Larval Length Research Articles

Selective feeding of the mullet larvae Liza haematocheila during ontogeny in Laizhou Bay, Bohai Sea, China: The importance of small copepods in mesozooplankton as prey

The mullet Liza haematocheila is widely distributed in low-salinity waters around the world and has high economic value. However, details regarding the foraging ecology of mullet larvae remain unclear. Larvae of L. haematocheila were sampled in Laizhou Bay of the Bohai Sea, China, in May 2016, and diet composition was detected using gut content analysis to compare differences in feeding parameters and diet shift in dominant prey during ontogeny. The results showed no linear relationship between gape size (GS) and standard length (SL) at larva length <7 mm (flexion larvae, FL), but linear increase was observed for SL >7 mm (post-flexion larvae, PFL). Maximum prey size (MPS) overlapped with GS during the FL stage but was never higher than GS during the PFL stage. Trends of increasing MPS and prey size range (PSR) during the PFL stage were lower than those during the FL stage, but prey number (PN) increased significantly during the PFL stage. Diet composition analyses in mullet larvae showed a total of 10 mesozooplankton species (or categories), of which 8 species were copepods (including copepods nauplii and copepodites), and showed the dominance of 4 small copepods (<1 mm). Analyses of the numerical proportion of dominant copepods showed that the largest prey (Paracalanus parvus) gradually increased as GS increased; conversely, the smallest prey (nauplii of Calanus sinicus) decreased. Collectively, these results suggest that PFL tends to exhibit increased PN but not prey size or size range, and diet shifts from smaller to larger prey during ontogeny in mullet larvae. All these indicate that PFL has higher prey selection ability compared with FL, specifically switching the diet to include larger small copepods during the PFL stage and increasing the prey number instead of increasing prey size. These determine the importance of small copepods in mesozooplankton as dominant prey and facilitate predictions of the impact of climate change on mesozooplankton and fish larvae.

Early Development Of Catfish Larvae Sangkuriang (Clarias gariepinus) From Feed With The Addition Of Curcumin

This study aims to identify the quality of spawning eggs and body length in the early development of catfish larvae from broodstock fed with the addition of curcumin. This research was conducted on October 22 2022 for 2 weeks on Jl. Great Aluminum No. 37, Tj. Mulia Hilir, Kec. Medan Deli, Medan City, North Sumatra 20241. The method used in this research is an experimental method. The sample used is sangkuriang catfish seeds (Clarias gariepinus) obtained from catfish breeding/cultivation. There are 2 pairs in total. Each pair consists of male and female catfish which are placed in the same pond but have been partitioned off. One pair of sangkuriang catfish will be given feed in the form of pellets with the addition of curcumin while the other pair will only be given pellets. The treatment in giving curcumin is 50% of the feed weight once a day the average body length of larvae has a body length and body weight that is higher than curcumin was not given so that the 0% curcumin treatment had the lowest body length. The increase in the diameter of the spawning larvae in the supplemented treatment group curcumin can be caused due to the bioactivity of curcumin as a hepatoprotector, and antioxidants. Curcumin supplementation is 50% of the total feed given to the parent showed more optimal results than the treatment other.

The relationships of female size with reproductive parameters, egg diameter and larval growth of striped catfish (Pangasianodon hypophthalmus)

This study aimed to quantify relationships between female weight and some reproductive parameters, yolk sac volume, and larval length of striped catfish (Pangasianodon hypophthalmus). Mature fish were selected from the broodstock conditioning tank in a recirculating system. Females (n = 36) weighing 1.7 to 7.0 kg were artificially propagated with the same male group. The results showed that realized fecundity (331,667 - 1,404,791 eggs/female) was positively correlated (P < 0.01), while relative fecundity (73,849 - 255,214 eggs/kg female) had a negative relationship with females’ weight (P < 0.01). Eighteen females were divided into 3 groups of weights (6 - 7 kg, n = 5; 5 - 5.5 kg, n = 8; and 3 - 4.8 kg, n = 5) to examine other reproductive parameters. Egg diameter (1,014 - 1,024 µm), fertilization rate (65.78 - 79.00%), and hatching rate (42.73 - 57.27%) were not significantly different among female groups. Larvae produced by medium and large-sized females appeared to grow (in length) faster than those by small-sized females, and these differences were significant at hatching, 24, and 72 h post-hatch (P < 0.05). Yolk sac volume was not different among the three groups (P > 0.05), ranging from 0.37 to 0.41 mm3 at hatching, and decreasing 62.2 - 68.3% after 36 h and 83.8 - 85.4% after 48 h post-hatch. In sum, females weighing 5 to 7 kg had higher realized fecundity and better growth of larvae during the first five days compared to small females.

Host range, damage extent and leaf consumptions by the bagworm, Thyridopteryx ephemeraeformis Haw. (Lepidoptera: Psychidae) in Bangladesh

Bagworm, Thyridopteryx ephemeraeformis Haw. (Lepidoptera: Psychidae) is a polyphagous pest in Northern America and southern Australia, causing severe damage to several host plants. A study was conducted to record the host plants, damage extent, and morphometrics of bagworms in Patuakhali Science and Technology University (PSTU) from 2015 to 2018. Results revealed a limited number of host plants for bagworm namely guava (Psidium guajava), arborvitae/juniper (Thuja standishii), rangan or jungles, geranium (Ixora grandiflora/Ixora coccinea), mussaenda (Mussaenda philippica), cropperleaf (Acalypha wilkesiana ‘Ceylon), henna (Lawsonia inermis), mango (Mangifera indica), pomegranate (Punica granatum) and betel nut (Areca catechu). The length of tiny larvae, fully-grown larvae, pupa, adult winged male moths, and wingless adult maggot-like females was 1.02 mm, 24.8 mm, 14 mm, 15 mm, and 48 mm, respectively. The average length of the bag was 24.7 mm with a range of 21-28 mm, and the average breadth in the middle of the bag was 6.9 mm with a range of 6-8 mm. The highest number of larval cases per branch was found in guava (56), and the lowest was in copperleaf (8). The highest percent of leaf damage (86.23%) per plant was also observed in the guava plant, and the lowest percent of leaf damage (37.46%) was in copperleaf. The highest number of infested leaves and bags per leaf was observed in the lower stratum of the guava branch, while the lowest infestation was in the top stratum. The highest percentage of leaf area (30%) damage was recorded 72 hours after release (HAR), and the lowest percentage of leaf area (10%) damage was at 24 HAR in guava. The maximum amount of leaf was consumed by bagworm larva at 72 HAR and the minimum amount was consumed at 24 HAR in guava. The maximum leaf area (13.46 cm2) consumption was recorded at 72 HAR, while the minimum amount (3.42 cm2) was consumed at 24 HAR. No significant damage by T. ephemeraeformis was observed in the case of mango, pomegranate, and betel nut plants. J. Asiat. Soc. Bangladesh, Sci. 48(1-2): 1-17, June-December 2022

Diafenthiuron causes developmental toxicity in zebrafish (Danio rerio)

Diafenthiuron, a broad-spectrum insecticide and acaricide used for agricultural crop protection, is highly toxic to nontarget organisms. However, the developmental toxicity of diafenthiuron and its underlying mechanisms are not fully understood. Thus, the purpose of this study was to investigate the developmental toxicity of diafenthiuron in zebrafish. Zebrafish embryos were exposed to diafenthiuron at different concentrations (0.01, 0.1, and 1 μM) from 3 to 120 h post fertilization (hpf). Diafenthiuron exposure significantly shortened the body lengths of zebrafish larvae and significantly decreased superoxide dismutase activity. It also downregulated the spatiotemporal expression of pomc and prl, marker genes involved in pituitary development. Moreover, diafenthiuron exposure downregulated the spatiotemporal expression of liver-specific marker, fabp10a, and inhibited the development of the liver, a detoxification organ. In conclusion, our data provide evidence of the developmental toxicity and hepatotoxicity of diafenthiuron in aquatic organisms, and they are instrumental for further environmental risk assessment of diafenthiuron in aquatic ecosystems.

Embryonic and Larval Development of Stinging Catfish, Heteropneustes fossilis, in Relation to Climatic and Water Quality Parameters.

In terms of hatchery-based seed production, one of the most important aquaculture species in Bangladesh is the stinging catfish (Heteropneustes fossilis). Scientific and evidence-based embryonic and larval development research on this fish species in the context of climate change is limited. This experimental study was conducted via induced breeding of stinging catfish using a conventional hatchery system, rearing the larvae in hapas placed in ponds. A series of microscopic observations using a trinocular digital microscope and an analysis of the relationship between larval growth and climate-driven water quality parameters such as temperature, pH, dissolved oxygen, total dissolved solids, alkalinity, and ammonia were performed. During embryonic development, the first cleavage was observed between 30 and 35 min of post-fertilization. Embryonic development (ranging from the 2-cell to the pre-hatching stage) took 21:00 h. Hatching occurred at 22:30 to 23:00 h after fertilization, with an average larvae length of 2.78 ± 0.04 mm. In the post-hatching stage, four pairs of tiny barbels appeared at 36:00 h, and the larvae started feeding exogenously after 72:00 h. These larvae fully absorbed their yolk sacs on the 6th day and attained an average length of 6.44 ± 0.06 mm. Aerial respiration of the larvae was investigated through naked-eye observation on the 10th day of hatching. The average length of the larvae was 32.00 ± 2.0 mm at the end of the 30-day post-hatching observation period. Bivariate correlation analysis showed significant correlations between key climatic variables and water quality parameters under hapa-based larval-rearing conditions. According to canonical correlation analysis, the first canonical function revealed the highest significant correlation between the two sets of variables (r1 = 0.791). The response variable weight of larvae (6.607) was linked to two explanatory variables: pH (0.321) and dissolved oxygen (0.265). For the second canonical correlation function, a positive correlation (0.431) was observed between the two sets of variables. Larval weight (-18.304) was observed to be linked to climatic variables, including air temperature (-0.316) and surface pressure (0.338). Results of this study reveal the subtle correlation between larval growth and water quality driven by climatic variables.

Predation efficiency of the carnivorous aquatic plant Utricularia australis against Asian tiger mosquito Aedes albopictus larvae: Implications for biological control

The Asian tiger mosquito, Aedes albopictus, one of the world’s worst invasive animal species and competent vector of many arboviruses, poses a serious threat to human health. An effective and environmentally friendly control strategy is required to mitigate the negative impacts of this pest. The aquatic carnivorous plants of the Utricularia genus, known as bladderworts, feed on invertebrates using their modified leaves as traps (bladders) and could be considered for biological control. The southern bladderwort, U. australis, was used in a no-choice experiment to test its predation ability against Ae. albopictus larvae. Larvae were divided in two size groups: 1st–2nd and 3rd–4th larval instars. Twenty Ae. albopictus larvae were placed inside 1 l plastic cups with a 30 cm long segment of the plant and left for a 7-day period. Twelve segments of U. australis were used, six for each larval size group, counting the number of bladders of each segment at the beginning of the experiment. The 7-day process was repeated five times for each segment/cup over a two-month period. The number of captured larvae and emerged adults was recorded daily. A total of 84 captured larvae were chosen to measure larval length, percentage of larval body trapped within the bladder, bladder perimeter and bladder area, in order to evaluate the ability of the bladders in capturing larvae, by complete or partial suction of the body, depending on the relative sizes of larvae and bladders. Results indicated that U. australis is an effective predator of Ae. albopictus larvae, with a higher efficiency against the 1st–2nd instar group (72%) compared to the 3rd–4th group (39%). The number of captured larvae depended on the number of bladders on each segment and instar group. The percentage of trapped larval body depended on the relationship between bladder size and larval length. Although the bladders effectively captured small larvae by complete suction of the body, they also killed 3rd–4th instar larvae by trapping a small portion of the body within the lumen. The plant segments continuously captured mosquito larvae, with an efficiency that did not decrease during the 2-month period. The use of U. australis as a biocontrol agent against Ae. albopictus larvae could be favoured by its ecological plasticity, broad distribution, its ability to thrive in small containers and the good overlap of the two species regarding phenology and habitat preferences.

Maternal transfer of florfenicol impacts development and disrupts metabolic pathways in F1 offspring zebrafish by destroying mitochondria

Maternal exposure to antibiotics existing in the environment is a predisposing factor for developmental malformation with metabolic disorders in offspring. In this study, female zebrafish (3 months) were exposed to 0.05 mg/L and 0.5 mg/L florfenicol (FF) for 28 days. After pairing and spawning with healthy male fish, F1 embryos were collected and developed to 5 d post-fertilization (dpf) in clear water. And the adverse effects on the F1 generation were examined thoroughly. The fecundity of F0 female fish and the hatchability, mortality, and body length of F1 larvae significantly decreased in the treatment group. Meanwhile, multi-malformation types were found in the exposure group, including delayed yolk sac absorption, lack of swim bladder, and spinal curvature. Metabolomic and transcriptomic results revealed alterations in metabolism with dysregulation in tricarboxylase acid cycle, amino acid metabolism, and disordered lipid metabolism with elevated levels of glycerophospholipid and sphingolipid. Accompanying these metabolic derangements, decreased levels of ATP and disordered oxidative-redox state were observed. These results were consistent with the damaged mitochondrial membrane potential and respiratory chain function, suggesting that the developmental toxicity and perturbed metabolic signaling in the F1 generation were related to the mitochondrial injury after exposing F0 female zebrafish to FF. Our findings highlighted the potential toxicity of FF to offspring generations even though they were not directly exposed to environmental contaminants.

Growth inhibition of offspring larvae caused by the maternal transfer effects of tetrabromobisphenol A in zebrafish

Tetrabromobisphenol A (TBBPA) is an industrial chemical and the most widely used brominated flame retardant, and has raised environmental health concerns. However, the maternal transfer toxicity of TBBPA is less studied in fish despite its frequency in the water environment, and limited evidence exists to confirm the major contributing factors. In this study, we performed a 28-d experiment on female and male zebrafish exposed to TBBPA (0, 5, 50, and 500 μg/L), and shortened body length of offspring larvae was observed at the maximum exposure concentration. By cross-mating control and exposed zebrafish (male or female), our results showed that the observed growth inhibition in the progeny was attributed to the maternal transfer effect. Although 28-d exposure resulted in the existence of TBBPA in ovaries and ova, the maternal transfer of TBBPA was not responsible for the shortened body length of offspring larvae, as evidenced through TBBPA embryo microinjection. Moreover, proteomic analyses in ova indicated that the abundance of apolipoproteins (apoa1, apoa1b, apoa2, apoa4b, and apoc1) was significantly downregulated in the ova, which may be partially responsible for the shortened body length of offspring larvae. Interestingly, these proteins did not differentially express in the ovaries. Therefore, our results demonstrate that TBBPA exposure disturbed maternal protein transfer from the ovaries to the ova, providing novel insights into the underlying maternal transfer effects.

Investigating the Applicability of Ichthyoplanktonic Indices in Better Understanding the Dynamics of the Northern Stock of the Population of Atlantic Hake Merluccius merluccius (L.)

Abundance indices are essential data for the application of stock assessment models to obtain fish abundance estimates. Abundance indices have usually been derived from fishery-dependent data, yet the increase in fisheries-independent surveys is now offering new opportunities for these calculations. In this study, we explored the usefulness of ichthyoplankton indices derived from scientific surveys in estimating spawning biomass. In addition, we also investigated whether the strength of the year–class of the commercial cohort of Atlantic hake, as a determinant, could be defined at an early life stage. We used samples collected during the triennial mackerel and horse mackerel egg surveys (MEGS), which cover the hake spawning area in the Bay of Biscay. The biomass indices were determined as the abundance of eggs in the early development stage (stage 1) when transformed into egg production (EP) from 1995 to 2019 in the months of March and April—which is considered a period of high spawning activity for hake in this area. Additionally, we built a metric for larval abundance and converted larval length into age. This was in addition to constructing a pre-recruit year-class index (YCI) while using the EVHOE bottom trawl abundance database for hake for the period of 1997 to 2016. The results of regression analysis of egg production and spawning stock biomass indicate that both parameters are significantly correlated (r = 0.76). By connecting the abundance of eggs and larvae in the adjoining stages, we are able to identify two periods of high mortality associated with the transition from “yolk-sac-first” to “feeding larvae” and “late larvae-YCI10”, but we were unable to discover when the strength of the recruitment year–class is determined. As such, it appears that for the northern stock of hake, recruitment is established in the late juvenile stages.

Potential inert diets to supplement Artemia in larviculture of the giant Africa river prawn Macrobrachium vollenhovenii (Herklots, 1857) (Crustacea: Palaemonidae)

The protocol of culture of Macrobrachium vollenhovenii the main indigenous candidate for freshwater prawn culture in Africa is still under study. Though just few information exists, the transition of larvae from stage V to stage VI has been reported as the critical rearing period in larviculture. This study was to evaluate the efficiency of two locally diets to supplement Artemia in the feeding scheme from stage V to post larvae in the larviculture of this species. The two experimental diets were differentiated by the main source of protein: fish silage (Diet 1) and shrimp meat (Diet 2). One batch of larvae was cultured till stage V. The experiment itself was conducted in triplicate with three treatments: feeding Artemia exclusively (TA, control); fed partial replacement of Artemia with inert diet 1 (T1) or fed partial replacement of Artemia with diet 2 (T2). Larval development in T2 was significantly faster than TA and T1. Survival rate was significantly higher in T2 (12.64±1.2%) than TA (6.57±0.29%) and T1 (6.77±0.17%). The total length of larvae in T2 was significantly higher than TA and T1. Though the highest survival obtained in this study is still low, it’s however higher than those reported in other studies with this species. Also, the importance of finding alternatives to Artemia and cheaper diets remains very important.

Effect of Artificial and Corn Leaves Diets on Development, Survival and Reproduction of <i>Spodoptera frugiperda</i> (Lepidoptera: Noctuidae) in Sierra Leone

The use of artificial diets to mass reared insect stock under laboratory conditions, promotes knowledge about the biology, behavior, and nutritional requirements of insects; with such information being fundamental for the formulation of efficient integrated pest management programs (IPM) strategies. However, the artificial diets used for rearing Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in the laboratory in this study, do not contain wheat germ, used for routine laboratory rearing. The aim of this study was to compare food preference and consumption by S. frugiperda larvae, as well as evaluate insect developmental parameters in the standard diet and the bean-based diets under laboratory conditions. Four artificial diets were used: a standard diet based on broad beans (Phaseolus vulgaris L.) used to rear S. frugiperda (D1), a diet with the substitution of two types of beans, cowpea (Vigna unguiculata L.) (D2) and pigeon pea (Cajanus cajan L) (D3); and a diet of fresh corn leaves (D4), the host plant of the pest species. Using a multiple-choice test, we observed that the larvae preferred diets D4 followed by D1. The relative consumption rate (RCR), relative growth rate (RGR), relative metabolic rate (RMR), approximate digestibility (AD), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), and the metabolic cost (CM) for S. frugiperda fifth instar larvae varied among diets. The diet D4 resulted in better ingestion, digestion, assimilation, and conversion of food, but with a metabolic cost to assimilate the food. The different bean varieties present in the diet influenced larval length, larval periods, larval survival, pupal periods, sex ratio, pupal weight, and pupal survival; but fecundity and longevity of adults were not affected. The different bean-based diets did positively influence population growth, with the most outstanding being D4. From the results of this study, the most adequate diet for rearing S. frugiperda in the laboratory is D4.

Effect of fermented laying hen manure and starter feed as growing media on black soldier fly larvae development

This study aimed to evaluate the development of Black Soldier Fly (BSF) larvae when reared on different feeding media, specifically using varying ratios of fermented laying hen manure and starter feed. The study employed a completely randomized design with five treatments and four replications. The treatments were as follows: T0: 100% fermented laying hen manure, T1: 75% fermented laying hen manure + 25% laying hen starter feed, T2: 50% fermented laying hen manure + 50% laying hen starter feed, T3: 25% fermented laying hen manure + 75% laying hen starter feed, and T4: 100% laying hen starter feed. Parameters measured in the study included larvae length and larvae width at 10 and 17 days. Data were analyzed using one-way analysis of variance followed by the Duncan post-hoc test. The study demonstrated that BSF larvae were successfully reared on growing media comprising 100% fermented laying hen manure (T0). However, the development of larvae in T0 remained relatively low. Notably, the use of laying hen starter feed particularly at 75% (T3) and 100% (T4) significantly improved (P<0.05) all larvae development parameters. It can be concluded that the Black Soldier Fly has significant potential as a bioconversion agent for laying hen manure. Moreover, the use of laying hen starter feed can be considered as a supplemental feeding media to enhance larvae development of Black Soldier Fly.

The larval stages of the variegated mud-loving beetle Heterocerus similis Grouvelle (Coleoptera: Heteroceridae)

Last instar larvae of the variegated mud-loving beetle Heterocerus similis Grouvelle are described and illustrated in detail. Comparative notes with earlier instars are also included. Based on the width of the head capsule and the prothorax four different instars were identified; considering that heterocerids show five larval instars, the four instars identified probably correspond to the last four. Larval length was not useful to recognize among different larval stages. The larva of H. similis is compared to that of H. freudei (Pacheco), the only other described South American heterocerid larva.

Toxicological signature for thyroid endocrine disruption of dichlorooctylisothiazolinone in zebrafish larvae.

Dichlorooctylisothiazolinone (DCOIT), which is one of the isothiazolinone preservatives, is applied to water-based adhesives in food packaging. This study investigated the effects of DCOIT on the embryonic growth and thyroid endocrine system using zebrafish. Organism-level (hatchability, survival, and growth), hormone-level (triiodothyronine (T3) and thyroxine (T4)), gene-level (genes associated with the hypothalamus-pituitary-thyroid axis), and microRNA-level (microRNAs related to thyroid endocrine disruption) endpoints were measured. Significant rise in embryonic coagulation and delayed hatching (≥0.3 μg/L), and decreased larval length (30 μg/L) were observed in fish exposed to DCOIT. Lower contents of T3 and T4 were observed after exposure to DCOIT, which was accompanied by the upregulation of genes associated with the thyrotropin releasing hormone and thyroid stimulating hormone and the downregulation of genes associated with the thyroid hormone receptors and deiodination. Strong influence of DCOIT on dre-miR-193b and -499 may be a critical mechanism to inhibit transcription of trαa and trβ, which in turn may affect thyroid hormones and development of the organism. Our findings suggest that hypothyroidism induced by the exposure to DCOIT is potentially associated with genetic and microRNA-level changes, which eventually affects development.

Maternal spawning experience and thermal effects on offspring viability of chub mackerel and their influence on reproductive success

Maternal effects on offspring viability significantly contribute to the productivity and resilience of exploited marine fish populations. The temporal trend of biomass of chub mackerel (Scomber japonicus) in the western North Pacific showed cyclic fluctuation patterns, but it has been rapidly increasing since 2011. Although there are several assumptions regarding the mechanisms of the population dynamics of this species in these waters, there is a contradiction in the effects of thermal environmental conditions on recruitment success. We explored the effects of maternal age and/or previous spawning experience on egg and offspring traits of captive chub mackerel in response to thermal conditions. Moreover, from the relationship between the growth rate and temperature experienced by captive fish, the experienced temperatures of wild specimens were assessed. The sizes of eggs spawned from females aged 1–3 years were negatively correlated with temperature, but the effects of maternal age on egg size and nutrition were significant with larger and nutrient-rich eggs spawned from 2- or 3-year-old females (repeat spawners) than those from 1-year-old females (first-time spawners) at a given temperature. Such temperature- and maternal-age-dependent egg traits reflected the standard length of first-feeding larvae. The effects of maternal age on the starvation tolerance of larvae after hatching and body sizes of first-feeding larvae were also evident in larvae derived from 3-year-old females showing longer starvation tolerance and larger body heights than those from 1-year-old females. Further, larvae derived from 3-year-old females grew significantly faster than those from 1-year-old females at the tested temperatures. The process of ontogenetic development and growth rate of captive specimens until age 25 days were positively correlated with temperature. Meanwhile, the estimated temperatures experienced by wild specimens until age 25 days ranged from 18.0 to 20.3°C. These findings suggested that there were opposing thermal responses between maternal and offspring traits of chub mackerel, but the temperatures experienced by the main recruit fish may be restricted within the range of temperatures available for spawning. We discuss the mechanisms of reproductive success of this species in accordance with the maternal spawning experience and thermal effects on life history traits.

Knockout of tanc2 causes autism-like behavior and sleep disturbance in zebrafish.

Tanc2 is a large multi-domain postsynaptic scaffold protein mainly expressed in the brain. In humans, tanc2 mutations have been associated with autism spectrum disorder (ASD) and other related neurodevelopmental disorders. However, the role of tanc2 in neurodevelopment and in controlling behaviors are not fully understood. Here, we generated and characterized a tanc2 knockout allele in zebrafish. Loss of tanc2 increases the larval brain size and body length by promoting proliferation and inhibiting apoptosis. We observed that the glutamatergic neuron population is significantly increased in tanc2 mutants while the GABAergic and the glycinergic neurons are not affected, suggesting that an excitatory/inhibitory (E/I) imbalance. Indeed, the tanc2 knockout larvae exhibited increase sleep. In adult zebrafish, the mutants display anxiolytic-behavior, reduced aggression, and impaired social preference. The alterations in these behaviors are phenotypically similar to the ASD patients carrying tanc2 mutations. Therefore, the tanc2 knockout allele could serve as a valuable model to further study the role of tanc2 in the nervous system.

Estimating risk of cardiovascular pharmaceuticals in freshwaters using zebrafish embryotoxicity test - statins threat revealed

Cardiovascular pharmaceuticals (CVPs) are globally present in inland waters and have also been found in the sediment and plasma of fish from the Sava River, Croatia. Based on the previous research, CVPs amiodarone (AMI), ramipril (RAM), simvastatin (SIM), and verapamil (VER) have been selected for this study. Their effect has been investigated, individually and in a mixture, on the development of the zebrafish embryo Danio rerio (Hamilton, 1822) within the first 96 h of development. Upon exposure to environmentally relevant concentrations of tested CVPs (0.1, 1, and 10 μg/L) zebrafish survival and development as apparent from observed morphological abnormalities, heartbeat rates and changes in behavior, hatching success, larval length and oxidative stress level were monitored. The CVP causing the highest mortality and pathological changes was SIM (1 and 10 μg/L), which corresponds well with the observed effects during zebrafish exposure to CVPs' mixtures (4 and 40 μg/L). All pharmaceuticals affected cardiac function and decreased heart rate. SIM (1 μg/L), VER and RAM (10 μg/L) decreased larval length, while induced oxidative stress was recorded in the SIM- and VER-exposed specimens. Behavioral alterations of zebrafish were observed only in AMI-treated group (10 μg/L). Our amino acid sequence comparison and structural and docking analysis showed a highly conserved binding site between human and zebrafish HMG-CoA reductase for SIM and its main metabolite simvastatin acid. Using these ecotoxicological bioassays on a zebrafish model with particular emphasis on sublethal endpoints, the risk of CVPs, especially statins, for fish in inland waters has been identified.

Identifying 3rd larval stages of common strongylid and non-strongylid nematodes (class: Nematoda) infecting Egyptian equines based on morphometric analysis

Strongylid and non-strongylid nematodes are one of the most important parasites infecting equines. The traditional method to identify these nematodes is through coproscopy and fecal culture. Because of the scarcity of data published in Egypt discussing the morphometric features of infective 3rd larvae of these nematodes, this study aims to provide a morphometric key for L3 of common strongylid and non-strongylid nematodes infecting Egyptian equines. For this reason, we cultured fecal samples containing GINs eggs and 3rd larval stages were identified based on their morphology (i.e., shape and number of intestinal cells (IC), shape of the esophagus, and shape of the tail sheath) in addition to computing their dimensions (i.e., length of larvae with sheath, length of the esophagus, length of intestinal cells, and body breadth). We identified 3rd larval stages of four strongylid nematodes (Cyathostomumsensulato, Strongylus vulgaris, Strongylus equinus, and Strongylus edentatus) as well as two non-strongylid nematodes (Strongyloides westeri, and Trichostrongylus axei). Statistically, our results revealed significant differences in terms of total length, body width, esophagus length, and gut length among 3rd larvae identified in the current study. The combination of both morphological and metric keys will allow the better identification of common strongylid and non-strongylid nematodes infecting equines.

Thyroid hormone-induced cell death in sea urchin metamorphic development.

Thyroid hormones (THs) are important regulators of development, metabolism and homeostasis in metazoans. Specifically, they have been shown to regulate the metamorphic transitions of vertebrates and invertebrates alike. Indirectly developing sea urchin larvae accelerate the formation of juvenile structures in response to thyroxine (T4) treatment, while reducing their larval arm length. The mechanisms underlying larval arm reduction are unknown and we hypothesized that programmed cell death (PCD) is linked to this process. To test this hypothesis, we measured larval arm retraction in response to different THs (T4, T3, rT3, Tetrac) and assessed cell death in larvae using three different methods (TUNEL, YO-PRO-1 and caspase-3 activity) in the sea urchin Strongylocentrotus purpuratus. We also compared the extent of PCD in response to TH treatment before and after the invagination of the larval ectoderm, which marks the initiation of juvenile development in larval sea urchin species. We found that T4 treatment results in the strongest reduction of larval arms but detected a significant increase of PCD in response to T4, T3 and Tetrac in post-ingression but not pre-ingression larvae. As post-ingression larvae have initiated metamorphic development and therefore allocate resources to both larval and the juvenile structures, these results provide evidence that THs regulate larval development differentially via PCD. PCD in combination with cell proliferation likely has a key function in sea urchin development.