The Common Targeted Organ in Zebrafish Embryos Exposed to Eight Toxic Chemicals

Zebrafish (Danio rerio) embryos are widely used in toxicity tests, especially in investigations on chlorinated or brominated flame retardants (BFRs) and metals. A key challenge in environmental risk assessment (ERA) is how to clarify the same or different sites of toxic action in a species after exposure to the individual chemicals or chemical mixtures and further provide the common toxic sites or organs for risk assessment of chemical mixtures. In this study, zebrafish embryo was used to evaluate the sublethal toxicity (gas bladder damage) of tris(2,3-dibromopropyl) isocyanurate (TBC), Chlorinated paraffins (CPs), hexabromocyclododecane (HBCD), and Cu, Cd, Pb, Ag, Zn, and corresponding sublethal molecular levels (and inflammation-related enzymes [deiodinase (DIO) enzymes]) in fish through optical microscopy methods. The tested chemicals all caused failed inflation of the gas bladder, as indicated by activity inhibition of type 2 iodothyroxine deiodinase enzyme. We put up with the common targeted sites or organs for further studying the toxic mechanisms underlying the chemical mixtures.

Larval development of Microgobius tabogensis Meek & Hildebrand, 1928 (Pisces: Gobiidae) from a coastal lagoon in the Gulf of California, México

In fish, the larval stage constitutes the most vulnerable phase in the life cycle and reveals important ecological and evolutive information of fish and fundamental data to manage marine ecosystems. However, their identity is one of the biggest gaps in knowledge, particularly for the Microgobius genus, where only three of 15 species have been described. In this study, the larval development of Microgobius tabogensis was described based on 116 specimens (2.75-14.20 mm standard length) from Ensenada de La Paz, Mexico. The typical gobiid body shape characterized larvae, a well-developed dorsally pigmented gas bladder, a curve at the hindgut, and 27 myomeres. The pigmentation pattern in M. tabogensis consisted of a series of melanophores along the ventral postanal midline, increasing from three to seven during the preflexion stage and up to 16 in the postflexion stage. It had three to five melanophores on the ventral preanal midline, one at the jaw angle and one on the dorsal postanal midline. Through all stages, one of the ventral melanophores was normally stellate, bigger than the others, and extended between the myomeres. A dorsal melanophore was located near the end of the intestine in the preflexion stage but disappeared with growth. Notochord flexion started at approximately 4.3 mm and ended at 5.1 mm. Anal fin development started at the beginning of the flexion stage, followed by the dorsal fin. All elements of the fins were formed by the late postflexion stage (14.2 mm).

Revision of the diagnostic characters of two morphologically similar snook species, Centropomus viridis and C. nigrescens (Carangiformes: Centropomidae)

Historically, the taxonomic identification of the two snook species, Centropomus viridis and C. nigrescens, has been challenging due to their morphological similarity and the inconsistency of the characters used for diagnosis. Therefore, this study aimed to evaluate the usefulness of the morphologic, meristic, and morphometric characters currently being used to identify C. viridis and C. nigrescens, based on molecular data. The results showed that the gas-bladder shape (i.e., C. viridis with diverticula and C. nigrescens without diverticula) was the only morphological character univocally related to genetic identification. Likewise, geometric morphometrics separated two groups; each corresponds to only one of two genetically (and gas bladder shape) identified species. Of all the meristic characters examined, only the second dorsal fin ray count (nine for C. viridis and ten for C. nigrescens) was related to the gas bladder shape and genetic identity; therefore, it is the only external character with a diagnostic utility to separate each species.

Simulation of a Hydraulic Pulsation Dampener Used for Pulsation Reduction Induced by Vibrations in a Hydraulic System

To reduce vibration-induced pulsations, various devices have been developed, including diaphragm chamber system or gas bladder, non-intrusive fluid wave actuator and fluid filled also known as reflection-type dampeners. However, they are not suitable used in a hydraulic system powered by a triplet piston pump. For example, pulsation dampeners incorporating gas bladders are effective, but there are a number of drawbacks. Loss of gas charge, incorrect gas charge or volume/mass ratio, elastomeric rupture, narrow range of pressure operation and pump speeds, routine maintenance, ineffective location and branch connection instead of in-line configuration are all integrity issues which the industry faces. In addition to having a structural integrity issue, branch connected devices do not perform as efficiently as in-line devices. If a pulsation dampener is responsible for safeguarding critical equipment or systems, premature rupture of a gas bladder can be catastrophic. This paper introduces a dynamic model and mathematical formulations of a spherical liquid pulsation dampener (U.S. patent number 3731709) that is commonly used to reduce harmful pulsations induced by a triplet piston pump source in fluid power systems. Based on the mathematically proven formulations, computer simulations and optimization procedures were developed in MATLAB to validate the model. Simulation results were then compared with field testing data to numerically verify the model and formulations. For the sake of simplicity, in this paper the pulsation dampener is in conjunction with a three-piston horizontal pump referred to as a triplex pump. The foundation of the simulation is based on a transfer function developed by electrohydraulic analogy resulting in a resistance-impedance-based model. This model takes into consideration all the components of the pulsation dampener and allows for a detailed relationship to its primary function of reducing magnitude spikes. After nonlinear impedances were linearized, MATLAB codes were able to recreate pressure pulsations before and after the pulsation dampener was applied to the system. This allowed for a comparison with field testing data, including mean pressures and range of pressure changes. The mean pressure values examined included 6.08 MPa, 15.20 MPa and 30.40 MPa. The key characteristics to properly analyze the comparison. The wave representing the pressure change over time via MATLAB and that of the field testing were consistent in pulsation reduction. With the validity of the transfer function confirmed, a meta-heuristic approach was utilized to find optimized dimensions of the pulsation dampener while maintaining the desired magnitude reduction. This method can be used to hone the precise dimensions for a variety of functions and even further reduce pulsations.