Abstract The present paper describes a new species of freshwater crayfish of the genus Parastacus Huxley, 1879 from the municipality of Amaral Ferrador in the state of Rio Grande do Sul, southern Brazil, evaluates its conservation status according to the IUCN Red List Criteria (sub-criterion B1), and updates the identification key for the genus. Parastacus longidactylus sp. n. differs from all analyzed species by the large eyes, the prominent and wide rostral carinae, surpassing the rostral basis and extending to the proximal third of the postorbital carinae, postorbital carinae and rostral carinae prominent and with similar lengths, chelipeds carpus dorsomedial surface not divided longitudinally by groove and long dactylus, surpassing the fixed finger. The possible extent of occurrence was estimated to be 6,968 km² and the species was recorded in only one location in the Camaquã River basin. The main threats to the region are the replacement of native vegetation by crops and livestock, water pollution and soil erosion. However, because there is only one known location where Parastacus longidactylus sp. n. occurs we suggest classifying the species as Data Deficient.

Abstract Cymothoa ianuariiSchioedte & Meinert, 1884 is rediscovered almost 136 years after its original description and redescribed from specimens collected in the state of São Paulo. This species is mainly characterized by adult females with cephalon with conspicuous eyes and not deeply immersed in pereonite 1, pereonites 5-6 much wider than 4, pleotelson twice as wide as long and pleopods 1-5 decreasing in size; Cymothoa excisaPerty, 1833 and C. oestrum (Linnaeus, 1758) are recorded from the state of Bahia. Illustrations and an updated distribution map for these species in Brazil are provided.

Abstract Two species of bopyrid isopods from the subfamily Athelginae are recorded from new localities in northeastern Brazil. Parathelges foliatus Markham, 1972 was recorded for the first time from Brazil, in the state of Ceará, parasitising the hermit crab Clibanarius symmetricus (Randall, 1840). Pseudostegias atlantica Lemos de Castro, 1965 is recorded from the state of Ceará, parasitising Clibanarius antillensis Stimpson, 1859. Illustrations, species diagnosis and an updated distribution map are given for each species.

Abstract Two new species of Parastacus Huxley, 1879 are described from the Atlantic Forest in southern Brazil: Parastacus buckupi sp. nov. from a highland stream in the hydrographic basin Maquiné river, Maquiné, state of Rio Grande do Sul; and Parastacus pilicarpus sp. nov. from a first order stream in the hydrographic basin Araranguá River, Morro Grande, state of Santa Catarina. Parastacus buckupi sp. nov. is distinguishable from all other Parastacus species via its large and globose chelipeds, by the presence of tufts of long and simple setae in the cutting edge of cheliped fingers, which are more abundant proximally and by possessing a telson with an acute distal margin. Parastacus pilicarpus sp. nov. is diagnosed mainly by the distal portion of the carpus which possess tufts of long, simple setae, and by having an epistome whose anteromedian lobe is heptagonal and as long as it is wide. Finally, P. pilicarpus antennal scales lateral margin terminates in a very strong terminal spine and mandibles incisive lobe has nine teeth, with the first tooth from the anterior margin being the largest. The conservation status based on the sub-criterion B1 of IUCN Red List allowed us to classify these species as “ENDANGERED” and “DATA DEFICIENT”, respectively.

Abstract Paguroids are usually detritivorous organisms and the occurrence of predation on mollusks is very unusual. This contribution reports the occurrence of a predatory behavior of the paguroid Dardanus venosus (H. Milne Edwards, 1848) on the snail Aurantilaria aurantiaca (Lamarck, 1816). Single specimen of paguroid was found attacking the snail in a sea grass meadow dominated by Halodule wrightii Ascherson on the coast of Ceará, northeastern Brazil. The paguroid and gastropod specimens were brought to the laboratory and placed in an aquarium and the behavior was recorded by photos. Paguroid behavior was characterized by sequencial movements of chelipeds in the attack to the snail when the snail was hold by paguroid ambulatory legs. External lip of shell aperture, operculum and foot of the gastropod were severely damaged.

Abstract In this contribution we describe a new species of burrowing crayfish of the genus Parastacus Huxley, 1879 from a swamp forest in southern Brazil and determine its conservation status. The distinction of the new species is based on morphology and the mitochondrial DNA marker 16S rRNA. The extinction risk was assessed according to the sub-criterion B1 of IUCN that estimates the Extent of Occurrence (EOO). Parastacus tuerkayi sp. nov. is morphologically distinguishable from all species of Parastacus by having three lines of verrucous tubercles on the dorsomesial margin of the cheliped propodus and a suborbital angle exceeding 90°. The EOO comprises 647,674 km², and the species is classified as “endangered”. Phylogenetic relationships indicate the distinct position of this new species in relation to the already described species.

The population biology and size at sexual maturity of Uca (Uca) maracoani were studied for the first time in a semi-arid tropical estuary of northeastern Brazil. A catch-per-unit-effort (CPUE) technique was used to sample the crabs, on the surface and inside burrows, for 60-min sampling periods by one person on a monthly basis during spring low tide periods from June 2013 to June 2014 in an estuary area of Baixa Grande Beach. A total of 406 crabs were obtained, of which 317 were males, 87 non-ovigerous females, and two ovigerous females. Males were larger than non-ovigerous females. The U. (U.) maracoani population presented unimodal size frequency distribution, which may reflect a continuous recruitment, with no disruption of classes and constant mortality rates, indicating a stable population. The overall sex ratio (3.5 males: 1 female) differed significantly from the expected 1:1 proportion. The major cheliped was on the right side in 45.1% of the males, as reported for other fiddler crabs populations. A total of 294 males and 89 females were used in the allometric study. The specimens were measured at carapace width (CW), the major propodus length (MPL) of males, and abdomen width (AW) of females. In males, the relationship between CW and MPL was 22.3 mm CW, which is considered the functional value at maturity. In females, the size at sexual maturity was 19.3 mm CW based on the relationship between CW and AW. The CPUE method is discussed as one of the reasons of the high sex ratio skewed towards males. This is the first account regarding population structure of U. (U.) maracoani in semi-arid tropical areas.

La estructura poblacional y la madurez sexual morfométrica del cangrejo Uca (Uca) maracoani fueron estudiadas en un manglar tropical en el noreste de Brasil. Los cangrejos fueron colectados mensualmente durante los periodos de marea baja de junio 2013 a junio 2014. Se utilizó la técnica de captura por unidad de esfuerzo (CPUE) con períodos de una hora de captura realizada por una persona. Se obtuvo un total de 406 cangrejos: 317 machos, 87 hembras no-ovígeras y dos hembras ovígeras. El tamaño de los machos fue significativamente mayor que el de las hembras no-ovígeras. La población mostró una distribución unimodal de frecuencias de tamaños, lo que puede reflejar un reclutamiento continuo, sin interrupción de las clases y las tasas de mortalidad constantes, lo que indica una población estable. La proporción sexual (3.5 machos: 1 hembras) se alejó significativamente de la proporción esperada 1:1. El quelípodo mayor estaba en el lado derecho en el 45,1% de los machos, según lo informado por otras poblaciones. Se realizaron mediciones del ancho del caparazón (CW) y longitud del propodio mayor (MPL) de 294 machos, y del ancho del caparazón (CW) y ancho del abdomen (AW) de 89 hembras. En los machos, el punto de inflexión se determinó en 22,3 mm CW, considerado el tamaño morfológico al inicio de la madurez. En las hembras, el tamaño de madurez sexual fue de 19,3 mm CW basado en la relación entre CW y AW. El método CPUE se discute como una de las razones que explican el elevada proporción sexual sesgada hacia los machos. Este es el primer estudio relacionado con la estructura poblacional de U. (U.) maracoani en zonas semiáridas tropicales.

ABSTRACT We report herein the occurrence of the infraorder Polychelida in Potiguar Basin, northeastern Brazil. Specimens were collected by the project "Avaliação da Biota Bentônica e Planctônica na porção offshore das Bacias Potiguar e Ceará", developed by the Brazilian Oil Company (PETROBRAS). Three species were recorded for the first time in this region: Pentacheles validus A. Milne-Edwards, 1880, Polycheles typhlops Heller, 1862, and Stereomastis sculpta (Smith, 1880) at 2000 m, 400 m and 2057 m depth, respectively. The Brazilian deep-sea floor remains poorly known, but progress has been made as a result of collections obtained by oceanographic expeditions and research projects developed by PETROBRAS in Campos Basin (Rio de Janeiro) and Potiguar Basin (Rio Grande do Norte), expanding the knowledge of the distribution area of Polychelidae in Brazilian deep sea waters.