Shedding light into Brazilian subterranean isopods (Isopoda, Oniscidea): expanding distribution data and describing new taxa Author Campos-Filho, Ivanklin Soares Author Sfenthourakis, Spyros Biodiversity and ecology laboratory, Department of Biological Sciences, University of Cyprus, Lefkosia (Nicosia) (Cyprus) ivanklin. filho @ gmail. com, isoare 01 @ ucy. ac. cy (corresponding author) Author Gallo, Jéssica Scaglione Author Gallão, Jonas Eduardo Author Torres, Dayana Ferreira Laboratório de Estudos Subterrâneos, Universidade Federal de São Carlos, São Carlos, São Paulo (Brazil) and Instituto Brasileiro de Estudos Subterrâneos, São Paulo (Brazil) Author Chagas-Jr, Amazonas Departamento de Biologia e Zoologia, Universidade Federal de Mato Grosso, Instituto de Biociências, Cuiabá, Mato Grosso (Brazil) Author Horta, Lília Grupo Bambuí de Pesquisas Espeleológicas, Belo Horizonte, Minas Gerais (Brazil) Author Carpio-Díaz, Yesenia Margarita Author López-Orozco, Carlos Mario Author Borja-Arrieta, Ricardo Grupo de Investigación en Biología Descriptiva y Aplicada, Programa de Biología, Universidad de Cartagena, Campus San Pablo, Cartagena de Indias (Colombia) Author Araujo, Paula Beatriz Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul (Brazil) Author Taiti, Stefano Istituto di Ricerca sugli Ecosistemi Terrestri, Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Firenze (Italy) and Museo di Storia Naturale, Sezione di Zoologia “ La Specola ”, Firenze (Italy) Author Bichuette, Maria Elina Laboratório de Estudos Subterrâneos, Universidade Federal de São Carlos, São Carlos, São Paulo (Brazil) and Grupo Bambuí de Pesquisas Espeleológicas, Belo Horizonte, Minas Gerais (Brazil) and Instituto Brasileiro de Estudos Subterrâneos, São Paulo (Brazil) text Zoosystema 2023 2023-10-18 45 19 531 599 https://sciencepress.mnhn.fr/sites/default/files/articles/pdf/zoosystema2023v45a19.pdf journal article 273569 10.5252/zoosystema2023v45a19 5c7fe3a8-433d-4fbe-85c3-f9ef16be4261 1638-9387 10027321 49E49578-3EC4-4088-B17E-E3387C70C247 Circoniscus caeruleus Campos-Filho, Sfenthourakis & Bichuette , n. sp. ( Figs 16-18 ; 21 ) urn:lsid:zoobank.org:act: 873D2089-7918-4F1C-B7ED-071A64C3C351 TYPE MATERIAL . — Holotype . Brazil • ♂ (parts in micropreparations); Caverna Lagoa Azul , Nobres , state of Mato Grosso ; 14°26’48.1”S , 56°1’33.2”W ; 350 m a.s.l. ; 24.IX.2017 ; J. E. Gallão , R . Machado & A. Chagas-Jr leg.; LES 27987 . Paratype . Brazil • 1 ♀ (parts in micropreparations); same locality as holotype; 5.V.2015 ; M. E. Bichuette , A. Chagas-Jr & G. A. Nunes leg.; LES 27988 . ETYMOLOGY . — The new species is named after the typical blue color of the water in the cave where the specimens were collected. DESCRIPTION Maximum body length: ♂ 3 mm , ♀ 6.5 mm . Animal without body pigments. Body ( Fig. 16A ) strongly convex; dorsal surface bearing small triangular scale-setae ( Fig. 16B ). Noduli laterales as in Figure 16A, G, I . Cephalon ( Fig. 16 CE) frontal shield rectangular, bent backwards over vertex, frontal margin broadly rounded; eyes composed of about 10-11 ommatidia. Pereonites 1 and 2 with ventral lobes; pereonites 1-4 with posterior margin straight, 5-7 gradually more concave; pereonite 1 epimera with anterior corners directed frontwards, those of 2-4 with outer margin rounded, and those of 5-7 subquadrangular ( Fig. 16A, E , G-J). Pleon ( Fig. 16A, K ) with epimera 3-5 well developed, directed backwards with acute apices; telson slightly broader than long, with slightly concave sides. Antennula ( Fig. 16L ) distal article longest, conical bearing about four lateral aesthetascs arranged in two rows and apical tip. Antenna ( Fig. 16M ) short and stout, not surpassing pereonite 1 when extended backwards; flagellum with subequal articles, distal article bearing two lateral aesthetascs; apical organ slightly longer than distal article of flagellum. Mandibles ( Fig. 17A, B ) with dense cushion of setae on incisor process, molar penicil consisting of about 10 branches. Maxillula ( Fig. 17C ) inner endite with two apical penicils, distal margin bearing outer tip; outer endite with 4+5 teeth, inner set with four teeth apically cleft. Maxilla ( Fig. 17D ) inner lobe rounded and covered with thick setae; outer lobe rounded, twice as wide as inner lobe, covered with thin setae. Maxilliped ( Fig. 17E ) palp with one strong seta on proximal article; endite subrectangular, medial seta short, not surpassing distal margin, distal margin covered with thin setae and bearing one seta on outer portion, rostral surface with setose sulcus ending with one short penicil. Pereopod 1 carpus with short antennal grooming brush; dactylus with two claws, ungual and dactylar setae simple, surpassing outer claw. Uropod ( Fig. 16K ) protopod enlarged, filling gap between pleonite 5 and telson, slightly surpassing distal margin of telson; exopod inserted on median margin, endopod twice as long as exopod and inserted proximally. Male Pereopod 1 ( Fig. 18A ) merus and carpus with sternal margin covered with short scales and sparse strong setae. Pereopod 7 ( Fig. 18B ) ischium elongated, sternal margin straight; merus bearing triangular lobe on rostral portion; carpus twice as long as merus. Pleopod 1 ( Fig. 18C ) exopod triangular, outer margin slightly concave on distal portion; endopod twice as long as exopod, distal portion bent outwards and bearing small setae on medial margin. Pleopod 2 ( Fig. 18D ) exopod triangular, outer margin concave; endopod flagelliform, slightly longer than exopod. Exopods of pleopods 3 and 4 as in Figure 18E and F , respectively. Pleopod 5 exopod ( Fig. 18G ) with outer margin sinuous, inner margin grooved to accommodate pleopod 2 endopod. REMARKS The genus Circoniscus comprises 10 species endemic to South America ( Schmidt 2007 ; Campos-Filho et al. 2018a ). To date, Brazil holds the highest diversity in the genus, with nine species present in the country, i.e., C. bezzii Arcangeli, 1931 , C. buckupi Campos-Filho & Araujo, 2011 , C. carajasensis Campos-Filho & Araujo, 2011 , C. gaigei Pearse, 1917 , C. hirsutus Schmidt, 2007 , C. incisus Souza & Lemos de Castro, 1991 , C. intermedius Souza & Lemos de Castro, 1991 , C. ornatus ( Verhoeff, 1941 ) , and C. pallidus Arcangeli, 1936 (see Campos-Filho et al. 2018a ). Circoniscus caeruleus Campos-Filho, Sfenthourakis & Bichuette , n. sp. differs from all other species of the genus in having a triangular lobe on the rostral surface of the male pereopod 7 merus. Only one species of the genus is recorded from the state of Mato Grosso , C. intermedius ( Schmidt 2007 ; Campos-Filho et al. 2014 ), from which it differs in having the eyes composed of 10-11 ommatidia (vs 20 in C. intermedius ), pereonite 2 epimera with ventral lobe (vs absent in C. intermedius ), telson slightly wider than long (vs as wide as long in C. intermedius ), and male pleopod 1 exopod triangular, and as wide as long (vs heart-shaped, and slightly wider than long in C. intermedius ) (see Souza & Lemos de Castro 1991 ; Schmidt 2007 ). FIG . 16. — Circoniscus caeruleus Campos-Filho, Sfenthourakis & Bichuette , n. sp. , male holotype, LES 27987: A , lateral habitus; B , scale-seta; C , cephalon and pereonites 1 and 2, frontal view; D , cephalon, dorsal view; E , cephalon, and pereonites 1 and 2, lateral view; F , cephalon, back view; G , pereonite 1 epimera, dorsal view; H , pereonite 1 epimera, ventral view; I , pereonite 2 epimera, dorsal view; J , pereonite 2 epimera, ventral view; K , pleonites 4 and 5, telson, and uropods; L , antennula; M , antenna. Scale bar: A, 1 mm. This species is considered to be a troglophile. However, its body is pigmentless and the number of ommatidia is reduced, characters typically observed in troglobitic species. The species has a preference for highly humid places, composed of silt and guano substrates. Moreover, in the aphotic zone, its abundance is reduced, probably due to the lack of resources. More sampling efforts should be paid outside caves to confirm its classification as a troglophile.