Background. The southern zone of the estuary of the Jamapa River, Veracruz, is a place of transition between the river and the marine environment to which sediments, compounds, and species of crustaceans are transported to the neritic zone where is the Parque Nacional Sistema Arrecifal Veracruzano. Objective. The responses of exposure of Potimirim mexicana postlarvae to diuron, glyphosate, and paraquat, as well as the relative abundance, diversity of the association of crustaceans, and values of temperature, salinity, oxygen, pH, and dissolved solids in the estuary were evaluated. Methods. Sampling was carried out with white light traps in November and March. Living Potimirim mexicana postlarvae were obtained from the samples to carry out the bioassays; the remaining individuals of the association were fixed in 70% alcohol for identification and quantification. The environmental factors were measured using a multiparameter Hanna HI 9828. Results. Dissolved oxygen was of 6-7 mgL -1 , pH of 8-9, temperature of 26-27° C, total dissolved solids of 700-1,500 ppm and salinity of 0.70-16 ups. Environmental conditions permit the presence of Potimirim mexicana postlarvae. Six taxa were found: postlarvae of Macrobrachium acanthurus, M. olfersii and Potimirim mexicana, megalopae of Callinectes sapidus and Armases ricordi, and zoeae of Brachyura. Diversity ranged from 1.55 to 1.77 bits*individual -1 , indicating an intermediate stability of the estuary. A total of 12,827 postlarvae of P. mexicana were obtained. The LC 50 values of diuron, paraquat, and glyphosate were 5.94, 1.51, and 221.05 mgL -1 , respectively. Conclusions. The values found here are consistent with those obtained by other authors for different species of crustaceans. Due to the important ecological in the food web of P. mexicana, its postlarvae can be used as sensitive test organisms in ecotoxicological studies.

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Farmers have increased the production of food by using chemical substances such as diuron; however, these components affect the water quality and the species found in these ecosystems. Macrobrachium acanthurus and M. olfersii postlarvae present in the estuary of Río Jamapa, Veracruz were collected to measure the LC50 and LD50 using the herbicide Karmex (diuron: (3-(3,4-dichlorophenyl)-1,1-dimethylurea [DCMU]). The captures of the prawns were made with light traps. Acute toxicity bioassays were carried out at 96 h to determine the mean lethal concentration (LC50). In the experimental design, a geometric series was used considering the control and five concentrations of the herbicide (1.75, 3.5, 6.99, 14, and 28 mg/L). The data analysis was carried out with the Probit method. A maximum LC50 of 10.233 mg/L and LD50 of 8.221 mg/L of Karmex were obtained for M. acanthurus and a maximum LC50 of 9.242 mg/L and LD50 of 7.504 mg/L of Karmex were obtained for M. olfersii. The average lethal concentration was consistent with those of other crustaceans, such as Artemia salina and Daphnia. Based on the response in the bioassays, Macrobrachium acanthurus and M. olfersii postlarvae can be used in toxicology studies.

Background. The Parque Nacional Sistema Arrecifal Veracruzano (PNSAV) is in the southern Gulf of Mexico and supports an important shrimp fishery based on three species of Dendrobranchiata: the brown shrimp, Penaeus aztecus, the white shrimp, P. setiferus and the pink shrimp, P. duorarum. Objective. Analyze the distribution and abundance of P. aztecus during the mysis stage and determine its relationship with environmental factors in the PNSAV. Methods. We measured temperature, salinity, and dissolved oxygen in situ. The planktonic samples from four transects were collected during cold fronts and rainy weather conditions from 2011 to 2013. Results. In rainy conditions the temperature varied from 27.49 ± 0.46 to 29.98 ± 0.02°C, salinity from 32.18 ± 0.06 to 35.40 ± 0.52, and dissolved oxygen from 3.64 ± 0.13 to 6.18 ± 0.64 mgL -1 ; during cold fronts the temperature varied from 23.21 ± 0.05 to 25.74 ± 0.37 °C, salinity from 34.59 ± 0.39 to 35.84 ± 0.17, and dissolved oxygen from 4.04 ± 0.06 to 6.02 ± mgL -1 . The highest average density with 6,938 ± 326 mysis 100 m −3 , was found during rainy season in 2011 in the southern transect nearshore, followed by 3,321 ± 339 mysis 100 m −3 in the offshoresouth-central transect during cold fronts weather conditions in 2013, and 3,056 ± 236 mysis 100 m −3 in the south-central foreshore transect during cold fronts weather condition in 2011. Conclusions. The highest density of P. aztecus during mysis stage was recorded in southward foreshore area from PNSAV, during rainy conditions and related to large values of dissolved oxygen concentrations.

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