Low Hatch Rate Research Articles

Optimizing and synchronizing Aedes aegypti colony for Sterile Insect Technique application: Egg hatching, larval development, and adult emergence rate

Mosquito Sterile Insect Technique (SIT) programs can be developed in smaller agencies through synchronization of the colony development to take advantage of the natural male early emergence. This paper examined key aspects of Ae. aegypti colony synchronization work, including egg hatching, larval development, and adult emergence to produce sufficient numbers of adult male mosquitoes within a specific timeframe for irradiation and release. Our data indicated that a relatively low percentage of males are required for colony propagation. Additional results highlighted that fresher Ae. aegypti eggs could yield as high as a 93 % hatching success than older eggs when placed under vacuum pressure in yeast infused water for 1.5 h. Eggs that were one-month old hatched (93 %) better than older eggs (0–32 %). A higher egg density in the hatching flask was correlated to a lower hatch rate, and higher larval density was related to unsynchronized pupae and delayed adult emergence. By keeping Ae. aegypti larvae at reasonable density, over 95 % of adults emerged on the first two days of emergence – indicating a high synchronicity. A standardized colony maintenance protocol therefore renders a synchronized larval development and adult male emergence which are critical in SIT programs.

Influence of Parental Age on Reproductive Potential and Embryogenesis in the Pepper Weevil, Anthonomus eugenii (Cano) (Col.: Curculionidae).

The pepper weevil (Anthonomus eugenii Cano) is a devastating pest that inflicts severe damage to pepper crops, leading to substantial economic losses. This study investigated the impact of aging on the reproductive success of the pepper weevil. Pepper weevil-infested fruit were harvested from pepper fields and subsequently transferred into an insect cage to facilitate the emergence of adults. The emerged adults were housed in separate cages and allowed to mature until they reached specified ages: 10 days old (young), 20 days old (middle-aged), and 30 days old (old) individuals. Eggs laid by each age group were carefully collected and incubated under controlled laboratory conditions (28 ± 1.5 °C). Several reproductive variables including the number of eggs laid, the percentage of hatched eggs, and the egg incubation period were recorded for each age group. Embryonic development was also monitored daily using a VHX digital microscope at a magnification of 200×. Differences in developmental stages such as the blastoderm, germ band, gastrulation, segmentation, and appendage formation were observed, and the time span of every stage was recorded. The results show that the 10-day-old weevils laid the most eggs and had the highest hatching rate and the shortest developmental time. The 30-day-old weevils laid the fewest eggs and had the lowest hatching rate and longest developmental time. Thus, the pepper weevil age significantly influenced the fecundity, length of time for each embryonic development stage, hatching rate, and incubation period, and should be considered when studying the reproductive biology of this pest insect. This first report of the effect of aging on the reproductive potential of the pepper weevil should enable pepper growers to adopt cultural practices aimed at reducing the pepper weevil populations, thereby helping to protect their crop from this important pest.

Comparative study on the gamete quality, artificial propagation and larval development of common goldfish, shubunkin, black moor, and oranda variants of goldfish (Carassius auratus)

Due to the origin and diversity of goldfish, it is a suitable model organism to investigate the effect of artificial selection on reproduction and larval development. In the present study, four, well-known variants of goldfish (common goldfish, shubunkin, black moor, oranda) with considerable phenotypical differences were compared within the framework of gamete quality assessment, propagation trial, larvae rearing and morphology assessment. In our first experiment, sperm concentration, sperm volume per fish (sperm volume) and volume of sperm per kg of body weight of males did not differ significantly between the variants. Concerning the measured Computer-Assisted Sperm Analysis (CASA) system parameters, shubunkin and oranda had significantly higher progressive motility (pMOT, %) than black moor. Tendencies in female gamete production were observed in the second experiment, despite not all cases displaying significant differences. For pseudo-gonadosomatic index (PGSI, %), higher values were recorded for the globular-bodied goldfish, while the contrary was seen for the number of eggs per gram. Out of the four variants, a significantly higher fertilization rate was determined for oranda, while a significantly lower hatch rate was calculated for black moor. In the third experiment, a significant difference in the body length of freshly hatched larvae was observed between common goldfish and shubunkin during larvae rearing. However, at 3 days post-hatching (dph), shubunkin and oranda had a significant difference in this parameter. At 10 dph, common goldfish and shubunkin had significantly lower body weights than black moor and oranda. Moreover, developmental variances between common goldfish and black moor were observed in larvae morphology. At the end of larvae rearing, a significantly higher survival rate was recorded for common goldfish than for shubunkin and oranda. Even though not all parameters show considerable differences between the variants, black moor is far behind the others in terms of hatching rate and morphological abnormalities.Thousands of years of artificial selection have had a noticeable mark on the reproductive capacity and larval development of goldfish variants studied. Our results may contribute to further research on the impact of artificial selection on reproductive biology.

Comparative Microbiome Analysis of Artemia spp. and Potential Role of Microbiotain Cyst Hatching.

Brine shrimp (Artemia spp.) is a significant factor in determining aquaculture production. Since the microbiota of Artemia can colonize the gut in larvae, various microorganisms transmitted from Artemia can affect host larval health. Although the microbiota composition of Artemia would be essential in determining aquaculture productivity, our understanding on microbiome of Artemia is still insufficient. Through our study, we identified the species of Artemia cysts supplied by three different manufacturers (P1, P2, and P3) with investigation of size and hatching efficiency. The species of Artemia from P1 was identified as A. tibetiana, and P2 and P3 was A. franciscana. A. tibetiana hatched from the P1 cysts had the largest body size with the lowest hatching rate. Furthermore, we conducted a comprehensive analysis of the microbiome present in the rearing water and the nauplius whole body from each product. We observed specific microbiota compositions, both beneficial and harmful, depending on the product types and the sample types. Additionally, we found that the microbiota composition in the rearing water was associated with the manufacturing environment, while the compositions in the nauplius whole body were species-specific. Notably, we discovered that an extract containing microbiota from the nauplius sample of P3 increased the hatching rate of A. tibetiana, indicating a positive role in Artemia culture. These findings demonstrate that the microbial communities present in Artemia vary according to the product and/or species, underscoring their significance in aquaculture production.

Dietary Moringa oleifera leaves to male rainbow trout (Oncorhynchus mykiss) broodstock: Effects on sperm quality and reproductive performance

Moringa oleifera leaves (MOL), a superfood rich in protein and vitamins, is native to the Indian subcontinent. Moringa were added to the broodstock trout diet to examine their influence on the reproductive performance of male broodstock rainbow trout (Oncorhynchus mykiss). Females were fed with a commercial broodstock trout diet without any inclusion of moringa leaves. In 12 circular fiberglass tanks, 36 male rainbow trout aged 3+ (1786.36 ± 35.36 g; 56.08 ± 0.94 cm) were divided into four groups (n = 9) (control, MOL-1, MOL-2, and MOL-3) with three parallels each. Fourteen weeks of feeding trials were performed where powdered moringa leaf was used in the diets at various levels: 0% (control), 4% (MOL-1), 8% (MOL-2), and 16% (MOL-3). Sperm quality parameters and fertilization success were investigated. Sperm motility parameters were examined at 10.5 °C using a computer-aided sperm analysis (CASA) system, and all samples were analyzed on the same day. Sperm volume and seminal plasma osmolality did not differ significantly across groups (p > 0.05). Spermatozoa concentration (6.71 ± 0.25, 7.54 ± 0.31, 8.44 ± 0.55, and 7.66 ± 0.35 × 109 cells ml−1 in control, MOL-1, MOL-2, and MOL-3 groups, respectively), spermatocrit ratio (18 ± 2.55%, 25 ± 3.16%, 38 ± 6.44%, and 28 ± 5.15%), and motility duration differed significantly (p < 0.05) among groups. Total motility percentage did not change, but progressive motility (74.72 ± 5.94%, 88.52 ± 4.35%, 89.36 ± 1.76%, and 90.47 ± 2.67%) was considerably higher in all three moringa groups than in control one (p < 0.05). Average Path Velocity (VAP), Straight Line Velocity (VSL), and Curvilinear Velocity (VCL) significantly differ between control and treatment groups (p < 0.05). The fertilization rate in the MOL-2 group was similar to the control and MOL-3 groups, while significant differences were observed from the eyeing stage, with the highest result observed in the MOL-2 group (p < 0.05). Hatching rates were also highest in the MOL-2 group (81.65 ± 0.49%), followed by MOL-3 (79.08 ± 1.27%) and MOL-1 (74.40 ± 2.32%), with the control group having the lowest hatching rate (74.24 ± 0.98%) (p < 0.05). Progressive motility, VAP, VSL, and VCL have significantly enhanced in the moringa-treated groups than the control one, hence boosting the fertilization success. The present study revealed that moringa leaves in the diet improve the sperm quality parameters and enhance the reproductive performance in broodstock male rainbow trout (Oncorhynchus mykiss). Therefore, 8% moringa leaf can be recommended as a supplement diet for male rainbow trout broodstock.

THE EFFECT OF TEMPERATURE DIFFERENCES ON HATCHING RATES OF LEKANG TURTLE (Lepidochelys olivacea) EGGS IN SEMI-NATURAL NESTS

This research was conducted on August 31, 2021 – December 7, 2021, at the UPTD KPSDKP, West Sumatra Province. The purpose of this study was to determine the effect of temperature differences on incubation time, hatching rate, and survival rate of turtle hatchlings (Lepidochelys olivacea). The method used in this study is an experiment that uses 3 trials plus 1 control, with 3 repetitions. Turtle eggs were incubated with the same depth and number of eggs with the addition of different temperatures from incandescent lamps with different powers. Then proceed with the calculation of incubation time, percentage of hatching, and survival of hatchling. Based on the results of the research, for the calculation of incubation time, the experimental unit with the shortest incubation period was produced by experimental unit B, with a temperature range of 27.5–29.5⁰C, which was 58 days. The incubation period that took the longest was the control experimental unit with an average temperature of 25⁰C, which was 65 days. For the results, the most optimal hatching rate was produced by experimental unit B, with an average hatching rate of 86%. Meanwhile, the lowest hatching rate was obtained from experimental unit C with an average hatching rate of only 53.3%. Then for the survival of the hatchlings after being quarantined for one week, all of them show the number 100%, which means that no hatchlings died during the quarantine

Transporting Tenebrio molitor Eggs: The Effect of Temperature, Humidity and Time on the Hatch Rate

Insect farming can be an important tool in the realization of a more sustainable future. With a growing insect industry, animal transportation between and within farms is expected to increase. For Tenebrio molitor, using eggs may be convenient as it eliminates the risk of cannibalism, food shortages and has a low risk of asphyxiation. However, there are at least three important variables during regular transport: time, temperature and relative humidity. For each one, as well as their interactions, there is a need to assess the effect on the hatch rate and establish lower and upper boundaries at which a good hatch rate of the eggs is possible. In this study, a total of 20 temperature/RH combinations were assessed (between 5–40 °C and 40–80% RH), with an exposure time ranging between 1 and 6 days for each combination. The results indicated that between 15 and 30 °C no negative effects were observed at any of the assessed RH or exposure times. Higher temperatures did result in a lower hatch rate; no eggs hatched at 40 °C, even after one day. Lower temperatures of 5 and 10 °C can be endured without pronounced adverse effects but only for a limited time (resp. 1 or 2 days). Including relative humidity in the model did improve the overall fit, but the effect is limited (compared to temperature or exposure time) with a slightly better hatch rate in dryer conditions at the extreme temperatures.

Environmental and Nesting Variables Associated with Atlantic Leatherback Sea Turtle (Dermochelys coriacea) Embryonic and Hatching Success Rates in Grenada, West Indies

Annual monitoring of leatherback sea turtle (Dermochelys coriacea) nesting grounds in Grenada, West Indies has identified relatively low hatch rates compared to worldwide trends. This study investigated the impact of selected environmental variables on leatherback sea turtle embryonic development and hatching success rates on Levera Beach in Grenada between 2015-2019. The mean number of nests per year and eggs per nest were 667.6 ± 361.6 and 80.7 ± 23.0 sd, respectively. Within excavated nests, 35.6% ± 22.0 sd of eggs successfully developed embryos and 30.6% ± 22.6 sd of eggs successfully hatched. The number of eggs per nest, along with embryo and hatching success rates, differed by nesting year. Embryo development success rate was associated with nest location, and both embryo development and hatching success rates were positively associated with nest depth and negatively associated with the percentage of eggs exhibiting microbial growth and with the presence of inspissated yolk. There was no embryo development or hatchling success association with month of the nesting season, distance from the high-water mark, distance from vegetation, nor maternal carapace length. The mean nest temperature was 31.7 °C ± 1.64 sd and mean temperatures during the middle third of egg incubation suggest clutches are highly skewed towards a preponderance of female hatchlings. Histopathologic findings in hatchling mortalities included severe, acute, multifocal, heterophilic bronchopneumonia with intralesional bacteria in 4/50 (8%) hatchlings. Data from this study guide conservation strategies by identifying risk factors and further avenues of research needed to support reproductive success of leatherback sea turtles in Grenada and the greater Caribbean region.

Hatching Failure in Wood Turtles (Glyptemys insculpta) Is Linked to Maternal Identity

Wood turtles (Glyptemys insculpta) have been suffering range-wide population declines since the 1900s. Most monitoring efforts of these turtles involve population surveys to assess population size and viability but relatively few investigate rates of reproductive success. We collected four consecutive years (2013–2016) of wood turtle nesting data at a nesting site in northwestern New Jersey; population-level hatching success was unusually low. Furthermore, annual, intra-individual hatch rates and comparisons between natural and artificial incubation revealed that approximately half of all females usually produced clutches with low (&amp;lt;50%) hatch rates, regardless of incubation conditions. In contrast, the annual hatch rates of other females were either consistently high (&amp;gt;50%) or highly variable, ranging from 0 to 100%. Thus, some adult females are potentially making much larger contributions to the next generation than others. A repeatability analysis suggested that approximately 60% of the hatch rate variability observed in this population can be attributed to maternal identity. The remaining 40% may be attributed to the random environmental factors that are often theorized to be potential reasons for reduced hatch rates in turtle populations (e.g., unsuitable incubation conditions, flooding, desiccation, egg infertility, egg damage due to improper handling by researchers, root and insect predation, and microbial infection). The ultimate causes of this population’s hatching success variability are uncertain, but maternally-linked hatching failure in turtle populations could be associated with inbreeding, infertility, senescence, inadequate maternal diets, or environmental contamination. This study indicates that commonly suggested hypotheses for hatching failure, such as unsuitable incubation conditions or infertility, are unlikely to explain all of the hatch rate variability in some turtle populations. This study also reveals a cryptic conservation implication for vulnerable turtle populations: that the presence of many nesting females and nests does not necessarily assure high or even sustainable reproductive rates. When coupled with the high rates of nest predation and low juvenile survival rates that are common in most turtle populations, the exceedingly low hatch rates observed in this population suggest that recruitment in some turtle populations could be severely hindered even when nests are protected in the field or incubated in laboratory settings.

Effects of Wolbachia elimination and B-vitamin supplementation on bed bug development and reproduction

Obligate blood feeders, such as Cimex lectularius (common bed bug), have symbiotic associations with nutritional endosymbionts that produce B-vitamins. To quantify the symbiont’s contribution to host fitness in these obligate mutualisms, the symbiont must be eliminated and its absence rigorously confirmed. We developed and validated procedures for complete elimination of Wolbachia (Wb) in bed bugs and quantified development and reproduction in bed bugs with and without Wb and with and without B-vitamins supplementation. Aposymbiotic bed bugs had slower nymphal development, reduced adult survivorship, smaller adult size, fewer eggs per female, and lower hatch rate than bed bugs that harbored Wb. In aposymbiotic bed bugs that were fed B-vitamins-supplemented blood, nymph development time, adult survivorship and hatch rate recovered to control levels, but adult size and egg number only partially recovered. These results underscore the nutritional dependence of bed bugs on their Wb symbiont and suggest that Wb may provide additional nutritional benefits beyond the B-vitamin mix that we investigated.

Combined blue light and daily thermocycles enhance zebrafish growth and development.

In the wild, the light/temperature environment cyclically oscillates insofar as the temperature rises after dawn and drops after dusk. In the underwater photo‐environment, light is filtered through the water column so that blue photons reach greater depths. This paper investigates the combined effects of both factors with two temperature regimes (constant temperature = 26°C, CTE vs. daily thermocycle = 28°C day:24°C night, TC) and three light wavelengths (white‐W, blue‐B, red‐R) on Danio rerio embryos and larvae from fertilization to 30 days post‐fertilization (dpf). It studied hatching rate, larval survival, growth, and food intake (gut content). It analyzed the expression of the genes involved in stress (crh), somatic growth (gh, ifg1a, igf2a), and food intake control (npy, agrp, ghrelin, orexin, mch1, mch2, grp, cck8) at 10 and 30 dpf. The results revealed that the lowest hatching rate was in R regardless of the temperature regime. The highest growth rate was for the larvae reared with B + TC, which was consistent with the highest expression values of the growth factors. The highest feeding and expression levels of the genes involved in food intake were for the larvae in B (regardless of the temperature regime) and W + TC. Conversely, the R + CTE combination obtained the worst growth and feeding results. These findings indicate that the best larval performance can be achieved with combinations of blue wavelengths and cyclic temperature regimes that come closer to those in the natural environment. These results should be considered when optimizing rearing protocols to improve the growth and welfare of the fish larvae.

The effect of salinity and temperature on egg hatching rate, hatching time and larval activity of Farfantepenaeus aztecus (Ives, 1891) (Decapoda: Penaeidae)

This study was conducted to determine the optimum temperature and salinity for the hatching rate, hatching time of eggs and larval activity of Farfantepenaeus aztecus (Ives, 1891). For this purpose, F. aztecus, which was caught from nature in the 4th gonad stage and were spawned on the same night in controlled laboratory conditions. The eggs were stocked in 2-l round bottom glass flasks and received one of nine temperature (24, 28 and 32°C) and salinity (30, 35 and 40 ppt) combinations as 50 eggs per liter after determining the fertility rate of the eggs. Although eggs hatched in all salinity and temperature combinations, water temperature, salinity and interaction had significant effects on hatching rate, hatching time and larval activity (P&amp;lt;0.05). Considering only salinity, the best hatching ratio was found at 35 ppt (48.44%), 40 ppt (47.89%) and the lowest hatching rate was found at 30 ppt (34.77%, P&amp;lt;0.05). It was found that the best hatching ratios were at 28°C (52.22%), at 32°C (48.33%) and followed by the eggs incubated 24°C (30.55%, P&amp;lt;0.05). The incubation time was shortened due to the increase in water temperature and changed between 11.40-17.10 hours. It was determined that the activities of the larvae incubated at lowest water temperature (24°C) and at 30 ppt were weaker than those incubated at 28°C and 35- 40 ppt salinities. The results show that 28-32°C water temperature and sea salinity slightly less than the salinity of the Mediterranean Sea (38.5 ppt) are optimal for the incubation eggs and for the production of high quality nauplii of F. aztecus found in the Northeastern Mediterranean.

Nature calls: intelligence and natural foraging style predict poor welfare in captive parrots.

Understanding why some species thrive in captivity, while others struggle to adjust, can suggest new ways to improve animal care. Approximately half of all Psittaciformes, a highly threatened order, live in zoos, breeding centres and private homes. Here, some species are prone to behavioural and reproductive problems that raise conservation and ethical concerns. To identify risk factors, we analysed data on hatching rates in breeding centres (115 species, 10 255 pairs) and stereotypic behaviour (SB) in private homes (50 species, 1378 individuals), using phylogenetic comparative methods (PCMs). Small captive population sizes predicted low hatch rates, potentially due to genetic bottlenecks, inbreeding and low availability of compatible mates. Species naturally reliant on diets requiring substantial handling were most prone to feather-damaging behaviours (e.g. self-plucking), indicating inadequacies in the composition or presentation of feed (often highly processed). Parrot species with relatively large brains were most prone to oral and whole-body SB: the first empirical evidence that intelligence can confer poor captive welfare. Together, results suggest that more naturalistic diets would improve welfare, and that intelligent psittacines need increased cognitive stimulation. These findings should help improve captive parrot care and inspire further PCM research to understand species differences in responses to captivity.

A Novel Recombinant Newcastle Disease Vaccine Improves Post- In Ovo Vaccination Survival with Sustained Protection against Virulent Challenge.

In ovo vaccination has been employed by the poultry industry for over 20 years to control numerous avian diseases. Unfortunately, in ovo live vaccines against Newcastle disease have significant limitations, including high embryo mortality and the inability to induce full protection during the first two weeks of life. In this study, a recombinant live attenuated Newcastle disease virus vaccine containing the antisense sequence of chicken interleukin 4 (IL-4), rZJ1*L-IL4R, was used. The rZJ1*L-IL4R vaccine was administered in ovo to naïve specific pathogen free embryonated chicken eggs (ECEs) and evaluated against a homologous challenge. Controls included a live attenuated recombinant genotype VII vaccine based on the virus ZJ1 (rZJ1*L) backbone, the LaSota vaccine and diluent alone. In the first of two experiments, ECEs were vaccinated at 18 days of embryonation (DOE) with either 104.5 or 103.5 50% embryo infectious dose (EID50/egg) and chickens were challenged at 21 days post-hatch (DPH). In the second experiment, 103.5 EID50/egg of each vaccine was administered at 19 DOE, and chickens were challenged at 14 DPH. Chickens vaccinated with 103.5 EID50/egg of rZJ1*L-IL4R had hatch rates comparable to the group that received diluent alone, whereas other groups had significantly lower hatch rates. All vaccinated chickens survived challenge without displaying clinical disease, had protective hemagglutination inhibition titers, and shed comparable levels of challenge virus. The recombinant rZJ1*L-IL4R vaccine yielded lower post-vaccination mortality rates compared with the other in ovo NDV live vaccine candidates as well as provided strong protection post-challenge.

Immune mechanisms of Texel sheep to adult and egg stages of Haemonchus contortus.

Experimental Haemonchus contortus (Hc) infections revealed that Texel sheep have faecal egg counts (FEC) comparable to parasite-resistant St. Croix but adult worm burden comparable to parasite-susceptible Suffolk sheep. The aim of these studies was to further investigate the mechanism causing this disparity. Cellular and humoral immune responses to adult- and egg stage Hc were compared amongst St. Croix, Texel and Suffolk sheep. Adult worms and eggs were exposed to peripheral blood mononuclear cells (PBMC) and serum from the three breeds in vitro. There was a greater IgA binding to eggs when treated with St. Croix and Texel serum (p<.05), and these eggs exhibited a lower hatch rate (p<.05) when exposed to serum and PBMC. Adult worms exposed to St. Croix and Texel-derived PBMC, and serum had greater binding around the head and reproductive structures than worms exposed to Suffolk-derived cells and serum. Consequently, egg release tended to be affected by breed (p=.09). To further examine differences, Suffolk and Texel lambs (n=5/breed) were infected with 10,000 Hc L3 for 30days. Suffolk sheep had greater egg release per worm than Texel (3.8 vs. 2.1eggs/worm). Taken together, these data would indicate one of the mechanisms in Texel's targeting adult-stage Hc reducing worm fecundity.

Elemental composition of alligator eggshell and eggshell membrane using micro-PIXE

Over the past years there has been a notable lack of success with regard to breeding alligator in commercial facilities. Farm-raised alligator eggs exhibit lower hatch rate in comparison with wild alligator eggs. Additionally, the hatch rates of the alligator eggs decrease in captivity until zero production is reached. This decline in production has been documented in over a twenty year study at the Rockefeller Wildlife Refuge. The lack of reproductive performance is attributed to the maternal diet and transfer of nutrients to the egg. Previous investigation on the eggshell and eggshell membrane of these reptiles lack comparisons between diet groups. The elemental compositions of the eggshell and eggshell membrane of wild and farm-raised A. mississippiensis were investigated using micro-PIXE. Eggs analyzed for this study were viable and the analysis showed that the major elements of the eggshell included calcium and aluminum, and that of membrane included sulfur and chlorine.

Hatching of nile tilapia (Oreochromis niloticus) egg in the hatching medium use salinity media and bromelain enzyme

This research aimed to observe the success of Nile Tilapia egg hatching in the hatching medium and the survival rate of larvae used salinity media and bromelain enzyme. This study was handled at laboratory of aquaculture, Fisheries and Marine Science Faculty, Brawijaya University on January-March 2020. This research used experimental method, completely randomized design with five treatments and three replications for every treatment. The salinity media was A (0 ppt), B (2.5 ppt), C (5 ppt), D (7.5 ppt), and E (10 ppt), and for every treatment was added 0.1223 µmol bromelain enzyme. The results showed that the highest percentage of hatching rate was obtained from 5 ppt with an average of 88.89%, while the lowest hatching rate was obtained in 0 ppt with an average of 67.78%. The results of the observation of abnormalities showed that abnormalities occurred in each treatment, except 0 ppt. The highest survival rate was obtained in 5 ppt with an average of 95.15%, while the lowest percentage of survival was obtained in 10 ppt with an average of 76.62%. The water quality was classified as good. The temperature of the hatching medium is obtained in the range 24° C - 27° C.

Effects of temperature and salinity on egg development and larval settlement of an invasive ascidian species, &lt;i&gt;Herdmania momus&lt;/i&gt; (Savigny, 1816)

The effects of temperature and salinity on egg development and settlement of the ascidian Herdmania momus were investigated. Adult specimens were collected from the Dodu Yacht facility in Jeju Island, Korea (33°30′30.54″N, 126°27′55.46″E) in August 2018. Egg development and larval settlement were observed and recorded at 8 h intervals using a stereomicroscope, under nine temperature (10, 13, 16, 19, 22, 25, 28, 31, and 34°C), and four salinity regimens (28, 30, 32, and 34 psu). The highest hatching rate (82.8±7%) was observed at 32 psu and 25°C and the lowest hatching rate (1.0±2%) was at 34 psu and 13°C. The developmental rate (0.222±0.0994) was highest at 28 psu and 28°C, and lowest (0.016±0.008) at 30 psu and 13°C. The highest settlement success rate (77.1±5%) was at 32 psu and 25°C and the lowest (0.1±1.0%) was at 30 psu, and 13°C. The rate of settlement (0.080±0.000) was highest at 28 psu and 28°C, and lowest (0.013±0.000) at 30 psu and 13°C. Both hatching and settlement success rates increased as temperature increased and tended to decrease beyond an optimal temperature range. Herdmania momus preferred 30-34 psu salinity and 22-25°C temperature. This study provides baseline information about the life history of H. momus, and important data to control the damage caused by the increase in number and distribution of this invasive ascidian.

A Biological Restoration Model for Contaminated Coastal Marshes and Islands Using the Life Cycle of Acheta domesticus to Establish Environmental Sustainability

Insects such as Acheta domesticus account for over half of marsh fish and migratory bird diet. Therefore, insects are very important to marsh and island ecosy stems and are susceptible to oil contamination, but little research has been done to study the effects of oil spills on cricket populations. The purpose of this experiment was to determine the effects of an oil spill event on Acheta domesticus mortality and hatch rate to establish environmental sustainability. The treatment groups included 0% oil contamination, 5% oil contamination and 10% oil contamination. The scientist counted the number of deaths in two-week, four-week, and six-week-old crickets after oil contamination. In addition, the scientist counted the number of hatchlings among treated cricket eggs. Error bar lines in the results section supported the scientist’s hypothesis that the crickets would be affected by oil contamination. In fact, over 90% of the 10% oil treatment group died and over 80% of the 5% oil treatment group died after five days of oil contamination in the six-week-old experiment. The scientist used a Gas Chromatography Mass Spectrometer to determine if benzene, toluene, ethylbenzene, or xylene (total) were present in the sediment samples. BTEX exposure is suspected to possibly cause insect mortality. These volatile organic compounds were present in the samples and were found in higher quantities in samples with higher concentrations of oil. The highest quantity of volatile organic compounds present was xylene. After studying the population dynamics of the tested Acheta domesticus, the scientist found that the two-week and four-week-old crickets’ survivability could fit a linear model while the six-week-old crickets fit an exponential model. The scientist used these models to observe how long it took each treatment group to approach zero, and the oiled groups grew closer to a population of zero significantly faster. For example, it took about twenty-seven days for the 10% treatment group’s population to approach zero whereas the control, 0% treatment group, took about seven days in the two-week-old cricket experiment. Overall, the six-week-old crickets had the highest mortality, and the cricket egg experiment resulted in extremely low hatch rate. Specifically, the highest number of crickets that hatched in an oiled replication either 5% or 10% oil was eight out of the five thousand eggs laid. Since the adult crickets are the most physically able to reproduce and the cricket eggs had low hatch rates, the cricket population would significantly decrease after an oil spill with 5% or more soil contamination. However, if the plant matter that crickets consume is still present in their environment, they may be able to recover.

Effects of thyroxine immersion on Sterlet sturgeon (Acipenser ruthenus) embryos and larvae: Variations in thyroid hormone levels during development

This study was planned to investigate the effects of immersion of Sterlet sturgeon (Acipenser ruthenus) eggs by thyroxine hormone (T4) on the embryonic survival rate (ESR), hatching rate (HR), larval survival rate (LSR), and thyroid hormone levels. Hence, oocytes of six females were pooled, fertilized with pooled semen of three males and 45 min after fertilization process, the eggs were placed 120 min in four batches that were immersed in T4 solutions as follows: D1 (the control treatment: T4-free, hatchery water), D2 (0.01 mg L−1 of T4), D3 (0.05 mg L−1 of T4), D4 (0.1 mg L−1 of T4), and D5 (1 mg L−1 of T4). Next, the eggs were transferred to the incubator. The ESR was recorded 6 h after fertilization while HR, and LSR were measured at 1 day post hatching. In addition, the levels of thyroid hormones were measured using the competitive enzyme immunoassay method three hours and three days after fertilization and at the five-day pre-larval stage. The highest ESR was obtained following D5 treatment (P < .05). Besides, the highest and lowest HR were observed in D5 and D1 treatments, respectively (P < .05). The D5 treatment resulted in the highest pre-larval SR. During all sampling times, the D5 treatment resulted in the highest level of thyroid hormones among the other treatments (P < .05). However, the T3:T4 ratio was significant only within the three days after fertilization in D1 treatment (P < .05). In general, it can be concluded that the immersion of Sterlet sturgeon eggs in T4 improved the ESR, hatching, and LSR of this species, resulting in a promising future for the aquaculture of Sterlet sturgeon and other sturgeon species.