The first troglobitic terrestrial isopod (Isopoda, Oniscidea) from Peru

Abstract The present work aims to describe the first troglobitic terrestrial isopod (Oniscidea) from Peru. Caecopactes chullachaqui sp. nov. is described from Cueva de Palestina, Department of San Martín. The new species constitutes the third troglobitic taxon known for the country and extends the knowledge of the distribution of the genus.

South America comprises some of the most important biodiversity hotspots at a global scale (Myers et al., 2000;Marchese, 2015).Considering the territorial extension of South America, only 2% of its territory shows suitable lithology for the development of karstic systems (Auler, 2017).
Considering all studies from South American caves, our knowledge on Peru's systems is still elementary (Ribera and Bellés, 1994;Trajano, 2019).Historically, Alexander von Humboldt is considered the pioneer of South American cave fauna.In 1799 he discovered, and later described, the "Guácharo" bird, Steatornis caripensis Humboldt, 1817, from Venezuela.In 1801, Humboldt carried out studies across many regions of Colombia, and at about the same period other naturalists studied bats and birds from Venezuela and Colombia.In the 20 th century, the first South American troglobitic species was described from Brazil, the catfish Pimelodella kronei (Miranda-Ribeiro, 1907).Later, during the 1950's and 1960's, the studies increased mainly in Venezuela and Brazil (Trajano and Bichuette, 2006).In 1972 the first studies on the caves of Peru appeared, comprising faunal inventories, and in 1994 the first cavefish was described, namely Astroblepus riberae (Cardona and Guerao, 1994).Since then, only occasional works with descriptions of species, such as the collembolan Acheroxenylla lipsae Palacios-Vargas, 2020(Palacios-Vargas, 2020), have been published.
The family Scleropactidae includes more than 110 species and 26 genera mainly distributed in circumtropical areas (Schmalfuss, 2003).The Neotropical representatives of the family had their phylogenetic relationships and taxonomy investigated, but until today the family's position within Crinocheta has not been unambiguously resolved (Schmidt, 2007;2008).
The present work aims to describe a new troglobitic species of Caecopactes Schmidt, 2007 from Cueva de Palestina, Department of San Martin, Peru.This species is the third troglobitic species for the country.In addition, ecological and conservation remarks are given.

MATERIAL AND METHODS
Specimens were collected by hand with the aid of tweezers and brushes, and were stored in 70% and 100% ethanol.Information about the microhabitat (entrance, twilight or aphotic zones) and environmental variables (temperature and relative air humidity) of the caves were also recorded.Descriptions are based on morphological characters with the use of micropreparation in Hoyer's medium (Anderson, 1954).For each new species, type material, description, Campos-Filho et al.
etymology and remarks are given.The habitus images were taken with the stereomicroscope model Zeiss SteREO Discovery.V12 Modular Stereo Microscope adapted with Zeiss AxioCam ERc 5s camera.The photographs were prepared with Adobe Photoshop CC Lite (v.17.1.1).The appendages were illustrated with the aid of a camera lucida mounted on a CH2 Olympus microscope.The final illustrations were prepared with the method proposed by Montesanto (2015;2016).A map highlighting the cave where the specimens where collected, as well the hydrological and geological attributes in the region, is presented.The distribution map was constructed with ArcMap (v.10.5).
The material is deposited in the scientific collections of Museo de Historia Natural Universidad Nacional Mayor de San Marcos (MUSM), Peru, and Laboratório de Estudos Subterrâneos (LES), Universidade Federal de São Carlos, São Carlos, Brazil.

Study Area
The region of Alto Mayo, San Martin, Nueva Cajamarca, is remarkable for its biodiversity.Alto Mayo is located in the Peruvian Amazon, including an area of the Amazon tropical rainforest (Fig. 1).The region borders with the Andes Cordillera to the east, and has borders with Brazil, Bolivia, Colombia, and Ecuador (Marchese, 2015).According to Köppens' criteria (Bedek et al., 2018;2020), the region has a Tropical rainforest climate (Af).Moreover, according to the Servicio Nacional de Meteorología e Hidrología, Peru (SENAMHI), the precipitation range is about 1,500 to 3,000 mm and the average annual temperature is about 24 °C.
The massif of Alto Mayo is with in the Amazonian Piedmont, province of Rioja, at the extreme north of the San Martin Region, northwestern Peru (CESPE-GBPE- GSBM, 2004a;2004b).This karst massif forms Cueva de Palestina (Fig. 2A) is located in the region of Alto Mayo and it has an extension of more than three kilometers, being the second largest cave in Peru.The specimens examined here were collected in the aphotic zone foraging on organic matter (Fig. 2B).Diagnosis.Modified from Schmidt (2007).Body pigments and eyes absent, animals with endoantennal conglobation, or rolling, ability, cephalon with frontal shield fused with vertex (not delimited by frontal line), pereonite 1 epimera with schisma on posterior corner, antenulla of 2 articles, antennal flagellum of 2 articles, mandible with molar penicil simple, maxillula inner endite bearing 2 penicils, maxilla bilobate, maxilliped endite with 2 strong setae on distal margin, pereopod dactylus of 2 claws, inner claw short, uropod protopod enlarged and surpassing distal margin of telson, and exopod inserted on medial margin, and pleopod exopods without respiratory areas.
Remarks.The genus Caecopactes was erected by Schmidt (2007) to include C. minimus from Napo Province, Ecuador.The genus was defined by animals of reduced size, body pigments and eyes absent, endoantennal conglobation ability, pereonite 1 epimera with schisma at the posterior corner, cephalon with concave frons, antennal peduncle with fourth and fifth articles triangular and corners projected ventrally, and antennal flagellum of two articles (see also Schmidt, 2007).The new species described here is tentatively placed into the genus mainly due to the shape of the cephalon, the pereonite 1 epimera with posterior schisma, and the shape of uropods (see also Schmidt, 2007).
Regarding the characters mentioned by Schmidt (2007), the reduced size of animals, cephalon with concave frons and the triangular shape of the fourth and fifth articles of the antennal peduncle probably represent specific characteristics of C. minimus.Moreover, within the Neotropical Scleropactidae no other genera have a cephalon shape as in Caecopactes, with the frontal shield fused with the vertex.In a loose comparison, the shape of Caecopactes cephalon resembles that of Aulaconiscus Taiti and Howarth, 1997 from Hawaii, and Kithironiscus Schmalfuss, 1995 from Greece; however, the genus differs in the animals having endoantennal conglobation (vs.exoantennal in Aulaconiscus), the pereonite 1 epimera with posterior schisma (vs.schisma absent in Aulaconiscus), pereonite 2 epimera without ventral lobe (vs.present in Aulaconiscus), telson with distal margin rounded (vs.triangular in Aulaconiscus and Kithironiscus), and uropod exopod inserted on medial margin (vs. on distal margin in Aulaconiscus and Kithironiscus) (see also Schmalfuss, 1995;Taiti and Howarth, 1997;Tabacaru and Girginca, 2003).
Antenna (Fig. 3M) not surpassing posterior margin of pereonite 1 when extended backwards; flagellum distal article about 3 times as long as proximal article bearing lateral aesthetascs.
Maxilla (Fig. 4D) inner lobe rounded and covered with thick setae; outer lobe twice as wide as inner lobe and covered with thin setae.
Pereopods 1-7 (Fig. 5A, B) gradually increasing in size, merus and carpus 1-7 bearing sparse setae and hyaline fringe of scales on sternal margin; carpus 1 with distal seta with double-serrate apex, antennal grooming brush longitudinal reaching about half of its length; dactylus with dactylar and ungual setae simple.
Etymology.The new species is named after the Peruvian Amazonian myth 'El Chullachaqui'.In Quechua native language, chulla = unlike, and chaqui (pre-Hispanic Peruvian) = foot.The Chullachaqui is a dwarf who inhabits the mountain forests of Amazon and can transform into any animal or person.It is also known as the guardian of the rainforests, taking care of the animals and plants from hunters.
Habitat.The specimens were collected in decomposing organic matter and guano in the aphotic zone.
Remarks.Caecopates chullachaqui sp.nov.differs from C. minimus in having a cephalon lamina frontalis with protruding lateral corners (vs.not protruding in C. minimus), antennal peduncle with fourth and fifth articles not triangular shaped (vs.triangular shaped in C minimus), maxillula outer endite with the outer set of teeth simple (vs.maxillula outer endite with outer set bearing two teeth apically cleft), male pleopod 1 endopod with distal portion bent outwards (vs.straight in C. minimus), male pleopod 2 exopod elongated (vs.short in C. minimus), and male pleopods 4 and 5 exopods with outer proximal portion depressed (vs.not depressed in C. minimus).

DISCUSSION
Despite the fact that our knowledge on subterranean biodiversity around the world has been increasing during the last decades (Deharveng and Bedos, 2019), most of South American karstic regions still remain largely unknown.On the other hand, scientific collections both at local and at wider scales are continuously growing in the numbers of collected specimens.
The Cueva de Palestina is a tourist cave with information being available in online public domains.However, the communities living around the cave area are committed to its conservation and employ several activities related to its environmental sustainability.All additions to our knowledge on the biodiversity of these caves are important contributions towards this goal, as they underline their importance for conservation.

Figure 2 .First
Figure 2. Cueva de Palestina.A, entrance zone of the cave , photo: A.O. Lobo; B, specimens foraging on guano on the cave floor.