LIVE BAIT TRADE AS A PATHWAY FOR THE INTRODUCTION OF NON-NATIVE SPECIES: THE FIRST RECORD OF Dilocarcinus pagei IN THE PARANAPANEMA RIVER BASIN

Brazil has one of the most significant diversity of freshwater fish in the world, and this drives trade and fishing tourism. Several species of sport fish have characteristics and behaviors that favor fishing tourism and its related activities. Live baits are widely used in fisheries across the country, and at the end of fisheries, is common that anglers may release the remaining bait in rivers, lakes or reservoirs. Here we report for the first time the crab Dilocarcinus pagei in the Paranapanema River basin, and list the freshwater species that were introduced similarly. During field samplings between 2012/2016, and 2018/2019, we captured 10 individuals of D. pagei. One female in the Rosana Reservoir; and two juveniles, one female and six males in the Taquaruçu Reservoir. The literature review revealed 16 species used as live bait, the crab D. pagei and 15 fish species. Gymnotiformes were the largest number of species used as live bait. The basins that had introduction cases were in the Upper Paraná, Iguaçu, and Paraíba do Sul Rivers. The Paraguay-Lower Paraná River was the system that contributed with nine species to the most invaded ecoregion in Brazil, the Upper Paraná River basin. Anglers and live bait farmers should be aware of the risks and consequences of these constant introduction actions (propagule pressure), not releasing baits. In addition, the live bait trade must be monitored and controlled to occur only with species in their original river basin.

NUEVA ESPECIE DE TEMNOCEPHALA BLANCHARD (PLATYHELMINTHES, TEMNOCEPHALIDA) ECTOSIMBIONTE EN DILOCARCINUS SEPTEMDENTATUS (DECAPODA, TRICHODACTYLIDAE) DE LA AMAZONÍA BRASILERA

Temnocephala longivaginata sp. n. ectosimbionte en Dilocarcinus septemdentatus (Herbst, 1783), es descrita del Estado de Pará, Amazonia brasilera. Cincuenta cangrejos fueron colectados en Rio Peixe- Boi, Municipio de Peixe-Boi. Dilocarcinus septemdentatus es el hospedero-tipo de Temnocephala microdactyla Monticelli, 1903, especie con una descripción original pobre, pero que fue re-descrita en otras dos ocasiones en diferentes hospederos: Sylviocarcinus australis Magalhães & Türkay, 1996 y Dilocarcinus pagei Stimpson, 1861. La nueva especie es más parecida con Temnocephala pignalberiae Dioni, 1967, de quien se diferencia por los siguientes caracteres: 1. cirro con un círculo de escleritos en la porción distal del introverto, seguida por una porción lisa (sin espinas o cristas); 2. porción proximal interna del introverto con cristas longitudinales; 3. vesicula 'intermedia' larga, sustituyendo los receptáculos seminales; 4. vagina larga, con una extensión en la porción distal, próximo al esfínter vaginal asimétrico; y 5. placas dorsolaterales, sincitiales 'excretoras' pequeñas y en forma de 'suela de zapato'. Hasta el momento, todas las especies de Temnocephala tienen el introverto del cirro liso o con espinas. Cristas en la pared interna del introverto y un círculo de escleritos son registrados por primera vez en Temnocephalidae.

Contrasting strategies of osmotic and ionic regulation in freshwater crabs and shrimps: gene expression of gill ion transporters

Owing to their extraordinary niche diversity, the Crustacea are ideal for comprehending the evolution of osmoregulation. The processes that effect systemic hydro-electrolytic homeostasis maintain hemolymph ionic composition via membrane transporters located in highly specialized gill ionocytes. We evaluated physiological and molecular hyper- and hypo-osmoregulatory mechanisms in two phylogenetically distant, freshwater crustaceans, the crab Dilocarcinus pagei and the shrimp Macrobrachium jelskii, when osmotically challenged for up to 10 days. When in distilled water, D. pagei survived without mortality, hemolymph osmolality and [Cl−] increased briefly, stabilizing at initial values, while [Na+] decreased continually. Gill V(H+)-ATPase, Na+/K+-ATPase and Na+/K+/2Cl− gene expressions were unchanged. In M. jelskii, hemolymph osmolality, [Cl−] and [Na+] decreased continually for 12 h, the shrimps surviving only around 15 to 24 h exposure. Gill transporter gene expressions increased 2- to 5-fold. After 10-days exposure to brackish water (25 ‰S), D. pagei was isosmotic, iso-chloremic and iso-natriuremic. Gill V(H+)-ATPase expression decreased while Na+/K+-ATPase and Na+/K+/2Cl− expressions were unchanged. In M. jelskii (20 ‰S), hemolymph was hypo-regulated, particularly [Cl−]. Transporter expressions initially increased 3- to 12-fold, declining to control values. Gill V(H+)-ATPase expression underlies the ability of D. pagei to survive in fresh water while V(H+)- and Na+/K+-ATPase and Na+/K+/2Cl− expressions enable M. jelskii to confront hyper/hypo-osmotic challenge. These findings reveal divergent responses in two unrelated crustaceans inhabiting a similar osmotic niche. While D. pagei does not secrete salt, tolerating elevated cellular isosmoticity, M. jelskii exhibits clear hypo-osmoregulatory ability. Each species has evolved distinct strategies at the transcriptional and systemic levels during its adaptation to fresh water.

Amazon freshwater crab Dilocarcinus pagei (Decapoda: Trichodactylidae): a view about burrow construction behavior

Crabs use burrows to prevent predation, environmental interference and shelter. The present study investigated the excavation behavior of the trichodactylid crab Dilocarcinus pagei, considering the biometric aspects of the burrows, the excavation time, the amount of bioturbation and the excavation behavior of the two sexes. The burrows of males had a mean diameter larger than the females, although the depth was similar for both sexes. Females had higher bioturbation than males, and showed enlargement in a camera format at the bottom, even closing the entrance of the burrows with a "plug" after their construction. Both the camera and the presence of the "plug" in the burrows of the females may be associated with reproduction. The presence of pellets observed at the entrance of burrows is associated with the cleaning of the pereiopods by crabs after the excavation. The sequence of behaviors for the construction of the burrows is described in detail, contributing to the knowledge about the biology and ecology of freshwater crabs of the Amazon.

Desiccation tolerance of two freshwater crabs of the Amazon: Dilocarcinus pagei and Sylviocarcinus pictus (Decapoda, Trichodactylidae)

This study investigated the resistance to desiccation of two species of freshwater crabs, Dilocarcinus pagei and Sylviocarcinus pictus. Dilocarcinus pagei survived almost twice as long as S. pictus, 127 ± 82.4 h and 69 ± 17.5 h, respectively. The females of both species survived longer than the males and the females of D. pagei survived longer than the females of S. pictus. Water loss until death was on average 30.12 ± 11.79% for D. pagei and 42.59 ± 7.49% for S. pictus. Dilocarcinus pagei showed a lower water loss than S. pictus until death and large S. pictus females and small D. pagei females exhibited a higher water loss, with differences between species and sex. The results reveal how these two species of crabs behave in extreme droughts in the Amazon floodplain. The females of both species were more resistant, although females of D. pagei were more resistant to desiccation than females of S. pictus, showing a higher degree of terrestriality.