Willow Shiner Research Articles

Role of free neuromasts in larval feeding of willow shiner Gnathopogon elongatus caerulescens Teleostei, Cyprinidae

It has been reported that the larvae of willow shiner Gnathopogon elongatus caerulescens have many free neuromasts on their body surface. This study examined the ability of the willow shiner larvae to feed on zooplankton by mechanoreception by the free neuromasts. Feeding experiments using untreated larvae and larvae treated with streptomycin, which impairs free neuromast function, were conducted under light and completely dark conditions. The larvae were put into Petri dishes, then nauplii of Artemia salina were introduced. The average number of Artemia eaten by the larvae was expressed as the average ingestion rate of Artemia/10 min. The ingestion rate of Artemia for untreated larvae was 12.3 under light conditions and 10.6 Artemia/10 min. even in complete darkness. The ingestion rate in the larvae treated with streptomycin was 11 under light conditions and only 0.8 Artemia/10 min under dark conditions. The low rate in the treated larvae under dark conditions must be due to impairment by the streptomycin. Therefore, the high ingestion rate for the untreated larvae under dark conditions would be surely dependent on mechanoreception. The results indicate that larval willow shiner is able to feed on zooplankton under limited light conditions.

Herbicides in water and fish from rivers flowing into lake Biwa

Surveys of twelve herbicides were performed for water and fish samples obtained from seven rivers flowing into Lake Biwa from April in 1994 to March in 1996. Eleven herbicides were detected at high frequency for molinate, simazine, bromobutide, simetryne, benthiocarb, preti‐lachlor, oxadiazon and mefenaset but at low frequency for terbucarb, butachlor and CNP. Molinate, simetryne, benthiocarb, oxadiazon and mefenaset were detected in ayu sweetfish, pale chub and dark chub but not for simazine, butachlor, pretilachlor and CNP in spite of their detections in the river water. These are probably due to their low bioconcentration potential or temporary contamination. The bioconcentration factors (BCF) of molinate, benthiocarb, oxadiazon and simetryne in the three species of fish calculated from the field data were approximately consistent with the BCF values from the laboratory data on willow shiner or topmouth gudgeon. However, the difference of fish species should be considered for the evaluation of the field BCF data by the laboratory BCF data.

Pesticides in water and fish from rivers flowing into Lake Biwa.

Surveys of twelve herbicides were performed for water and fish samples obtained from seven rivers flowing into Lake Biwa from April in 1994 to March in 1996. Eleven herbicides were detected at high frequency for molinate, simazine, bromobutide, simetryne, benthiocarb, preti‐lachlor, oxadiazon and mefenaset but at low frequency for terbucarb, butachlor and CNP. Molinate, simetryne, benthiocarb, oxadiazon and mefenaset were detected in ayu sweetfish, pale chub and dark chub but not for simazine, butachlor, pretilachlor and CNP in spite of their detections in the river water. These are probably due to their low bioconcentration potential or temporary contamination. The bioconcentration factors (BCF) of molinate, benthiocarb, oxadiazon and simetryne in the three species of fish calculated from the field data were approximately consistent with the BCF values from the laboratory data on willow shiner or topmouth gudgeon. However, the difference of fish species should be considered for the evaluation of the fiel...

Development of Free Neuromasts with Special Reference to Sensory Polarity in Larvae of the Willow Shiner, Gnathopogon elongatus caerulescens (Teleostei, Cyprinidae)

To find how larval fish sense mechanical stimuli via their free neuromasts, we examined morphological changes in free neuromasts in the larval willow shiner, Gnathopogon elongatus caerulescens. Free neuromasts were found on the body surface of newly hatched larvae and their number increased on both the head and trunk with larval growth. The apical surface of free neuromasts changed in outline from a circle to a lozenge shape as the number of sensory cells increased in the prelarval stage, and then the cupulae of the free neuromasts changed from a stick-like to a blade-like shape. Seven-day-old larvae were at the postlarval stage and had many free neuromasts that were nearly mature. All free neuromasts contained sensory cells of opposing polarity. The orientation of the maximum sensitivity of free neuromasts, decided from the polarity of the sensory cells, coincided with the minor axis of the lozenge-shaped outline of the apical surface of the free neuromasts, and was in the same axis as the direction in which the blade-like cupulae bent. The change to a blade-like shape would cause a stimulus parallel to the minor axis to be perceived as being stronger than the same stimulus from other directions. The polarity of trunk neuromasts was usually oriented along the antero-posterior axis of the fish body, but a few had dorso-ventral orientation. On the head, free neuromasts were oriented on lines tangential to concentric circles around the eye.

Cupular Growth of Embryonic Free Neuromasts in the Willow Shiner <i>Gnathopogon elongatus caerulescens</i> and the Pattern in the Changes in Cupular Length after Hatching

This study examined the length of embryonic cupulae of willow shiner. Before hatching, embryos had long cupulae, but after hatching the cupulae became short length.

THE RELATIONSHIP BETWEEN THE LENGTH OF THE CUPULAE OF FREE NEUROMASTS AND FEEDING ABILITY IN LARVAE OF THE WILLOW SHINER GNATHOPOGON ELONGATUS CAERULESCENS (TELEOSTEI, CYPRINIDAE)

Free mechanosensory neuromasts of larval fishes have been described as playing a complementary role to vision in feeding behaviour (Disler, 1971; Iwai, 1972a,b). In certain species or under limited conditions, free neuromasts play a major role in detecting prey. The larvae of mottled sculpin Cottus bairdi can feed on Artemia in the dark by using free neuromasts (Jones and Janssen, 1992). Artificially blinded surface-feeding Aplocheilus lineatus can detect insects on the water surface by means of free neuromasts (Muller and Schwarts, 1982; Tittel et al. 1984; Bleckmann, 1988; Bleckmann et al. 1989). Furthermore, vibrations produced by swimming crustaceans are known to be a potent natural stimulus for the lateral line system in the Antarctic fish Pagothenia borchgrevinki (Montgomery and Macdonald, 1987; Montgomery, 1989). We found that larvae of a plankton feeder, the willow shiner Gnathopogon elongatus caerulescens (Sauvage) (Cypriniformes, Cyprinidae), fed on nauplii of Artemia in complete darkness. Ototoxic compounds, such as streptomycin, have been shown to disturb the function of the lateral line organ or free neuromasts (Kaus, 1987; Blaxter and Fuiman, 1989; Janssen, 1990; Jones and Janssen, 1992). Willow shiner larvae treated with streptomycin sulphate no longer feed on Artemia in the dark (Y. Mukai, in preparation). The willow shiner inhabits calm lakes and feeds on zooplanktonic prey (Nakamura, 1949). The larvae show a high sensitivity to minute water displacements. From these observations and from our findings, it appears that larval willow shiner must feed on zooplankton by using free neuromasts in the dark. In larval willow shiner, the vane-like cupulae of the free neuromasts protrude from the body surface and the long cupulae are 100-250 microm in length (Mukai and Kobayashi, 1991). The prey is detected by the free neuromasts as a result of a slight bending of the cupula in response to local water movements. The shape of the cupula, especially its length, must therefore be related to the sensitivity of the free neuromast, as inferred from the results of Coombs and Janssen (1989) and van Netten and Kroese (1989).

Accumulation and excretion of pesticides used as insecticides or fungicides in agricultural products by the willow shiner Gnathopogon caerulescens

The average bioconcentration factors (BCF) in the whole body of willow shiner ( Gnathopogon caerulescens) after 24–336 hr exposure were 810 for chlorpyriphosmethyl, 802 for vamidothion, 110 for edifenphos, 25 for ethoprophos, 83 for bendocarb, 39 for pirimicarb and 114 for methyl parathion. The correlations between a logarithm of 48 hr- Lc 50 to carp (log Lc 50 and the parameters (a logarithm of n-octanol-water partition coefficiens (log P ow) and log BCF in willow shiner) were investigated for the pesticides studied here and already reported. The correlation factor ( r) was −0.136 ( N = 21) for log Lc 50 vs log P ow and 0.039 ( N = 24) for log Lc 50 vs log BCF. The excretion rate constants ( k) from the whole body of the fish were 0.01 hr −1 for chlorpyriphosmethyl, 0.03 hr −1 for vamidothion, 0.11 hr −1 for edifenphos, 0.27 hr −1 for ethoprophos, 0.18 hr −1 for bendiocarb, 0.01 hr −1 for pirimicarb and 0.08 hr −1 for methyl parathion. The correlation between log k and log BCF was investigated for 22 pesticides already reported and studied here. The r value was not so high (−0.537, N = 22) but higher (−0.672, N = 2) in the case of excluding simetryne.

Pesticides in water and fish from rivers flowing into Lake Biwa (III)

Surveys of seventeen organophosphorous pesticides were performed for water and fish samples obtained from seven rivers flowing into Lake Biwa in 1991. Seven pesticides were detected at high frequency for diazinon, IBP, fenthion and fenitrothion, and at low frequency for malathion, phenthoate and edifenphos in the water samples. The field data on accumulation and excretion of these pesticides by ayu sweetfish (Plecoglossus altivelis), pale chub (Zacco platypus) and dark chub (Zacco temminckii) were approximately consistent with their bioconcentration factors (BCF) and excretion rates calculated from the laboratory data on willow shiner. From these data, it has become apparent that the contamination of the fishes by these pesticides in the field can be approximately estimated from the laboratory data.

Extremely Long Cupulae of Embryonic Neuromasts in Cyprinid Fish

Willow shiner delayed hatching embryo had extremely long cupulae. The length was about 500 μm. Especially delayed hatching embryo had longer cupulae.

Accumulation and excretion of organophosphorous pesticides by willow shiner

Bioconcentration and excretion of 8 organophosphorous pesticides were studied for willow shiner ( Gnathopogon caerulescens ). The average bioconcentration factors (BCF) in the whole body of the fish after 24 – 168 hr exposure were 0.8 for dichlorvos, 76 for salithion, 18 for methidathion, 29 for pyridaphenthion, 481 for fenthion and 36 for phosmet, Further, the BCF values of the other pesticides after 168 hr exposure were 713 for phenthoate and 1682 for EPN. The correlation between n-octanol-water partition coefficients (P OW) and BCF in willow shiner was investigated for 19 pesticides studied here and already reported. The correlation factor (r) was not so high (0.6819, n=19) but higher (0.9085, n=18) in case excluding captan. The excretion rate constants (k) from the whole body of willow shiner were 0.20 hr −1 for salthion, 0.05 hr −1 for phenthoate, 0.27 hr −1 for methidathion, 0.20 hr −1 for pyridaphenthion, 0.07 hr −1 for fenthion, 0.04 hr −1 for EPN and 0.28 hr −1 for phosmet.

Pesticides in water and fish from rivers flowing into Lake Biwa (II)

Surveys of pesticides (diazinon, IBP, malathion and MEP) were performed for water and fish samples obtained from seven rivers flowing into Lake Biwa in 1990. The field data on accumulation of pesticides by pale chub ( Zacco platypus ) and ayu sweetfish ( Plecoglossus altivelis ) were compared with the laboratory experimental data on willow shiner ( Gnathopogon caerulescense ) and topmouth gudgeon ( Pseudorasbora parva ). The bioconcentration factors (BCF) of pesticides in the field could not be satisfactorily estimated from the experimental data. This is not only due to the difference of fish species but also the reason that the concentrations of these pesticides in the river water are changeable and those in the fish body do not reach plateaus instantly.

Accumulation and excretion of pesticides used in golf courses by carp ( Cyprinus carpio) and willow shiner ( Gnathopogon caerulescens)

1. The average bioconcentration factors (BCF) in whole body of willow shiner ( Gnathopogon caerulescens) were 3.9 for simazine, 18 for chlorothalonil and 350 for captan. 2. The average BCF values in whole body of carp ( Cyprinus carpio L.) were 220 for tolclofos-methyl, 460 for chlorpyriphos, 20 for flutolanil, 27 for isoprothiolane, 25 for chlorothalonil, 100 for captan, 440 for isoxathion and 360 for iprodione. 3. The correlations between n-octanol-water partition coefficients ( P ow) and BCF in willow shiner and carp were investigated for the pesticides studied here and already reported. Correlation factors ( r) except captan were 0.9391 ( N = 10) for willow shiner and 0.7747 ( N = 15) for both fishes. 4. The excretion rate constants ( k) from whole body of willow shiner were 0.77 hr −1 for simazine, 0.04 hr −1 for chlorothalonil and 0.02 hr −1 for captan. 5. The k values from whole body of carp were 0.04 hr −1 for tolclofos-methyl, 0.02 hr −1 for chlorpy-riphos, 0.12 hr −1 for flutolanil, 0.19 hr −1 for isoprothiolane, 0.01 hr −1 for captan and 0.03hr −1 for isoxathion.bl]

Accumulation and excretion of tri- n-butyltin chloride and triphenyltin chloride by willow shiner

1. The bioconcentration factors (BCF) of both Bu 3SnCl and Ph 3SnCl via gill intake of willow shiner ( Gnathopogon caerulescens) reached plateaus after 28 days of exposure. The average BCF values of Bu 3SnCl and Ph 3SnCl ( N = 2) were 3620 and 2300, respectively, after 28–35 days of exposure. 2. The BCF values by oral intake of willow shiner reached plateaus after 42 days for Bu 3SnCl and probably after the same period for Ph 3SnCl. The average BCF values of Bu 3SnCl and Ph 3SnCl ( N = 2) were 0.08 and 0.10, respectively, after 42–49 days of exposure. 3. The order of these compounds (Bu 3SnCl > Ph 3SnCl) in the accumulation potential via gill intake was reversed compared with that by oral intake.

Pesticides in water and fish from rivers flowing into Lake Biwa

Surveys of twelve herbicides were performed for water and fish samples obtained from seven rivers flowing into Lake Biwa from April in 1994 to March in 1996. Eleven herbicides were detected at high frequency for molinate, simazine, bromobutide, simetryne, benthiocarb, preti‐lachlor, oxadiazon and mefenaset but at low frequency for terbucarb, butachlor and CNP. Molinate, simetryne, benthiocarb, oxadiazon and mefenaset were detected in ayu sweetfish, pale chub and dark chub but not for simazine, butachlor, pretilachlor and CNP in spite of their detections in the river water. These are probably due to their low bioconcentration potential or temporary contamination. The bioconcentration factors (BCF) of molinate, benthiocarb, oxadiazon and simetryne in the three species of fish calculated from the field data were approximately consistent with the BCF values from the laboratory data on willow shiner or topmouth gudgeon. However, the difference of fish species should be considered for the evaluation of the fiel...

Accumulation and excretion of oxadiazon, CNP and chlomethoxynil by willow shiner

1. The concentrations of oxadiazon, CNP and chlomethoxynil in whole body of willow shiner ( Gnathopogon caerulescens) reached plateaus in 7 days exposure. 2. The average bioconcentration factors (BCF) in whole body of the fish were 1226 for oxadiazon, 5689 for CNP and 3930 for chlomethoxynil after 7–14 days exposure. 3. The excretion rate constants from whole body of the fish were 0.30 day −1 for oxadiazon, 0.10 day −1 for CNP and 0.21 day −1 for chlomethoxynil, assuming their excretion process to be first-order kinetics.

Bioconcentration and excretion of diazinon, IBP, malathion and fenitrothion by willow shiner

Bioconcentration and excretion of diazinon (diethyl 2‐isopropyl‐4‐methyl‐6‐pyrimidinyl phosphorothionate), IBP (S‐benzyl diisopropyl phosphorothiolate), malathion (S‐1,2‐bis(ethoxycarbonyl)ethyl dimethyl phosphorothiolothionate) and fenitrothion (dimethyl 4‐nitro‐m‐tolyl phosphorothionate) was studied for the fresh‐water fish, willow shiner (Gnathopogon caerulescens). The concentrations of these pesticides in whole body of fish reached plateaus in 6–48 h exposure (IBP 6h, fenitrothion and malathion 24 h, diazinon 48 h). The average values of bioconcentration factors (BCF) in whole body of fish were 33.2 for IBP, 398.5 for fenitrothion, 34.4 for malathion and 247.9 for diazinon through the 168 h exposure period. The excretion rate constants from whole body offish were 0.07b‐1 for diazinon, 0.07b‐1 for fenitrothion and 0.49h‐1 for malathion assuming their processes to be first‐order kinetics. For IBP, the rate constant was 0.0017gng‐lh‐1 assuming the process to be second‐order kinetics.

Bioconcentration and excretion of benthiocarb and simetryne by Willow Shiner

Bioconcentration and excretion of benthiocarb and simetryne was studied for willow shiner (Gnathopogon caerulescens). Average values of logarithm of the bioconcentration factors (logBCF) for 14 days were 1.82 for benthiocarb and 0.31 for simetryne. Excretion of benthiocarb and simetryne from willow shiner was carried out in clean water for 7 days after bioconcentration of these chemicals in the test water for 14 days. The excretion rate constants were 0.073h‐1 for benthiocarb and presumed to be about 0.13h‐1 for simetryne assuming their processes to be first‐order kinetics.

Comparative studies on additive effects of sodium dodecylbenzensulfonate and sodium stearate on uptake of chemicals by willow shiner ( Gnathopogon caerulescens)

1. 1. Comparative studies between sodium dodecylbenzenesulfonate (DBS) and sodium stearate (SNa) were performed on the additive effects of the uptake of chemicals in a fresh water fish, the willow shiner ( Gnathopogon caerulescens), by the use of a continuous flow water system. 2. 2. The chemicals selected were 2,4,6-trichlorophenyl-4′-nitrophenyl ether (CNP) as a non-polar lipophilic substance and cadmium salt (Cd) as polar hydrophilic substance. 3. 3. DBS had no promotive and depressed effects on the uptake of Cd. 4. 4. SNa had no promotive and depressed effects on the uptake of CNP and Cd.

Correlative studies on changes in lipid composition of gills and uptake of chemicals of willow shiner fish ( Gnathopogon caerulescens) by exposure to detergent

1. 1. One group of willow shiner ( Gnathopogon caerulescens) was exposed to 0.1 mg/l dodecylbenzenesulfonate (DBS) for analysis of lipid composition of gill extracts. 2. 2. Another group of fish was exposed to 0.0003 mg/l 2,4,6-trichlorophenyl-4′-nitrophenyl-ether (CNP) after regular intervals of pre-exposure to 0.1 mg/l DBS for analysis of uptake of CNP. 3. 3. The whole body residues of CNP were characterized by a 60% drop in DBS pre-exposure for 14 and 21 days. 4. 4. The cholesterol/total phospholipid ratio increased to 0.22 and 0.28 after 14 and 21 days from the normal of 0.18. 5. 5. These biochemical results might be correlated with the changes observed by the uptake of CNP.

魚類のカロテノイドに関する比較生化学的研究 ＩＶ カマツカ亜科６魚種のカロテノイド成分

Carotenoid pigments from the fin and skin of willow shiner, slender-head shiner, deep-head shiner, Japanese barbel, gudgeon and oily shiner were investigated. Cynthiaxanthin was most predominant (34-60%) in all six species followed by zeaxanthin (10-31%) which was found in all with the exception of gudgeon. Lutein (4-19%), known to be characteristic of freshwater fishes, was present in relatively moderate amounts. In addition to these three major pigments, cryptoxantnin, tunaxanthin, diato-xanthin, triol and tetraol (β-carotene type), astacene and β-doradecin were found present only in small amounts.