Emersion behavior of the semi-terrestrial crab Neohelice granulata during hypoxic conditions: Lactate as a trigger.

Climate changes affecting aquatic environments are increasing, and the resultant environmental challenges require animals to adopt alternative compensatory behavioral and physiological strategies. In particular, low levels of dissolved O2 are a regular problem for estuarine animals, leading to activation of a series of behavioral and physiological responses. This study on the semi-terrestrial crab Neohelice granulata examined patterns of emersion behavior under different levels of dissolved O2 availability and the role of lactate in this behavior. Emersion behavior was recorded for 4.5 h for crabs in water at four different levels of dissolved O2 (6, 3, 2, and 1 mg O2/L) and with free access to air. Oxygen consumption and hemolymphatic lactate levels were measured using the same experimental design. Emersion behavior was also recorded for 70 min in normoxic water after lactate or saline injections. Crabs increased their emersion behavior only in severe hypoxia (1 mg O2/L), and O2 consumption decreased under more severe hypoxic conditions. Despite the increase in emersion behavior, which leads to higher O2 availability, an increase in hemolymphatic lactate levels indicates that the animals still need to resort to anaerobic pathways to fulfill their metabolic demand. Furthermore, animals injected with lactate showed higher emersion behaviors than animals injected with a saline solution even in normoxia. These results suggest that the increase in hemolymphatic lactate can act directly or indirectly as a trigger for the increase in emersion behavior in the semi-terrestrial crab N. granulata.

Effects of Experimental Lead Exposure on Testis of the Chestnut Capped Blackbird Chrysomus ruficapillus.

Lead (Pb) effects on testis histology, as well as sperm quality and oxidative status were evaluated in male Chestnut Capped Blackbird (Chrysomus ruficapillus). Wild blackbirds were captured, immediately sampled (field group) or kept in captivity and treated with a single intraperitoneal injection of saline solution (control) or saline solution with Pb acetate (50 or 100 mg/kg Pb). Seven days after injection, whole blood, ductus deferens and testis samples were collected. Increased Pb concentrations were observed in whole blood and testis of Pb-exposed blackbirds with respect to those from field and control blackbirds. Sperm cells of Pb-exposed blackbirds showed loss of membrane integrity, mitochondrial functionality, and DNA integrity. Also, oxidative damage was observed in testis of blackbirds injected with 100 mg/kg Pb. These findings indicate that Pb is accumulated in testis of C. ruficapillus, inducing severe morphological and biochemical injury that can compromise the reproductive performance of male blackbirds. Although the exposure scenario (Pb acetate, high dosage and intraperitoneal injection) tested in the present study would likely not occur in the wild, it was adequate to show potential and relevant toxic effects of Pb in wild birds.