Effects of Diflubenzeron on the Ontogeny of Phototaxis by Palaemonetes pugio

The phototaxis by larvae of the grass shrimp Palaemonetes pugio that hatched from embryos which were exposed to a single pulse concentration of diflubenzuron (DFB; Dimilin®) was quantified. Stage IV embryos (6-day-old) were exposed to 0.5 µg/L of DFB for 4 days followed by transfer into clean seawater for the rest of the incubation period. The photoresponses of light-adapted larvae from untreated embryos and embryos treated with 0.5 µg/L DFB were monitored from 1 day through 8 day post hatch for phototactic responses to 500 nm light. Larvae from untreated embryos exhibited strong positive phototaxis at high light intensities (3 x 10-2 and 3 x 10-1 Wm-2) but became negatively phototactic at lower light intensities (3 x 10-5 to 3 x 10-3 Wm-2). This phototactic pattern continued during the monitoring period. On the other hand, larvae from DFB-treated embryos exhibited altered phototaxis for the first 3 days. Alterations were especially evident on Day 1, as larvae were only negatively phototactic. By Day 4, these larvae reverted to the normal pattern of photoresponses shown by untreated larvae. These results indicated that the alterations in photoresponses of larvae caused by embryonic exposure to DFB are only transitory and can be corrected within 4 days of hatching if the larvae are exposed to water lacking DFB

Effects of Diflubenzeron on the Ontogeny of Phototaxis by Palaemonetes pugio

The phototaxis by larvae of the grass shrimp Palaemonetes pugio that hatched from embryos which were exposed to a single pulse concentration of diflubenzuron (DFB; Dimilin®) was quantified. Stage IV embryos (6-day-old) were exposed to 0.5 µg/L of DFB for 4 days followed by transfer into clean seawater for the rest of the incubation period. The photoresponses of light-adapted larvae from untreated embryos and embryos treated with 0.5 µg/L DFB were monitored from 1 day through 8 day post hatch for phototactic responses to 500 nm light. Larvae from untreated embryos exhibited strong positive phototaxis at high light intensities (3 x 10-2 and 3 x 10-1 Wm-2) but became negatively phototactic at lower light intensities (3 x 10-5 to 3 x 10-3 Wm-2). This phototactic pattern continued during the monitoring period. On the other hand, larvae from DFB-treated embryos exhibited altered phototaxis for the first 3 days. Alterations were especially evident on Day 1, as larvae were only negatively phototactic. By Day 4, these larvae reverted to the normal pattern of photoresponses shown by untreated larvae. These results indicated that the alterations in photoresponses of larvae caused by embryonic exposure to DFB are only transitory and can be corrected within 4 days of hatching if the larvae are exposed to water lacking DFB

Effects of pesticides on crab cheliped regeneration

The mud crab cheliped regeneration bioassay has proven to be a sensitive and reliable bioassay in studies of the potential sublethal effects of pesticides, including teratogenesis, spontaneous autotomy, and duration of the various stages of development. The assay has also been demonstated to be a useful indication of mortality associated with the impact of these chemicals of anthropogenic origin during the megalopal and early postlarval stages of development. Four pesticides were tested here using the cheliped regeneration bioassay technique. Although carbofuran is approximately 5--6 times more toxic than methomyl, both compounds yield very similar results in terms of sublethal effects

Chave ilustrada para identificação das zoés de Brachyura do estuário da Lagoa dos Patos (RS) e região costeira adjacente

The goal of this study is to provide an illustrated identification key to distinguish zoeal phase of Brachyuran larvae that occur in the estuarine and nearby coastal region of the Patos Lagoon. The key includes species, collected monthly, using a conical net (165 cm long, 60 cm mouth and 330 μm mesh). Sampling was carried out on surface and deep waters. The identification was based on specimens reared under laboratory conditions as well as from previous published studies. This key was constructed upon external morphological characters, easy to observe under a stereomicroscope and moreover, the presentation of figures allows a non-specialist to make identifications more easily.O objetivo do presente estudo é a elaboração de uma chave de identificação ilustrada das espécies de Brachyura que ocorrem no estuário da Lagoa dos Patos e sua região costeira adjacente. A chave abrange espécies as quais foram coletadas mensalmente, usando uma rede de plâncton (165 cm de comprimento, 60 cm de boca e 330 μm de malha). As amostragens foram realizadas na superfície e fundo. Os especimens foram identifcados mediante comparação com larvas cultivadas em laboratório e com descrições já existentes. A chave utiliza caracteres que não sofrem grandes transformações ao longo do desenvolvimento, e a utilização de figuras para ilustrar a chave permite a não especialistas facilmente identificar as espécies