Abstract
ABSTRACT Macrobrachium olfersii (Wiegmann, 1836) is a prawn that lives in shallow and transparent freshwater in Southern Brazil. Aquatic organisms that inhabit these systems can be exposed to incident UV radiation. Many studies have demonstrated the effects of ultraviolet (UV) radiation on the development, survival rate, morphological abnormalities, and impairments in swimming behavior in crustaceans. However, fewer studies have elucidated how the embryos of crustaceans respond to the exposure of UV radiation. Thus, the aim of this study was to evaluate whether UVA and UVB affect biometrical and morphological parameters of eggs and embryos of M. olfersii. Embryos were divided into two groups: Group I, composed of embryonic day 7 (E7) to E10 and Group II, composed of E11 to E14. Both groups were irradiated with 60 min UVA and 30 min UVB. Non-irradiated embryos at the same stages were used as controls. UVA and UVB radiation induces variations in morphometric parameters, such as egg volume, egg water content, and eye index. UVB radiation also induced an increase of embryonic cell death. We conclude that the embryonic cells of M. olfersii respond differentially to UVA and UVB radiation in accordance with the evaluated parameters.
Highlights
The freshwater prawn Macrobrachium olfersii (Wiegmann, 1836) is widely distributed in tropical and subtropical regions, ranging from the southwestern United States to the south of Brazil (Holthuis and Provenzano, 1970)
Taking into account that (i) UV radiation is able to penetrate into aquatic environments, depending on the depth of the water column and the amount of suspended organic matter (Häder et al, 2007); (ii) M. olfersii inhabit shallow and clear waters (Ammar et al, 2001), and (iii) the ovigerous females carry embryos in an external brood pouch, we suggest that the eggs of this species are subject to the direct incidence of environmental UV radiation
Non-irradiated eggs of M. olfersii showed a significant increase in volume between groups I (0.042 ± 0.0005 mm3) and II (0.060 ± 0.001 mm3; p < 0.01) (Tab. 1)
Summary
The freshwater prawn Macrobrachium olfersii (Wiegmann, 1836) is widely distributed in tropical and subtropical regions, ranging from the southwestern United States to the south of Brazil (Holthuis and Provenzano, 1970). Males and females of M. olfersii present similar body size until sexual maturity, similar to other palemonids (Bond-Buckup and Buckup, 1989). Males invest energy in somatic growth, becoming the bigger individuals of the population, while females invest energy in yolky egg production and parental care, such as egg incubation in a brood pouch (Adiyodi and Subramonian, 1983). Decapods with yolky eggs exhibit different incubation times, ranging from 10 days for Palaemon argentinus (Nobili, 1901) (Nazari et al, 2000), 20 days for Macrobrachium rosenbergii (de Man, 1879) (Habashy et al, 2012), and 180 days for Homarus americanus H. Macrobrachium olfersii ovigerous females carry out approximately 2,000 eggs per spawning in an external brood pouch for 14 days (24 ± 1°C) (Simões-Costa et al, 2005)
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