Interactions Between Feeding Protocols, Larval Density, and Methylene Blue During Zebrafish Larval Development.

Simple SummaryDiabetes is predicted to become a major global pandemic in the not too distant future; subsequently, there is an urgent need to develop new drugs to treat this disease and its associated complications. Animal studies form an integral component of drug development, as they provide information concerning safety and efficacy of new drugs in an experimental setting reflecting the complexity of human physiology. Over the past decade, research has firmly established that zebrafish represent a convenient preclinical animal model. While genetic manipulation has given rise to numerous target specific models, these mutant zebrafish are unfortunately also associated with serious disadvantages. Therefore, wild-type zebrafish may be a preferred option for many researchers; however, information relating to their use in diabetes research remains scattered. This review collates existing scientific literature specifically pertaining to wild-type zebrafish and highlights the value of wild-type zebrafish larvae as a suitable animal model. Details regarding organ development, including similarities to mammalian counterparts, are discussed to indicate relevance. In addition, information covering experimental design and endpoint analysis provides an overview of the technical aspects when using wild-type zebrafish larvae as an experimental tool to mimic diabetes and its associated complications.Zebrafish have become a popular alternative to higher animals in biomedical and pharmaceutical research. The development of stable mutant lines to model target specific aspects of many diseases, including diabetes, is well reported. However, these mutant lines are much more costly and challenging to maintain than wild-type zebrafish and are simply not an option for many research facilities. As an alternative to address the disadvantages of advanced mutant lines, wild-type larvae may represent a suitable option. In this review, we evaluate organ development in zebrafish larvae and discuss established methods that use wild-type zebrafish larvae up to seven days post fertilization to test for potential drug candidates for diabetes and its commonly associated conditions of oxidative stress and inflammation. This provides an up to date overview of the relevance of wild-type zebrafish larvae as a vertebrate antidiabetic model and confidence as an alternative tool for preclinical studies. We highlight the advantages and disadvantages of established methods and suggest recommendations for future developments to promote the use of zebrafish, specifically larvae, rather than higher animals in the early phase of antidiabetic drug discovery.

Exposure to tris(1,3-dichloro-2-propyl) phosphate for two generations aggravates the adverse effects on survival and growth of zebrafish at environmentally relevant concentrations

Deficiency of leap2 promotes somatic growth in zebrafish: Involvement of the growth hormone system

Effects of larval and algal culture density and diet composition on development and survival of temperate asteroid larvae were studied in the laboratory at Santa Cruz, California, USA, during summer and fall of 1990. Larvae of Asterina miniata were reared at two densities, 0.5 or 1.0 ml-1, and fed one or two species of cultured phytoflagellates — Dunaliella tertiolecta alone or mixed with Rhodomonas sp. — at three concentrations of 5x102, 5x103, and 5x104 total cells ml-1. Algal concentration strongly influenced larval development; however, larval density also had a marked effect. Development progressed further with increasing algal concentration. Larval growth and differentiation were sometimes uncoupled; i.e., growth measures were directly related to food level, while differentiation indicators were less so. At the lowest food level, growth was negative and differentiation was arrested at early precompetent stages; these larvae never formed juvenile rudiments or brachiolar attachment structures. Development times of larvae given more food ranged from 26 to 50 d and depended directly on food availability. Development time to metamorphosis at the highest food concentration was similar for siblings fed D. tertiolecta alone or mixed with Rhodomonas sp. In contrast, when food level was an order of magnitude lower, larvae fed the algal mixture metamorphosed significantly earlier than larvae fed the unialgal diet. This suggests interactive effects of food quantity and food quality. Survival was little affected by larval or food density, except at the lowest ration. Feeding experiments in well-controlled laboratory conditions are useful to predict and compare the physiological or developmental scope of response of larvae to defined environmental factors; however, results from such studies should not be extrapolated to predict rates and processes of larval development in nature.

Spatiotemporal variability in Newfoundland capelin (Mallotus villosus) larval abundance and growth: Implications for recruitment

Factors regulating the emergence and survival of capelin (Mallotus villosus) larvae from their beach gravel nest sites were investigated in the spring and summer of 1978 and 1979. In both years, the pattern of larval emergence was characterized by intermittent abrupt increases in the numbers of larvae in the nearshore waters and corresponding precipitous declines in the density of preemergent larvae in the beach gravel. Both events were strongly correlated with onshore wind-induced wave action which disturbed the beach. Larval emergence patterns were unrelated to changes in tidal amplitude or day–night variation. The generality of this wind-induced larval emergence hypothesis was tested and confirmed using published data from two separate studies conducted at three different Newfoundland sites during 1927, 1929, 1930, and 1941. The density of larvae in the beach gravel was positively correlated with the length of time separating the occurrence of onshore winds. The result was a pronounced temporal clumping of larvae hatching at different times, periodic releases of large numbers of larvae into the aquatic environment, and a progressive deterioration in the physical condition of larvae emerging as beach residence time increased. The frequency of onshore winds during the hatching period was 50% greater in 1979 relative to 1978. Egg densities were similar in 1978 and 1979 but larval densities (no./m3) in the nearshore environment were 60% greater in 1979. This increase in larval density conformed to the increase in the proportion of larvae exiting the beach in good physical condition in 1979.Key words: capelin, Mallotus villosus; Newfoundland, larval emergence, larval survival, wind, population biology, beach spawning, coastal environments, year-class strength

In the underwater environment, the properties of light (intensity and spectrum) change rapidly with depth and water quality. In this article, we have described how and to what extent lighting conditions can influence the development, growth, and survival of zebrafish. Fertilized eggs and the corresponding larvae were exposed to different visible light wavelengths (violet, blue, green, yellow, red, and white) in a 12-h light-12-h dark (LD) cycle until 30 days posthatching (dph), when the expression of morphometric parameters and growth (igf1a, igf2a)- and stress-related (crh and pomca) genes were examined. Another group of larvae was raised under constant darkness (DD) until 5 or 10 dph, after which they were transferred to a LD of white light. A third group remained under DD to investigate the effects of light deprivation upon zebrafish development. The results revealed that the hatching rate was highest under blue and violet light, while total length at 30 dph was greatest under blue, white, and violet light. Red light led to reduced feeding activity and poor survival (100% mortality). Larvae raised under constant white light (LL) showed a higher proportion of malformations, as did larvae raised under LD violet light. The expression of growth and stress factors was upregulated in the violet (igf1a, igf2a, pomca, and chr) and blue (igf2a) groups, which is consistent with the higher growth recorded and the higher proportion of malformations detected under the violet light. All larvae kept under DD died before 18 dph, but the survival rates improved in larvae transferred to LD at 5 dph and at 10 dph. In summary, these findings revealed that lighting conditions are crucial factors influencing zebrafish larval development and growth.

The acute and 7-d subchronic toxicity of methylene blue were determined for fathead minnow larvae using U.S. Environmental Protection Agency methods. The 96-h lethal concentration (LC50) was 45 and 15 mg/L at 20 and 25°C, respectively. The 7-d chronic value for survival under laboratory light and low light was the same (2.1 mg/L). However, under laboratory light, larval growth was impaired at lower concentrations (chronic value = 0.6 mg/L) than under low light (chronic value = 2.1 mg/L). To assess prior methylene blue treatment on larval sensitivity, embryos, larvae <24 h old, and embryos followed by larvae were treated with 3 mg/L methylene blue. Cadmium LC50 values were similar between methylene blue-treated and untreated control groups. When larvae treated with methylene blue as embryos were subchronically exposed to an effluent, survival was similar to that of the untreated group. However, dry weight of the treated larvae was significantly lower. Differences in dry weight between treated and untreated groups were reduced as the age of the larvae at test initiation increased. Treatment of incubating embryos using 3 mg/L methylene blue does not appear to affect larvae sensitivity to cadmium but may affect the growth of larvae used in subchronic testing.

Simple SummaryThe gypsy moth, Lymantria dispar, is a forest pest that is grouped into two biotypes: the European gypsy moth (EGM), found in Europe and North America; and the Asian gypsy moth (AGM), found in China, Russia, Korea, and Japan. Outbreaks of this pest result in high-density populations of larvae that can cause enormous damage to trees and forests. Studies have identified an influence of larval population density on gypsy moth development, but it is not known how EGM and AGM populations differ in their response to changing larval densities. We examined the effects of varying larval density on three colonies established from one EGM population and two AGM populations. All three colonies exhibited an optimal degree of larval survival and optimal rates of pupation and adult emergence at an intermediate density of five larvae/rearing container. The duration of larval development was fastest at the same intermediate density for all three colonies. Although differences in larval development time, survival, pupation and emergence were observed among the three colonies under the conditions of our study, our findings indicate that density-dependent effects on the development of different gypsy moth biotypes follow the same trends.The life-history traits of the gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae), have been observed to vary with larval population density, which can increase significantly during an outbreak of this pest. Laboratory studies on density-dependent variation in gypsy moth development have focused on single populations and were limited to comparing solitary larvae with groups of larvae reared at a single density. To evaluate how density-dependent impacts on development vary with different populations and subspecies of L. dispar, we compared the effects of rearing larvae of a European gypsy moth (L. dispar dispar L.) population from Connecticut, USA; and larvae of two populations of the Asian gypsy moth (L. dispar asiatica Vnukovskij) from Guizhou and Hebei provinces in China. Larvae were reared on an artificial diet at densities of one, three, five, seven, and nine larvae per 115 mL container, and the duration of larval development, percentage of surviving larvae, and the rates of pupation and emergence were measured at each density. A two-tailed response to density variation with values falling away on both sides from a peak or climbing from a base was observed for all three populations tested, with the most rapid larval development and the highest values of survival, pupation, and emergence observed at a density of five larvae/container. Although differences in larval development time, survival, pupation and emergence were observed among the different populations under the conditions of our study, our findings indicate that density-dependent effects on the development of different gypsy moth subspecies and populations follow the same trends.

Crowding conditions of larvae may have a significant impact on commercial production efficiency of some insects, such as Tenebrio molitor L. (Coleoptera: Tenebrionidae). Although larval densities are known to affect developmental time and growth in T. molitor, no reports were found on the effects of crowding on food utilization. The effect of larval density on food utilization efficiency of T. molitor larvae was studied by measuring efficiency of ingested food conversion (ECI), efficiency of digested food conversion (EDC), and mg of larval weight gain per gram of food consumed (LWGpFC) at increasing larval densities (12, 24, 36, 48, 50, 62, 74, and 96 larvae per dm(2)) over four consecutive 3-wk periods. Individual larval weight gain and food consumption were negatively impacted by larval density. Similarly, ECI, ECD, and LWGpFC were negatively impacted by larval density. Larval ageing, measured as four consecutive 3-wk periods, significantly and independently impacted ECI, ECD, and LWGpFC in a negative way. General linear model analysis showed that age had a higher impact than density on food utilization parameters of T. molitor larvae. Larval growth was determined to be responsible for the age effects, as measurements of larval mass density (in grams of larvae per dm(2)) had a significant impact on food utilization parameters across ages and density treatments (in number of larvae per dm(2)). The importance of mass versus numbers per unit of area as measurements of larval density and the implications of negative effects of density on food utilization for insect biomass production are discussed.

The toxicities of short-chain primary alcohols and the accumulation of storage bodies in the larval fat body of Drosophila melanogaster

Declines in lake whitefish larval densities after dreissenid mussel establishment in Lake Huron

Present experiment was conducted to determine the effect of different feeds with varying protein levels on the growth, survival and reproductive performance of zebrafish, Danio rerio. The control diet (T1) was wild-collected zooplankton from local fish ponds, while test diets with 350 g kg−1 protein (T2), 400 g kg−1 protein (T3) and 450 g kg−1 protein (T4) were formulated and fed to fish for a period of 210 days. The significantly (P 0.05) differences were observed in brood survival rate, fertilization and hatching rate among the dietary treatments. The highest (P < 0.05) fry survival rate was recorded in T1, followed by T3 and T4. Thus, it is suggested that control diet i.e. mixed zooplankton exhibited better growth, reproductive performance and fry survival rate. However, diet containing 400 g kg−1 crude protein also gave comparable results in terms of growth, survival and reproductive performance of zebrafish.

Natural Antioxidants Dietary and Lipid Oxidation Analysis in Zebrafish (Brachydanio rerio) Tissue

Autoxidation of lipids is related to flesh deterioration and discoloration, as well as unpleasant flavors produced during processing and storage. This becomes a major factor determining fresh and frozen seafood products price. The aims of this research were to investigate the effect of two novel dietary supplementation antioxidants Vinlife grape seed extract and Herbalox rosemary extract on lipid oxidation during post-mortem storage of zebrafish (Brachydanio rerio) and the relationships between dietary antioxidants with the enzymatic antioxidant activities. Herbalox supplemented diet showed no harmful effects on growth or survival of zebrafish. However, the diet could not inhibit Thiobarbituric Acid Reactive Substances (TBARS) formation in zebrafish during post-mortem storage at 4 oC. Dietary Herbalox and Vinlife supplementation also showed no deleterious effects on growth or survival of zebrafish. The Vinlife supplementation efficiently suppressed TBARS formation in the zebrafish but the Herbalox supplementation. The two novel antioxidants had significant effects on catalase and glutathione S-transferase but not on glutathione peroxidase. These findings suggested that the supplementation with Vinlife was more effective than with Herbalox in inhibiting the formation of lipid oxidation products in zebrafish. Hence, Vinlife supplementation, could be a safe alternative method to improve oxidative stability of fish lipid contents. Key words: natural antioxidant, lipid oxidation, TBARS, GPx, CAT, GST