Color vision, spectral sensitivity, accommodation, and visual acuity in juvenile masu salmon Oncorhynchus masou masou

ABSTRACT:   Color vision, spectral sensitivity, accommodation, and visual acuity were examined in juvenile masu salmon Oncorhynchus masou masou to obtain fundamental information about the visual system. Two types of S-potentials were recorded from 415 horizontal cells in isolated retinas from 34 cultured freshwater masu salmon (114–219 mm standard length, SL). Although horizontal cells recording S-potentials were not identified, the horizontal cells were confirmed because their responses were maintained while the stimulus remained. The variety of chromaticity (C)-type S-potentials indicated well-developed color vision. The analysis of the luminosity (L)-type S-potentials indicated that the peak spectral sensitivity was at 522 nm. S-potentials were also recorded in response to ultraviolet light. The direction and extent of lens movement induced by electrical stimulation was measured in 12 cultured masu salmon (99.0–142.5 mm SL). The results indicated that the visual axis was upward and forward, and that the range of accommodation was from 0.79 × SL in front of the eye to infinity. In histological analysis of the retinas of five wild smolts (100–118 mm SL), the maximum cone densities (276–345 cones/0.01 mm²) were detected in the ventral to temporal regions. The visual acuities assessed by histological methods were 0.069–0.075.     

大口黑鲈北方亚种和佛罗里达亚种及其杂交子代的遗传分析

用18对微卫星引物对大口黑鲈北方亚种(Micropterus salmoides salmoides,N)、佛罗里达亚种(M.salmoides floridanus,F)及其正交子代(N♀×F♂)和反交子代(F♀×N♂)进行遗传多样性和遗传结构分析。结果表明,18对引物扩增出的等位基因数为2~8个,平均等位基因数为5.0。检测到6对(Jzl48、Jzl68、Jzl84、MiSaTPW76、Msal21、Mdo6和Mdo7)亚种间特异性引物,其中有2对引物(Jzl48和Mdo7)可以用来鉴别大口黑鲈北方亚种、佛罗里达亚种和其杂交子代。平均有效等位基因数、平均期望杂合度和平均多态信息含量均为杂交组合F♀×N♂最高,分别为3.199 7,0.638 9和0.570 6,平均观测杂合度为杂交组合N♀×F♂最高(0.848 8)。对亲代与杂交子代间的遗传分化分析表明,正反交子代均与北方亚种的遗传分化最小(0.092和0.119 6)。基于Nei’s遗传距离构建的UPGMA系统进化树显示正交子代N♀×F♂与母本N聚为一支,反交子代F♀×N♂与父本N聚为一支。     

Visual acuity and spectral sensitivity of Jacopever Sebastes schlegeli

Understanding the behavior of Jacopever Sebastes schlegeli to visual stimulation is important and requires determination of visual sensitivity through the use of effective stimulation. In the present study, we measured the visual acuity, visual accommodation and spectral sensitivity of Jacopever. Visual acuity was calculated from the maximum cone density in the retina. In five specimens, the total length ranged from 17.6 to 24.5 cm and the calculated minimum resolving angles and visual acuities were 9.5–10.7 min and 0.09–0.11, respectively. Measurement of lens movement for visual accommodation indicated a mean distance and direction of movement of 0.31 mm and 16.0° in an upward and forward direction, respectively. The direction of accommodation and visual axis measured from the retinal area of maximum cone density were almost identical. The calculated focal distance was 0.74-fold the total length in the nearest point to infinity. We also determined the spectral sensitivity electrophysiologically by recording S-potentials from 45 specimens of total length of 15.4–47.5 cm. The S-potentials were recorded from 300 horizontal cells in the retina. All responses showed a similar spectral pattern, consisting of hyperpolarization in response to various wavelengths of stimulating light; the maximum amplitude of the response was recorded at 522 nm.     

Comparison of visual acuity and visual axis of three flatfish species with different ecotypes

ABSTRACT:   The visual acuity, visual axis and visual accommodation of pointhead flounder, slime flounder, and red halibut were determined to obtain basic knowledge for developing appropriate fishing gear and fishing methods for sustainable fisheries. Each of these species has a different ecotype in terms of habitat, depth and prey species. Thus, it was hypothesized that they may differ in terms of visual acuity, visual axis and visual accommodation. Few studies have compared these characters in flatfishes from different ecotypes. We used histological methods to determine visual acuity (i.e. cone cell density) and visual axis (i.e. cone cell distribution) in each of these species. The maximum visual acuity was 0.127 in pointhead flounder (total length, TL 344 mm), 0.092 in slime flounder (TL 372 mm) and 0.109 in red halibut (TL 336 mm). Based on the cone cell distribution in the retina, the visual axis was upward and forward in pointhead flounder, forward and downward in slime flounder, and downward in red halibut. Finally, the mean angle of lens movement was −2° in pointhead flounder, −13° in slime flounder and −32° in red halibut. This measurement of lens movement indicated that the average near-point distance was 0.87 × TL in pointhead flounder, 0.65 × TL in slime flounder and 1.02 × TL in red halibut. At similar TL (336–355 mm), the visual acuity of these species differs depending on the direction in which they are looking.     

Visual acuity and spectral sensitivity of the elkhorn sculpin <Emphasis Type="Italic">Alcichthys alcicornis</Emphasis>

ABSTRACT:   In this study, the visual acuity, visual accommodation, and spectral sensitivity of the elkhorn sculpin were determined. The elkhorn sculpin Alcichthys alcicornis is a typical groundfish that has conspicuously large eyes. They are caught by bottom gillnets, trawl nets, bottom line angling, and other fishing methods. Although fish behavior arising from visual stimuli is important in these fishing methods, there is little information available regarding the visual sensitivity of the elkhorn sculpin . Three specimens, with total lengths of 300–310 mm, were studied. Visual acuity was calculated, from the maximum cone density in the retina, to be between 0.10 and 0.14. The minimum separable angles were calculated to be 7.14–10.37 min. Measurement of lens movement in five specimens indicated that the near-point distance was between 0.87 and 1.53 times the total length. Lens direction was estimated to be 11–22° in the downward visual axis. Spectral sensitivity was also determined electrophysiologically by recording S-potentials. Three types of response were obtained from 21 specimens, including L responses that showed hyperpolarization at all wavelengths of stimulating light, and two C responses that showed wavelength-dependent hyperpolarization and depolarization. Based on these results, the elkhorn sculpin has color vision and its sensitivity is most acute in light with a wavelength of 554 nm.     

Persistence of Florida largemouth bass alleles in a northern Arkansas population of largemouth bass, Micropterus salmoides Lacèpéde

Abstract– Lake Ashbaugh, located in northeast Arkansas, was constructed in 1981, and initially stocked with Florida largemouth bass followed by supplemental stockings of northern largemouth bass. Allele frequencies of three discriminant allozyme loci (sAAT-B, sIDH-B, sMDH-B) between Florida and northern largemouth bass were determined for 414 largemouth bass collected between 1994 and 1996. F_x bass dominated our sample, with 62.3% possessing Florida largemouth bass alleles. A high incidence of Hardy-Weinberg disequilibrium was observed, indicative of genetic change within the population. No significant differences were identified for frequency of age classes, relative weight, and length at age between the northern, F₁ and F_x phenotypes. Despite being located north of what is generally considered suitable for stocking Florida largemouth bass, it was demonstrated that temperature is not selective at present against bass possessing Florida largemouth bass alleles. However, caution should prevail when introducing non-native stock into native gene complexes, as introduced genes persist through many generations.     

Evaluation of alternative pond production systems for raising largemouth bass,Micropterus salmoides

This study evaluated three different pond‐based production systems for raising largemouth bass, Micropterus salmoides, for the food fish market, using nine 0.04‐ha ponds. Treatments included traditional ponds (TP), intensively aerated ponds (IAP), and split‐pond systems (SPS). TP and SPS ponds were aerated at 9.3 kW/ha, while IAP was aerated at 18.6 kW/ha. TP was stocked at 7,500 fish per ha (three replicates per treatment), and the other two production systems (SPS, IAP) were stocked with 12,500 fish per ha. Feed‐habituated advanced fingerlings (128 ± 47.6 g mean individual weight) were cultured for 157 days. Fish were fed a formulated diet (42% protein, 16% lipid) four times a day, feeding with a maximum allowance of 3% of total body weight and readjusted to the initial body weight biweekly. Fish raised in the SPS displayed a significantly lower specific growth rate, lower individual final weight, and lower weight gain, but the biomass gained was significantly higher than TP but not IAP. Final biomass gained was 50% higher in the SPS and IAP than in the TP. Survival rate and feed conversion ratio were not significantly different among treatments and ranged from 71 to 79% and 1.64 to 2.14, respectively.     

Effects of season, maturity, and sex on lipid class dynamics in largemouth bass (Micropterus salmoides Lacepede)

Abstract Factors that can influence changes in lipid class concentrations in specific tissues have not been reported for largemouth bass Micropterus salmoides. We investigated patterns of lipid composition by measuring seasonal levels of total lipid and major lipid classes in the muscle and liver tissues of juvenile and adult largemouth bass and gonad tissue of adults. Fish were collected in December, February, April and July to correspond with key stages of the sexual cycle. Total lipid concentrations were substantially greater in hepatic (32.8 [female] to 56.6 [male] mg. g^?1) and gonadal tissues (34.4 [F] to 204.0 [M] mg. g^?1) than in muscle (7. 5 [F] to 11.4 [M] mg. g^?1). Muscle lipid concentrations in juveniles were significantly higher (10.9 [F] and 11.4 [M] mg. g^?1) in summer than in winter in adult muscle tissue (8.6 [F] and 9.4 [MI mg. g^?1). A 44% increase in ovary lipid was observed from preparatory to prespawn stages, followed by a 78% decline after the spawn. Additionally, seasonal hepatic lipid concentrations were substantially higher in juveniles. Concentrations of lipid classes (free cholesterol [C], triacylglycerol [TAG], free-fatty acids [FFA], esterified cholesterol [CE] and phospholipid [PL]) of all tissue types varied significantly among season, sex, and maturity categories. Changes with all lipid classes in the ovary coincided with those occurring in total ovarian lipid. Mobilization and transport of TAG and PL from the liver to the ovary appeared to occur during gametogenesis. All class concentrations in juveniles were invariably higher in liver than in muscle, but seasonally variable among hepatic and gonad tissues of adults. Juvenile males showed slightly greater hepatic C concentrations than other groups. Muscle and hepatic C were generally higher in juveniles.     

Diet of the largemouth bass, Micropterus salmoides (Lacepède), in Lake Naivasha, Kenya

Abstract The major food items of adult largemouth bass, Micropterus salmoides (Lacepède), in Lake Naivasha, Kenya are not markedly different from those in its native range. Although insects and their larvae are major components of the diet for both temperate and equatorial populations of juvenile bass, the equatorial population also eats Procambarus clarkii (Girard), juvenile fish and aquatic weeds. In temperate populations they also eat crustaceans, rotifers and oligochaetes. The frequency of occurrence of the major prey organisms in the stomachs of M. salmoides varies seasonally with population peaks in these organisms. Similar to North American populations, the Naivasha population feeds during the day between dawn and dusk. In contrast to temperate populations, the population of M. salmoides in this equatorial lake feeds throughout the year, with feeding intensity correlated with water temperature.     

Activity patterns of largemouth bass in a subtropical US reservoir

Abstract  Nine largemouth bass, Micropterus salmoides Lacepède, >1.5 kg were implanted with radio tags and tracked for 1 year in an embayment of Lake Seminole, Georgia, USA. Most largemouth bass movement was <50 m h⁻¹ in all seasons and at all times of day. During the day largemouth bass were offshore in deeper water near large woody structures and moved little. Movement was lower during dusk and night periods, and a general movement towards shoreline areas was evident. Water depths where largemouth bass were located had bimodal distributions in all seasons and diel periods, with one mode typically at depths <1 m and another around 3 m. Home ranges were typically largest in the summer and smallest in the winter. Largemouth bass appeared to divide their time between an offshore resting area, primarily occupied during the day, and a near-shore area, where foraging presumably occurred, primarily used during low-light periods. The largemouth bass population in Lake Seminole consists of multiple overlapping subpopulations, offering the opportunity for embayment-specific management.     

Arginine requirement and effect of arginine intake on immunity in largemouth bass,Micropterus salmoides

An 8‐week feeding test was conducted to quantify the dietary arginine requirement of juvenile largemouth bass (LMB) (25 ± 0.4 g). Six isonitrogenous and isolipidic (459 g crude protein and 122 g crude lipid kg^?1 dry diet) diets were formulated to contain graded levels of arginine (17.0–30.1 g kg^?1 dry diet). Zein‐coated crystalline amino acid mixtures were supplemented to simulate, except for arginine, the amino acid profile of the muscle protein of LMB. Each diet was randomly assigned to quadruplicate tanks of 35 fish reared in a flow‐through system. Fish were fed to apparent satiation twice daily. Weight gain (WG) was significantly affected by dietary arginine level. Nitrogen retention was significantly lower in fish fed D17.0. Arginine retention significantly decreased with dietary arginine increased. Threonine, leucine and lysine concentrations in whole body were significantly affected by dietary arginine level. Serum lysozyme activity, serum protein and respiratory burst of head kidney leucocytes were significantly affected, while complement activity (CH₅₀) showed no difference among treatments. Based on broken‐line analysis for WG against dietary digestible arginine level, the arginine requirement of LMB was 19.1 g kg^?1 of dry diet (41.6 g kg^?1 of crude protein).     

大口黑鲈蛙病毒分子流行病学及组织病理分析

为探讨大口黑鲈蛙病毒（LMBV）的分子流行规律及在感染后的组织病理变化,实验对2019—2021年采集的723份患病大口黑鲈样品进行荧光定量PCR （qPCR）检测。结果显示,LMBV的阳性率为63.62%,挑选阳性样品接种鳜脑细胞（Chinese perch brain cells,CPB）,共获得93株LMBV。通过对分离株MCP、ATP酶、DNA聚合酶和甲基转移酶基因进行PCR扩增与测序分析,发现上述基因在LMBV分离株中均保守,其中MCP、ATP酶基因一致性均为100.0%、甲基转移酶基因一致性为99.7%～100.0%、DNA聚合酶基因一致性为99.8%～100.0%。选取1株LMBV毒株感染健康大口黑鲈,采用qPCR方法对不同组织中的病毒载量进行检测,结果显示,大口黑鲈蛙病毒在心脏、肝脏、脾脏、肾脏、胃、肠和脑等组织中均有分布,人工感染LMBV后的前5天病毒载量逐步升高;感染后第5天,心脏中病毒载量最高（9.5×10⁵个/mg拷贝）,脑组织中病毒载量最低（2.9×10²个/mg拷贝）。组织病理结果表明,LMBV可导致大口黑鲈多种组...     

维生素C对大口黑鲈生长与非特异性免疫的影响

以不同维生素C水平(添加量分别为0、500、1000、2000和4000mg·kg-1)的5种饲料喂养初始体重为19g左右的大口黑鲈1个月,每个处理50尾鱼,各处理3个重复,研究维生素C对大口黑鲈生长及非特异性免疫的影响。结果显示:饲料中添加维生素C能显著促进大口黑鲈的生长和脾体指数(P<0·05),然而对大口黑鲈的成活率以及肝体指数等不产生影响(P>0·05);饲料中添加维生素C能显著促进大口黑鲈血清中超氧化物歧化酶活力和溶菌酶活力(P<0·05);随着饲料中维生素C添加水平的提高,大口黑鲈肝脏中维生素C的积累量显著升高(P<0·05)。实验证明,Vc作为免疫刺激剂能有效地提高大口黑鲈的生长与非特异性免疫能力。     

Frequency, composition and stability of associations among individual largemouth bass (Micropterus salmoides) at diel, daily and seasonal scales

Abstract –  A whole-lake acoustic telemetry observatory situated in eastern Ontario was used to continuously monitor the three-dimensional position of 20 largemouth bass ( Micropterus salmoides ) over a 120-h period during the winter and a separate 120-h period during the early spring. These data were used to evaluate the frequency and stability of associations among fish to provide an understanding of seasonal aggregations and the sociobiology of largemouth bass. The temporal and spatial proximity of each fish relative to the other 19 individuals was assessed and, based on our definition of spatial/temporal proximity (i.e., two fish having an average hourly position <2 m apart), associations were shown to vary among fish, as well as diurnally, daily and seasonally. Associations during the winter were found to be more stable and involved fewer fish than associations during the spring. Of those fish that formed pair aggregations during the winter and spring study periods, male–female pairs occurred more often than male–male and female–female pairs. Our analysis also demonstrated that associations occurred primarily during daylight hours, suggesting that fish may use visual cues to form these aggregations.     

Dietary synbiotics improved the growth,feed utilization and intestinal structure of largemouth bass (Micropterus salmoides) juvenile

This study investigated the effect of dietary synbiotics on the growth, feed utilization and intestinal histology of largemouth bass (Micropterus salmoides). A commercial synbiotic product containing dried powder of yeast, Bacillus subtilis and mannan oligosaccharides was supplemented in basal diet with 0 g/kg (control), 1.0, 2.0, 4.0 and 6.0 g/kg, respectively, and then, the five diets were fed to largemouth bass with body weight of 4.5 ± 0.1 g for 8 weeks. The results showed that the supplementation of 2.0, 4.0 and 6.0 g/kg synbiotics increased weight gain by 20.6%, 17.7% and 11.8% (p < .05) and decreased feed conversion ratio by 0.20, 0.18 and 0.12 (p < .05), respectively, when compared to the control. The protein retention, lipid retention, apparent digestibility coefficient of dry matter and crude protein, and the intestinal villus height and width of 2.0 and 4.0 g/kg synbiotic groups were significantly higher than those of the control (p < .05). The intestinal protease activity and serum lysozyme activity were increased by the addition of 2.0 and 4.0 g/kg synbiotics (p < .05). In conclusion, dietary synbiotics improved the growth, feed utilization and intestinal structure of juvenile largemouth bass, and the recommended inclusion level was 2.0–4.0 g/kg.     

大口黑鲈对饲料中蛋氨酸需求量的评定

为了评定大口黑鲈对饲料中蛋氨酸的最适需求量,配制了蛋氨酸含量分别为0.61%,0.82%,0.98%,1.21%,1.42%和1.59%的6水平等氮等能饲料(44.39%粗蛋白质,0.30%胱氨酸,19.81 kJ/g总能),以初始体重为(37.88±0.40)g的大口黑鲈为试验对象,进行了66 d的饲养试验。饲养试验在室内循环水养殖系统中进行,每饲料处理设3个重复,每重复放养试验鱼25尾。饲养试验采取表观饱食投喂,每天投喂两次(8:30和15:30)。试验期间水温(27±1)℃,溶解氧6 mg/L以上。结果表明,试验鱼的特定生长率、饲料效率、蛋白质效率、蛋白沉积率随着饲料中蛋氨酸水平从0.61%到1.21%的升高而显著提高(P<0.05),此后则呈降低的趋势。饲料中蛋氨酸水平对全鱼和肌肉中粗蛋白含量有显著影响(P<0.05);但各组间水分、粗脂肪和粗灰分含量差异不显著(P>0.05)。0.61%蛋氨酸的饲料组的肝体比和脏体比显著大于其他组(P<0.05),其他组间无显著差异(P>0.05)。饲料中蛋氨酸水平显著影响血清溶菌酶活力,头肾白细胞吞噬活性及其呼吸爆发活性(P<0.05)。以特定生长率为评价指标经二次回归分析得出,当饲料中的胱氨酸占饲料蛋白质的0.68%时,大口黑鲈对饲料中蛋氨酸的最适需求量为1.22%,占饲料蛋白质的2.75%。     

Diel habitat selection of largemouth bass following woody structure installation in Table Rock Lake,Missouri

Largemouth bass Micropterus salmoides (Lacepède) use of installed habitat structure was evaluated in a large Midwestern USA reservoir to determine whether or not these structures were used in similar proportion to natural habitats. Seventy largemouth bass (>380 mm total length) were surgically implanted with radio transmitters and a subset was relocated monthly during day and night for one year. The top habitat selection models (based on Akaike's information criterion) suggest largemouth bass select 2–4 m depths during night and 4–7 m during day, whereas littoral structure selection was similar across diel periods. Largemouth bass selected boat docks at twice the rate of other structures. Installed woody structure was selected at similar rates to naturally occurring complex woody structure, whereas both were selected at a higher rate than simple woody structure. The results suggest the addition of woody structure may concentrate largemouth bass and mitigate the loss of woody habitat in a large reservoir.     

大口黑鲈苗种致病性类志贺邻单胞菌的分离和鉴定

对江苏南京某养殖场温室养殖的患病大口黑鲈鱼种进行病原分离,得到1株优势菌株,命名为Q-1.对其进行生化检测以及回归感染试验,结合16S rRNA基因序列测定,确定菌株Q-1为类志贺邻单胞菌(Plesiomonas shigelloides).药敏试验结果表明,菌株Q-1对恩诺沙星、硫酸新霉素、氟苯尼考、盐酸多西环素和氟...