Three new species of genus Caridina are described from the northernmost part of Australia. Caridina darwin n. sp. resembles Caridina temasek Choy & Ng, 1991 from Singapore but differs in the armature of the rostrum, development of epipods on pereiopods and in lacking an appendix interna on male´s first pleopods. Caridina magnovis n. sp. resembles Caridina serratirostris de Man, 1892 but differs from this species in the armature of the ventral margin of the rostrum, a shorter stylocerite, a stouter carpus of first pereiopod, number and size of spiniform setae on third and fifth pereiopods, the shape of the preanal carina and in egg size. Caridina wilsoni n. sp. resembles Caridina gracilirostris de Man, 1892 but differs in egg size and some length to wide ratio of segments of the pereiopods. Detailed morphological descriptions of all three new species are given. A molecular phylogeny (mt DNA 16S) supports the morphospecies hypotheses and illustrates the phylogenetic relationship with morphologically similar species from outside Australia.

In order to study the burrowing crab Neohelice granulata (Dana, 1851) in the northern limit of its distribution and to test the hypothesis that mesoscale factors are more deterministic than latitudinal variation in this crab life history, the population dynamics of this specie was studied in the Caceribú river (Rio de Janeiro state, Brazil). The sex ratio was female-biased over the year. Males were significantly larger (t-test = 3.53, p < 0.05) than females (CW mean = 29.14 mm and 27.32 mm, respectively), which were predominant in the intermediary-size classes. The breading season took place from February to November, with a peak in May. The recruitment was observed all over the year, but mostly from October to December. The size at maturity was estimated at 19.0 mm for females and 23.9 mm for males. Average fecundity was 20,419 eggs (±12,627.12) and showed a decrease from the first to the last stage of embryonic development. The asymptotic size was similar between males (CW∞ = 24.86 mm) and females (CW∞ = 24.50 mm). Longevity was estimated in 1.33 and 1.23 years in males and females, respectively. Mortality rates were slightly higher in males (Z = 3.71) than in females (Z 0 3.41). Analysing the results of this study and the literature we conclude that the population dynamics of N. granulata do not follow a latitudinal trend. This strengthens the hypothesis that brachyurans’ life histories are mainly driven by mesoscales factors than latitudinal variation.

The Southern king crab, Lithodes santolla, is an important fishery resource in the inner seas of Chilean Patagonia. The fishing gear used to catch Southern king crab (bait trap) and its operation at different depths over several months provide the opportunity to gather information about relative abundance. The aim of the present study was to analyze the information collected from the catches of Southern king crab and its associated fauna in the Magdalena Fjord to study the biodiversity and ecology of scavenging decapod crustaceans. Specifically, the study aimed to determine the bathymetric patterns of abundance by species, to model the abundance by season (winter and spring) and to determine the structuring pattern of scavenging decapods assemblage. Samples were collected between June and November 2019 by deploying traps in four bathymetric strata: 1 = 0–50 m; 2 = 51–100 m; 3 =101–150 m; 4 = 151–200 m. We registered a total of 673 decapod specimens associated with the Southern king crab fishery, representing five species: Lithodes santolla (n = 96), Libidoclaea smithii (n = 10), Metacarcinus edwardsii (n = 58), Munida gregaria (n = 507) and Peltarion spinulosum (n = 2). The abundance of decapod species varied by month and bathymetric strata. We found bathymetric patterns for L. santolla abundance, M. gregaria, M. edwardsii, and total species abundance. The most informative model to explain scavenging decapod abundance by GLM included species and season. The null model of species co-occurrence analysis revealed that all species associations during the sampled months were random. Our study is the first that provides evidence about patterns of bathymetrical and temporal variation of scavenging decapod abundance and expands the body of knowledge regarding the biodiversity of scavenger decapods in the Magdalena Sound, which currently is affected by multiple stressors such as climate change and anthropic activities (aquaculture and fisheries).