合浦珠母贝不同壳色选育系F6数量性状的相关性和通径分析

为深入了解不同壳色合浦珠母贝(Pinctada fucata)形态性状与体重间的关系,为亲贝的选择提供策略,本研究使用合浦珠母贝传统壳色、金壳色、白壳色、红壳色和黑壳色5种壳色选育系F6各1000只个体的性状数据进行通径分析和聚类分析。测量的性状包括壳长(SL,mm)、壳高(SH,mm)、壳宽(SW,mm)、绞合线长(HL,mm)和体重(BW,g)。结果显示,5种壳色合浦珠母贝所有形态性状与体重间的相关系数均达到极显著(P0.01)。通径分析表明,壳长对传统壳色和白壳色贝体重的直接影响最大,壳高对金壳色和红壳色贝体重的直接影响最大,壳宽对黑壳色贝体重的直接影响最大。利用多元回归方法构建不同壳色合浦珠母贝形态性状与体重(BW,g)间的回归方程,其中传统壳色:BW=-24.999+0.467SL+0.387SH-0.259SW+0.244HL;金壳色:BW=-38.661+0.305SL+0.477SH+0.242SW+0.375HL;白壳色:BW=-4.130+0.332SL+0.300SH-0.307SW+0.088HL;红壳色:BW=-27.307+0.327SL+0.321SH+0.252SW+0.305HL;黑壳色:BW=-40.921+0.278SL+0.335SH+1.076SW+0.269HL。聚类分析显示,传统壳色与金壳色形态特征相近,而白壳色、红壳色和黑壳色形态特征相近。     

Evaluation of three phytoplankton species as food for the pearl oyster <Emphasis Type="Italic">Pinctada fucata</Emphasis>

In the pearl cultivation farms of the Ehime Prefecture, Japan, mass mortalities of the pearl oyster Pinctada fucata have occurred since 1994. The occurrences of mass mortality roughly coincided with a shift of the dominant phytoplankton from Skeletonema and Chaetoceros to Chaetoceros and Nitzschia all of which belong to Bacillariophyceae. Hence, we evaluated Nitzschia, together with Chaetoceros and Isocrysis, as food for the oyster. Wet weights, lengths, widths, glycogen contents, and growth rates in terms of wet weight of the oysters in all the feeding treatments were significantly higher than those in the non-feeding treatment. The highest glycogen content (2.34%) and growth rate (2.21 g month⁻¹) were found in the Chaetoceros treatment. Growth rate in the Isocrysis treatment (1.63 g month⁻¹) was also high, although glycogen content in this treatment (0.41%) was low. In the Nitzschia treatment, growth rate of the oyster (0.94 g month⁻¹) was the lowest and glycogen content (0.83%) was also low relative to that in the Chaetoceros treatment. Chlorophyll a concentration in fecal pellets was lowest in the Nitzschia treatment (<2.7 μg mg⁻¹), suggesting more complete digestion of Nitzschia by the oyster. Thus, Nitzschia was edible and digestible but not assimilated by P. fucata. We propose the following scenario for the relationship between Nitzschia dominance and mass mortality. When Nitzschia dominates in a culture area, the physiological condition of P. fucata deteriorates due to low assimilation of Nitzschia by the oyster, followed by susceptibility of the oyster to infection by agents lethal to the oyster.     

Natural hybridization between <Emphasis Type="Italic">Pinctada fucata</Emphasis> and <Emphasis Type="Italic">Pinctada maculata</Emphasis> inferred from internal transcribed spacer regions of nuclear ribosomal RNA genes

ABSTRACT:   Genetic evidence of the occurrence of natural hybridization between female Pinctada fucata and male Pinctada maculata among wild pearl oysters ( n  = 20) collected for use as the mother shell for private pearl farming in the Oshima Strait at Amami-o-shima, Kagoshima Prefecture, Japan, were obtained. A polymerase chain reaction-based species identification method for Pinctada was developed using polymorphisms in the internal transcribed spacer (ITS) region of the nuclear ribosomal RNA (rRNA) gene. This method enabled the amplification of the ITS regions using a primer set specific for P. maculata and P. fucata . However, 10 of 20 individuals morphologically identified as P. fucata had sequences specific to both P. maculata and P. fucata in the ITS region. These putative hybrids showed sequences of a maternally inherited mitochondrial 16S rRNA gene, identical to that of P. fucata . Shells of the putative hybrids were difficult to discriminate from those of P. fucata exhibiting similar taxonomic traits. Moreover, the hybrids exhibited slower growth than P. fucata but faster growth than P. maculata .     

Fouling and predation; how do they affect growth and survival of the blacklip pearl oyster, Pinctada margaritifera, during nursery culture?

This paper reports on 5 experiments conducted to assess the effect of cleaning regime and predation on growth and survival of blacklip pearl oyster (Pinctada margaritifera) juveniles in north Queensland, Australia. P. margaritifera juveniles with a mean (±SE) dorso-ventral shell height (DVH) of 4.5 ± 0.1 mm were placed into plastic mesh trays and cleaned either every 4 or 8 weeks or left uncleaned for 16 weeks. Cleaning regime had a significant effect on growth and survival (P < 0.005). Lowest DVH (16.2 ± 1.0) was shown by oysters in uncleaned trays during 16 weeks compared to oysters in cleaned trays; however, there was no significant difference in DVH between oysters held in trays cleaned every 4 (19.4 ± 1.2) or 8 weeks (21.2 ± 0.8). In contrast lowest survival was shown by oysters held in trays that were cleaned every 4 weeks (30 ± 5%), but no differences were noted between oysters cleaned every 8 weeks (63 ± 4%) and oysters that were left uncleaned for 16 weeks (75 ± 8%). Predators of P. margaritifera in northern Australia included crabs, stomatopods, flatworms, gastropods and fish. The stomatopod, Gonodactylus falcatus, was the most destructive predator with individuals consuming in excess of 20 juvenile pearl oysters per week. The leather jacket, Paramonocanthus japonicus, did not kill pearl oysters, but trimmed the margin of oysters shells significantly reducing DVH when compared to control groups cultured without fish. Removing predators monthly had a significant effect on growth of pearl oysters compared to oysters in non-inspected trays; however monthly inspection of culture trays did not significantly improve oyster survival. This revised version was published online in August 2006 with corrections to the Cover Date.     

Suspension feeding and growth of ark shell <Emphasis Type="Italic">Anadara granosa</Emphasis>: comparison with ubiquitous species <Emphasis Type="Italic">Scapharca subcrenata</Emphasis>

The ark shell Anadara granosa is a species peculiar to the Ariake Sound. To determine why distribution of A. granosa in Japan is largely confined to this area, we examined feeding and growth of A. granosa as functions of environmental and biological variables. The results were compared with those of another ark shell Scapharca subcrenata, which is ubiquitous in Japan. Feeding experiments indicated that A. granosa is eurythermal and euryhaline, as is S. subcrenata, but is adapted to temperature slightly higher than S. subcrenata. Weight-specific clearance rate (CR) of A. granosa as a function of soft-body dry-weight (w) followed the power function of w (CR=2.7×w ^−0.37), with coefficient and exponent very close to those for S. subcrenata. Growth rate of A. granosa increased linearly with daily ration, similar to S. subcrenata. Thus, feeding and growth characteristics of A. granosa were comparable to those of S. subcrenata and no ‘peculiarities’ of the former were detected. Therefore, the factors that make A. granosa a species restricted to the sound are probably not directly related to feeding or growth characteristics.     

Effects of glycopeptides on development,growth and non‐specific immunity of pearl oyster Pinctada fucata (Gould)

The effects of glycopeptides, prepared from pearl oyster Pinctada fucata, on embryonic development, larval and juvenile growth and adult non‐specific immunity of P. fucata were investigated in this study. Glycopeptides had a pronounced stimulatory effect on embryonic development and larval and juvenile growth of P. fucata. enhancing with increased glycopeptide concentrations. All of haemocytes, phagocytosis, aggregation, serum microbiostatic activity and bacteriocidal activity all showed significant increases after 60‐day feeding, relative to unfed controls. The major conclusion is that glycopeptides had a pronounced stimulatory effect on the non‐specific immunity of pearl oysters.     

Sterols from bivalves <Emphasis Type="Italic">Calyptogena soyoae</Emphasis> and <Emphasis Type="Italic">Bathymodiolus septemdierum</Emphasis> living in deep sea

From the two species of bivalves, Calyptogena soyoae around a cold seep and Bathymodiolus septemdierum near hydrothermal vents in the sea, sterols were isolated using high-pressure liquid chromatography analysis of the lipid fraction guided by characteristic ¹H NMR signals of the sterol skeleton. The minor sterol composition of C. soyoae included 24-methylenecycloartanal, cycloeucalenol, and obutusifoliol, which are known phytosterols. From B. Septemdierum, lathosterol and cholesterol as main sterols together with more diverse sterols were obtained. The difference between these species and their sterol contents is most likely because of feeding modes and metabolism of nutrients from their habitat.     

Species identification of <Emphasis Type="Italic">Pinctada imbricata</Emphasis> using intergenic spacer of nuclear ribosomal RNA genes and mitochondrial 16S ribosomal RNA gene regions

ABSTRACT:   For pearl production, pearl oyster seeds from foreign pearl oysters as well as hybrids between native and such foreign pearl oysters are produced in Japanese hatcheries. However, it is very difficult to identify these pearl oysters and hybrids based on morphological measurements. Thus, a molecular identification method for distinguishing Atlantic pearl oysters Pinctada imbricata from the Indian-Pacific pearl oyster group including P. martensii and P. fucata , was developed. The polymerase chain reaction (PCR) products of the partial intergenic spacer (IGS) of nuclear ribosomal RNA (rRNA) genes exhibited length polymorphism between P. imbricata (590 bp) and the other two species (427 bp). The restriction fragment length polymorphism analysis of the PCR products (PCR-RFLP) cleaved with Mse  I observed in the IGS of nuclear rRNA genes also gave different profiles between P. imbricata and the other two species. The difference in PCR-RFLP using Alu  I was also detected in the mitochondrial 16S rRNA gene regions between P. imbricata and the other two species. Thus, the method developed enables the distinction of P. imbricata from P. martensii and P. fucata .     

Phenotypic indicators for cultured pearl size improvement in the black‐lipped pearl oyster (Pinctada margaritifera): towards selection for the recipient growth performance

The black‐lipped pearl oyster, Pinctada margaritifera, is the most important farmed species in French Polynesia and the basis of the most valuable export industry. Mass production of black pearls relies on a surgical operation requiring tissue from a donor pearl oyster to be grafted, together with a nucleus made of shell, into the gonad of a recipient oyster. Improving pearl size through family selection remains one of the main challenges for future aquaculture development. This study analyses the relative contribution of donor and recipient oysters to pearl size. To this end, hatchery‐produced donor oysters of two batches, large and small (based on shell height), were used to supply grafts for recipients, which were then monitored individually for their growth performance by recording shell height, width, and thickness, and total live weight (flesh + shells) every 6 months (four biometric measurement times) over 20 months of culture. Pearls issued from the two batches of donors showed no significant differences in nacre weight or thickness. In contrast, recipient oyster shell height and total weight were increasingly positively correlated with these pearl size parameters over the culture period, becoming significant at 8 months post‐grafting. Potential therefore exists to use shell height and oyster weight as phenotypic indicators for selective breeding of recipient oysters with high growth performance to increase pearl size in P. margaritifera.     

Annual variation of potential predation impacts on larval and juvenile marbled sole <Emphasis Type="Italic">Pseudopleuronectes yokohamae</Emphasis> by sand shrimp <Emphasis Type="Italic">Crangon uritai</Emphasis> in Hakodate Bay,Hokkaido

An investigation was conducted to evaluate the annual variation in potential predation impact (PPI) on larval and juvenile Pseudopleuronectes yokohamae by Crangon uritai in Hakodate Bay using predator-prey size relationships. Laboratory experiments were designed to estimate the favorable prey size of C. uritai through back-calculation of body length (BL) of P. yokohamae from sagittal otolith diameter observed in the stomachs of C. uritai. The most favorable prey-predator size ratio (BL of P. yokohamae-total length (TL) of C. uritai) class was 0.15–0.19, and ranged from 0.12–0.31. There was a significant positive correlation between the BL increase of P. yokohamae and the bottom water temperature in the field, such that BLs stagnated during the cold year of 1999 from April to June, and increased during the warm year of 2002. In contrast, no significant correlation was found between the TL increase of C. uritai and the bottom water temperature. Moreover, there were no significant differences in the mean TL of C. uritai between months (April–June) or years (1998–2002). Variation of PPI depended on the relationships between the growth rates of P. yokohamae and bottom water temperature. Therefore, the warm year of 2002 resulted in higher potential predation impact (PPI≥20), and it was at least 20 days shorter than that of the cold year of 1999. These results suggest that increased bottom water temperature in the nursery area was one of the most important factors for cumulative predation loss.     

Masculinization of Convict Cichlid (<Emphasis Type="Italic">Cichlasoma nigrofasciatum</Emphasis>) by immersion in <Emphasis Type="Italic">Tribulus terrestris</Emphasis> extract

We have examined the effects of Tribulus terrestris (TT), a non-toxic herb, on sex reversal in the Convict Cichlid Cichlasoma nigrofasciatum with the aim of introducing a new environmentally friendly method for masculinization in C. nigrofasciatum. TT is a natural plant product that elevates the testosterone levels in humans and animals. Different concentrations (0.0, 0.10, 0.20 and 0.30 g/l) of TT extract were tested for their effect on sex reversal in C. nigrofasciatum by immersing newly hatched offspring once weekly for 2 months in TT extract. Of the dosages used in the present study, 0.30 g/l TT was the most effective in terms of masculinization, resulting in a maximum male ratio of 87.23% (P < 0.001). Sex ratios of 79 and 85% at 0.10 and 0.20 g/l TT, respectively, were also significantly different from the expected 1:1 ratio (P < 0.001). Histological examinations revealed that the testes of fish treated with TT extract contained all stages of spermatogenesis, clearly demonstrating that the administration of TT extract to C. nigrofasciatum stimulated spermatogenesis. Total survival rates in all treatments and the control were uniformly high, ranging from 88.57 to 90% (P > 0.05). We concluded that TT had no negative effect on the survival rate of C. nigrofasciatum. In addition, all groups of TT-treated fish exhibited successful growth acceleration compared to the control group, but only the 0.30 g/l TT treatment significantly improved the growth rate of C. nigrofasciatum. (P < 0.01). Sex reversal in C. nigrofasciatum demonstrated that TT-treated 0-day-old larvae showed successful sex reversal, spermatogenesis and a better growth rate than untreated progenies.     

Induction of diploid gynogenesis in turbot <Emphasis Type="Italic">Scophthalmus maximus</Emphasis> with left-eyed flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> sperm

Turbot Scophthalmus maximus exhibits sexually dimorphic growth, with females growing faster and reaching larger adult sizes than males. Thus, development of techniques for preferentially producing females is necessary to optimize production of these species. In this paper, gynogenetic diploids of turbot were induced by activating egg development with ultraviolet (UV)-irradiated left-eyed flounder Paralichthys olivaceus sperm combined with cold shock to prevent extrusion of the second polar body. The results of UV irradiation experiments showed that survival, motility, and duration of activity of P. olivaceus sperm generally decreased with increase in UV dose. The typical Hertwig’s effect was observed after fertilized turbot eggs with UV-irradiated P. olivaceus sperm and the optimal UV dose for gynogenetic haploid production was 36,000 erg mm⁻². At 15°C, appropriate timing of cold shock for retention of the second polar body in turbot eggs was at 6 min after fertilization. Results of different combinations of two shock temperatures (1 or 3°C) and four shock durations (15, 25, 35 or 45 min) at 6 min after fertilization demonstrated that shock of 25 min at 1°C gave the highest production of diploid gynogens (39.58% relative to its diploid control). The results of this study reveal that the use of UV-irradiated P. olivaceus sperm for activation of turbot eggs and cold shock for polar body retention is an effective method to produce gynogenetic offspring.     

Reproductive condition of the pearl oyster, Pinctada imbricata, Röding, in Port Stephens, New South Wales, Australia

In an investigation of the potential for pearl production in New South Wales (NSW), Australia, changes in the physical and reproductive condition of the pearl oyster, Pinctada imbricata, were monitored for over 2 years. Using wild oysters gathered from close to the southern extent of the species' range in Port Stephens, NSW, a series of macroscopic and histological observations were made. Reproductive activity in P. imbricata was greatest from late spring to early autumn with oysters in poor reproductive condition during winter. Peaks in reproductive indices occurred in November 1998, March 1999, December 1999 and April 2000. Four indices of physiological condition were used: shell growth, byssal attachment, mantle thickness and mucoprotien layer. With the exception of the thickness and extent of the mucoprotein layer, these indices either showed little variation or the variation that occurred was not related to seasonal or reproductive changes. Changes in the mucoprotein layer were correlated with water temperature and suggest that this layer is metabolized during periods of high demand such as during gonadogenesis. Collectors deployed at two sites in Port Stephens demonstrated that spatfall occurs largely in the months of December and January following the spring and early summer peaks in reproductive activity (November 1998 and December 1999). Spatfall was not observed following the autumnal peaks (March 1999 and April 2000) in reproductive activity. Overall, reproductive patterns in P. imbricata are poorly suited to spat supply in Port Stephens. Farmers require spat in early spring (September) to allow maximum use of the ‘growing’ season (September–May). Reproductively capable oysters are not available from the wild until September and quantity of natural spatfall is too variable and occurs too late in the season (December–January). As a result, oysters are being conditioned in the hatchery in July, spawned in August and spat are supplied to farmers in mid September.     

Determination of hormones inducing oocyte maturation in <Emphasis Type="Italic">Chalcalburnus tarichi</Emphasis> (Pallas, 1811)

Chalcalburnus tarichi is an endemic cyprinid species living in the Lake Van basin, in eastern Anatolia, Turkey. The present study was undertaken to determine which hormones induce oocyte maturation in C. tarichi. The levels of 17α,20β,21-trihydroxyprogesterone (20β-S), progesterone (P), 17α-hydroxyprogesterone (17α-HOP), 11-deoxycortisol (11-DOC), and 17α-hydroxy-20β-dihydroprogesterone (17,20β-P) were measured in fish caught from Lake Van and the Karasu River, and injected with human chorionic hormone (hCG) (1,000 and 1,500 IU/kg). Oocytes of fish caught from the lake were also incubated in vitro with different doses (50, 200, and 1,000 ng/ml) of 20β-S, 17α-HOP, 11-DOC, and 17,20β-P. 11-DOC was found to be the most effective hormone among those measured for inducing oocyte maturation in vivo and in vitro. 17,20β-P could not be determined in the plasma of any fish in vivo (P < 0.05). 1,000 IU/kg dose of hCG given by injection caused a statistically significant increase in all plasma hormone levels (P < 0.05). It was found that there was a significant decrease in the P level only at 1,500 IU/kg dose of hCG injected (P < 0.05), while the level of other hormones increased at this dose (P < 0.05). It was also determined that all the hormones were effective in germinal vesicle breakdown (GVBD) in in vitro oocyte culture (P < 0.05). However, 11-DOC was found to be the most effective hormone in GVBD at a dose of 200 ng/ml (70% GVBD). In conclusion, 11-DOC synthesized during final oocyte maturation in C. tarichi was found to be a potent inducer of GVBD, which shows that 11-DOC may be described as an oocyte maturation steroid in this species.     

Genetic variation in mitochondrial genes and intergenic spacer region in harmful algae <Emphasis Type="Italic">Chattonella</Emphasis> species

In this study, nuclear ribosomal RNA gene internal transcribed spacer regions and the cox2-cox1 fragment of the mitochondrial (mt) genome were sequenced in 24 strains of Chattonella spp. Variability in both regions showed that the mt genome sequences of Chattonella spp. have a higher evolutionary rate than the nuclear rRNA gene sequences. A maximum likelihood tree based on the mt sequence grouped the Japanese Chattonella strains into two groups (Groups A and B), although no correlation was observed amongst the phylogenetic groups, their morphologies, or the isolated areas. Groups A and B were clearly identified by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay using Fokl, without the need for a sequencing experiment. The PCR-RFLP assay revealed that Chattonella cells obtained from sea water in Oita, Japan, in 2004 and 2005 belonged to Group B. This is the first report showing the genetic variation in Chattonella spp. using a PCR-RFLP identification protocol.     

A comparative account of the structure of the growth hormone encoding gene and genetic interrelationship in six species of the genus <Emphasis Type="Italic">Labeo</Emphasis>

The growth hormone (GH) gene isolated and cloned from various Labeo species (L. rohita, L. calbasu, L. fimbriatus, L. gonius, L. bata, and L. kontius) is shown to contain a single copy in the haploid genome, with an overall size of ∼2.5 kb. The GH gene in all the Labeo species studied has five exons and four introns of various sizes with the exon/intron boundary sequence of GT/AG. The length variation of the GH gene between the species is found to be due to length variation in the form of several deletions in the third intron. The length of individual exons is the same in all the species with an open reading frame (ORF) of 630 bp (210 amino acids) except in L. rohita, which has a 9 bp deletion in the fourth exon, resulting in a shorter GH of 621 bp (207 amino acids). The similarity in the nucleotide and amino acid sequences between the different Labeo species is greater than 97%, in spite of eight amino acids being altered in the GH protein of Labeo that reside outside the conserved domain sequence required for its function. Nucleotide substitutions are seen in the form of 20 transitions and three transversions in the ORF of the GH gene. Both types of transitions (A–G; T–C) and only one type of transversion (A–C) are detected in the GH gene. Codon preference in GH gene shows a strong preference for G and C in the wobble position of the codons. Genetic interrelationships determined between Labeo and other species of fishes using nucleotide sequence of GH cDNA supports the overall teleost classification of Nelson (Fishes of the World. Wiley, New York, 1984) with separate clades for Ostariophysi, Protacanthopterygii, and Acanthopterygii. Besides, the unweighted pair group method with arithmetic means (UPGMA) analysis clearly distinguishes between the species having five exons and four introns in the GH gene from the species having six exons and five introns in the same gene. The Labeo species analyzed in the present study could be clustered into two groups using the maximum-parsimony method on the intron sequences data of the GH gene.     

Parentage testing for hatchery-produced abalone <Emphasis Type="Italic">Haliotis discus hannai</Emphasis> based on microsatellite markers: preliminary evaluation of early growth of selected strains in mixed family farming

This study dealt with the detection of parentage in a mixed family tank of abalone Haliotis discus hannai using microsatellite DNA markers. As a preliminary investigation, the early growth rate between selected and non-selected abalone families, which were reared together in the mixed family tank from settlement stage to juvenile stage (7 months of age), was also compared. The selected families were derived from seven parents (three females and four males) selected for larger size in shell length at about 1-year-old, and the non-selected families originated from five wild captives (three females and two males). Parentage analysis based on eight microsatellite markers unambiguously allocated the 170 juveniles sampled from the single tank to the 17 parental pairs. The family size was highly heterogeneous among families, as two males in the selected families and one male in the non-selected families dominated the contribution to the offspring pool (>80%). The mean shell length of the selected families was approximately 23% larger than that of the non-selected families (Student’s t-test, P<0.001). This study demonstrated that the use of microsatellite markers is effective for parentage determination in the mixed family farming, commonly used in abalone hatcheries, and selective operations for larger size could improve the growth of the next generation.     

Variation in clearance and ingestion rates by larvae of the black-lip pearl oyster (Pinctada margaritifera, L.) feeding on various microalgae

Clearance rate (CR) and ingestion rate (IR) of different sizes (89, 125 and 188 μm shell length) of Pinctada margaritifera larvae were determined when feeding on various microalgae. The microalgae tested were the diatoms, Chaetoceros muelleri and C. simplex, and flagellates, Tahitian Isochrysis aff. galbana, Pavlova lutheri and P. salina at 5 or 10 cells μL^–1. Both CR and IR of microalgae tested in this study increased with increasing larval size; but at all larval sizes, diatoms resulted in lower CR and IR. Of the microalgae tested, P. margaritifera larvae showed greatest CR and IR with the two Pavlova spp. Maximum CR for P. salina was 10.5, 21.2 and 29.7 μL h^–1 for larvae with shell lengths of 89, 125 and 188 μm, respectively. The highest IR values for P. margaritifera larvae with shell lengths of 89, 125 and 188 μm were 8.7, 81.0 and 165.7 cells·larva^–1 h^–1, respectively. CR and IR of P. salina were approximately five times higher than those recorded for C. muelleri and C. simplex.     

Feeding habits of stone flounder <Emphasis Type="Italic">Platichthys bicoloratus</Emphasis> larvae in Mutsu Bay,Japan

To clarify the feeding strategy of pelagic larvae of stone flounder in Mutsu Bay, the dietary composition and pray size was investigated from February to April during 1989–1999. Diets were compared with the numerical and volumetric compositions and frequency of occurrence of each prey species. Mensuration formulae were applied to estimate individual prey volume in the diet, while the length of planktonic species was measured from net and water samples. Prey shapes were assumed as sphere, cylinder, ellipsoid, pyramid, two elliptical cones, or a combination of ellipsoid and cylinder. Prey-size range increased as the larvae grew. Preflexion larvae fed mainly on copepod nauplii. Flexion and postflexion larvae ingested primarily appendicularians, with a suggestion that these larvae might depend on some parts of the microbial food web. Low frequencies of flexion and postflexion larvae with empty guts (1.7 and 1.4%, respectively) might be derived from feeding on slow-swimming appendicularians. From a size comparison between ‘house’-like organ length and trunk length of the appendicularian Oikopleura sp., almost all house-like organs with trunks in the larval diet were nonexpanded ‘house rudiments’, not expanded ‘houses’. Thus, stone flounder larvae may not chew the houses, but swallow the house rudiments with trunks.     

Effects of triploidy on the Caspian salmon <Emphasis Type="Italic">Salmo trutta caspius</Emphasis> haematology

The aim of this study was a comparison of key haematological features of diploid (2n) and triploid (3n) Caspian salmon (Salmo trutta caspius). Morphometric indices of erythrocytes were determined on blood smears by light microscopy. Triploidy significantly (P < 0.001) increased all morphometric indices measured in the erythrocytes including cell size, cell surface area, and cell volume. The increase in cell size was larger for the major (27%) axis than for the minor (22%) axis, thus making erythrocytes of 3n Caspian salmon more ellipsoidal. The estimated increase in erythrocyte nuclear volume (87%) was bigger than the theoretical expected 50% increase. Haematological indices were measured manually by hemocytometry. Triploids had lower numbers of red blood cells (RBC: 1,120,000 cells/mL in 2n vs. 700,000 cells/mL in 3n; P < 0.001) but they were larger in size (mean erythrocytic volume [MEV]: 363.1 nm³ in 2n vs. 483.3 nm³ in 3n; P < 0.001). The decrease in RBC number was not compensated by the increase in MEV and, thus, triploidy affected the haematocrit (Hct: 38.8% in 2n vs. 33.06% in 3n; P < 0.05). Total blood hemoglobin concentration was lower in triploid fish (Hb: 9.9 g/dL in 2n vs. 8.9 g/dL in 3n; P < 0.05). In contrast, mean erythrocytic hemoglobin (MEH: 95 μg in 2n vs. 133.2 μg in 3n; P < 0.001) was higher for 3n Caspian salmon as a result of their larger erythrocytes, although MEH concentration (MEHC: 0.26 g/dL in 2n vs. 0.27 g/dL in 3n) did not significantly differ (P > 0.05). White blood cell (WBC) counts (lymphocytes and neutrophiles) were measured and WBC/RBC ratios were calculated. There were no significant differences in WBC (15,710 cells/mL in 2n vs. 12,683 cells/mL in 3n; P > 0.05), lymphocytes, and neutrophils as %WBC as well as WBC/RBC ratios between two ploidy levels (P > 0.05). Triploid Caspian salmon showed higher erythrocyte abnormalities such as ‘twisted’, ‘tailed’, and ‘anucleated’ cells as well as high portions of immature RBC in blood smears in comparison with diploids (P < 0.001).