Seasonal and environmental influences on recruitment patterns and habitat usage among resident and transient fishes in a World Heritage Site subtropical estuary.

This study investigated whether the fish communities inhabiting shallow non-vegetated habitats in two divergent bays in a subtropical World Heritage Site estuarine system differed according to wet (spring-summer) and dry (autumn-winter) seasons or polyhaline and mesohaline zones, within the broader objective of facilitating spatio-temporal management. Species richness (total of 74 taxa; total length, LT = 11-552 mm) and abundance (51 109 individuals) were mostly greater in the wet than dry season and in polyhaline than mesohaline areas. There was a major effect of rainfall on recruitment, particularly among transient fishes, which could be the result of enhanced survival of young via greater productivity (food resources) and protection from predators (via turbidity reducing visual cues). Salinity had strong interactive effects with rainfall and temperature in one bay, with greater species richness and overall abundances as well as large abundances of four key species [Anchoa januaria and Atherinella brasiliensis (pelagic residents), Cetengraulis edentulus (pelagic transient) and Diapterus rhombeus (demersal transient)] during the wet season in polyhaline areas; possibly reflecting a biodiversity hotspot that might be affected by distance to the estuary mouth and convergence hydrology. Regionally, the results support enforcing spatio-temporal restrictions to minimize anthropogenic activities within statutory (but not always enforced) protected areas. Globally, the data reiterate the need to identify and understand biotic and abiotic effects on estuarine ichthyofaunal distributions and abundances as a precursor to their management.

Nippostrongylus brasiliensis: cytokine responses and nematode expulsion in normal and IL-4-deficient mice.

Infection with the nematode, Nippostrongylus brasiliensis, results in a Th2-dominated immune response. We describe the dynamics of this response in both local and systemic environments. Th2-type responses were evident first in the mesenteric lymph node, with parasite antigen-specific proliferation and IL-4/IL-5 release peaking at Days 7-9 postinfection, shortly before expulsion of the adult worms from the gut. IFN-gamma responses were not observed in the mesenteric lymph node. Responses in the spleen generally followed those in the mesenteric lymph nodes by 2-3 days and showed a greater degree of Th1-type cytokine production. N. brasiliensis was shown to be a powerful inducer of IL-4 responses with as few as six infective N. brasiliensis larvae eliciting IL-4 production in the mesenteric lymph node, but only high doses of larvae (600) elicited IL-4 secretion in the spleen. Similar levels of IL-4 production by lymph node cells stimulated with Con A or parasite antigen postinfection indicated the extent of polyclonal Th2 stimulation by this parasite. Infection of IL-4-deficient mice showed that despite the absence of IL-4-dependent Th2 responses, these mice were able to curtail egg production and expel adult N. brasiliensis in a time frame similar to that of fully immunocompetent animals. These results emphasize the magnitude of the Th2 response to N. brasiliensis and also show that IL-4 is not a prerequisite for the development of immunity to N. brasiliensis.