326 10350586 996315A6-A209-4DF7-B59C-0B7662741F37 Leucon (Crymoleucon) pseudograndidentatus sp. nov. ( Figs. 1A , 5 , 6 and 7 ) Material examined. Holotype : Female 4.6 mm , #SANSED1 B8- R2 (0–2), MNRJ 30553 . Paratypes : female, 5 mm , #HAB3 B08, MNRJ 28943 (dissected, lost in the fire) ; female, 4.2 mm , #SANSED1 B09- R1 (0–2) , MNRJ 30552 (dissected) ; 2 females , 4.7 and 1.8 mm , #SANSED1 C08- R3 (0–2) , MNRJ 30554 ; 3 females , 4.3– 2.8 mm #SANSED1 D08- R1 (0–2) , MNRJ 30555 ; male, 3.7 mm , female, 2.9 mm , #SANSED1 D08- R2 (0–2) , MNRJ 30556 ; female, 3.4 mm , #SANSED2 E06- R2 (0–2) , MNRJ 30557 ; male, 3 mm , #SANSED4 H08- R1 (0–2) , MNRJ 30558 ; male, 1.7 mm , #SANSED3 P03- R3 (0–2) MNRJ 30559 ; male, 3.3 mm , #SANSED7 B07- R2 (0–2) , MNRJ 30560 ; female, 4.4 mm , #SANSED7 D07- R1 (0–2) , MNRJ 30561 ; 2 female , 3.2– 1.7 mm , #SANSED7 D08- R1 (0–2) , MNRJ 30562 ; female, 3 mm , #SANSED7 D08- R1 (2–5) , MNRJ 30563 ; female, 2.9 mm , #SANSED7 D08- R2 (0–2) , MNRJ 30564 ; female, 2.5 mm , #SANSED7 D09- R3 (0–2) , MNRJ 30565 ; 3 females, 4- 2.8 mm , male, 2.7 mm , #SANSED7 E06- R 1 (0–2), MNRJ 30566; female, 3.6 mm , #SANSED7 E06- R 2 (0–2), MNRJ 30567; male, 2.6 mm , #SANSED7 E08- R 1 (0–2), MNRJ 30568; female, 3.8 mm , #SANSED8 F06- R 1 (0–2), MNRJ 30569. Additional material (lost in the fire): 2 females , 1.8 and 3.2 mm , #HAB3 A8; female, 5 mmm, #HAB3 B8; male, 2.6 mm , #HAB3 C9; 2 males , 1.9 and 3.6 mm , #HAB3 I8; male, 3.5 mm , 2 females , 2.9 and 4.6(broken) mm. #HAB3 C8; 2 females , 1.7 and 4.5 mm , #HAB6 D7; females, 2.6 and 3.6 mm , #HAB8 A8; females, 2.5 mm , #HAB8 B8; male, 2.1 mm , #HAB9 I8; male, 2.2 mm , #HAB9 I9; male, 3.9 (broken) mm, #HAB11 E6; male, 2.3 (broken) mm, #HAB11 C6; 3 females , 1.8–1,9 and 2.5 mm , # AMB5 A6; male, 2.9 mm , # AMB5 B5; male, 2.6 mm , # AMB5 C5; male, 3.5 mm , # AMB6 CAN7; 2 females , 2.3–3.1 mm , # AMB11 A6; female, 3.2 mm . # AMB11 A7; female, 5 mm . # AMB12 B6; male, 3.9 mm . # AMB12 D6; female, 3.6 mm . # AMB12 E6; Development. Females: mature longer than 4.2 mm , preparatory between 3.6–4.2 mm , immature between 1.8–3.6 mm , manca shorter than 1.8 mm . Males: mature and preparatory unknown, second immature between 3.5 and 3.9 mm , first immature between 2.1 and 3.3 mm , manca shorter than 1.7 mm . Type locality. Santos Basin, SC, Brazil , 26°47’58”S – 45°58’41”W ; 996 m . Distribution. Brazil : Santos Basin (SC, PR , SP, RJ), Campos Basin (RJ), Espírito Santo Basin (ES); 381–1731 m . Etymology. The name pseudograndidentatus is given for the similarity between the new species and Leucon ( Crymoleucon ) grandidentatus Mühlenhardt-Siegel, 2011 . Diagnosis. Pseudorostrum 0.7 times length carapace, 0–3 ventral teeth. Dorsal serration dorsally on carapace from 7–11 teeth. Anteroventral corner rounded with serration. Pereopod 2, dactylus with 12 long plumose setae. Pereopod 3–5 with plumose setae on basis, propodus at least 4 times longer than dactylus. Uropodal peduncle with a long dorsodistal seta, exopod slightly longer than endopodal article 1. Description: Holotype , mature female, MNRJ 30553. Mature female, 4.6 mm . Carapace as long as pereon including pseudorostrum, with dorsal serrations of 11 teeth (last three broken), frontal margin with serration of 5 teeth; pseudorostrum acute, 0.7 times carapace length (measured from frontal lobe to posterior margin), with 3 teeth on ventral margin; antennal notch small; anteroventral corner rounded with row of teeth along its margin. Pleon 0.5 times total body length ( Figs. 1A and 5 ). Paratype . Mature female, MNRJ 28943 (lost in the fire) . Mature female, 5 mm . Antenna 1, not geniculate between articles 1 and 2; article 1, about as long as article 2, naked; article 2 as long as or slightly longer than 3, with few simple setae; article 3 with simple setae; main flagellum of 3 articles, article 1 with 3 simple setae on outer margin, article 3 with 3 simple setae and 2 aesthetascs; accessory flagellum of 1 article, about as long as main flagellum articles 1 and 2 together ( Fig. 6 a 1 ). Antenna 2 rudimentary ( Fig. 6 a 2 ). Mandibles, basis truncate, incisor with 2 distal simple setae, lacinia mobilis with 3 cusps ( Fig. 6 md). Maxilla 1 with 2 endites, palp with one bristle (broken during dissection) ( Fig. 6 mx1). Maxilla 2 with 3 endites; broad endite with row of distal plumose setae; narrow endites with simple setae ( Fig. 6 mx2). Maxilliped 1, basis with long plumose seta; ischium absent; carpus and propodus with long plumose setae at outer distal corner and numerous simple setae on inner margin; dactylus with strong terminal and 2 subterminal simple setae ( Fig. 6 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 inner distal margin; carpus about 10 plumose setae along inner margin; propodus with long plumose seta on outer margin and about 8 plumose setae on inner margin; dactylus with strong terminal and 2 subterminal simple setae ( Fig. 6 mxlp2). Maxilliped 3, basis 0.9 times length of remaining articles together, with plumose setae on anterior inner margin and on inner face, distolateral corner with 3 long plumose setae; ischium with tiny simple setae on inner margin; merus with small tooth and long plumose setae on outer margin; carpus with plumose seta on outer margin and small simple seta at outer corner; exopod, flagellum with 3 articles ( Fig. 6 mxlp3). Pereopod 1, basis 0.5 times length of remaining articles together, with plumose setae on inner margin, serration on outer face and cuspidate seta at inner distal corner; ischium with simple setae and tooth at inner corner; merus, carpus and propodus with simple setae; dactylus with strong terminal setae and 4 pairs of subterminal setae; exopod, flagellum with 4 articles ( Fig. 7 p 1 ). FIGURE 6. Leucon ( Crymoleucon ) pseudograndidentatus sp. nov. Paratype (lost in the fire): mature female, 5 mm, #HAB3 B08, MNRJ 28943. Habitus (pseudorostrum broken), antenna 1–2, mandible, maxilla 1–2 and maxillipeds. FIGURE 7. Leucon ( Crymoleucon ) pseudograndidentatus sp. nov. Paratype (Lost in the fire): mature female, 5 mm, #HAB3 B08, MNRJ 28943. Pereopods and uropod. Pereopod 2, basis 0.7 times length of remaining articles together, with simple and plumose setae; ischium quite short with plumose seta on outer margin; merus with plumose setae; carpus with plumose setae; propodus naked; dactylus with 13 long plumose setae; exopod, flagellum with 4 articles ( Fig. 7 p 2 ). Pereopod 3, basis 1.25 times length of remaining articles together, with plumose setae; ischium and merus with plumose setae; carpus with plumose annulate seta; propodus with simple annulate setae; dactylus small with long simple setae; exopod, flagellum with 4 articles ( Fig. 7 p 3 ). Pereopod 4, basis 1.25 times length of remaining articles together, with plumose setae; ischium with simple seta; merus with plumose setae; propodus with simple annulate setae; dactylus small with long simple seta ( Fig. 7 p 4 ). Pereopod 5, basis 1.4 times length of remaining articles together, with simple and plumose setae; ischium, merus and carpus with plumose setae; propodus with annulate seta; dactylus small with simple long seta ( Fig. 7 p 5 ). Uropod, peduncle longer than pleonite 6 with 4 simple setae on inner margin and long dorsodistal simple seta; endopod 2-articulate, article 1, 2.5 times article 2 length, with 7 cuspidate setae on inner margin, article 2 with 6 cuspidate setae; exopod as long or slightly longer than endopodal article 1 with 4 plumose setae on inner margin, 3 long terminal annulate setae ( Fig. 7 u ). Variations. Carapace calcification varies between specimens collected in summer and winter, with winter specimens usually less calcified. Dorsal serration may present 7–11 teeth, the first seven teeth are large, from the 8th to the 11th tooth, they can be very small or absent, frontal margin with serration of 5–8 teeth ( Fig. 5 h ). Immature stages are less calcified and present more setae over the body. Manca stages have uropodal rami subequal in length, exopod becomes proportionally shorter at further stages. Remarks. Leucon ( Crymoleucon ) pseudograndidentatus sp. nov. is similar to L. ( C ) grandidentatus Mühlenhardt-Siegel, 2011 and L. ( C ) longirhinus Mühlenhardt-Siegel, 2011 in the presence of a long pseudorostrum, antenna 1 accessory flagellum much longer than article 1 of main flagellum, maxilliped 3 merus with small tooth on outer margin ( Mühlenhardt-Siegel 2011b ). Leucon ( C ) pseudograndidentatus sp. nov. shares exclusively with L. ( C ) grandidentatus the dorsal serration of 7–11 teeth on carapace, pereopod 3–5 propodus at least 4 times longer than dactylus. Leucon ( C ) pseudograndidentatus sp. nov. and L. ( C ) longirhinus present similarities at the uropods (peduncle with 4 setae on inner margin, exopod slightly longer than endopodal article 1, endopodal article 1 with 7 setae on inner margin) ( Mühlenhardt-Siegel 2011b ). Leucon ( C ) grandidentatus and L. ( C ) longirhinus are found in the deep-sea regions of Antarctica , at depths ranging from 3784 to 4698 m and 1983 to 4676 m , respectively ( Table 1 , Mühlenhardt-Siegel 2011b ). On the other hand, L. ( C ) pseudograndidentatus is found in the south and southwest coast of Brazil , at depths ranging from 381 to 1731 m . Leucon ( C ) pseudograndidentatus differs from L. ( C ) grandidentatus in the pseudorostrum 0.7 times carapace length and has 3 ventral teeth ( versus 0.4 times carapace length, with one ventral tooth), maxilliped 2 without fringe of setae on the basis and tuft of hair-like setae on merus outer margin ( versus fringe of setae on the basis and tuft of hair-like setae on merus outer margin), pereopod 2 with many plumose setae along articles ( versus few setae along articles), uropodal peduncle with 4 setae on inner margin and a long dorsodistal seta ( versus uropodal peduncle with a single setae on inner margin and dorsodistal seta absent), exopod and endopodal article 1 subequal in length ( versus much longer than endopodal article 1), uropodal endopod article 2 with 3 setae on inner margin ( versus 5 setae on inner margin) ( Mühlenhardt-Siegel 2011a ). Leucon ( C ) pseudograndidentatus differs from L. ( C ) longirhinus in the pseudorostrum 0.7 times carapace length with 3 ventral teeth ( versus 0.6 times carapace length, with 2 ventral teeth), pereopod 2 dactylus with 12 plumose setae ( versus 7 plumose setae and 3 simple setae), pereopod 3–4 propodus about 4 times longer than dactylus ( versus only 3 times longer than dactylus), uropodal peduncle with a long dorsodistal seta ( versus lacks dorsodistal setae) ( Mühlenhardt-Siegel 2011b ).