Body Length Ratio Research Articles

Body Morphometry and Development of the Digestive System of Grey Partridge (Perdix Perdix) Depending on Age and Gender

ABSTRACT The experiment used 100 grey partridges (Perdix perdix L.), which were reared first in confinement and later in aviaries. Partridges were lighter and had greater body dimensions at 36 weeks compared to 12 weeks except for trunk length. Older birds showed greater values (p>0.05) of compactness and lower values of massiveness and long-leggedness. Significant differences were found for keel length in females. At 36 weeks, male and female partridges had significantly greater total intestinal length, males had significantly longer small intestine and rectum, and females were characterized by significantly longer caeca and greater (p<0.05) intestine to body length ratio. Older birds had significantly greater gizzard weight and percentage and heart percentage (males and females), as well as significantly lower liver weight (males) and spleen weight and percentage. The present study provided information on the growth and development of farmed grey partridges before release into the natural environment.

The constant threat from a non-native predator increases tail muscle and fast-start swimming performance in Xenopus tadpoles.

ABSTRACTPredator-induced phenotypic plasticity is the ability of prey to adapt to their native predator. However, owing to environmental changes, encounters with unknown predators are inevitable. Therefore, study of prey and non-native predator interaction will reveal the primary stages of adaptive strategies in prey-predator interactions in the context of evolutionary processes. Here, Xenopus tadpoles exposed to a non-native predator, a larval salamander, showed a significant increase in body weight and tail length to body length ratio. The Tmax2 test indicated a significant enhancement of the tail muscle and decrease in the relative ventral fin height in tadpoles exposed to predation risk, leading to significantly higher average swimming speeds. The analysis of muscle-related metabolites revealed that sarcosine increased significantly in tadpoles exposed to non-native predators. Multiple linear regression analysis of the fast-start swimming pattern showed that the fast-start swimming speed was determined by the time required for a tadpole to bend its body away from the threat (C-start) and the angle at which it was bent. In conclusion, morphological changes in tadpoles were functionally adaptive and induced by survival behaviors of Xenopus tadpoles against non-native predators.

A re-description of Longicyatholaimus maldivarum Gerlach, 1964 (Nematoda, Cyatholamidae) with an emended identification key of the genus

Longicyatholaimus maldivarum was a species erected by Gerlach in 1964 from specimens found in the Maldivian archipelago. Due to the finding of additional representatives of this species, L. maldivarum is re-described with the addition of new morphological details mainly about males, because the information about female in the original description are very scarce. The newly found specimens showed a total body length higher than in the type specimens (1936–2063 µm vs. 1330 µm long) as well as the ratio of the total body length divided by maximum body diameter (22–28 vs. 27). The multispiral amphideal fovea showed 5 turns vs. 4 turns and Gerlach did not notice the presence of sub-ventral teeth that were clearly observed in the present specimens. The copulatory apparatus that perfectly matched the Gerlach description showed a central lamella mainly visible under confocal microscopy. A slightly lower ratio of the spicule length divided by anal body diameter (1 vs. 1.4) and longer gubernaculum (25–32 vs. 25 µm long) were noticed as well. Pre-cloacal supplements appeared very interesting for the presence of stout and conical setae protruding from cup-shaped structures. Supplements were more than in type species (8–9 vs. 7). Also the tail revealed some differences with a lower ratio of its total length divided by anal body diameter 6 vs. 7–8. The current list of 15 valid species of the genus was reduced to 10 species. In detail, we considered Longicyatholaimus heterurus and Longicyatholaimus sp. 3 species inquirendae for the absence of male specimens in the original description. We also excluded L. filicaudatus and L. tenuicaudatus because they were considered species inquirendae by Wieser &amp; Hopper (1967) and L. zosterae because it was transferred by Lorenzen (1972) to the genus Paralongicyatholaimus. The new morphological details observed for Longicyatholaimus maldivarum and the modified number of valid species of the genus required also a revision of the identification key.

Experimental study on the effect of turbulence in pipelines on the mortality of Limnoperna fortunei veligers

Golden mussels (Limnoperna fortunei), an invasive species of Mytilidae, settle on the inside surfaces of water pipelines with high density, often resulting in heavy biofouling and pipe clogging. The species invades pipelines during its planktonic veliger stage, which is apt to be killed by high frequency turbulence produced by turbulence-generating materials (TGMs), such as pore plates, which can be installed inside the pipelines. However, little is known about the influence of different types of TGMs on the pipeline hydraulics and veliger-killing mechanism. An experimental study was conducted to investigate the veliger-killing mechanism and pick out the most efficient TGM for veliger killing and prevention of golden mussel invasion in pipelines. Four types of TGMs, plates with hole diameters of 3mm (PP3) and 6mm (PP6) and wires with mesh spacings of 3mm (WM3) and 2mm (WM2), were installed in a 12.6m-long experimental pipeline with sparse (space between two PP or WM=50cm) and intensive (space=25cm) layouts. The flow field downstream of the TGMs was measured by an Acoustic Doppler Velocimeter (ADV). The experimental results revealed that the TGMs caused a short disturbance both transversely and longitudinally downstream. The disturbance was significant for PP6 and weakened for the intensive layout. The WMs exhibited little influence on the discharge capacity of the pipe and enhanced the downstream flow velocity within a short distance for the intensive layout. The distribution of the downstream turbulence intensity of the TGMs presented a uniform transverse pattern except for WM2. The TGMs enlarged the frequency of the dissipation range in the energy spectra for turbulence and consequently reduced the length scale of the dissipative eddies, i.e. the Kolmogorov length scale. A positive relation was identified between the downstream (d*)max (the maximum ratio of the veliger body length to the Kolmogorov length) and the killing rate (increase of the veliger mortality rate after treated by the turbulence generated in the experimental pipeline). The test results indicated that the veliger community would be heavily damaged when the dissipation range (the Kolmogorov scale) had a similar or smaller length scale than the veliger body length. Therefore, (d*)max was considered to be a representative indicator for the evaluation of the killing effect of TGMs. The TGM could be considered to have high and steady killing capacity if (d*)max>1. PP6 with a sparse layout is recommended for the control of golden mussel veligers considering both the killing efficiency and economic efficiency.

A strategy to apply quantitative epistasis analysis on developmental traits

BackgroundGenetic interactions are keys to understand complex traits and evolution. Epistasis analysis is an effective method to map genetic interactions. Large-scale quantitative epistasis analysis has been well established for single cells. However, there is a substantial lack of such studies in multicellular organisms and their complex phenotypes such as development. Here we present a method to extend quantitative epistasis analysis to developmental traits.MethodsIn the nematode Caenorhabditis elegans, we applied RNA interference on mutants to inactivate two genes, used an imaging system to quantitatively measure phenotypes, and developed a set of statistical methods to extract genetic interactions from phenotypic measurement.ResultsUsing two different C. elegans developmental phenotypes, body length and sex ratio, as examples, we showed that this method could accommodate various metazoan phenotypes with performances comparable to those methods in single cell growth studies. Comparing with qualitative observations, this method of quantitative epistasis enabled detection of new interactions involving subtle phenotypes. For example, several sex-ratio genes were found to interact with brc-1 and brd-1, the orthologs of the human breast cancer genes BRCA1 and BARD1, respectively. We confirmed the brc-1 interactions with the following genes in DNA damage response: C34F6.1, him-3 (ortholog of HORMAD1, HORMAD2), sdc-1, and set-2 (ortholog of SETD1A, SETD1B, KMT2C, KMT2D), validating the effectiveness of our method in detecting genetic interactions.ConclusionsWe developed a reliable, high-throughput method for quantitative epistasis analysis of developmental phenotypes.

Two new species of digeneans (Lecithasteridae and Haploporidae) of the intertidal blenny Scartichthys viridis (Valenciennes) from the central coast of Chile.

Two new digenean species are described from the intertidal blenny Scartichthys viridis (Valenciennes) (Blenniidae) collected off the coasts of Chile. The digenean Monorchimacradena viridis n. sp. (Lecithasteridae: Macradenininae) differs from the only known species described in the genus, M. acanthuri Nahhas and Cable 1964, in the presence of Drüsenmagen in the caeca, the location of the seminal vesicle between the testis and ovary (anterior to the testis in M. viridis n. sp.), and the pre-ovarian vitellarium. Megasolena littoralis n. sp. (Haploporidae), which is also reported from Scartichthys gigas (Steindachner), differs from the five valid species of Megasolena in that the post-caecal region (from the posterior edge of the caeca to the end of the body) is larger in M. viridis n. sp., meaning that the caeca are shortest in this species. Also, M. littoralis n. sp. is distinguished, from the other congeneric species, in a combination of characteristics, e.g., body length, suckers, pharynx, testes, hermaphroditic sac and sucker-length ratio. Sequences of ITS2 rDNA were generated for specimens of both species from various localities, indicating that it was invariant within the species. This study describes species of Monorchimacradena and Megasolena in Chilean waters, here reported for the first time off the Pacific Coast of South America.

Evolution of body morphology and beak shape revealed by a morphometric analysis of 14 Paridae species.

BackgroundMorphological characters of birds reflect their adaptive evolution and ecological requirements and are also relevant to phylogenetic relationships within a group of related species. The tits (Paridae) are known to be outwardly homogeneous in shape, with one aberrant member, the Ground Tit (Pseudopodoces humilis), which is quite different from its relatives in both body morphology and beak shape. We combined traditional measurements and geometric morphometrics to quantify the variation in body morphology and beak shape of 14 Paridae species distributed in China. Based on these results, we sought to assess the contribution of phylogeny, altitude and species interactions to the evolution of morphological traits.ResultsThe basic features for discriminating among the 14 species studied here were overall body size, the ratio of body and tail length to culmen and tarsus length, and beak shape (long/slender/pointy vs. short/robust/blunt). These dimensions clearly separate Ps. humilis and Melanochlora sultanea from the other species in shape space. Body length and PC3 of beak shape (round outline vs. straight outline) show significant phylogenetic signals. Across 14 species, altitude is related to tarsus, culmen length and PC1 of beak shape. Within Parus major, altitude is related to body weight, body length, culmen length and PC1 of body morphology. Morphological distances and geographic distances among species are positively correlated.ConclusionsThe body morphology of Paridae species shows extensive evolutionary changes, while their beak has mainly evolved along the long/slender/pointy vs. short/robust/blunt dimension. Only body length and beak curvature show a phylogenetic signal. Altitude correlates with multiple traits both across and within species, suggesting that altitude is an important factor in promoting morphological divergence. The deviant appearance of Ps. humilis corresponds to its foraging and feeding adaptations to high-altitude steppe habitats. Our results also show a higher level of morphological divergence with greater difference in distribution ranges among the Paridae species involved in this study.Electronic supplementary materialThe online version of this article (doi:10.1186/s12983-016-0162-0) contains supplementary material, which is available to authorized users.

A new species of the genus Oreonectes (Cypriniformes: Nemacheilidae)from Guizhou, China.

This study examined the morphological and phylogenetic characteristics of Oreonectes shuilongensis sp. nov. The genus Oreonectes is distributed only in southwestern China and northern Vietnam. Sixteen specimens of cavefish were captured in the Shuilong Township in Guizhou Province of China and identified as a new species of Oreonectes (Cypriniformes: Nemacheilidae). Maximum likelihood was used to construct phylogenetic trees based on data for Nemacheilidae species accessible on GenBank. Molecular phylogenetic analyses showed that O. shuilongensis is closely related to O. platycephalus from which it is distinguished by having 6 vs. 5 branched anal rays, ratio of body length to body height 7.0-7.9 vs. 5.6-7.0, ratio of head length to distance between eyes 3.5-4.9 vs. 2.0-2.4, naked vs. scaly body, densely distributed fine black stains except on abdomen, and semitransparent body. Oreonectes shuilongensis is the only species of the genus not distributed in Guangxi Province. This study has contributed to the overall knowledge about the distribution of Oreonectes.

Re-description of Echiniscus cavagnaroi Schuster & Grigarick, 1966 (Tardigrada: Heterotardigrada: Echiniscoidea: Echiniscidae) from type material, with new records from Hawaii and Bermuda.

The description of Echiniscus cavagnaroi Schuster & Grigarick, 1966 (Tardigrada: Heterotardigrada: Echiniscoidea: Echiniscidae) is emended with new morphometric measurements of the holotype and eleven paratypes. The length of Cirrus A in the holotype (25.2 μm) was only half the 50 μm reported in the original description. Moreover, the largest values for Cirrus A length and Cirrus A to body length ratio for any specimen (40.6 μm, 21%) were also lower than in the original description. Variation in the presence or absence of spines was considerably greater than originally described. Spines C, D^d and E were not present on all specimens (C present in 67%, D^d in 67%, E in 50%). The length of spines D^d and E, when present, varied greatly among specimens. The geographical range of E. cavagnaroi is expanded by new records from the Hawaiian Islands and Bermuda. The species has been reported from southern China; however, the published description of these specimens differs markedly from type specimens in several respects. The presence of E. cavagnaroi sensu stricto in China needs to be confirmed. The high variability in presence or absence and length of spines in Echiniscus cavagnaroi underscores the importance of assessing variability in these characteristics when identifying unknown specimens or describing new species in the genus. This requires using as many specimens as possible and fully reporting variability.

Migration and population structure characteristics of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea

Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from 2003 and 2013 were employed to evaluate the variation in the resource distribution and biological characteristics (especially body length and sex ratio) in the population on a decadal scale. The results indicated that the small yellow croaker migrated from the Shawai fishing ground to the Dasha fishing ground in spring and was mainly distributed in the central and western parts of the Dasha fishing ground in April and May. Larimichthys polyactis in the Dasha fishing ground migrated eastward to offshore wintering grounds in autumn and reached the central Dasha fishing ground in October and November. The small yellow croaker entered the western waters of the Shawai fishing ground in winter. A large number of age 0+ fish occurred in the Shawai and Jiangwai fishing grounds in October of 2003 and 2013. The body lengths of the spawning stock and wintering stock in 2013 were larger than those in 2003, and the monthly sex ratios (female to male) were significantly less than 1 in both years. The monthly distribution of this fish in the southern Yellow Sea was consistent with a previous finding that “the stock migrated between the wintering grounds in the west of Jeju Island and the Lusi spawning grounds” but tended to move more northward, with the spawning grounds extending outward. In the past decade, body length variation experienced a decline after an increase, rather than a steady decrease. The sex ratio in the single-stick stow net showed a tendency to increase over the decade, but was either less than or more than 1 depending on the fishing gear; therefore, further studies should be conducted to determine the sex structure.

A new Minisauripus site from the Lower Cretaceous of China: Tracks of small adults or juveniles?

Because skeletal remains of very small theropods are delicate and rare, diminutive tracks provide valuable, additional evidence of body size. The distinctive Asian ichnogenus Minisauripus has assumed importance in this debate and has played a role in the challenging question about whether it represents a small trackmaker species or juveniles of a larger species. New discoveries of Minisauripus footprints from the Lower Cretaceous Feitianshan Formation at Yangmozu in Sichuan Province, China, support the conclusion that all known examples of this ichnotaxon are small. The main Yangmozu site reveals 65 theropod tracks (~20 trackways) of different-sized trackmakers. Three trackways, comprising 10 pes imprints of 2.5–2.6cm length, are assigned to Minisauripus. The remaining 17 trackways represent small–medium-sized theropods (track lengths 9.9–19.6cm), including one assigned to cf. Jialingpus. All unequivocally identified Minisauripus tracks from Korea (five sites) and China (three sites) fall in the size range of ~1.0–6.1cm. Assuming a small adult trackmaker, and based on standard foot length, leg length and body length ratios, all Minisauripus tracks indicate trackmakers with hip heights of <~5.0 and ~28.0cm and body lengths in the range of ~12.0–72.0cm. Based on lack of large tracks (longer than 6.1cm) at any known sites, and various precedents in the ichnological literature we infer that Minisauripus represents a small theropod species. However, we cannot completely exclude the possibility that such tracks represent juveniles of larger trackmaking species.

Use of computed tomography for measurement of kidneys in dogs without renal disease.

OBJECTIVE To determine the size of the left and right kidneys by use of CT in dogs of various breeds without evidence of renal disease. DESIGN Retrospective, observational study. ANIMALS 21 client-owned dogs. PROCEDURES Renal length, diameter of the abdominal aorta, and length of the L2 vertebral body were measured independently on multiplanar reformatted non-contrast-enhanced CT images by 3 observers at 3 time points. Intraobserver and interobserver agreement for renal length were determined. Associations of renal length with body weight, aorta diameter, and L2 vertebral body length were assessed by calculation of Pearson correlation coefficients and 95% confidence intervals. Renal measurements were normalized to patient size by calculating renal length-to-aorta diameter and renal length-to-L2 vertebral body length ratios for comparison with previously published radiographic and ultrasonographic measurements. RESULTS All kidneys were identified and measured on CT images by all observers. Intraobserver and interobserver agreement were excellent. Body weight, aorta diameter, and length of the L2 vertebral body were significantly correlated with renal length. Renal length-to-aorta diameter and renal length-to-L2 vertebral body length ratios (7.4 and 2.7, respectively) fell within the ranges of previously published values for these measurements. CONCLUSIONS AND CLINICAL RELEVANCE As CT becomes more widely available in general practice, knowledge of typical renal measurements and anatomic ratios obtained with this modality in dogs may be useful. A prospective study with a larger population of dogs, ideally including formulation of a reference range, is needed.

Investigation of a longfin inshore squid's swimming characteristics and an underwater locomotion during acceleration

In the present study, locomotion of a real longfin inshore squid (Doryteuthis pealeii) was numerically investigated. Geometry of a real squid was obtained using computed tomography (CT) images. In addition to a two-dimensional axisymmetric squid model, a modified squid model with no cavities around her head and an ellipse shaped model were generated with a fineness ratio (the ratio of body length to maximum body diameter) of 7.56. These numerical models were exposed to an acceleration with two different velocity programs. Added mass and basset forces on bodies were calculated during acceleration of the squid models starting from rest. Pressure and viscous drag forces were also calculated due to pressure variation along the squid models and friction on the surface of the models. The effect of a nozzle diameter on jet velocities and propulsive efficiency at all bodies were evaluated when time dependent velocity profiles (from 0 to 10m/s in 0.5 and 1s time durations) were set for the inlet of computational domain. The modified squid model required least thrust force during acceleration phase of time dependent velocity profile compared to the other models while the 0.02m nozzle diameter provided largest propulsive efficiency for all models.

Self-sustaining infrapopulation or colony? Redial clonal groups of Himasthla elongata (Mehlis, 1831) (Trematoda: Echinostomatidae) in Littorina littorea (Linnaeus) (Gastropoda: Littorinidae) do not support the concept of eusocial colonies in trematodes.

Trematode sporocysts and rediae reproduce by parthenogenesis, forming clonal groups in the molluscan host. It has recently become popular to consider these groups as eusocial colonies, with division of labour between rediae morphs: small 'soldiers' incapable of reproduction defend the colony, while large rediae reproduce. Alternatively, clonal groups can be considered as self-sustaining infrapopulations. We tested these two hypotheses in the light of new data on rediae of Himasthla elongata (Mehlis, 1831) from snails Littorina littorea (Linnaeus) concerning ultrastructure, growth character and composition of their groups. Clonal groups under study contained rediae of different age and maturity stages: small (young) rediae, rediae with early cercarial embryos, rediae with late embryonic cercariae, rediae with fully formed motile cercariae, rediae with redial embryos and degenerating rediae. Small rediae had a reproductive organ, the germinal mass, whereas most large rediae with developing cercariae did not, which contradicts the eusocialconcept. Overall distribution of rediae by size and by gut to body length ratio was bimodal, which agrees with the eusocial concept ('soldiers' and 'reproductives' as modal size classes). On closer inspection, however, the bimodal size-frequency distributions (SFD) turned out to be the sum of unimodal SFD of rediae at various stages of maturity. The overall bimodality was determined by the character of redial growth resulting in a relatively low occurrence of intermediate morphs and by the developmental arrest in young rediae. The facts that small rediae can attack other rediae and concentrate in the anterior parts of the mollusc can be explained by age-related feeding preferences and niche segregation. They are unlikely to be associated with the 'colony' defence against invaders. To sum up, clonal groups of H. elongata rediae in our study represented self-sustaining infrapopulations. We failed to find any arguments in favour of their eusocial organisation.

M aritrema corai n. sp. (Digenea: Microphallidae) from the white ibis Eudocimus albus (Linnaeus) (Aves: Threskiornithidae) in Mexico.

M aritrema corai n. sp. is described based on material from the intestine of the white ibis Eudocimus albus (L.) (Threskiornithidae) in Mexico. The new species can be distinguished morphologically from all congeners by the unique combination of the following morphological features: a very long cirrus sac attenuated distally [cirrus sac to body length ratio 1:0.90-1.29 (mean 1:1.07)]; a large, elongate-oval seminal receptacle, located dorsally between the cirrus sac and ovary; and long, filiform, unarmed, evaginable cirrus. Phylogenetic analyses of 28S ribosomal DNA (rDNA) sequences for the new species and for Maritrema spp. and Microphallus spp. depicted strong support for the two genera (excluding Microphallus fusiformis) and revealed close relationships between Ma. corai n. sp. and the clade formed by Maritrema novaezealandense Martorelli, Fredensborg, Mouritsen & Poulin, 2004, Maritrema heardi (Kinsella & Deblock, 1994) and Maritrema cf. eroliae.

Allometric Scaling of the Radula in the Atlantic SlippersnailCrepidula fornicata

ABSTRACT This study examined the scaling of the radula of the Atlantic slippersnail Crepidula fornicata with body size. As a suspension feeder, the prediction was that the radula may be more important (longer relative to body size) for younger animals, as younger animals are likely to also graze the benthos whereas adults primarily suspension feed. Smaller snails had a disproportionately longer radula than larger snails, likely reflecting a more important role of the radula when animals are small. Furthermore, the radula of C. fornicata is short compared with its body size among caenogastropods. This small radula to body length ratio would be expected if the radula is not used for grazing, except possibly in smaller snails.

AN INVERTEBRATE PERSPECTIVE TO HUTCHINSON’S RATIO USING CO-OCCURRING TIGER BEETLE (COLEOPTERA: CICINDELIDAE) ASSEMBLAGES

Tiger beetles co-occur for cryptic advantage, interspecific hybridization, reproductive synchrony and thermoregulation. Successful co-occurrence relies on the absence of competition and Hutchinson (1959) has proposed body size ratios for co-occurrence of bird and mammal taxa. The present study calculates body size ratios for co-occurring tiger beetle assemblages and investigates similarities with ratios for co-occurring birds and mammals. Ratios obtained using measurements of different morphological characters are considered and compared. Association of body size ratios of co-occurring tiger beetles with habitat type and number of species in co-occurring tiger beetle assemblage are determined. The study revealed a body weight ratio and body length ratio for co-occurring tiger beetles that was similar to Hutchinson’s ratios for birds and mammals. Different ratios were obtained when using different morphological parameters. Body size ratios inferred using mandible lengths differed significantly according to habitat type. Further, relatively higher values were observed for assemblages occupying terrestrial habitats while lower values were found for assemblages of aquatic habitats.

Further morphological and molecular studies of driftwood hoppers (Crustacea: Amphipoda: Talitridae) from Mediterranean/north-east Atlantic coastlines

An unknown talitrid was discovered in 2011 in the Swale, UK, living in driftwood. Sequencing of multiple mitochondrial and nuclear genes (cytochrome oxidase I, 18S rDNA and 28S rDNA) confirms that the unknown taxon was close to Orchestia mediterranea A. Costa 1857. The driftwood in which it was found was of Douglas fir (Pseudotsuga menziesii), probably imported from North America. Relative growth methods allow us to reject the null hypothesis that the unknown taxon was a juvenile Orchestia mediterranea. This is because the unknown taxon initiates sexual maturation at an earlier moult number (neoteny) and is predicted to reach terminal moult stages at a much smaller size (dwarfism) than its closest relative O. mediterranea. Both molecular and morphological data confirm that the unknown taxon from the Swale, UK, is a new driftwood specialist taxon, distantly related to the driftwood specialist genus Macarorchestia. Additional data for body length and sex ratios are presented for Macarorchestia. In addition, relative growth methods have shown that the driftwood species Orchestia microphtalma Amanieu and Salvat 1964 is closer to the genus Macarorchestia rather than to the wrack generalist one, Orchestia. This evidence is in line with the molecular results that do not cluster morphologically defined species of Orchestia monophyletically.

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.

Effect of copper on the growth of shrimps Litopenaeus vannamei: water parameters and copper budget in a recirculating system

Shrimps (Litopenaeus vannamei) were intensively cultured in a recirculating aquaculture system for 98 days to investigate effects of 0.3 mg/L Cu on its performance, Cu budget, and Cu distribution. Shrimps in Cu-treated systems had greater mean final weight (11.10 vs 10.50 g), body length (107.23 vs 106.42 mm), survival rate (67.80% vs 66.40%), and yield (6.42 vs 5.99 kg/m3), and lower feed conversion ratio (1.20 vs 1.29) than those in control systems but the differences were not significant. Vibrio numbers remained stable (104–106 colony forming units/mL) in the rearing tanks of both control and treated systems. Total ammonium-N, nitrite-N, nitrate-N, pH, chemical oxygen demand, 5-day carbonaceous biochemical oxygen demand, and total suspended solids were similar in controls and treatments. Dissolved Cu concentration in the treated systems decreased from 0.284 to 0.089 mg/L while in the control systems it increased from 0.006 2 to 0.018 mg/L. The main sources of Cu in the treated systems were the artificially added component (75.7% of total input), shrimp feed (21.0%), water (2.06%), and shrimp biomass (1.22%). The major outputs of Cu occurred via the mechanical filter (41.7%), water renewal (15.6%), and draining of the sediment trap (15.1%). The foam fractionator removed only 0.69% of total Cu input. Harvested shrimp biomass accounted for 11.68% of Cu input. The Cu concentration of shrimps in the Cu-treated systems (30.70 mg/kg wet weight) was significantly higher than that in control systems (22.02 mg/kg). Both were below the maximum permissible concentration (50 mg/kg) for Cu in seafood for human consumption in China. Therefore, recirculating systems can be used for commercial on-growing of Litopenaeus vannamei without loss of shrimp quality, even in water polluted by 0.30 mg/L Cu. The mechanical filter is the main route for Cu removal.