Inflated Swim Bladders Research Articles

Spawning, egg and larval description of the brazilian basslet Gramma brasiliensis Sazima, Gasparini & Moura, 1998 in captivity.

Brazilian basslet Gramma brasiliensis is a fish highly appreciated by the marine ornamental industry. There is an increasing interest in the development of a breeding protocol for this species. However, descriptions of the reproductive biology, eggs and larval development are scarce. This study was the first to describe the spawning, eggs and larvae of G. brasiliensis in captivity, including mouth size information. Six spawning events produced egg masses with 27, 127, 600, 750, 850, and 950 eggs. Larger egg masses showed embryos with at least two different developmental stages. Eggs are spherical (∼1.0 mm diameter), held together by filaments entangling chorionic projections. Larvae with fewer than 12 hph (hours post-hatch) presented 3.55 mm standard-length, well developed eyes, fully absorbed yolk sac, an inflated swim bladder and mouth opened. Exogenous feeding on rotifers began within 12 hph. The average mouth width at first feeding was 0.38 mm. The first settled larva was noted by day 21. This information should help to determine appropriate diets and prey-shift time during the larviculture of the species.

First Results on Spawning and Larval Rearing of the Brown Meagre (Sciaena umbra)

The aim of the present study is to investigate spawning and larval rearing of brown meagre (Sciaena umbra). This is an important species in the Mediterranean Sea because of its beauty, calm swimming, large otoliths, souvenir potential, aggregative behaviour, excellent flesh and accessibility. Although this species is regarded as Near Threatened (in IUCN Red List Status), the demand increases the fishing. Green water technique was used for rearing the brown meagre larvae. Diameter of eggs was recorded as 1457.31±47.29 µm. Yolk was homogenous with oil globules of 371.59±18.15 µm at the centre. Hatching process began after 39 hours. Hatching rate (HR) was observed as 92.17±0.24%, and larvae inflated swim bladder around 97.33±0.94%. The brown meagre juveniles reached to 40.08±1.98 mm of total length (TL) with 10.96±0.08 mm body height (BH) and 662.27±21.23 mg body weight (BW) after 55 days of post-hatching. Survival (SR) was recorded as 72.5±0.70% at the end of study. Since the brown meagre is a threatened species, with high economic interest, is a possible candidate for commercial aquaculture both food and restocking the depleted natural fisheries.

Analysis of sinking death using video images of the swimming performance of Pacific Bluefin tuna (Thunnus orientalis) larvae

In this study, we aimed to clarify the mechanism of sinking death during the larval stage of Pacific Bluefin tuna Thunnus orientalis by investigating the effects of swimming performance on sinking death, using a behavioral approach. Swimming performance was examined 3–9 days after hatching (DAH) under day and night light conditions in cuboid experimental tanks. Swimming behavior variables such as swimming speed and swimming angle were measured under both light conditions. Larvae in the daytime experiment and larvae with inflated swim bladders at night were distributed on the surface layer of the water column. In contrast, larvae with uninflated swim bladders at night were frequently observed swimming vertically or sinking to the bottom of the tank. Larvae with inflated swim bladders at night were always distributed beneath the surface until the next morning (survival rates were 100 %). However, larvae with uninflated swim bladders at night swam upward repeatedly and later sank to the bottom of the tank (survival rates were 60 % and 38 % at 5 and 9 DAH, respectively). Larvae with uninflated swim bladders were not always able to maintain their swimming depth by swimming until the next morning. Additionally, their swimming speed and vertical swimming frequency (ratio) depended on the illumination and swim bladder conditions. Our findings show that larvae with uninflated swim bladders at night were associated with a higher risk of sinking death. The swimming energy capacity of Pacific Bluefin tuna larvae, which indicates the total amount of the energy that enables individuals to swim throughout the night without feeding, was found to be linked to sinking death.

A novel approach for induced out-of-season spawning of Eurasian perch, Perca fluviatilis

In this study, the systematic development of a protocol allowing an effective advanced spawning of wild Eurasian perch with the use of salmon gonadoliberin analogue (sGnRHa) was undertaken. The novel approach used in this study involved the application of a strategy of the repeated administration of sGnRHa (i.e., the hormone was given in two doses: priming and resolving) along with an additional thermal stimulation of ovulation. Additionally, the developed protocol was tested for its suitability in the controlled reproduction of domesticated broodstock. The obtained results suggested that the best interval between the hormonal treatments is 7 days when a water temperature of 10 °C is kept constant between the two injections and when the resolving injection is followed by rapid increments of temperature up to 12 °C, at which spawning is expected. This study revealed that the most suitable priming dose of sGnRHa was 10 μg kg−1, at which the highest embryonic survival rates (>80%) and spawning efficiency indexes (>500 larvae kg−1) (SEI: representing the number of larvae with an inflated swim bladder obtained from 1 kg of a spawned female) were recorded. Furthermore, in most cases, the application of the resolving injection yielded an embryonic survival rate of over 85% with the highest ovulation rate (100%) and SEI values observed in the group injected with 10 and 25 μg kg−1 at the priming and resolving doses, respectively. Repeated administrations of sGnRHa were more effective than a previous strategy typically applied for the induction of ovulation in Eurasian perch (a single application of sGnRHa or human chorionic gonadotropin). Moreover, the protocol applied to wild perch can be fully transferrable to domesticated broodstock, which makes it a valuable tool for the improvement of controlled reproduction of this species for intensive aquaculture purposes.

CB1 and CB2 receptors play differential roles in early zebrafish locomotor development.

Endocannabinoids (eCBs) mediate their effects through actions on several receptors, including the cannabinoid receptors CB1R and CB2R. The role played by eCBs in the development of locomotor systems is not fully understood. In this study, we investigated the roles of the eCB system in zebrafish development by pharmacologically inhibiting CB1R and CB2R (with AM251 and AM630, respectively) in either the first or second day of development. We examined the morphology of motor neurons and we determined neuromuscular outputs by quantifying the amount of swimming in 5days post-fertilization larvae. Blocking CB2R during the first day of development resulted in gross morphological deficits and reductions in heart rate that were greater than those following treatment with the CB1R blocker AM251. Blocking CB1Rs from 0 to 24h post-fertilization resulted in an increase in the number of secondary and tertiary branches of primary motor neurons, whereas blocking CB2Rs had the opposite effect. Both treatments manifested in reduced levels of swimming. Additionally, blocking CB1Rs resulted in greater instances of non-inflated and partially inflated swim bladders compared with AM630 treatment, suggesting that at least some of the deficits in locomotion may result from an inability to adjust buoyancy. Together, these findings indicate that the eCB system is pivotal to the development of the locomotor system in zebrafish, and that perturbations of the eCB system early in life may have detrimental effects.

Alcalase enzyme treatment affects egg incubation and larval quality in pikeperch (Sander lucioperca)

Although egg de-adhesion has been the subject of research in pikeperch of late, the possible effect of this technological procedure on larval viability under intensive rearing conditions has not yet been evaluated. The aim of the present study was to evaluate the effect of the Alcalase enzyme on egg incubation and larviculture success compared to a commonly used procedure with milk and kaolin clay suspension. Preliminary research was conducted in order to find the minimal exposure time of eggs in Alcalase enzyme solution for the total elimination of adhesiveness. Further on, stripped eggs from three females were divided into two equal portions, and each portion was treated according to the abovementioned procedures. Efficiency of the procedures was evaluated and compared through egg incubation and larviculture. Alcalase-treated eggs exhibited significantly shorter incubation time (121 ± 12 h vs. 157 ± 10 h), hatching period (16 ± 7 h vs. 48 ± 21 h) and lower embryo survival (82.5 ± 2.4% vs. 87.7 ± 1.4%) with a significantly higher hatching rate (98.5 ± 1.0% vs. 72.0 ± 35.3 %). The larviculture yielded significantly lower production efficacy in eggs treated with Alcalase manifested as the share of larvae with an inflated swim bladder in the total number of stocked eggs (5.8 ± 2.4%) compared to larvae hatched in eggs treated with milk and kaolin (20.1 ± 11.9%). The Alcalase enzyme treatment reduced the incubation time and diminished the larval performance; therefore, its application in eggs of pikeperch should be reconsidered.

Swim bladder inflation failure affects energy allocation, growth, and feed conversion of California Yellowtail (Seriola dorsalis) in aquaculture

This study examines the effects of swim bladder inflation failure, a common developmental abnormality in finfish aquaculture, on the energy allocation, growth, and development of California Yellowtail (Seriola dorsalis). Health and fitness metrics including oxygen consumption, aerobic scope, critical swimming speed, feed conversion ratio, and growth rate, were monitored over a 32-week growout period in three groups of S. dorsalis: aquaculture-reared fish that failed to inflate their swim bladders (uninflated), aquaculture-reared fish with properly inflated swim bladders (inflated), and wild-caught individuals (wild). After the growout period, the uninflated fish had significantly lower body mass (636.1 ± 80.4 g vs. 758.6 ± 92.7 g inflated), shorter body length (36.5 ± 1.9 cm vs. 39.6 ± 2.0 cm inflated), and smaller girth (21.5 ± 1.2 cm vs. 23.2 ± 1.1 cm inflated) than the inflated fish. In addition, the uninflated fish had the least efficient feed conversion ratio (2.08 uninflated vs. 1.49 inflated, 1.41 wild), needing 39.8% more feed than the inflated fish, and 47.8% more feed than the wild fish to gain equivalent mass. These differences in growth and feed conversion appear to be primarily attributed to differences in energy allocation. Measures of oxygen consumption using a swim tunnel respirometer at two time points during the growout period showed that uninflated fish had significantly higher metabolic costs than both the inflated and wild groups over a large range of the swimming speeds tested. In addition, the uninflated fish were often observed swimming faster in their growout tank, likely to generate enough lift to compensate for the lack of a buoyant swim bladder. The wild-caught fish had the lowest feed conversion ratios and had significantly lower metabolic costs than both the inflated and uninflated aquaculture-reared fish at the beginning of the growout period (shortly after capture from the wild). The results of this study show that rearing S. dorsalis without a functional swim bladder is not economically feasible based on their poor growth and feed conversion ratios, and suggest that there is room for improvement in the metabolic efficiency of cultured S. dorsalis with properly inflated swim bladders.

Osteological development and deformities in hatchery-reared longtooth grouper (Epinephelus bruneus ): Vertebral column, dorsal-fin supports and caudal-fin skeleton

Skeletal deformities are one of the serious problems in hatchery-reared longtooth grouper (Epinephelus bruneus). In this study, seed production of longtooth grouper was carried out in four large hatchery-grade tanks. Osteological development of the vertebral column, caudal-fin skeleton and dorsal-fin supports in larvae and juveniles was described. The vertebral ontogeny started at 4.8 mm total length (TL) with the formation of neural spines 2 and 3, and the vertebral centra began forming at 5.3 mm TL. By 16 mm TL, all vertebral bony elements were formed except for the dorsal ribs. The onsets of the ontogeny of the caudal-fin skeleton and dorsal-fin supports occurred at approximately 5.1 mm and 3.9 mm TL, respectively, and the completion of these bony elements occurred at approximately 20 mm TL. The incidence of deformity was examined; some type of deformity was observed in 57%–68% of the specimens. These deformities mainly occurred as three types: lordosis, around vertebrae 1–5; saddleback-like syndrome, around vertebrae 7–11; and vertebrae fusion, around vertebrae 22–24. The incidence of prehaemal lordosis was significantly higher among individuals with an uninflated swim bladder than among those with an inflated swim bladder.

Toxicity of effluents from gasoline stations oil-water separators to early life stages of zebrafish Danio rerio

Used petroleum hydrocarbons and gasoline stations runoff are significant sources of polycyclic aromatic hydrocarbons (PAHs) to aquatic ecosystems. Samples of the final effluent of oil-water-separators were collected at gasoline stations in the metropolitan region of Recife, Brazil, before release to sewage or rainwater systems. Effluent soluble fractions (ESF) were prepared and bioassays were performed according to the Fish Embryo Toxicity Test. The test involved exposing zebrafish Danio rerio embryos to dilutions of the ESFs for 96 h, with daily examination of lethality and sublethal morphological effects integrated through the General Morphology Score (GMS), based on the achievement of developmental hallmarks. Frequencies of abnormalities were recorded after exposures. ESF LC50-96h (lethal concentration to 50% of exposed embryos) in the most toxic effluent achieved 8.9% (v/v), equivalent to 11 μg phenanthrene equivalents L−1. GMS scores indicated significantly delayed embryo-larval development at ESF dilutions of 10% and 20% from effluents of all gas stations. Major abnormalities detected after the 96 h exposure included the presence of a yolk sac not fully absorbed coupled with the lack of an inflated swim bladder, lack of both pectoral fins, and the failure to develop a protruding mouth. Effective equivalent PAH concentrations that induce a 50% frequency of larvae without an inflated swim bladder (EC50) were 4.9 μg phenanthrene L−1, 21.8 μg naphthalene L−1, and 34.1 μg chrysene L−1. This study shows that PAHs in ESFs from gas stations oil water separators are toxic to zebrafish, contributing to the toxicity of urban storm waters.

Swim bladder inflation as a possible cause of saddleback-like syndrome malformation in hatchery-reared red spotted grouper Epinephelus akaara

Saddleback-like syndrome is one of the most frequently observed malformations in hatchery-reared red spotted grouper Epinephelus akaara. Saddleback-like syndrome is characterized by a V-shaped dorsal-profile depression behind the head region accompanied by deformities or misalignments of the first to fourth neural spines on the vertebral column and the first to fourth pterygiophores of the dorsal fin. Abnormal swim bladder inflation in several finfish species leads to malformations, particularly of the vertebral column. The present study examined the influence of swim bladder inflation on saddleback-like syndrome in hatchery-reared red spotted grouper. The incidence of saddleback-like syndrome increased as swim bladder inflation rate increased. Additionally, the incidence of saddleback-like syndrome among juveniles with inflated swim bladders was significantly higher than that among juveniles with uninflated swim bladders. The larval swim bladder is located just below the first to fifth vertebrae and the first to fifth dorsal spines, where saddleback-like syndrome occurs. Our results suggest that an inflated swim bladder increases the risk of saddleback-like syndrome in hatchery-reared red spotted grouper.

Dive to survive: effects of capture depth on barotrauma and post-release survival of Atlantic cod (Gadus morhua) in recreational fisheries

Abstract Atlantic cod (Gadus morhua) caught in recreational fisheries are commonly released, often with barotrauma after rapid decompression. Mouth-hooked, non-bleeding cod kept in a floating net pen showed mortalities ≥40% when angled from >50 m depth, likely because of cumulative stress from ongoing barotrauma and exposure to warm surface water. In a natural setting, however, cod have the opportunity to descend after release and are not restricted to the surface. In a follow-up study, 97.8% of similarly selected cod managed to dive following immediate release, whereas 2.2% were floaters. No mortality was observed for divers kept in cages, which were lowered to capture depth for 72 h. While the floaters would likely have died in a natural setting, no mortality was observed when they were recompressed and kept at capture depth for 72 h. The occurrence of swim bladder ruptures, swollen coelomic cavities, venous gas embolisms, and gas release around the anus was significantly influenced by capture depth (range 0–90 m). A supplementary radiology study showed inflated swim bladders in 87% of the cod after 72 h, and most barotrauma signs had disappeared after 1 month. This study encourages investigation of survival potential for physoclistous species when high mortalities are assumed but undocumented. Matching natural post-release and containment environment is essential in the experimental setup, as failure to do so may bias survival estimates, particularly when a thermocline is present. Assuming minimal predation, short-term mortality of cod experiencing barotrauma is negligible if cod submerge quickly by themselves and are otherwise not substantially injured. Survival of floaters may be increased by forced recompression to capture depth. Sublethal and long-term impacts of barotrauma remain to be studied. To ensure that cod have sufficient energy to submerge, anglers are encouraged to avoid fighting the fish to exhaustion and to minimize handling before release.

Effect of water surface condition on survival, growth and swim bladder inflation of yellowfin tuna,Thunnus albacares(Temminck and Schlegel), larvae

Early-stage mortality due to surface water tension-related death and due to sinking to the tank bottom was investigated for yellowfin tuna, Thunnus albacares (YFT), larvae. Different aeration rates and rearing water surface conditions were examined to evaluate the effect on larval survival, swim bladder inflation and growth. The percentage survival of yolk sac larvae was significantly higher when the rearing water surface was covered with fish oil at aeration rates of 0 and 50 mL min−1. The highest mortality occurred at the highest aeration rate of 250 mL min−1 regardless of surface water condition. A second experiment was conducted twice under different water surface conditions: the water surface was covered by fish oil (FO), skimmed of fish oil (SS), and was not treated (NC). The percentage survival was not significantly different between treatments after 7 days of feeding. In contrast to the survival, the proportion of larvae with inflated swim bladders was significantly higher for the NC and SS groups than that of the FO group. Results of these experiments indicate that the addition of oil to the rearing water surface without its removal interferes with the initial swim bladder inflation in YFT larvae. These results also indicate that YFT larvae need to obtain (gulp) air at the water surface for initial swim bladder inflation, and success of initial swim bladder inflation may be crucial for their survival.

PFOS affects posterior swim bladder chamber inflation and swimming performance of zebrafish larvae

Perfluorooctane sulphonate (PFOS) is one of the most commonly detected perfluorinated alkylated substances in the aquatic environment due to its persistence and the degradation of less stable compounds to PFOS. PFOS is known to cause developmental effects in fish. The main effect of PFOS in zebrafish larvae is an uninflated swim bladder. As no previous studies have focused on the effect of PFOS on zebrafish swim bladder inflation, the exact mechanisms leading to this effect are currently unknown. The objective of this study was to determine the exposure windows during early zebrafish development that are sensitive to PFOS exposure and result in impaired swim bladder inflation in order to specify the mechanisms by which this effect might be caused. Seven different time windows of exposure (1–48, 1–72, 1–120, 1–144, 48–144, 72–144, 120–144h post fertilization (hpf)) were tested based on the different developmental stages of the swim bladder. These seven time windows were tested for four concentrations corresponding to the EC-values of 1, 10, 80 and 95% impaired swim bladder inflation (EC1=0.70mgL−1, EC10=1.14mgL−1, EC80=3.07mgL−1 and EC95=4.28mgL−1). At 6 days post fertilization, effects on survival, hatching, swim bladder inflation and size, larval length and swimming performance were assessed. For 0.70mgL−1, no significant effects were found for the tested parameters while 1.14mgL−1 resulted in a reduction of larval length. For 3.07 and 4.28mgL−1, the number of larvae affected and the severity of effects caused by PFOS were dependent on the time window of exposure. Exposure for 3 days or more resulted in significant reductions of swim bladder size, larval length and swimming speed with increasing severity of effects when the duration of exposure was longer, suggesting a possible effect of accumulated dose. Larvae that were only exposed early (1–48hpf) or late (120–144hpf) during development showed no effects on the studied endpoints. The results demonstrate that PFOS does not affect the budding phase, and does not cause deflation of already inflated swim bladders. PFOS clearly affects processes that take place during the inflation phase and might also have an effect on the formation of the tissue layers forming the swim bladder.

Ontogeny of swim bladder inflation and caudal fin aspect ratio with reference to vertical distribution in Pacific bluefin tuna Thunnus orientalis larvae

It is necessary to understand the processes involved in sinking death in Pacific bluefin tuna Thunnus orientalis aquaculture in order to develop methods to prevent or minimize this problem. We observed the nighttime vertical distribution of Pacific bluefin tuna in the water column on 2–9 DAH and the morphological characteristics of the larvae, in order to clarify the processes involved in sinking death. A cuboid tank (height 300 cm) was used to measure vertical distribution. The number of larvae was counted in each of 4 regions in the observation tank: upper layer (water depth 0–100 cm), middle layer (100–200 cm), lower layer (200–300 cm), and bottom area. The distribution of larvae in these regions at 4 days after hatching was polarized to the upper layer and bottom area. Individuals with inflated swim bladders were observed in the upper layer 3 days after hatching. No larvae with inflated swim bladders were observed in the bottom area on any day after hatching. Total body length and caudal fin aspect ratio of larvae with both inflated and un-inflated swim bladders were greater in the upper layer than those of larvae in the bottom area. Larvae with un-inflated swim bladders that failed to develop sufficiently for swimming sank to the tank bottom and died. Swim bladder development and caudal fin swimming ability are strongly related to sinking death.

Relationship between uninflated swim bladder and skeletal anomalies in reared gilthead seabream (Sparus aurata)

Abstract The higher mortalities and lower morphological quality of juveniles with a non-inflated swim bladder still remain a major problem in intensive farming. The aim of this study was to investigate a possible relationship between the presence of an abortive swim bladder and skeleton anomalies in gilthead seabream juveniles. A batch of 109 DAH (LS range: 16–47 mm) gilthead seabream was split into two groups on the basis of the presence (SB group)/absence (WSB group) of a normally inflated swim bladder, and processed for skeletal anomaly and meristic count analysis. The presence of pectoral fin anomalies and the absence of any clear-cut and sound relationship between abortive swim bladder and axis deviations characterize the WSB group. Rarer anomalies, such as scoliosis and lordosis in the pre-haemal vertebrae, kyphosis in the haemal vertebrae, pre-haemal and haemal vertebrae body anomalies, exclusively affected the WSB seabream. This result contradicts what is observed in other species, where abortive swim bladder is shown to cause axis deviation. The authors hypothesize that when gilthead seabream larvae with uninflated swim bladder encounter difficulty in maintaining the level in the water column, they have to overuse flapping of the pectoral fins (which appear more deformed in the seabream without swim bladder of this study). This determines a hyper-activity of the pectoral muscles, which then exerts an intense mechanical load on pre-haemal muscles and ossifying vertebrae. Vertebrae and axis anomalies in the pre-haemal and in haemal (in this study still rare in the WSB lot) regions may be later effects, as postural consequences due to the uninflated swim bladder.

Developmental toxicity of thyroid-active compounds in a zebrafish embryotoxicity test.

Zebrafish embryos were exposed to concentration ranges of selected thyroid-active model compounds in order to assess the applicability of zebrafish-based developmental scoring systems withinan alternative testing strategy to detect the developmental toxicity ofthyroid-active compounds. Model compounds tested included triiodothyronine (T3), propylthiouracil (PTU), methimazole (MMI), sodium perchlorate (NaClO4) and amiodarone hydrochloride (AMI), selected to represent different modes of action affecting thyroid activity. Tested time windows included 48-120 hours post fertilization (hpf), 0-72 hpf and 0-120 hpf. All tested compounds resulted in developmental changes, with T3 being the most potent. The developmental parameters affected included reflective iridophores, beat and glide swimming, inflated swim bladders, as well as resorbed yolk sacs. These effects are only evident by 120 hpf and therefore an existing General Morphology Score (GMS) system was extended to create a General Developmental Score(GDS) that extends beyond the 72 hpfscoring limit of GMS and includes additional parameters that are affected by exposure to model thyroid-active compounds. Moreover, the GDS is cumulative as it includes not only the scoring of developmental morphologies but also integrates developmental dysmorphologies. Exposures from 48-120 hpf did not provide additional information to exposures from 0-120 hpf. The results indicate that the zebrafish GDS can detect the developmental toxicity of thyroid toxicants and may be of use in an integrated testing strategy to reduce, refine and in certain cases replace animal testing.

Use of the swim bladder and lateral line in near-field sound source localization by fishes

We investigated the roles of the swim bladder and the lateral line system in sound localization behavior by the plainfin midshipman fish (Porichthys notatus). Reproductive female midshipman underwent either surgical deflation of the swim bladder or cryoablation of the lateral line and were then tested in a monopolar sound source localization task. Fish with nominally 'deflated' swim bladders performed similar to sham-deflated controls; however, post-experiment evaluation of swim bladder deflation revealed that a majority of 'deflated' fish (88%, seven of the eight fish) that exhibited positive phonotaxis had partially inflated swim bladders. In total, 95% (21/22) of fish that localized the source had at least partially inflated swim bladders, indicating that pressure reception is likely required for sound source localization. In lateral line experiments, no difference was observed in the proportion of females exhibiting positive phonotaxis with ablated (37%) versus sham-ablated (47%) lateral line systems. These data suggest that the lateral line system is likely not required for sound source localization, although this system may be important for fine-tuning the approach to the sound source. We found that midshipman can solve the 180 deg ambiguity of source direction in the shallow water of our test tank, which is similar to their nesting environment. We also found that the potential directional cues (phase relationship between pressure and particle motion) in shallow water differs from a theoretical free-field. Therefore, the general question of how fish use acoustic pressure cues to solve the 180 deg ambiguity of source direction from the particle motion vector remains unresolved.

Effect of feeding rotifers enriched with taurine on the growth and survival of larval amberjack Seriola dumerili

The effect of feeding rotifers enriched with taurine on the growth performance and survival of larval amberjack Seriola dumerili was investigated. Rotifers were enriched with a commercial taurine supplement at four levels (0, 200, 400, and 800 mg/l). The larvae were fed the enriched rotifers in triplicate from 3 days post-hatch for 7 days under static conditions. The average taurine contents of the rotifers were 1.5, 2.7, 4.2, and 7.2 mg/g dry matter, respectively. The growth of the fish fed rotifers enriched with the taurine supplement at 800 mg/l was significantly (P < 0.05) improved compared with that of the fish fed the rotifers without taurine enrichment. The survival rate improved proportionally up to a taurine supplement level of 400 mg/l, but no significant differences in survival were observed among treatments. The fraction of the larvae with inflated swim bladders did not vary significantly between treatments. Taurine content in the whole fish body increased with the taurine level in the rotifers. These results suggest that taurine enrichment of rotifers is an effective method of enhancing the growth of amberjack larvae.

Ahr2-dependence of PCB126 effects on the swim bladder in relation to expression of CYP1 and cox-2 genes in developing zebrafish

The teleost swim bladder is assumed a homolog of the tetrapod lung. Both swim bladder and lung are developmental targets of persistent aryl hydrocarbon receptor (AHR22Zebrafish cytochrome P450 family 1 genes/mRNAs and proteins are referred to as CYP1 and CYP1 according to Nelson et al. (1996). For other genes/mRNAs and proteins in zebrafish we have followed the approved guidelines for zebrafish, e.g., ahr2 and Ahr2 (https://wiki.zfin.org/display/general/ZFIN+Zebrafish+Nomenclature+Guidelines). The aryl hydrocarbon receptor is denoted AHR when not referring to a particular species.) agonists; in zebrafish (Danio rerio) the swim bladder fails to inflate with exposure to 3,3′,4,4′,5-pentachlorobiphenyl (PCB126). The mechanism for this effect is unknown, but studies have suggested roles of cytochrome P450 1 (CYP1) and cyclooxygenase 2 (Cox-2) in some Ahr-mediated developmental effects in zebrafish. We determined relationships between swim bladder inflation and CYP1 and Cox-2 mRNA expression in PCB126-exposed zebrafish embryos. We also examined effects on β-catenin dependent transcription, histological effects, and Ahr2 dependence of the effect of PCB126 on swim bladder using morpholinos targeting ahr2. One-day-old embryos were exposed to waterborne PCB126 or carrier (DMSO) for 24h and then held in clean water until day 4, a normal time for swim bladder inflation. The effects of PCB126 were concentration-dependent with EC50 values of 1.4 to 2.0nM for induction of the CYP1s, 3.7 and 5.1nM (or higher) for cox-2a and cox-2b induction, and 2.5nM for inhibition of swim bladder inflation. Histological defects included a compaction of the developing bladder. Ahr2-morpholino treatment rescued the effect of PCB126 (5nM) on swim bladder inflation and blocked induction of CYP1A, cox-2a, and cox-2b. With 2nM PCB126 approximately 30% of eleutheroembryos33Fish embryos that have hatched but are still dependent on yolk as a nutrition source are technically “eleutheroembryos”, but for simplicity we will refer to them generically as “embryos” for the remainder of this paper. Once independent feeding begins (days 6–7 post fertilization in zebrafish), the fish are then called larvae. failed to inflate the swim bladder, but there was no difference in CYP1 or cox-2 mRNA expression between those embryos and embryos showing inflated swim bladder. Our results indicate that PCB126 blocks swim bladder inflation via an Ahr2-mediated mechanism. This mechanism seems independent of CYP1 or cox-2 mRNA induction but may involve abnormal development of swim bladder cells.

Oocyte quality indicators in Eurasian perch, Perca fluviatilis L., during reproduction under controlled conditions

This study examined embryo survival and viability of Eurasian perch, Perca fluviatilis L., larvae in relation to the fragmentation of oil droplets in ovulated oocytes. The study was conducted after controlled reproduction. Four (I–IV) categories of egg-ribbons quality were distinguished, based on the degree of oil droplet fragmentation (where at least one oil droplet with minimum 0.39 mm diameter were certified in all oocytes in egg-ribbon — categories I and II) and percentage of eggs with highly fragmented oil droplets (where diameter of oil droplets did not exceed 0.35 mm — categories III and IV) in the egg-ribbon. The dynamics of survival and some morphological parameters were investigated during embryonic and larval development up to 10 days post-hatch (DPH), under laboratory conditions. The laboratory-obtained results were compared to semi-commercial incubation and initial larval rearing. The fragmentation of oil droplets was accompanied by a decrease in egg quality. Oil droplets were found to coalesce after activation of eggs in water and during incubation process. Thus, the presented categorization may be used in non-activated eggs only. In both experiments, at 10 DPH the percentages of feeding larvae and those with an inflated swim bladder were recorded. The best results of laboratory-conducted incubation were obtained in category I and II (92.80 and 74.20% in the eyed-egg stage respectively). In category IV, the mortality rate of embryos exceeded 90%. The highest body deformation rate of freshly hatched larvae was observed in category III (67.86%) and IV (86.14%) that was related with fragmentation of oil droplets. These results were confirmed under semi-commercial conditions. The obtained results indicate that the proposed categorization may be a valuable tool for the quality evaluation of Eurasian perch egg-ribbons. It could be successfully applied in both commercial fish production and scientific activity.