Exploiting the Freshwater Shrimp Neocaridina denticulata as Aquatic Invertebrate Model to Evaluate Nontargeted Pesticide Induced Toxicity by Investigating Physiologic and Biochemical Parameters

As a nicotinoid neurotoxic insecticide, imidacloprid (IMI) works by disrupting nerve transmission via nicotinic acetylcholine receptor (nAChR). Although IMI is specifically targeting insects, nontarget animals such as the freshwater shrimp, Neocaridina denticulata, could also be affected, thus causing adverse effects on the aquatic environment. To investigate IMI toxicity on nontarget organisms like N. denticulata, their physiology (locomotor activity, heartbeat, and gill ventilation) and biochemical factors (oxidative stress, energy metabolism) after IMI exposure were examined. IMI exposure at various concentrations (0.03125, 0.0625, 0.125, 0.25, 0.5, and 1 ppm) to shrimp after 24, 48, 72 h led to dramatic reduction of locomotor activity even at low concentrations. Meanwhile, IMI exposure after 92 h caused reduced heartbeat and gill ventilation at high concentrations. Biochemical assays were performed to investigate oxidative stress and energy metabolism. Interestingly, locomotion immobilization and cardiac activity were rescued after acetylcholine administration. Through molecular docking, IMI demonstrated high binding affinity to nAChR. Thus, locomotor activity and heartbeat in shrimp after IMI exposure may be caused by nAChR blockade and not alterations caused by oxidative stress and energy metabolism. To summarize, N. denticulata serves as an excellent and sensitive aquatic invertebrate model to conduct pesticide toxicity assays that encompass physiologic and biochemical examinations.

Functional coupling in the evolution of suction feeding and gill ventilation of sculpins (Perciformes: Cottoidei)

Suction feeding and gill ventilation in teleosts are functionally coupled, meaning that there is an overlap in the structures involved with both functions. Functional coupling is one type of morphological integration, a term that broadly refers to any covariation, correlation, or coordination among structures. Suction feeding and gill ventilation exhibit other types of morphological integration, including functional coordination (a tendency of structures to work together to perform a function) and evolutionary integration (a tendency of structures to covary in size or shape across evolutionary history). Functional coupling, functional coordination, and evolutionary integration have each been proposed to limit morphological diversification to some extent. Yet teleosts show extraordinary cranial diversity, suggesting that there are mechanisms within some teleost clades that promote morphological diversification, even within the highly integrated suction feeding and gill ventilatory systems. To investigate this, we quantified evolutionary integration among four mechanical units associated with suction feeding and gill ventilation in a diverse clade of benthic, primarily suction-feeding fishes (Cottoidei; sculpins and relatives). We reconstructed cottoid phylogeny using molecular data from 108 species, and obtained 24 linear measurements of four mechanical units (jaws, hyoid, opercular bones, and branchiostegal rays) from micro-CT reconstructions of 44 cottoids and 1 outgroup taxon. We tested for evolutionary correlation and covariation among the four mechanical units using phylogenetically corrected principal component analysis to reduce the dimensionality of measurements for each unit, followed by correlating phylogenetically independent contrasts and computing phylogenetic generalized least squares models from the first principle component axis of each of the four mechanical units. The jaws, opercular bones, and branchiostegal rays show evolutionary integration, but the hyoid is not positively integrated with these units. To examine these results in an ecomorphological context, we used published ecological data in phylogenetic ANOVA models to demonstrate that the jaw is larger in fishes that eat elusive or grasping prey (e.g., prey that can easily escape or cling to the substrate) and that the hyoid is smaller in intertidal and hypoxia-tolerant sculpins. Within Cottoidei, the relatively independent evolution of the hyoid likely has reduced limitations on morphological evolution within the highly morphologically integrated suction feeding and gill ventilatory systems.

Developmental cardiorespiratory physiology of the air-breathing tropical gar, Atractosteus tropicus

The physiological transition to aerial breathing in larval air-breathing fishes is poorly understood. We investigated gill ventilation frequency ( fG), heart rate ( fH), and air breathing frequency ( fAB) as a function of development, activity, hypoxia, and temperature in embryos/larvae from day (D) 2.5 to D30 posthatch of the tropical gar, Atractosteus tropicus, an obligate air breather. Gill ventilation at 28°C began at approximately D2, peaking at ∼75 beats/min on D5, before declining to ∼55 beats/min at D30. Heart beat began ∼36–48 h postfertilization and ∼1 day before hatching. fH peaked between D3 and D10 at ∼140 beats/min, remaining at this level through D30. Air breathing started very early at D2.5 to D3.5 at 1–2 breaths/h, increasing to ∼30 breaths/h at D15 and D30. Forced activity at all stages resulted in a rapid but brief increase in both fG and fH, (but not fAB), indicating that even in these early larval stages, reflex control existed over both ventilation and circulation prior to its increasing importance in older fishes. Acute progressive hypoxia increased fG in D2.5–D10 larvae, but decreased fG in older larvae (≥D15), possibly to prevent branchial O2 loss into surrounding water. Temperature sensitivity of fG and fH measured at 20°C, 25°C, 28°C and 38°C was largely independent of development, with a Q10 between 20°C and 38°C of ∼2.4 and ∼1.5 for fG and fH, respectively. The rapid onset of air breathing, coupled with both respiratory and cardiovascular reflexes as early as D2.5, indicates that larval A. tropicus develops “in the fast lane.”

The Influence of Symmetrical Feed:Fast Regimes on Oxytetracycline Uptake and Otolith Score in Yellow Perch

Periods of growth from symmetric feed:fast regimes (i.e., days fed followed by the same number of days fasted) may increase the uptake of oxytetracycline (C22H24N2O9 .HCL[OTC]) compounds in fishes; however, little empirical data exists. Therefore, we experimentally determined if such feeding regimes influenced the concentration of OTC incorporated in muscle and skeletal (e.g., otoliths) tissues. Individually-reared female and batch-reared (male and female), age-1 yellow perch Perca flavescens were subjected to one of four experimental feeding regimes: control (i.e., fed daily), D2 (i.e., 2d feed, 2d deprivation), D6, or D12 symmetrical feed:fast regimes. Following several feeding cycles on these feeding regimes, fish were submersed in a 600mg/L buffered OTC solution; otoliths and muscle tissue were excised and processed to determine OTC uptake via mark quality and concentrations. Ranked otolith scores (mark quality) were significantly lower for the D2 feeding regime than control, D6, and D12 scores for both individual and batch trials suggesting that frequent food deprivation restricts osteogenesis, while daily or extended feeding periods contribute to osteogenesis. In batch-reared fish, total OTC and 4-epioxytetracycline peak concentrations in muscle tissue did not significantly differ among treatments but were significantly greater for smaller individuals within treatments suggesting that the OTC uptake and elimination response is mechanistically related to higher gill ventilation volume and gastric ingestion rate of small fish providing increased chemical assimilation and decreased clearing time following OTC immersions. Increased otolith mark quality derived from such feeding protocols may be of particular interest to fisheries managers conducting stock contribution assessments of yellow perch, but this induction strategy may apply to other species as well as therapies for hatchery stocks.

RESEARCH INTO THE EFFECT OF HEAVY METALS AND THEIR BINARY MIXTURE ON THE CARDIO-RESPIRATORY SYSTEM OF FISH LARVAE / SUNKIŲJŲ METALŲ IR JŲ BINARINIO MIŠINIO POVEIKIO ŽUVŲ KARDIORESPIRACINEI SISTEMAI ANKSTYVOJOJE ONTOGENEZĖJE TYRIMAI

This article investigates toxic effects of heavy metals (Ni, Cu) and their binary mixture (Ni+Cu) on the cardio-respiratory system of rainbow trout (Oncorhynchus mykiss) larvae depending on the type of metal, metal concentration and the duration of their exposure. The one-day larvae of rainbow trout were exposed to Ni (0,1; 0,2 mg/l, respectively), Cu (0,25; 0;5 mg/l, respectively) and their binary mixture. During long-term exposure (30 days), the physiological parameters of larvae, e.g. heart rate (counts/min), gill ventilation frequency (counts/min) after 5, 10 and 20 days of exposure were recorded. During experimental studies, the effects of heavy metals and their binary mixture on the heart rate and gill ventilation frequency of rainbow trout larvae depending on the type of metal, their concentrations and exposure duration were determined. Consequently, comparative studies on toxic effects of heavy metals and their binary mixture on the cardio-respiratory system of rainbow trout larvae showed that the binary mixture was more toxic to larvae than to single metals. Santrauka Šiame straipsnyje nagrinėjamas sunkiųjų metalų (Ni, Cu) ir jų binarinio mišinio (Ni + Cu) toksinis poveikis vaivorykštinio upėtakio (Oncorhynchus mykiss) lervų kardiorespiracinei sistemai, priklausomai nuo veikiamo metalo rūšies, metalų koncentracijos ir ekspozicijos trukmės. Vaivorykštinio upėtakio vienadienės lervos buvo veikiamos Ni (0,1; 0,2 mg/l), Cu (0,25; 0,5 mg/l) ir jų binariniu mišiniu. Ilgalaikio tyrimo metu (30 parų) buvo registruojami lervų fiziologiniai rodikliai – širdies ir kvėpavimo dažniai (krt./min.) po 5, 10 ir 20 parų ekspozicijos. Atlikus eksperimentinius tyrimus, nustatytas sunkiųjų metalų ir jų binarinio mišinio poveikis vaivorykštinio upėtakio lervų širdies ir kvėpavimo dažniams, priklausomai nuo veikiamo metalo rūšies, koncentracijos ir ekspozicijos trukmės. Tyrimo rezultatai rodo, kad atskirų sunkiųjų metalų (Ni, Cu) poveikis lervų kardiorespiracinei sistemai silpnesnis, nei veikiant metalų binariniu mišiniu.

Ecotoxicity and genotoxicity relating to fish in wastewaters discharged from the Vilnius treatment plant

The toxicity and genotoxicity of untreated raw (RWW) and treated wastewaters (TWW) samples from Vilnius wastewater treatment plant was assessed using fish (rainbow trout) at different stages of development. The survival of larvae and fish exposed to RWW in short-term and longterm tests reduced, whereas gill ventilation frequency, heart rate and relative body mass increase of larvae decreased significantly. The long-term exposure of fish to TWW induced significant decreases in white blood cell count and significant increases in micronuclei in blood of treated Oncorhynchus mykiss. The physical, chemical analysis of oil products (C14-C28), benzo(a)pyrene, suspended solids, and heavy metals (Pb, Cd, Zn, Cu, Hg) in RWW demonstrated that the concentrations of xenobiotics and some heavy metals did not exceed their Maximum Permissible Concentrations in the sewerage system and concentrations of substances in TWW corresponded to their criteria for effluents discharged into receiving waters.