Two new troglobitic species of Scleropactidae ( Crustacea : Isopoda : Oniscidea ) from Pará , Brazil

The South America Scleropactidae includes 53 nominal species distributed in 14 genera. In Brazil, there are 16 species recorded in the north and southeast regions. Here, two new species of Scleropactidae are described based on material collected in caves in the state of Pará, both troglobitic and allocated in the genus Circoniscus. Circoniscus buckupi sp. nov. can be distinguished from its congeners by the long second article of antennal flagellum, inner endite of maxillula with a small hook-like spine at the apex, a long dactylar organ with pectinate apex conferring a knife-shaped appearance and the absence of schisma in adults. Circoniscus carajasensis sp. nov. can be distinguished from Circoniscus buckupi sp. nov. by the presence of schisma on pereionite 1 in adults and dactylar organ with a fringe

The present work describes the first troglobitic species of Circoniscus, based on material collected in caves in the state of Pará, in the municipalities of Parauapebas and Canaã dos Carajás.A diagnosis of the genus can be found in Schmidt (2007).
Appendages: Antennule triarticulate, distal article approximately four times as long as second article, with eight aesthetascs in three rows and with a small hook-like protuberance at the apex (Fig. 1E).Antenna short, when extended backward reaching approximately midlength of first pereionite, fourth and fifth articles more robust than others, distal portion with one long ornamental seta; antennal flagellum with two articles, distal article longer, around two times as long as proximal article, with 8-10 aesthetascs (faintly visible), apical organ longer than distal article and showing sensory hairs enclosed by a common tubelike sheath, and with simple short free sensilla (Fig. 1F).Mandibles with at least seven branches on pars molaris, right mandible with two penicils on incisor process, and left mandible with three penicils (Figs.1G, H).Inner endite of maxillula with two short penicils, inserted almost transversely, distal portion rounded with small hook-like protuberance, outer endite with 4 stout, simple setae, an accessory small tooth and a slender seta, and inner set with five teeth cleft, one simple, and slender (Fig. 1I).Lateral lobe of maxilla approximately three times broader than median lobe, distal margin slightly rounded, with trichiform setae; median lobe quadrate with distal margin rounded, and covered with trichiform setae (Fig. 1J).Maxilliped with rectangular base, sparse tricorn-like setae, and distal margin prominent with slender setate fringe, endite rectangular, with inner and outer lateral margins with slender setae, distal margin slightly prominent, inner portion with short penicil, and seta overpassing the margin, outer portion with one seta, palp tapering, with 3 tufts of setae, proximal article with 1 long inner seta (Fig. 1K).Pereiopods with typical scleropactid scale fields, sparse setae with gradual elongation, and apex tricorn and robust, carpus 1 with transverse antennagrooming brush and one hand-like apex seta, merus 7 without lateral ridge, dactylus with long outer and inner claws, ungual seta long with simple apex and reaching distal margin of outer claw, dactylar organ long with pectinate apex, conferring a knife-shaped appearance (Figs.2A-C).Pleopods with respiratory fields faintly visible.Uropod with insertion of endopod and exopod at different levels, protopod enlarged, endopod two times longer than exopod, inner lateral margin with sparse setae with fringed appearance continuous with protopod, exopod insertion covered by protopod (Fig. 3E).
Sexual dimorphism: female pleopod 1 exopod more elongated than in male, pleopod 2 exopod and 5 with distal part not elongated.

Etymology:
The species name honors Professor Ludwig Buckup for his contributions to the knowledge of Crustacea.
Remarks: Circoniscus buckupi sp.nov. shares characteristics found in its congeners, such as the second antenna with flagellum biarticulate and the outer endite of maxilulle with inner set of cleft teeth.The new species can be distinguished by the absence of the schisma on pereionite 1 in adults, long second article of antennal flagellum, dactylar organ with pectinate apex conferring a knife-shape appearance, pleopod 1 exopod with the distal margin slightly sinuous and the respiratory fields faintly visible.The well developd schisma in young individuals allowed us to allocate the species in the genus Circoniscus.Thereby we consider that the absence of schisma in adults as a secondary loss of character.
Appendages.Antennule triarticulate, distal article approximately three times as long as second article, with seven aesthetascs in rows (one group of three and two groups of two plus apical one) (Fig. 4F).Antenna short, when extended back reaching midlength of first pereionite, fourth and fifth articles of peduncle more robust than others, antennal flagellum with two subequal articles, distal article with 8-10 aesthetascs (faintly visible), apical organ longer than second article of flagellum, bearing sensory hairs enclosed by a common tubelike sheath, and with simple and short free sensilla (Fig. 4G).Mandibles with at least eight branches on pars molaris, right mandible with two penicils on incisor process (not illustrated), and left mandible with three penicils (Fig. 4I).Inner endite of maxillula with two short penicils, inserted almost transversely, distal portion rounded with small hook-like protuberance, outer endite with 4 stout, simple setae, an accessory small tooth and a slender seta, and inner set with five teeth cleft, one simple, and slender (Fig. 4J).Lateral lobe of maxilla twice as broad as median lobe, distal margin slightly sinuous, covered with trichiform setae, median lobe quadrate, distal margin slightly rounded and covered with trichiform-setae (Fig. 4K).Maxilliped with rectangular base, sparse tricorn-like, distal margin truncated, with slender setae fringe, endite rectangular, distal margin slightly prominent, with short penicil, setose lateral margin, outer portion with one seta and lateral margin with sparse setae; palp with three tufts of setae, proximal article with one long inner seta (Fig. 4L).Pereiopods with typical scleropactid scale-fields, sparse setae, merus and carpus 1 and 2 robust, carpus 1 with transverse antenna-grooming brush and two hand-like apex setae, merus 7 elongated, without a lateral ridge, dactylus with long outer claw, shorter inner claw, ungual seta long and simple, long dactylar organ, with brushlike apex, ungual and dactylar setae reaching distal margin of outer claw (Figs.5A-C).Pleopods with respiratory fields faintly visible.Uropod with insertion of endopod and exopod at different levels, protopod enlarged, endopod two times longer than exopod, inner lateral margin with sparsely fringed appearance, continuous with protopod, exopod insertion covered by protopod (Fig. 6D).Male: pleopod 1 exopod ovoid, with rounded apex, endopod 1 with small setae on distal part (Fig. 5D); pleopod 2 exopod triangular, outer lateral margin convex relative to insertion, rounded apex, sulcus marginalis present, endopod 2 slender, reaching pleopod 5, with apex curved and rounded (Fig. 5E); pleopods 3 and 4 as in Figures 6A and 6B; pleopod 5 exopod triangular, distal part narrow, covered by fringe scales, and a longitudinal furrow to receive the pleopod 2 endopod (Fig. 6C).Genital papilla with ventral shield and two subapical orifices (Fig. 5D).
Etymology: The species name refers to the location where the specimens were collected: FLONA (National Forest) -Carajás.Remarks: Circoniscus carajasensis sp.nov. shares characteristics with its congeners such as the coxal plate 1 with schisma, second antenna with flagellum bi-articulate, and outer endite of maxilulle with inner set of cleft teeth.The new species can be distinguished from the other troglobitic species, Circoniscus buckupi sp.nov.by the presence of schisma on pereionite 1, dactylar organ with a fringe appearance and the ovoid shape of the pleopod 1 exopod.
in labels.