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The freshwater crayfish genus Parastacus Huxley, 1879 (Parastacidae) is reviewed. Seven species are redescribed: Parastacus brasiliensis (von Martens, 1869), P. defossus Faxon, 1898, P. laevigatus Buckup & Rossi, 1980, P. pilimanus (von Martens, 1869), P. pugnax (Poepigg, 1835), P. promatensis Fontoura & Conter, 2008, and P. varicosus Faxon, 1898. In addition, five new species are described: Parastacus bah, P. heterochaelis, P. manezinho, P. quasimodo and P. rudolphi. Descriptions, diagnoses, and synonyms of the genus and species are provided. In addition, information on the geographical distribution and an identification key is presented for all species.

The genus Hyalella Smith, 1874 occurs exclusively in the Americas. In Brazil, the states of Santa Catarina and Rio Grande do Sul have the largest number of records with 20 species. This paper presents two new species for the state of Santa Catarina, Brazil. The serrate setae with accessory seta, a new type of seta, is registered for the genus and observed on gnathopods 1 and 2. Additionally, microtrichs are reported on articles, a detail that has not been mentioned in previous studies. Hyalella carsone sp. nov. is characterized by gnathopod 1 with comb-scales from the basis to the carpus, gnathopod 2 dactylus with proximal margin strongly serrated and the presence of serrate setae on the articles of gnathopods 1 and 2. Hyalella wangarie sp. nov. is characterized by gnathopod 2 palm not sinuous with margin inconspicuously serrated, peduncle and inner ramus of the pleopod with simple setae, presence of curved seta on uropod 1 of male and gnathopod 1 palm on female slightly serrated. In this work we expand the number of species from Brazil and increase the morphological knowledge of the genus Hyalella.

In this contribution, we describe two new species of burrowing crayfish species complex Parastacus brasiliensis from forestry areas in the central region of the state of Rio Grande do Sul, southern Brazil. We used an integrative taxonomy approach with morphology and the mitochondrial DNA 16S rRNA gene and also evaluated their conservation status according to the IUCN Red List Criteria. Parastacus guapo sp. nov. was collected near the municipality of Pantano Grande and it differs from all other congeneric species in having an epistome anterolateral section with a large conical projection ending in a big sharp spine on both sides. It also differs from P. brasiliensis sensu stricto in the shape of the rostral surface, sub-orbital angle, postorbital carina straight, sub-orbital angle > 90, postorbital carinae prominent in anterior and middle portions, carpal spine present, the internal surface of chelipeds palm with sparse tubercules, areola narrow and pleon short. Parastacus gomesae sp. nov. was collected in the municipality of So Jernimo, it differs from all analysed species for rostral spine absent, epistome anteromedian lobe heptagonal and mandible incisive process with seven teeth (the second tooth from the anterior margin is the largest). It is also distinguished of P. brasiliensis sensu stricto in the sub-orbital angle > 90, postorbital carinae prominent in anterior and middle portions, 34 rows of verrucose tubercles irregularly distributed on the palm dorsal surface of chelipeds, areola narrow and pleon short. Phylogenetic relationships confirmed the distinct position of these new species to the already described species. The extent of occurrence (EOO) / area of occurrence (AOO) of P. guapo sp. nov and P. gomesae sp. nov. were estimated at 937 km / 1,87 km, and 2.107 km / 23,9 km respectively. The main threats identified were continued decline in the quality of habitats, resulting from deforestation and forestry areas. However, as we know only one point of occurrence for each new species, we suggest that both be categorized as Data Deficient.

This study describes and illustrates the morphology of the second juvenile stage of the blue-fingered burrowing crayfish Parastacus caeruleodactylus. One female carrying 20 juveniles was collected in January 2019 from a swamp forest in the municipality of Dom Pedro de Alcântara, state of Rio Grande do Sul, southern Brazil. Juveniles were dissected and the appendages were mounted in slides. The general morphology and the pattern of attachment of the second juvenile stage of P. caeruleodactylus correspond to that reported for other parastacids. The main differences among the co-generic species are related to the number of articles in the flagella of the antennae, the number of spines in the antennal scale, the number of setae in the articles of the appendages, the number of teeth in the mandible molar and incisor processes, the absence of segmentation in the exopod flagellum of the maxillipeds and the number of teeth in the crista dentata of the ischium of maxilliped 3.

Neognathophausia ingens (Dohrn, 1870) is a bathypelagic crustacean distributed worldwide. In the western Atlantic it has been recorded off the La Plata region, Argentina, and off the coast of Brazil, from the state of Bahia to Rio de Janeiro. We provide new records of N. ingens from the state of Rio Grande do Sul, Brazil, about 1188 km south of its previous distribution limit off Brazil, filling the gap between the central West Atlantic and Argentina. Five specimens were analyzed and drawings for all body regions and appendages are presented. Mandible, thoracopods 2, 4, 5, 6 and 8 and pleopods are illustrated and described for the first time. An updated synonym list and a distribution map for this species in Brazil are provided.

The use of molecular data in association with classical taxonomy has helped to alleviate the taxonomic impediment through the discovery, delimitation and description of new species. Terrestrial isopods are the largest suborder of Isopoda; however, there are very few active taxonomists in this group and a representative part of the terrestrial isopods world diversity remains unexplored. The genus Atlantoscia comprises five species in which diagnostic characters are few and show subtle differences among the species. The objective of this study was to delimit and describe two new species of the genus Atlantoscia from southern Brazil by using traditional taxonomy coupled with genetic information. Specimens were analyzed morphologically and by the aid of two molecular markers, mitochondrial COI and nuclear 18S rRNA. The validity of the new species Atlantoscia antennamaculata sp. nov. and Atlantoscia australis sp. nov. was corroborated, unambiguously, by morphological approach, phylogenetic analysis and species delimitation methods. Our study reinforces the fact that, despite the undeniable importance of comparative morphology in species discovery, new methods and data, particularly molecular ones, are becoming prominent and an integrative part of the taxonomy practice.

Invasive species are one of the main threats to biodiversity. When an alien species is introduced into a new environment, fast identification and definition of management strategies may avoid or minimize impacts. When an invasive species is already established, the most adopted approaches are population control and monitoring. In order to perform such strategies, assessment of characteristics of the invasive population is imperative. This study tested a new method of population size estimation and monitoring in an invasive population of crayfish Procambarus clarkii in a conservation area in the Atlantic Rain Forest (Southeastern Brazil). The population dynamics was studied for 1 year to examine the efficacy of the selected method and to evaluate if the population is stable. Later, the effect of periodical removal of animals on the population size was tested. The method of population estimation used in this study proved to be very effective. We recommend using it to monitor invasive populations of P. clarkii. The population size varied discretely over the year with variable but low growth rate, indicating that the population is already established which introduce a notable threat to native species. The continuous removal of specimens proved to be inefficient since the growth rate was higher after the removal. One intensive removal event might be more effective than a continuous moderate removal as the one applied in this study.

A new species of Pseudione Kossmann, 1881 is described from two parasitized specimens of the clawed lobster Nephropsis aculeata Smith, 1881, collected from Brazilian waters in the southwestern Atlantic. It is the second species of the genus from Brazil and is the fourth species parasitizing nephropid lobsters in the world.

The type specimen of Parastacus nicoleti (Philippi, 1882) was not designated and the material used for the description has never been found. We designate herein the neotype of P. nicoleti based on the examination of specimens from the type locality deposited in the Museo Nacional de Historia Natural of Chile previously analyzed by Bahamonde (1958), who confirmed the identity and validated the species. To improve the species description we included new drawings and provide additional morphological characters. A synonym list and updated distribution map of this species are also provided.

Two new species of Parastacus Huxley, 1879 are described from material collected in the state of Rio Grande do Sul, southern Brazil: Parastacus fluviatilis sp. nov. from highland streams and Parastacus caeruleodactylus sp. nov. from wetlands. Parastacus fluviatilis sp. nov. is distinguished mainly by large chelipeds with dense setae cover on the cutting edge of fingers, telson subtriangular with two lateral blunt spines and strongly concave ventral surface of lateral process of thoracic sternites 6 and 7. Parastacus caeruleodactylus sp. nov. is distinguished mainly by blue cheliped fingers and a large gap between them, reduced abdomen, dorsal and ventral margins of dactylus, propodus and carpus of second pair of pereiopods with tufts of long setae and mid-dorsal carina of exopod of uropods unarmed. According to IUCN Red List criteria both species are considered endangered. Habitat characterization and a method for defining the shape of second abdominal pleura are also provided.

The neotropical genus Benthana (Philosciidae) is reviewed. Fourteen species are redescribed: Benthana picta, B. olfersii, B. longicornis, B. schubarti, B. albomarginata, B. werneri, B. santosi, B. longipenis, B. bocainensis, B. moreirai, B. dimorpha, B. iporangensis, B. sulcata, and B. longicaudata. Additional characters were proposed for B. convexa, B. taeniata, B. serrana, B. trinodulata, B. araucariana, and B. cairensis. New records are provided for 13 species, and four new species are described: Benthana aimores sp. nov., Benthana goitacas sp. nov., Benthana tupinamba sp. nov. and Benthana canastraensis sp. nov.. Two Chilean species are considered incertae sedis. A pictorial key and distribution maps for the species are provided.

Two new species of Hyalella from Brazil are described. Hyalella veredae sp. n. shows the following characters: eyes reduced or absent in some specimens; antenna 1 and antenna 2 of similar size, and a curved seta on the inner ramus of male uropod 1. Hyalella formosa sp. n. is characterized by the absence of eyes, antenna 1 longer than antenna 2 and a curved seta on the inner ramus of male uropod 1. The species were found on caves located in two private properties, both under the impact of agricultural activities, which demonstrates a potential threat to these subterranean environments.

Terrestrial isopods are widely infected with Wolbachia. However, little is known about the presence of bacteria in the Neotropical species. The objective of this study was to test the hypothesis of presence of Wolbachia infection in the native species of terrestrial isopods, Atlantoscia floridana and Circoniscus bezzii, and in the introduced species Burmoniscus meeusei.

The goal of this study was to compare the feeding rates of Balloniscus sellowii on leaves of different decomposition stages according to their phenolic and flavonoid content. Leaves from the visually most abundant plants were offered to isopods collected from the same source site. Schinus terebinthifolius,the plant species consumed at the highest rate, was used to verify feeding rates at different decomposition stages. Green leaves were left to decompose for one, two, or three months, and then were offered to isopods. The total phenolic and flavonoid contents were determined for all decomposition stages. Consumption and egestion rates increased throughout decomposition, were highest for two-month-old leaves, and decreased again in the third month. The assimilation rate was highest for green leaves. The mode time of passage through the gut was two hours for all treatments. Ingestion of leaves occurred after two or three days for green leaves, and on the same day for one-, two- and three-month-old leaves. The speed of passage of leaves with different decomposition stages through the gut does not differ significantly when animals are fed continuously. However, it is possible that the amount retained in the gut during starvation differs depending on food quality. The digestibility value was corrected using a second food source to empty the gut of previously ingested food, so that all of the food from the experiment was egested. The digestibility value was highest for green leaves, whereas it was approximately 20% for all other stages. This was expected given that digestibility declines during decomposition as the metabolite content of the leaves decreases. The phenolic content was highest in the green leaves and lowest in three-month-old leaves. The flavonoid content was highest in green leaves and lowest after two months of decomposition. Animals ingested more phenolics when consumption was highest. The estimated amount of ingested flavonoids followed the same trend as assimilation rate. Flavonoids accounted for a large portion of total phenolics, and the estimated amount of flavonoids consumed was similar for one-, two- and three-month-old leaves. Our results suggest that the high phenolic and flavonoid concentrations in green leaves are feeding deterrents. Isopods may discriminate among concentrations of flavonoids and modify their consumption rates to maintain their intake of flavonoids when ingesting leaves with lower flavonoid content.

Many arthropods, including terrestrial isopods, are capable of entering a state of tonic immobility upon a mechanical disturbance. Here we compare the responses to mechanical stimulation in three terrestrial isopods Balloniscus glaber, Balloniscus sellowii and Porcellio dilatatus. We applied three stimuli in a random order and recorded whether each individual was responsive (i.e. showed tonic immobility) or not and the duration of the response. In another trial we related the time needed to elicit tonic immobility and the duration of response of each individual. Balloniscus sellowii was the least responsive species and Porcellio dilatatus was the most, with 23% and 89% of the tested individuals, respectively, being responsive. Smaller Balloniscus sellowii were more responsive than larger individuals. Porcellio dilatatus responded more promptly than the Balloniscus spp. but it showed the shortest response. Neither sex, size nor the type of stimulus explained the variability found in the duration of tonic immobility. These results reveal a large variability in tonic immobility behavior, even between closely related species, which seems to reflect a species-specific response to predators with different foraging modes.