Marsupial development in the mysid Neomysis integer (Crustacea: Mysidacea) to evaluate the effects of endocrine-disrupting chemicals.

Embryonic development is a crucial time window within an organism's life history. Relatively few studies have focused on understanding the potential effects of endocrine disruptors on embryogenesis in invertebrates. Mysids (Crustacea: Mysidacea) have been used extensively in regulatory toxicity testing and they are the only invertebrate model currently included in the U.S. EPA's Endocrine Disruptor Screening and Testing Program. We developed a method for studying mysid embryonic development in multiwell plates until the release of free-swimming juveniles. This method was used to evaluate the potential effects of the insecticide methoprene, a juvenile hormone analog, on mysid embryogenesis. Embryos were exposed to nominal concentrations 0.01, 1, and 100 microg methoprene/L. Average percentage survival, hatching success, total development time and duration of each developmental stage were analyzed. Embryos exposed to 1 and 100 microg methoprene/L had a significantly lower hatching success and lower survival rates. Our study indicates that in vitro embryogenesis can be used as a valuable tool to study the impact of endocrine disruptors in mysids.

Testosterone metabolism in Neomysis integer following exposure to benzo(a)pyrene.

Cytochromes P450 (CYPs) are important enzymes involved in the regulation of hormone synthesis and in the detoxification and/or activation of xenobiotics. CYPs are found in virtually all organisms, from archae, and eubacteria to eukaryota. A number of endocrine disruptors are suspected of exerting their effects through disruption of normal CYP function. Consequently, alterations in steroid hormone metabolism through changes in CYP could provide an important tool to evaluate potential effects of endocrine disruptors. The aim of this study was to investigate the potential effects of the known CYP modulator, benzo(a)pyrene (BaP), on the testosterone metabolism in the invertebrate Neomysis integer (Crustacea; Mysidacea). N. integer were exposed for 96 h to 0.43, 2.39, 28.83, 339.00 and 1,682.86 microg BaP L(-1) and a solvent control, and subsequently their ability to metabolize testosterone was assessed. Identification and quantification of the produced phase I and phase II testosterone metabolites was performed using liquid chromatography coupled with multiple mass spectrometry (LC-MS2). Significant changes were observed in the overall ability of N. integer to metabolize testosterone when exposed to 2.39, 28.83, 339.00 and 1,682.86 microg BaP L(-1) as compared to the control animals.

Prediction from ultrasonographic measurements of the expected delivery date in two species of bottlenosed dolphin (Tursiops truncatus and Tursiops aduncus).

Ultrasonographic measurements were made at least once a month during 14 gestations in seven Tursiops truncatus and 12 gestations in five Tursiops aduncus (bottlenosed dolphins). The 121 measurements of the fetal biparietal diameter and 139 measurements of the fetal thoracic diameter in T truncatus and the 97 measurements of the biparietal diameter and 97 measurements of the thoracic diameter in Taduncus were used to establish regression lines for the increases in the diameter of the head and thorax of the fetus with time. From these relationships an easy-to-use computer program was developed to predict the date of birth of the two species of bottlenosed dolphin, and its predictions were compared with the actual dates of birth of other calves of both species. The births occurred within the range of predicted dates, and even when only a few measurements were available, the program provided accurate predictions.