“…Despite its wide geographical range and the large number of described species, the morphology of aeglid crabs is surprisingly uniform, resulting in restricted morphological characters useful for species identification. Morphological similarity among nominal species of Aegla is not always positively correlated with genetic relatedness, in such a way that cryptic species are more common than intuitively accepted by taxonomists (Bartholomei‐Santos et al., 2019; Jara et al., 2018).…”
Cryptic species are a major challenge for morphologically based species identification. Molecular approaches to species delimitation can be a valuable tool to provide preliminary taxonomic hypotheses and significantly complements morphological taxonomy. In South America, the freshwater crabs of the genus Aegla have sparked much interest as they are key species in the often‐endangered freshwater ecosystems and themselves are often considered endangered species. Morphological similarity among Aegla species is not always positively correlated with genetic relatedness and growing evidence suggests that several putative single taxa are actually assemblages of cryptic species. We coupled broad geographically sampling (Argentina, Brazil and Uruguay) with multilocus (COI, 16S and ANT) phylogenies to investigate the diversity of Aegla uruguayana. Our species delimitation analyses suggested that 19 aeglid populations form a well‐supported clade, although individuals from 10 populations possibly represent a complex of cryptic species. The significant amount of cryptic diversity found in aeglids seem to rely on several factors, including habitat fragmentation, life history features, morphological stasis, convergent evolution and recent divergence. The search for new diagnostic characters and the description of the cryptic species that remain unnamed will probably be the next challenge for this unique group of crustaceans.
“…Despite its wide geographical range and the large number of described species, the morphology of aeglid crabs is surprisingly uniform, resulting in restricted morphological characters useful for species identification. Morphological similarity among nominal species of Aegla is not always positively correlated with genetic relatedness, in such a way that cryptic species are more common than intuitively accepted by taxonomists (Bartholomei‐Santos et al., 2019; Jara et al., 2018).…”
Cryptic species are a major challenge for morphologically based species identification. Molecular approaches to species delimitation can be a valuable tool to provide preliminary taxonomic hypotheses and significantly complements morphological taxonomy. In South America, the freshwater crabs of the genus Aegla have sparked much interest as they are key species in the often‐endangered freshwater ecosystems and themselves are often considered endangered species. Morphological similarity among Aegla species is not always positively correlated with genetic relatedness and growing evidence suggests that several putative single taxa are actually assemblages of cryptic species. We coupled broad geographically sampling (Argentina, Brazil and Uruguay) with multilocus (COI, 16S and ANT) phylogenies to investigate the diversity of Aegla uruguayana. Our species delimitation analyses suggested that 19 aeglid populations form a well‐supported clade, although individuals from 10 populations possibly represent a complex of cryptic species. The significant amount of cryptic diversity found in aeglids seem to rely on several factors, including habitat fragmentation, life history features, morphological stasis, convergent evolution and recent divergence. The search for new diagnostic characters and the description of the cryptic species that remain unnamed will probably be the next challenge for this unique group of crustaceans.
“…Aegla Leach, 1820 is the only living genus of the family Aeglidae and its lifecycle is entirely restricted to freshwater environments of southern South America. This genus is composed of 87 species (Santos et al, 2017;Páez et al, 2018;Jara et al, 2018). Aeglids are animals with a high degree of endemism, making some species highly vulnerable or endangered.…”
The carapace length (CL) at the onset of morphological sexual maturity (MSM) in Aegla paranaSchmitt, 1942was estimated in a population located at Negro River Sub-basin, Upper Iguaçu Basin, southern Brazil. The animals were captured with Surber net and with baited traps in Negro River and in its tributary Totó River, in December/2017, June and July/2018. Carapace length of each individual was measured from the tip of the rostrum to the posterior margin of the carapace, with a digital caliper or under a digital microscope. Length of the major cheliped propodus (LMAP) of males and width of the abdomen (LA) of females were measured for relative growth analysis. The CL at the onset of MSM was estimated as the inflection points on the scatter plots with the REGRANS program. In Negro River, 107 males (CL range 6.90- 50.25 mm) and 95 females (10.37-39.36 mm) were obtained, while in Toto River, 225 males (4.92-25.65 mm) and 160 females (5.18- 26.45 mm). MSM is attained by males at 23.15 mm CL and females at 17.85 mm CL. The smallest ovigerous female measured 19.00 mm CL. Aegla parana reaches the highest maximum size and males attain MSM with the highest CL value among the known species of the genus.
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