Circoniscus paradisus, Ferreira, 2025

Ferreira, Júlia Barbosa Galo Giovanna Monticelli Cardoso Rodrigo Lopes, 2025, In the depths of the Amazon rainforest: a new troglobitic species of Circoniscus (Isopoda: Scleropactidae) from Brazil, Nauplius (e 20250545) 33, pp. 1-11 : 4-6

Circoniscus paradisus sp. nov.

( Figs. 2–5 )

Zoobank: urn:lsid:zoobank.org:act:D7C59294-8B57-4E2D-A523-190E2B3B5817

Type material. Holotype: Male (ISLA96886), Brazil, state of Pará, municipality of Aveiro, Paraíso Cave (04º04’31,5”S 55º27’31,6”W), 05.X.2020 . Paratypes: 1 male ( ISLA 96887, in slide), same data as holotype ; 1 juvenile ( ISLA 96888) same data as holotype ; 1 female ( ISLA 96889), same data as holotype , 07.X.2020; 4 males, 4 females ( ISLA 96891), same data as holotype , 06.X.2020; 2 males, 2 females ( ISLA 96892), same data as holotype .

Etymology. The new species is named after the cave where it was found. The Portuguese word “Paraíso” is translated to “paradise” in English, and, in Latin, paradisus .

Diagnosis. Circoniscus paradisus sp. nov. is characterized by absence of eyes and body pigment; presence of schisma on pereonite 1 in all specimens; antennula with 2+9 aesthetascs; pleonites3–5 epimera inner face with continuous ridge; distal margin of male pleopod 1 exopod elongated; and endopod apex curved inward.

Description. Maximum body length: male 8.7 mm; female: 9.5 mm. Eyes and body pigments absent. Body convex, endoantennal conglobation ( Fig.2A )covered by small triangular scale-setae. Noduli lateralis and glandular pores not visible ( Fig. 4E )

Cephalon ( Figs. 2B , 4A ) wider than long, frontal shield continuous with pereonite 1, frontal margin broadly rounded.

Pereonite 1 epimera ( Fig. 5 ) with schisma in all specimens;pereonites 2and 3( Fig.4D,E ): with ventral lobes; pereonites epimera inner face ( Fig. 4E, F ) with continuous ridge.

Pleon ( Fig. 2A ) outline continuous with pereon, epimera 3–5 well developed, telson triangular, wider than long, rounded apex.

Telson( Figs. 2C , 4G ) triangular, anterior margin concave, lateral margins following outline of pleonite 5, distal margin acute.

Antennula ( Fig. 2D ) 3-articulated, distal article approximately 4 times longer than second article, conical bearing 9 aesthetascs in 4 rows, plus 2 apical.

Antenna ( Figs. 2E , 4B, C ) short and stout, not surpassing pereonite 1 when extended backwards;

f lagellum with 2 subequal articles; distal article bearing 2 lateral sets of 2 and 3 aesthetascs; apical organ as long as distal article of flagellum.

Figures

Figure 2.Schematic drawings of Circoniscus paradisus sp. nov., male, paratype (ISLA96887): A, habitus, lateral view; B, cephalon, dorsal view; C, pleonites 3–5, telson and uropods, dorsal view; D, antennula; E, antenna; F, left mandible; G, right mandible; H, maxillula; I, maxilla; J, maxilliped.

Figure 3.Schematic drawings of Circoniscus paradisus sp.nov., male,paratype (ISLA96887):A, uropod; B, pereopod 1; C, pereopod 7; D, pleopod 1; E, pleopod 2; F, pleopod 3 exopod; G, pleopod 4 exopod; H, pleopod 5 exopod.

Figure 4.Scanning electron micrographs of Circoniscus paradisus sp. nov., male, paratype (ISLA96891): A, cephalon, frontal view; B, aesthetascs on the second antennal flagellum; C, apical cone of antenna; D, epimera 1–3, dorsal view; E, epimera 1 and 2, ventral view; F, pereonites 3–5, ventral view; G, pleonite 5, telson and uropod, dorsal view; H, pereopod 1 carpus; I, pleopod 1 exopod.

Figure 5. Circoniscus paradisus sp. nov., whole specimens (lateral view): A, female, paratype (ISLA96889); B, male, holotype (ISLA96886); C, juvenile, paratype (ISLA 96888).