ABSTRACT
In this study, we investigated the growth dynamics and otolith shape asymmetry of two fish species, Chrysichthys nigrodigitatus (CN) and Oreochromis niloticus (ON), within urbanized watersheds of the southern lagoon system, Nigeria. Using the von Bertalanffy growth model (VBGM), in addition to sediment metal concentration indices such as the average shale content, index of geoaccumulation (Igeo), contamination factor (CF), pollution load index (PLI), and potential ecological risk (PER) index, contamination levels were classified, and ecological risks were assessed. Notably, a lower growth potential (t0) was observed in CN at Ikorodu than at Epe, with similar trends for ON in the Epe during the dry season. Otolith asymmetry patterns, particularly in the CN at Ikorodu and ON in the Epe during the dry season, exhibited distinct ecological variations, indicating heightened stress levels at Ikorodu. Sediment analyses revealed moderate to strong contamination (Cd, Pb, Ni, and Cr) in both Lagos Lagoon (Ikorodu) and Epe Lagoon, with Ikorodu exhibiting notably high to moderate contamination levels according to the CF index. Elevated PLI values for Cd and Pb in Ikorodu, in addition to greater PER, indicated increased risk, with Cd posing a high risk (61.42%) and Pb posing a moderate risk (49.50%). Additionally, the reduced asymptotic length in the Epe during the dry season suggests that Chrysichthys nigrodigitatus is adaptable to seasonal variations, while divergent growth patterns in both areas indicate the existence of trade-off mechanisms in response to changing conditions. Habitat-specific otolith asymmetry and metal contamination underscore species adaptability, with wider stressor variability in Lagos than in Epe. Furthermore, multidimensional scaling analysis highlights the intricate relationship between otolith shape variables and environmental factors, emphasizing the need for tailored conservation efforts in urbanized watersheds.
Subject(s)
Cichlids , Environmental Monitoring , Otolithic Membrane , Urbanization , Water Pollutants, Chemical , Animals , Cichlids/growth & development , Nigeria , Otolithic Membrane/growth & development , Water Pollutants, Chemical/analysis , Geologic Sediments/chemistry , SeasonsABSTRACT
Ocean acidification could modify the bioavailability and chemical properties of trace elements in seawater, which could affect their incorporation into the calcareous structures of marine organisms. Fish otoliths, biomineralized ear stones made by aragonite, are suspended within the endolymph fluid of teleosts, indicating that the elemental incorporation of otoliths might also be susceptible to ocean acidification. In this study, we evaluated the combined effects of CO2-induced ocean acidification (pH 8.10, 7.70, and 7.30, corresponding to ocean acidification scenarios under the representative concentration pathway 8.5 model as projected by the Intergovernmental Panel on Climate Change) and water elemental concentrations of strontium (Sr) and barium (Ba; low, medium, and high) on elemental incorporation into otoliths of the flounder Paralichthys olivaceus at early life stages. Our results revealed that the elemental incorporation of Sr and Ba into otoliths was principally dependent on the corresponding water elemental concentrations rather than on ocean acidification. Moreover, the partition coefficients (DMe) of Sr and Ba may stabilize after dynamic equilibrium is reached as the water elemental concentration increases, but are not affected by ocean acidification. Therefore, the incorporation of Sr and Ba into otoliths of the flounder at early life stages may not serve as an effective indicator of ocean acidification. In other words, the findings suggest that ocean acidification does not impact the incorporation of Sr and Ba incorporation into otoliths when tracing the temperature or salinity experiences of the flounder. Our findings will provide new knowledge for understanding the potential ecological effects of ocean acidification on the recruitment dynamics of fish species.
Subject(s)
Barium , Flounder , Otolithic Membrane , Seawater , Strontium , Animals , Strontium/analysis , Otolithic Membrane/chemistry , Otolithic Membrane/growth & development , Barium/analysis , Seawater/chemistry , Flounder/growth & development , Hydrogen-Ion Concentration , Carbon Dioxide , Flatfishes/growth & development , Flatfishes/metabolism , Climate Change , Ocean AcidificationABSTRACT
Otolith shape is often used as a tool in fish stock identification. The goal of this study was to experimentally assess the influence of changing temperature and ontogenic evolution on the shape component of the European seabass (Dicentrarchus labrax) otolith during early-life stages. A total of 1079 individuals were reared in a water temperature of 16°C up to 232 days post hatch (dph). During this experiment, several specimens were transferred into tanks with a water temperature of 21°C to obtain at the end of this study four different temperature treatments, each with varying ratios between the number of days at 16 and 21°C. To evaluate the otolith morphogenesis, samples were examined at 43, 72, 86 and 100 dph. The evolution of normalized otolith shape from hatching up to 100 dph showed that there were two main successive changes. First, faster growth in the antero-posterior axis than in the dorso-ventral axis changed the circular-shaped otolith from that observed at hatching and, second, increasing the complexity relating to the area between the rostrum and the anti-rostrum. To test the effect of changing temperature, growing degree-day was used in three linear mixed-effect models. Otolith morphogenesis was positively correlated to growing degree-day, but was also dependent on temperature level. Otolith shape is influenced by environmental factors, particularly temperature, making it an efficient tool for fish stock identification.
Subject(s)
Bass , Morphogenesis , Otolithic Membrane , Temperature , Animals , Otolithic Membrane/growth & development , Bass/growth & development , Bass/physiology , Bass/anatomy & histologyABSTRACT
Japanese flounder Paralichthys olivaceus is one of the most valuable coastal flatfish species in East Asia. To investigate post-settlement growth and mortality, juveniles were sampled in Tango Bay (Japan) weekly throughout the settlement period in 2007 and 2008. Otolith (lapillus) microstructure analysis enabled the categorization of juveniles into six biweekly cohorts each year. Later cohorts exhibited higher growth rates possibly because of higher water temperatures. A key observation was the direct relationship between high mortality and high density in mid-season cohorts in both years, pointing to density-dependent mortality. This increased mortality may be attributed to predation, including cannibalism by earlier cohorts. Furthermore, growth-selective mortality was evident soon after settlement, underscoring the vulnerability of slow growers to predation during the early juvenile stage. Although earlier and later cohorts were less abundant but showed promising recruitment potential, the prospective contribution of mid-season cohorts to the adult population remained uncertain. The results clearly highlight the importance of density-dependent mortality in population regulation in post-settlement Japanese flounder.
Subject(s)
Flounder , Seasons , Animals , Flounder/growth & development , Flounder/physiology , Japan , Population Dynamics , Bays , Population Density , Otolithic Membrane/growth & development , MortalityABSTRACT
The age and daily growth of fish are registered through the deposition of increments in their otoliths, which are concretions formed by the precipitation of substances present in the endolymphatic fluid, mainly calcium carbonate (CaCO3). Faced with the need to fill some of the gaps in the knowledge on the occurrence and duration of the initial stages of snapper species' life cycles in the Abrolhos Bank, this study aimed to describe the growth rates, age, and period of pelagic larval duration (PLD) of three snapper species during the larval pre-settlement phase, in the Abrolhos Bank region. The post-larvae were captured using light traps. Otoliths were removed from 117 samples of snapper species; however, only 69 were viable for age estimation, of which 15 were Lutjanus analis, 25 were Lutjanus jocu, and 29 were Lutjanus synagris. Together, the samples presented individuals with total lengths ranging from 16.14 to 24.76 mm and ages from 21 to 39 days. Settlement marks were found for all three species, and the average PLD was ~25 days. The somatic growth of the snapper species was positively correlated with otolith growth. L. jocu presented the greatest daily growth compared to the other species. The three species use the Abrolhos Bank as a larval settlement site, demonstrating plasticity by using different habitats throughout their lives.
Subject(s)
Larva , Otolithic Membrane , Animals , Larva/growth & development , Otolithic Membrane/growth & development , Otolithic Membrane/chemistry , Perciformes/growth & development , Parks, Recreational , Perches/growth & development , Perches/physiologyABSTRACT
Growth and maximum age are two key parameters that inform resilience of fish populations to exploitation. Existing information on those for greater weever inhabiting the eastern North Sea is based on the analysis of whole otoliths. Here, we present a reanalysis using sectioned otoliths. The results reveal a different growth pattern and a higher maximum age than that previously reported. The higher maximum age makes greater weever populations more vulnerable to exploitation. Such information can serve as a basis for the estimation of the growth curve that can be used for future assessment of the species.
Subject(s)
Otolithic Membrane , Animals , Otolithic Membrane/growth & development , Otolithic Membrane/chemistry , North Sea , Perciformes/growth & developmentABSTRACT
To date the study of ocean acidification on fish otolith formation has been mainly focused on larval and juvenile stages. In the present pilot study, wild-captured adult Atlantic cod (Gadus morhua) were exposed to two different levels of pCO2, 422µatm (ambient, low pCO2) or 1091µatm (high pCO2), for a period of 30 weeks (from mid-October to early April 2014-2015) in order to study the effects on otolith size, shape and CaCO3 crystallization amongst other biological parameters. We found that otoliths from cod exposed to high pCO2 were slightly smaller (- 3.4% in length; - 3.3% in perimeter), rounder (- 2.9% circularity and + 4% roundness) but heavier (+ 5%) than the low pCO2 group. Interestingly, there were different effects in males and females; for instance, male cods exposed to high pCO2 exhibited significant changes in circularity (- 3%) and roundness (+ 4%) compared to the low pCO2 males, but without significant changes on otolith dimensions, while females exposed to high pCO2 had smaller otoliths as shown for length (- 5.6%), width (- 2%), perimeter (- 3.5%) and area (- 4.8%). Furthermore, while the majority of the otoliths analysed showed normal aragonite deposition, 10% of fish exposed to 1091µatm of pCO2 had an abnormal accretion of calcite, suggesting a shift on calcium carbonate polymorph crystallization in some individuals under high pCO2 conditions. Our preliminary results indicate that high levels of pCO2 in adult Atlantic cod might affect otolith growth in a gender-specific way. Our findings reveal that otoliths from adult cod are affected by ocean acidification, and we believe that the present study will prompt further research into this currently under-explored area.
Subject(s)
Calcium Carbonate , Carbon Dioxide/adverse effects , Gadus morhua , Otolithic Membrane , Animals , Calcium Carbonate/chemistry , Female , Hydrogen-Ion Concentration , Male , Otolithic Membrane/growth & development , Pilot Projects , Seawater/chemistryABSTRACT
Scorpaeniformes are an important component of commercial and recreational fisheries world-wide. The Neosebastes species, found in the western Pacific and south-east Indian Ocean, have received little attention from a research perspective. Samples of the bighead gurnard perch, Neosebastes pandus, collected from the lower west and south coasts of Western Australia, were used to undertake the first comprehensive investigation of the biological characteristics of a Neosebastes species. Opaque zones in sectioned sagittal otoliths were validated as forming annually. Female N. pandus grow to a significantly larger size, on average, than males and dominate the largest size classes, while males, growing to a smaller size, accumulate in the intermediate size classes. Although males were far less numerous than females in those age classes in which both sexes were found, males and females attain similar maximum ages >25 years. Neosebastes pandus spawns over a brief period between May (austral late autumn) and July (austral mid-autumn) when water temperature and day length are declining. The mean monthly gonadosomatic indices (GSI, IGS ) values of females during the spawning period are 37-50 times higher than those of males, which mature at an earlier age and smaller length compared to females. Histological examination of the ovaries of females indicate that their structure is consistent with "general" teleost ovarian anatomy and thus differs from Scorpaena, Helicolenus and Sebastes species whose ovaries are adapted for specialized reproductive modes. The reproductive strategy of N. pandus of maximizing the reproductive output of females, by this sex attaining a larger size than males and pair spawning (i.e., large disparity in IGS values) demonstrates the close lineage between the Neosebastes and other Scorpaeniformes, such as the Scorpaena, Helicolenus and Sebastes.
Subject(s)
Body Size/physiology , Life History Traits , Perciformes/growth & development , Reproduction , Animals , Female , Fisheries , Indian Ocean , Male , Otolithic Membrane/growth & development , Ovary/anatomy & histology , Perciformes/anatomy & histology , Reproduction/physiology , Seasons , Sex Characteristics , Western AustraliaABSTRACT
The Chilean jack mackerel (Trachurus murphyi) is a predominantly Southeast Pacific Ocean species. It is relatively difficult to determine its age, and multiple studies of its growth off South America have produced markedly different sets of von Bertalanffy parameters. T. murphyi was first identified from New Zealand waters in the mid-1980s and has comprised part of the commercial landings of Trachurus species (along with Trachurus declivis and Trachurus novaezelandiae) since then. Results from 13 years of age determination of New Zealand samples using sectioned otoliths indicate that a partially validated age determination method has been developed, with a precision level (average percentage error) of 4.6%. The best available von Bertalanffy growth parameters for the New Zealand population (sexes combined) are as follows: L∞ , 51.9 cm fork length; K, 0.223 per year; t0 , -0.5 year. Analyses by sex showed that males have a significantly larger L∞ than females. Estimated annual catch-at-length and catch-at-age distributions from the fishery are presented for 2007-2019. There have been at least two episodes of immigration of T. murphyi from international waters, but little evidence of spawning success to maintain the New Zealand population.
Subject(s)
Otolithic Membrane/growth & development , Perciformes/physiology , Animal Distribution , Animals , Female , Male , New Zealand , Pacific Ocean , Perciformes/growth & developmentABSTRACT
Somatic growth is a critical biological trait for organismal, population, and ecosystem-level processes. Due to its direct link with energetic demands, growth also represents an important parameter to estimate energy and nutrient fluxes. For marine fishes, growth rate information is most frequently derived from sagittal otoliths, and most of the available data stems from studies on temperate species that are targeted by commercial fisheries. Although the analysis of otoliths is a powerful tool to estimate individual growth, the time-consuming nature of otolith processing is one barrier for collection of comprehensive datasets across multiple species. This is especially true for coral reef fishes, which are extremely diverse. Here, we provide back-calculated size-at-age estimates (including measures of uncertainty) based on sagittal otoliths from 710 individuals belonging to 45 coral reef fish species from French Polynesia. In addition, we provide Von Bertalanffy growth parameters which are useful to predict community level biomass production.
Subject(s)
Body Size , Coral Reefs , Fishes/growth & development , Otolithic Membrane/growth & development , Animals , Biomass , PolynesiaABSTRACT
Otolith biochronologies combine growth records from individual fish to produce long-term growth sequences, which can help to disentangle individual from population-level responses to environmental variability. This study assessed individual thermal plasticity of Atlantic cod (Gadus morhua) growth in Icelandic waters based on measurements of otolith increments. We applied linear mixed-effects models and developed a century-long growth biochronology (1908-2014). We demonstrated interannual and cohort-specific changes in the growth of Icelandic cod over the last century which were mainly driven by temperature variation. Temperature had contrasting relationships with growth-positive for the fish during the youngest ages and negative during the oldest ages. We decomposed the effects of temperature on growth observed at the population level into within-individual effects and among-individual effects and detected significant individual variation in the thermal plasticity of growth. Variance in the individual plasticity differed across cohorts and may be related to the mean environmental conditions experienced by the group. Our results underscore the complexity of the relationships between climatic conditions and the growth of fish at both the population and individual level, and highlight the need to distinguish between average population responses and growth plasticity of the individuals for accurate growth predictions.
Subject(s)
Gadus morhua/growth & development , Otolithic Membrane/growth & development , Temperature , Age Factors , Animals , IcelandABSTRACT
Age-reading of fish otoliths (ear stones) is important for the sustainable management of fish resources. However, the procedure is challenging and requires experienced readers to carefully examine annual growth zones. In a recent study, convolutional neural networks (CNNs) have been demonstrated to perform reasonably well on automatically predicting fish age from otolith images. In the present study, we carefully investigate the prediction rule learned by such neural networks to provide insight into the features that identify certain fish age ranges. For this purpose, a recent technique for visualizing and analyzing the predictions of the neural networks was applied to different versions of the otolith images. The results indicate that supplementary knowledge about the internal structure improves the results for the youngest age groups, compared to using only the contour shape attribute of the otolith. However, the contour shape and size attributes are, in general, sufficient for older age groups. In addition, within specific age ranges we find that the network tends to focus on particular areas of the otoliths and that the most discriminating factors seem to be related to the central part and the outer edge of the otolith. Explaining age predictions from otolith images as done in this study will hopefully help build confidence in the potential of deep learning algorithms for automatic age prediction, as well as improve the quality of the age estimation.
Subject(s)
Fishes/growth & development , Neural Networks, Computer , Otolithic Membrane/growth & development , Animals , Otolithic Membrane/anatomy & histologyABSTRACT
Slender sole Lyopsetta exilis is an abundant groundfish on the continental shelf and inner waters of British Columbia, Canada, where it reaches a maximum standard length of 44 cm. Benthic image surveys coupled with oxygen measurements in Saanich Inlet document a dense population in bottom conditions near anoxia (0.03 ml l-1 oxygen) where diel migrating zooplankton intersect the bottom; we confirm this species is a planktivore, which limits its depth range to the base of the migration layer. In a comparison with slender sole from a nearby well-oxygenated habitat, several probable effects of living in severe hypoxia emerge: both sexes are significantly smaller in Saanich and the sex ratio is male-skewed. Otoliths from the Saanich fish were difficult to read due to many checks, but both sexes were smaller at age with the largest female (20 cm) from the hypoxia zone registering 17 years. Hypoxia appears to have a direct consequence on growth despite good food supply in this productive basin. Hyperventilation, a low metabolic rate and a very low critical oxygen tension help this fish regulate oxygen uptake in severely hypoxic conditions; it will be particularly resilient as the incidence of hypoxia increases on the continental shelf. Data from small-mesh bottom-trawl surveys over four decades reveal an increase in mean annual catch per unit effort in southern regions of the province, including the outer shelf and the Strait of Georgia. The California Cooperative Oceanic Fisheries Investigations (CalCOFI) ichthyoplankton database records a general decline in fish larvae on the Oregon-California shelf since 1990, but slender sole larvae are increasing there, as they are in the Strait of Georgia. We project that the slender sole will gain relative benefits in the future warming, deoxygenated northeast Pacific Ocean.
Subject(s)
Flounder , Hypoxia , Animals , Body Size , British Columbia , Climate Change , Ecosystem , Flounder/anatomy & histology , Flounder/growth & development , Flounder/metabolism , Otolithic Membrane/anatomy & histology , Otolithic Membrane/growth & development , Oxygen/metabolism , Pacific Ocean , Population Dynamics , Sex Ratio , Stress, Physiological , Water/chemistryABSTRACT
This study examines age and growth of Brauer's lanternfish Gymnoscopelus braueri and rhombic lanternfish Krefftichthys anderssoni from the Scotia Sea in the Southern Ocean, through the analysis of annual growth increments deposited on sagittal otoliths. Otolith pairs from 177 G. braueri and 118 K. anderssoni were collected in different seasons from the region between 2004 and 2009. Otolith-edge analysis suggested a seasonal change in opaque and hyaline depositions, indicative of an annual growth pattern, although variation within the populations of both species was apparent. Age estimates varied from 1 to 6 years for G. braueri (40 to 139 mm standard length; LS ) and from 0 to 2 years for K. anderssoni (26 to 70 mm LS ). Length-at-age data were broadly consistent with population cohort parameters identified in concurrent length-frequency data from the region for both species. The estimated values of von Bertalanffy growth curves for G. braueri were L∞ = 133.22 mm, k = 0.29 year-1 and t0 = -0.21 year and the values for K. anderssoni were L∞ = 68.60 mm, k = 0.71 year-1 and t0 = -0.49 year. There were no significant (P > 0.05) differences in growth between sexes for either species, suggesting that males and females have similar growth and development trajectories in the Scotia Sea. A positive allometric relationship between LS and wet mass was found for each species, as well as a significant (P < 0.0001) linear relationship between otolith size and LS . Growth performance (Ф') was similar between the two species and congruent with other myctophid species across the Southern Ocean. This study provides important parameters for future Southern Ocean ecosystem studies in a resource management context.
Subject(s)
Fishes , Otolithic Membrane/growth & development , Age Distribution , Animals , Antarctic Regions , Body Size , Conservation of Natural Resources , Ecosystem , Female , Fishes/anatomy & histology , Fishes/classification , Fishes/growth & development , Food Chain , Male , Oceans and Seas , Otolithic Membrane/anatomy & histology , SeasonsABSTRACT
This paper examines the life history of humpback red snapper Lutjanus gibbus, an important fishery species for coastal communities across the Indo-Pacific, in southern New Caledonia, where the species is lightly exploited. A total of 243 L. gibbus were sampled between January 2013 and December 2016 from occasional harvests of commercial fishers. Examination of sectioned otoliths revealed that opaque increment formation occurred annually between November and March, coinciding with the species' spawning season. Estimates of maximum age were similar between sexes, with observed ages of 38 and 36 years for females and males, respectively, extending the reported longevity of this species by at least 11 years. Growth differed significantly between sexes, with males reaching greater length at age and greater asymptotic length than females (38.88 v. 31.46 cm fork length (LF ). Total mortality for all samples was estimated as 0.13 and was slightly higher for males (0.16) than females (0.11). Estimates of natural and fishing mortality were low and slightly higher for males than females. Male L. gibbus were found to mature at slightly greater lengths and younger ages than females, with the length and age at which 50% of individuals attained maturity estimated to be 25.8 cm LF and 3.9 years of age for females and 26.8 cm LF and 3.4 years of age for males. The results provide key baseline information from which to assess the effect of fishing on the species for populations in New Caledonia and adjacent locations and, when viewed with those of other studies, highlight the importance of understanding spatial patterns in demography of harvested fish species across gradients of exploitation and environmental influences.
Subject(s)
Longevity , Perciformes/growth & development , Animals , Female , Fisheries , Male , New Caledonia , Otolithic Membrane/growth & development , Reproduction , Seasons , Sex RatioABSTRACT
Variation in the life cycle of diadromous fishes can be explained by differential food availability between marine and freshwater habitats, since migration is often interpreted as a mechanism for exploiting food resources. Theoretically, a migration pattern of mainly remaining in freshwater occurs in tropical and subtropical habitats where fluvial productivity possibly exceeds marine productivity. However, in Yakugachi River, Amami-Oshima Island, southern Japan, low nutrient concentrations in the river suggest that food availability is limited for the subtropical Ryukyu-ayu Plecoglossus altivelis ryukyuensis. Since Ryukyu-ayu is an amphidromous fish that mainly grows in rivers after spending 2 months in the sea, limited food availability in rivers would force this species to migrate to other habitats with better food availability. Otolith increment and Sr:Ca analyses of 48 adult Ryukyu-ayu collected from the Yakugachi River revealed that all individuals visited estuaries more than three times after moving upstream. Although the specific growth rates of this species in the river had no correlation with the salinity profile in the fluvial period, this movement may be an adaptive choice because the salinity profile significantly affected the body size at maturity. Our results highlighted individual-based variations in amphidromous migration for utilizing estuaries, which could be explained by relatively higher productivity in estuarine than in freshwater and marine habitats.
Subject(s)
Ecosystem , Estuaries , Life Cycle Stages , Osmeriformes/growth & development , Animal Migration , Animals , Body Size , Japan , Otolithic Membrane/growth & development , Rivers , SalinityABSTRACT
Genypterus brasiliensis, a demersal fish of large size (1.3 m of total length), occurs in the southwest Atlantic (23 to 38oS) and well appreciated due to the quality of its flesh. It was analyzed through longline and trawl fisheries, and the average length and weight of 724 specimens were significantly different between them, with the biggest and heaviest specimens caught by the former. The weight-length relationships were significantly different based upon sex: females Wt=4x10-7Lt3.3799; r2=0.97; n=262; p<0.001, and males: Wt=4x10-7Lt3.3886; r2=0.95; n=190; p<0.001. Using the otoliths readings for 153 specimens (APE of 2% and CV of 4.2%), the growth parameters estimates reveal statistical differences between sexes (p=0.05; r2=0.889). The fisheries were composed of individuals aged 1 to 13 (females) and 1 to 14 years old (males), with ring formation in late spring. The back calculated parameters (VBGF) were: Loo=1,452.38 mm, K=0.0996, t0=-0.2757 yr-1 (females) and Loo=983.07 mm, K=0.155, t0=-0.236 yr-1 (males), and longevity as 29.8 and 19.1 years old, respectively. The low biological production allied to the slow growth and a late complete maturation and its endemism, allow classify G. brasiliensis as a vulnerable resource, jeopardizing a sustainable fishery. Until reliable quantitative biological data are available, precautionary management must be considered.
Subject(s)
Fisheries/statistics & numerical data , Fishes/growth & development , Life History Traits , Animals , Atlantic Ocean , Body Weight/physiology , Brazil , Female , Longevity , Male , Otolithic Membrane/growth & development , Population Dynamics , Sex CharacteristicsABSTRACT
Otolith consisting largely of calcium carbonate, ï¬brous and proteins, is vital for maintaining body balance and/or hearing of fish. The formation of otolith involves Ca2+ transport and deposition. In the present study, we investigated the effects of Cd2+ on otoliths development by using zebrafish embryos as model. The results showed that exposure to Cd2+ inhibited the utricular and saccular otoliths growth, indicated by reduced lateral areas. Swimming speeds were reduced and a losing balance control was observed in Cd2+ exposed larvae. The genes related to Ca2+ transport (e.g. plasma membrane Ca2+-ATPase isoform 2, pmca2; Ca2+-ATPase isoform 2, atp2b1a) and regulation (e.g. parathyroid hormone ligand type-1, pth1; stanniocalcin isoform 1, stc1) were significantly downregulated. However, the adverse effects of Cd2+ on otoliths growth and swimming activity can be protected by supplementation of Ca2+ in exposure medium. Body burden of Cd2+ in larvae was reduced upon the supplement with Ca2+. The overall results suggest that exposure to Cd2+ can inhibit influx of Ca2+, leading to less deposition of CaCO3 for otolith growth, and finally result in impaired balance control and swimming activity in zebrafish larvae.
Subject(s)
Behavior, Animal , Cadmium/toxicity , Environmental Exposure , Otolithic Membrane/growth & development , Zebrafish/physiology , Animals , Behavior, Animal/drug effects , Calcium/analysis , Larva/drug effects , Motor Activity/drug effects , Otolithic Membrane/drug effects , Time Factors , Toxicity Tests , Transcription, Genetic/drug effects , Water Pollutants, Chemical/toxicity , Zebrafish/embryology , Zebrafish/genetics , Zebrafish Proteins/geneticsABSTRACT
Otolith growth increments in wild-caught alizarin complex one (ALC)-marked honmoroko Gnathopogon caerulescens were examined to verify the veracity of the age determination method in cyprinids. ALC-marked G. caerulescens recaptured from their natural environment had lapilli increment counts outside the ALC ring mark that had formed on a daily basis during the juvenile stage. This apparently being the first direct evidence of daily periodicity of otolith increment formation in wild-caught cyprinids.
Subject(s)
Cyprinidae/growth & development , Otolithic Membrane/growth & development , Animals , Anthraquinones , Environment , Fisheries , Fluorescent DyesABSTRACT
This assesses features of otoliths from laboratory-reared embryos, larvae and juvenile European chub Squalius cephalus from hatching to 180 days post-hatching (dph). We observed the development of the three pairs of otoliths (lapilli, sagittae and asterisci) and more precisely shape changes, as well as timing and deposition rate of increments of the lapilli. The lapilli and the sagittae were present at hatching, whereas the asterisci formed between 20 and 30 dph. The lapillus and sagitta shapes were round until 20 dph. From 60 dph the anterior and the posterior rostra of the sagittae were well developed, but very thin, making this otolith too fragile to manipulate for further studies of shape and validation of otolith increment deposition rate. The lapilli provided reliable age estimates for free embryos, larvae and juveniles up to 120 dph. However, caution should be taken when ageing fish older than 150 dph as an underestimation was noticeable. The regression of the number of otolith increments on age showed a slope and an intercept not significantly different from 1 and 0, respectively, which indicated that otolith growth increments were deposited on a daily basis, with the first microincrement occurring at hatching. Increment counts were consistent between three interpreters, indicating a consistent and reliable age estimate. This study validates that the otolith increment deposition rate can be used to assess hatching dates and daily growth of wild S. cephalus under 150 dph and in environments similar to the conditions used in this study.