Japonicus Eggs Research Articles

First Nationwide Monitoring Program for the Detection of Potentially Invasive Mosquito Species in Austria.

Simple SummaryIn the last years several alien mosquito species have been introduced into Austria. Those species pose a threat, as they—especially the Asian tiger mosquito (Aedes albopictus)—can transmit many pathogens. The aim of this study is a nationwide overview on the situation of alien mosquitoes in Austria. Using traps representing ideal breeding sites for those mosquitoes, we collected, counted and identified the species of the mosquito eggs laid in the traps. The Asian tiger mosquito was found at two sites, once in Tyrol, where this species has been reported before, and for the first time in the province of Lower Austria. The Asian bush mosquito (Aedes japonicus) was widespread and abundant in Austria. Although it was found in all provinces, the Asian bush mosquito was more often found in the South than the North and more eggs were collected in urban/industrial/transport areas than in (mostly) natural areas. Further, more eggs from the Asian bush mosquito were found in samples collected at higher daily mean temperatures, and fewer eggs in samples collected at higher daily maximum wind speeds. The results of this study will help to better understand the risk from alien mosquitoes to human health in Austria and will be useful to show future changes in the distribution of those species.In Austria, only fragmented information on the occurrence of alien and potentially invasive mosquito species exists. The aim of this study is a nationwide overview on the situation of those mosquitoes in Austria. Using a nationwide uniform protocol for the first time, mosquito eggs were sampled with ovitraps at 45 locations in Austria at weekly intervals from May to October 2020. The sampled eggs were counted and the species were identified by genetic analysis. The Asian tiger mosquito Aedes albopictus was found at two sites, once in Tyrol, where this species has been reported before, and for the first time in the province of Lower Austria, at a motorway rest stop. The Asian bush mosquito Aedes japonicus was widespread in Austria. It was found in all provinces and was the most abundant species in the ovitraps by far. Aedes japonicus was more abundant in the South than in the North and more eggs were found in habitats with artificial surfaces than in (semi-) natural areas. Further, the number of Ae. japonicus eggs increased with higher ambient temperature and decreased with higher wind speed. The results of this study will contribute to a better estimation of the risk of mosquito-borne disease in Austria and will be a useful baseline for a future documentation of changes in the distribution of those species.

Bacterial microbiome of dusky kob Argyrosomus japonicus eggs and rearing water and the bacteriostatic effect of selected disinfectants

The dusky kob Argyrosomus japonicus is an emerging aquaculture species in South Africa. To support industry growth, existing hatcheries frequently sell or donate excess eggs to neighbouring farms, raising concern over the potential transfer of infectious disease agents. Chemical disinfectants are frequently used to prevent transmission of diseases, but their application has shown large variations between finfish species and very little is known about the efficacy and impact of disinfectants on dusky kob eggs or larvae. A thorough understanding of the bacterial communities associated with specific fish species can inform the need for specific chemical agents and guide a more targeted approach for disease control and treatment. Therefore, this study used next generation sequencing (NGS, 16S rDNA gene) and downstream bioinformatics analysis to describe the bacterial microbiome associated with the eggs and rearing water of dusky kob. Four chemical disinfectants [chloramine-T (C-T), povo‑iodine (PI), hydrogen peroxide (H2O2) & formaldehyde (CH2O)], applied at different concentrations and times, were then tested for their ability to disinfect eggs and seawater. The impact of each disinfectant on early larval development was also assessed. A total of 11,605 individual bacterial operational transcriptional units (OTUs) were identified from the dusky kob egg (7352 OTUs) and hatchery water (4253 OTUs) samples. Non-metric multidimensional scaling (NMDS) analysis revealed distinct differences in the composition of the microbiota associated with the egg and seawater samples. A moderate level of bacterial diversity was observed in all samples, with the seawater samples dominated by Rhodobacteraceae (65%) and Flavobacteriaceae (14%); whereas egg samples were dominated by Pseudoalteromonadaceae (49%), Vibrionaceae (27%) and Colwelliaceae (8%). A classical univariate statistical comparison identified 6 differentially abundant OTUs at phylum level, 12 at family level and 19 at genus level; with members of the family Vibrionaceae found to be significantly (P = 0.0011) more abundant on dusky kob eggs samples. All tested chemical disinfectants were capable of reducing the bacterial load in seawater in a dose dependent manner, with the number of culturable bacteria on eggs decreasing significantly following exposure to PI and CH2O for five minutes (43% and 88% reduction in CFUs, respectively), compared with C-T and H2O2 (3% & 10%). Similarly, PI and CH2O significantly decreased the culturability of Vibrio species on eggs (79% & 75%), compared with C-T and H2O2 (12% & 14%). None of the disinfectants appeared to have any adverse impact on larval growth and morphology.

Emergence of the invasive Asian bush mosquito, Aedes (Finlaya) japonicus japonicus, in an urban area, Romania

BackgroundA study conducted at the International Airport of Cluj-Napoca, Romania, with the aim of investigating the presence/absence of invasive Aedes mosquito species resulted in finding Aedes japonicus japonicus (Theobald 1901) eggs in one of the ovitraps placed on site.MethodsThe study was carried out between 30 June and 29 September 2020. On 24 August, 26 eggs were collected and later hatched at the University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca’s insectary. On 15 October another adult female Ae. japonicus was caught entering a building in the center of the city, about 7 km from the first sampling spot.ResultsThe mosquitoes were identified morphologically and confirmed by molecular analysis, based on the genetic analysis of the mitochondrial gene cytochrome c oxidase subunit 1 (COI).ConclusionThis is the first report of the species in Romania, highlighting the need for surveillance and implemented control methods. However, in Romania to our knowledge only Aedes albopictus has been established; further studies are required to learn about this new invasive species' status in Romania.Graphical

Phenology of Rock Pool Mosquitoes in the Southern Appalachian Mountains: Surveys Reveal Apparent Winter Hatching of Aedes japonicus and the Potential For Asymmetrical Stage-Specific Interactions.

The North American rock pool mosquito, Aedes atropalpus, has reportedly decreased in abundance following the introduction of Ae. japonicus japonicus to the USA, but the specific mechanisms responsible for the reduction remain unclear. Thus, there is a need for field studies to improve our knowledge of natural rock pool systems where both species co-occur. We sampled rock pool invertebrates over a 12-month period along the Chattooga River at a high-elevation site (728 m) near Cashiers, NC, and at a lower-elevation site (361 m) near Clayton, GA. We identified 12 orders of macroinvertebrates representing at least 19 families and 5 mosquito species. Aedes j. japonicus was present year-round at both sites. We observed overwintering Ae. j. japonicus larvae in pools with water temperatures as cold as 3°C and detected apparent winter egg hatching in water below 10°C. Aedes atropalpus was rarely encountered at the high-elevation site but was highly abundant in the summer months at the low-elevation site. Late-stage Ae. j. japonicus larvae inhabited pools in March 2019 when Ae. atropalpus first appeared in the same pools, creating the potential for asymmetrical stage-specific interactions. Our observations provide evidence of overwintering and early hatching of Ae. j. japonicus in the southeastern climate. Further study of the importance of stage-dependent competition and winter egg hatching of diapausing Ae. j. japonicus eggs is warranted.

Oviposition of Aedes japonicus japonicus (Diptera: Culicidae) and associated native species in relation to season, temperature and land use in western Germany

BackgroundAedes japonicus japonicus, first detected in Europe in 2000 and considered established in Germany 10 years later, is of medical importance due to its opportunistic biting behaviour and its potential to transmit pathogenic viruses. Its seasonal phenology, temperature and land use preference related to oviposition in newly colonised regions remain unclear, especially in the context of co-occurring native mosquito species.MethodsFocussing on regions in Germany known to be infested by Ae. japonicus japonicus, we installed ovitraps in different landscapes and their transition zones and recorded the oviposition activity of mosquitoes in relation to season, temperature and land use (arable land, forest, settlement) in two field seasons (May–August 2017, April–November 2018).ResultsAe. japonicus japonicus eggs and larvae were encountered in 2017 from June to August and in 2018 from May to November, with a markedly high abundance from June to September in rural transition zones between forest and settlement, limited to water temperatures below 30 °C. Of the three native mosquito taxa using the ovitraps, the most frequent was Culex pipiens s.l., whose offspring was found in high numbers from June to August at water temperatures of up to 35 °C. The third recorded species, Anopheles plumbeus, rarely occurred in ovitraps positioned in settlements and on arable land, but was often associated with Ae. japonicus japonicus. The least frequent species, Aedes geniculatus, was mostly found in ovitraps located in the forest.ConclusionsThe transition zone between forest and settlement was demonstrated to be the preferred oviposition habitat of Ae. japonicus japonicus, where it was also the most frequent container-inhabiting mosquito species in this study. Compared to native taxa, Ae. japonicus japonicus showed an extended seasonal activity period, presumably due to tolerance of colder water temperatures. Higher water temperatures and arable land represent distribution barriers to this species. The frequently co-occurring native species An. plumbeus might be useful as an indicator for potentially suitable oviposition habitats of Ae. japonicus japonicus in hitherto uncolonised regions. The results contribute to a better understanding of mosquito ecology and provide a basis for more targeted monitoring, distribution modelling and risk management of mosquitoes. Graphical

Neutral Lipids, Glycolipids, and Phospholipids, Isolated from Sandfish (Arctoscopus japonicus) Eggs, Exhibit Anti-Inflammatory Activity in LPS-Stimulated RAW264.7 Cells through NF-κB and MAPKs Pathways.

Total lipids were extracted from sandfish (Arctoscopus japonicus), and then they were separated into the following three lipid fractions: neutral lipids, glycolipids, and phospholipids. In this study, we analyzed the lipid fractions of A. japonicus eggs and we determined their anti-inflammatory activity in RAW264.7 macrophage cells. In these three lipid-fractions, the main fatty acids were as follows: palmitic acid (16:0), oleic acid (18:1n-9), docosahexaenoic acid (DHA, 22:6n-3), and eicosapentaenoic acid (EPA, 20:5n-3). Among the lipid fractions, phospholipids showed the highest concentration of DHA and EPA (21.70 ± 1.92 and 18.96 ± 1.27, respectively). The three lipid fractions of A. japonicus significantly suppressed the production of NO in macrophages. Moreover, they also significantly inhibited the expression of iNOS, COX-2, IL-6, IL-1β, and TNF-α, in a dose-dependent manner. Furthermore, the lipid fractions of A. japonicus suppressed the nuclear translocation of NF-κB p65 subunits in a dose-dependent manner. In addition, they attenuated the activation of MAPKs (p38, ERK1/2, and JNK) phosphorylation in LPS-stimulated RAW264.7 cells. These results indicate that all the lipid fractions of A. japonicus exert anti-inflammatory activity by suppressing the activation of NF-κB and MAPK pathways. Therefore, the lipid fractions of A. japonicus might be potentially used as anti-inflammatory agents.

Anti-Inflammatory Effects of Lipids Extracted from Arctoscopus japonicus Eggs on LPS-Stimulated RAW264.7 Cells.

Arctoscopus japonicus is a cold-water marine fish. The present study investigated the fatty acid composition of A. japonicus egg lipids and their anti-inflammatory effects on LPS-stimulated RAW246.7 macrophages. The results showed that A. japonicus egg lipids contained primarily polyunsaturated fatty acids (52.9% of the total fatty acid content; mostly eicosapentaenoic acid [EPA, 21.2 ± 0.5%] and docosahexaenoic acid [DHA, 25.9 ± 0.1%]), followed by monounsaturated fatty acids and saturated fatty acids (23.7% and 23.4%, respectively). A. japonicus egg lipids significantly decreased nitric oxide (NO) production and suppressed the expression of immune-associated genes such as iNOS, COX-2, IL-1β, IL-6, and TNF-α LPS-stimulated RAW246.7 macrophages in dose-dependent manner. A. japonicus egg lipids also reduced the phosphorylation levels of NF-κB p-65, p38, ERK1/2, and JNK, key components of the NF-κB and MAPK pathways, suggesting that the lipid-induced anti-inflammatory activity is related to these signaling pathways. These results indicate that the lipids extracted from A. japonicus eggs have potential biofunctions and might be useful for regulating inflammation in macrophages.

Winter monsoon promotes the transport of Japanese temperate bass Lateolabrax japonicus eggs and larvae toward the innermost part of Tango Bay, the Sea of Japan

AbstractNorthwesterly cold winds characteristic of the East Asian Winter Monsoon (EAWM) dictate winter climatic conditions over the Japanese Archipelago. Japanese temperate bass Lateolabrax japonicus is a commercially important coastal fish that spawns offshore in winter and uses shallow waters as nursery habitats. To investigate the effects of EAWM on the planktonic period of L. japonicus, eggs, larvae, and juveniles were quantitatively collected in Tango Bay on the Sea of Japan side in winter and spring from 2007 to 2017. Although eggs occurred close to the mouth of the bay, planktonic larvae occurred further inside as they developed. The horizontal distribution of planktonic larvae, combined with water velocity data obtained from mooring observations, indicated that planktonic larvae are transported south‐ to westward through Ekman current and an anticyclonic circulation, which are driven by northwesterly winds. To evaluate survival during the planktonic period in each year class, the abundance of benthic larvae/juveniles was divided by winter total landings of Lateolabrax spp. (proxy of the spawning stock size). This survival index exhibited a positive correlation with the northwesterly component of winter winds, and a negative correlation with winter air temperature (average from December to February, Spearman's correlation, p < .05). There was, however, no significant correlation with winter water temperature or winter freshwater discharge in the bay. We conclude that northwesterly cold winds of EAWM play a critical role in transporting L. japonicus eggs and larvae toward nursery habitats, specifically beaches and estuaries fringing the innermost part of Tango Bay.

Morphological Differentiation of the Eggs of North American Container-Inhabiting Aedes Mosquitoes.

Aedes aegypti , Ae. albopictus, Ae. japonicus japonicus, and Ae. triseriatus eggs are described with the aid of color images and images from scanning electron microscopy. All eggs were broadly cigar shaped with Ae. triseriatus and Ae. j japonicus eggs being dull or matte black, while Ae. albopictus and Ae. aegypti eggs were shiny jet black. Aedes triseriatus eggs were lighter in color and had a rougher appearance when compared to those of Ae. j. japonicus. Aedes albopictus and Ae. aegypti eggs can be differentiated by the distinct presence of micropylar collars in Ae. aegypti. Our results reduce the need to rear these mosquitoes, reducing labor and time while providing an accurate identification of the vector mosquitoes.

Distribution of mackerel, Scomber japonicus eggs and larvae in the coast of Jeju island, Korea in spring

Distribution of mackerel, Scomber japonicus eggs and larvae in the coast of Jeju island, Korea in spring

Pengaruh Perasan Biji Pepaya (Carica papaya) terhadap Kerusakan Telur Argulus japonicus <Br><I>[The Influence of Papaya Seed (Carica papaya) Toward The Damage Eggs of Argulus japonicus]<I>

Abstract Argulus japonicus being parasite with blood sucking the host, do infestations by piercing the skin of the host through a maxillule and preoral stylet. The infestation causes ulceration and bleeding, thus giving access to secondary infection by bacteria, fungi, viruses, and causes death. The act of controlling against Argulus japonicus can be done by reduce in population which began in eggs stadium. Control over A.japonicus can use natural insecticide that is papaya seeds. Papaya seeds contain the active substance that are saponins, tannins, flavonoids, alkaloids which act as a natural insecticide. The research design was a completely randomized design with a treatment that were 0 ppt, 70 ppt, 80 ppt, 90 ppt, 100 ppt, and five replications. Data were analyzed by using analysis variance (ANAVA). The results showed that the juice of papaya seeds affect the egg damage of Argulus japonicus. Concentration of 100 ppt juice of papaya seeds can broken A. japonicus eggs with the largest percentage is 100%. Concentration of 90 ppt that percentage of eggs of A. japonicus were damaged by 83%, 74,25% of 80 ppt concentration, 59% of 70 ppt concentration, and 0% of control. Optimal concentration of papaya seeds which resulted in the amount of damage more than 50% of Argulus japonicus eggs is 80 ppt.

Revisiting morphological identification of Japanese jack mackerel Trachurus japonicus eggs preserved in formalin

Since formalin-preserved eggs of Japanese jack mackerel Trachurus japonicus have been considered difficult to identify, egg abundance of this species has not been estimated, and subsequently information on their spawning habitat is limited. The present study provides a practical identification of Japanese jack mackerel eggs from formalin-preserved samples based on morphological characteristics with validations through DNA sequencing and a rearing experiment. Eggs obtained by artificial fertilization from mature adults were reared in the laboratory, and developmental changes of morphological characteristics in the formalin-preserved samples were examined. The morphological descriptions were detailed to identify jack mackerel eggs from field-captured egg samples preserved in formalin. Moreover, the identification was validated through DNA sequencing and a rearing experiment. Overall, the diagnostic characteristic for identification was the egg diameter and the segmentation of the yolk, which was maintained in formalin-preserved samples even long after fixation. The presented morphological description with its developmental changes for formalin-preserved eggs is anticipated to promote stock assessments and biological studies for jack mackerel based on the egg and larval surveys.

Annual variability of ichthyoplankton in the Yangtze River estuary of China from August 2002 to 2009

Abstract The annual variability of ichthyoplankton in the Yangtze River estuary, located at the junction of the East China Sea and the Yellow Sea, on the continental shelf at the western rim of the Pacific Ocean, was studied using vertical tows at twenty stations from August 2002 to August 2009. Basic oceanographic parameters such as temperature and salinity were also measured to evaluate their relationship to the abundance of ichthyoplankton. The eggs or larvae of a total of 34 fish species were present in the samples. Only 8 species were found to occur during every year. Engraulis japonicus and Stolephorus commersonii eggs, as well as Coilia mystus and Stolephorus commersonii larvae, were highly abundant during this period. Additionally, water storage in the Three Gorges Reservoir, which began in June 2003, had significant effects on the abundance of estuarine species, as well as on the composition and diversity of ichthyoplankton; this became evident when these values were compared to the findings from 2002. The number of species (species richness) and abundance of each species varied among the stations relative to the salinity in the estuary during the study period.

Temperature effects on early development and biochemical dynamics of a marine fish, Inimicus japonicus

A study was undertaken to evaluate the development and metabolic substrates (carbohydrate, protein, lipid and fatty acids) dynamics during the embryonic and yolk-sac larval stages of the devil stinger, Inimicus japonicus, at different water temperatures (18, 21, 24, 27 and 30°C). The hatching time was significantly shortened when the temperature increased (P<0.05). Only 14.5% of embryos hatched at 30°C, while the hatching rate was 92.5% at 24°C. Larvae incubated at 21°C displayed the greatest survival at mouth-opened larva stage (96.5%), but the rate dropped sharply when the temperature surpassed 24°C (P<0.05). The full length and yolk-sac volume of newly hatched larva at 18°C and 30°C were significantly smaller than those at 21, 24 and 27°C. Larva at 21°C always had the largest full length during early development. The advent of mouth-opened larvae was closely related to temperature, so were the full length and yolk volume of the mouth-opened larva. As the incubation temperature declined, the mouth-opened larva obtained longer full length and less yolk remain. Lipid was, to a large extent (47.0% of the initial amount), a fuel for development when the embryo was incubated at 18°C. The depletion of protein in the embryo was significantly higher at 30°C (67.6%) than that at 21°C (31.3%). Consumption of carbohydrate was observed only in embryo at 18°C. During the development of yolk-sac larva, a lower incubation temperature induced more protein anabolism and less lipid consumption. In I. japonicus, polar lipids (PL) constituted the principal class of lipid in eggs (74.0% of the total lipid); and it was the most consumed portion during embryogenesis in all treatments. The lipid composition in mouth-opened larva was affected by the incubation temperature. The storage triglycerides (TG) tended to comprise a higher proportion in larva incubated at 30°C than in those at lower temperatures. The PL proportions in larva at 18°C and 30°C were lower than those in larvae at 21°C, 24°C and 27°C. Low concentrations of polyunsaturated fatty acid (PUFA) in embryos and larvae were correlated with increased temperatures; this indicated that the rapid development at higher temperatures was at the cost of more PUFA loss. It is concluded that 21–24°C is an appropriate range for incubation of I. japonicus eggs and larvae and that 24°C is optimal in terms of shortening the endogenous nutritional stage and improving metabolic efficiency.

Size variability and natural mortality dynamics of anchovy Engraulis japonicus eggs under high fishing pressure

Size variability and natural mortality dynamics of anchovy Engraulis japonicus eggs under high fishing pressure

Developmental styles and larval morphology of hybridized sea cucumbers (Echinodermata: Holothuroidea)

The sea cucumber Apostichopus japonicus has many colour variations. In order to compare the ability of colour variants of A. japonicus to hybridize and investigate differences in the development of hybrid larvae, we developed a genetic marker of their body colours. Differences in the sequence of the internal transcribed spacer 1 region of ribosomal RNA were correlated with the red variant. Reciprocal crosses of red and green variants produced hybrids that developed to the auricularia, doliolaria and pentactula developmental stages. In crosses between A. japonicus eggs and Parastichopus nigripunctatus sperm, the hybrid embryos developed into auricularia larvae with a post-oral ciliary band. This indicates that the paternal line influences their morphology because this band is not present in A. japonicus. These larvae subsequently metamorphosed into the pentactula and juvenile developmental stages. In crosses between A. japonicus eggs and Cucumaria japonica sperm, the auricularia-like larvae developed into two forms that had different hydrocoel and ciliary band positions. Thus, this larval development type involves a change in the body axes (i.e. dorsal–ventral and right–left). The generation of two larval forms also suggests that the egg fertilized genetically heterogeneous spermatozoa. These results demonstrate that larvae from congeneric crosses have an indirect developmental style (i.e. a long-feeding larva stage). Larvae from interspecific crosses also had indirect developmental styles during ontogenesis but failed to metamorphose to the pentactula and juvenile stages.

Pengaruh Pemberian Garam (NaCl) terhadap Kerusakan Telur Argulus Japonicus &lt;br&gt;&lt;i&gt;[Effect of Salt (NaCl) Against Damage of Argulus japonicus Egg]&lt;i&gt;

Abstract A. japonicus is a freshwater parasite which belonging as obligate parasite. Prevention and control of A. japonicus attacks still used an insecticides, such as organophosphates and other chemicals which are used as a control. The chemicals can damage environment and around the ecosystems. Salt (NaCl) can be used as control of A. japonicus infestation. NaCl is often used as A. japonicus control. The residues effect of using NaCl in fish culture is not known clearly. Therefore, NaCl can still be known as safety chemicals for aquaculture activities. This study aimed to inhibit hatching rate of A. japonicus. Definition the damage of egg is difference the egg condition from early condition and not whole return. In addition to, the damage process is refer to osmose dehydration. The study method was done by experiment with the experimental design was used Completely Randomized Design (CRD) with six treatments and five replicates. NaCl which used are 60 g/l, 70 g/l, 80 g/l, 90 g/l, 100 g/l and control. The main parameter is the percentage of hatching rate of A. japonicus. The support parameter on the research are otemperature (C), pH, DO (mg/l). Data analysis is using Analysis of Variance (ANOVA). The results showed that dipping with NaCl the influence of damage of A. japonicus eggs, but the analysis statistic did not provide the real difference treatment.

Distribution of moon jellyfish Aurelia aurita in relation to summer hypoxia in Hiroshima Bay, Seto Inland Sea

Biological and physical surveys were conducted in order to investigate the relationship between environmental conditions and the distribution of moon jellyfish Aurelia aurita in Hiroshima Bay, western Seto Inland Sea, Japan. Moon jellyfish and ichthyoplankton were collected at 13 stations in Hiroshima Bay during monthly surveys from July to September in 2006 and 2007. Surface temperature in 2006 was significantly lower during the August and September cruises and surface salinity was lower during all cruises than in 2007. Moon jellyfish was the most dominant gelatinous plankton collected, accounting for 89.7% in wet weight. Mean moon jellyfish abundance in 2006 was higher than that in 2007 from July through September, with significant inter-year differences for July and September. Variability in precipitation and nutritional input from the Ohta River, northernmost part of Hiroshima Bay, were suggested as possible factors affecting the inter-annual variability in moon jellyfish abundance in the coastal areas of northern Hiroshima Bay. Moon jellyfish were more abundant in the coastal areas of northern Hiroshima Bay, where the dissolved oxygen (DO) concentration was lower, while low in the central part of the bay. Japanese anchovy Engraulis japonicus eggs were most dominant (58.1% in number) among the ichthyoplankton and were abundant in the central area of Hiroshima Bay. Explanatory analysis was conducted to detect possible effects of environmental conditions on the abundance of moon jellyfish and Japanese anchovy eggs during the summer months in Hiroshima Bay. Of the environmental conditions tested (temperature, salinity and DO of surface and bottom layers at each sampling station), bottom DO had the most significant effect on the moon jellyfish abundance: there was a negative correlation between the bottom DO and the moon jellyfish abundance in Hiroshima Bay during summer.

Comparison of laboratory-reared eggs, embryos and larvae of five labrid fishes

Eggs, embryos and larvae of five labrid fishes, Thalassoma cupido, Pteragogus flagellifer, Pseudolabrus japonicus, Halichoeres tenuispinnis, and H. poecilopterus, reared in the laboratory are described and compared. The eggs were buoyant and spherical, with a single, spherical oil globule. P. japonicus eggs were unique in lacking melanophores on the oil globule. Eggs of the remaining species closely resembled each other, except in diameter. Incubation periods were short, ranging from ca. 19 h in H. poecilopterus to ca. 31 h in P. japonicus. The newly-hatched embryos also resembled each other, having a short tail and large oval or pear-shaped yolksac, the anterior tip of which extended beyond the snout. The single oil globule was located at the anterior tip of the yolk. As the yolksac diminished with growth, its anterior tip moved posteriorly. The yolk and oil globule were completely absorbed 3 or 4 days after hatching. In all free embryos and larvae except for Pteragogus flagellifer, needle-like projections appeared on both the dorsal and anal finfold margins 12 h to 1 day after hatching. Although morphology of free embryos and larvae of all five species was very similar, differences in pigmentation, location of the anus, and the needle-like projections were apparent. Artificial keys to the newly-hatched embryos and larvae are given.

Quantitative analysis of the process and propagation of cortical granule breakdown in sea urchin eggs.

Cortical granule breakdown in sea urchin eggs has been investigated with a video microscope system using Nomarski differential interference contrast optics, when induced by fertilization, microinjecting inositol 1,4,5-trisphosphate (IP3) or Ca-EGTA buffer solution into the egg, or perfusing a medium containing 1 mM Ca2+ to isolated cortices. The cortical granule increased up to 1.2 times in diameter and broke down within 40 msec. These values were almost constant among the three methods used to induce cortical granule breakdown. Upon fertilization, the cortical granule breakdown propagated over the egg surface at a speed of 3.3 microns/sec in Clypeaster japonicus eggs, which indicates that cortical granule breakdown propagated through the 3.3-microns-wide egg surface within 1 sec. In such a small area of the egg surface, however, it took much more than 1 sec for all cortical granules to break down because the maximal rate of breakdown was 7.6%/sec; that is, it took 9 sec and 18 sec for 50% and 90% respectively, of cortical granules to break down. Moreover, the rate did not simply decrease with time, and a shoulder was found during the reducing phase, which suggests that cortical granules are divided into fast and slow breakdown groups according to the responsiveness to the breakdown stimulus. The cortical granule breakdown induced by microinjecting the Ca-EGTA buffer and IP3 solutions propagated at 68 microns/sec and 35 microns/sec, respectively. The stimulus for cortical granule breakdown is discussed concerning the transient intracellular Ca2+ increase.