Response of bighead carp Aristichthys nobilis and Asian catfish Clarias macrocephalus larvae to free-living nematode Panagrellus redivivus as alternative feed

The use of Panagrellus redivivus as live feed for bighead carp and Asian catfish larvae was tested. In experiment 1, carp larvae were given Artemia nauplii (control) or Panagrellus twice daily for 21 days. A third treatment consisted of unfed larvae. The same three treatments were used in experiment 2 plus another with a commercial entomopathogenic nematode (EPN). Bighead carp larvae given Panagrellus in experiment 1 had much lower growth and survival than those fed Artemia nauplii. This could be due to low nematode density (5–30 mL^?1 water) during feeding. The unfed larvae had 100% mortality by days 11–13. In experiment 2, growth and survival of carp larvae given Artemia nauplii (5–10 mL^?1) and Panagrellus (50 mL^?1) did not differ significantly (P > 0.05). All unfed larvae had died by day 13, while larvae fed EPN were all dead by day 8. Two experiments on Asian catfish were likewise conducted. In experiment 1, the catfish larvae were fed Tubifex (ad libitum), Panagrellus (50–100 mL^?1 per feeding) orArtemia (5 nauplii mL^?1 per feeding) three times daily for 14 days. In experiment 2, larvae were fed Artemia alone (10 nauplii mL^?1 per feeding), Panagrellus alone (100 mL^?1 per feeding), or their combination with a 38% protein dry diet twice daily. For both experiments, catfish larvae fed Panagrellus had significantly lower growth and survival than those fed Tubifex or Artemia. The combination of Panagrellus and dry diet created little improvement in the growth and survival of catfish larvae.     

Growth and reproductive performance of the Asian catfish Clarias macrocephalus (Gunther) fed artificial diets

Four natural ingredient diets similar in nutrient composition (crude protein = 42–44%; P/E ratio = 115–120 mg/kcal) but different in protein sources, were formulated and fed to hatchery-reared catfish to measure the relative performance of the catfish fed alternative broodstock diets. The control feed was a combination of fish-by-catch and commercial fish pellets. In trial I, growth of the catfish was slow over a 36-week period, but some fish became gravid. Diets 1, 2, and 3 and the control feed were tested in trial II. Growth of fish did not differ significantly (P > 0.05) and female fish in all treatments became gravid. For fish induced to spawn from April to August (1994), hatching rate showed significant differences among treatments (P < 0.05). Relative fecundity, fertilization and hatching rates, and production of 3-day-old larvae were significantly different among fish induced to spawn in November (1994) when another incubation setup was used. Among the diets, diets 2 and 3 best enhanced reproductive performance of the catfish.     

Induced spawning by LHRHa and pimozide in the Asian catfish Clarias macrocephalus (Gunther)

Experiments were conducted to determine the optimum dose of luteinizing hormone-releasing hormone analogue (LHRHa) and pimozide (PIM) injected simultaneously to yield a high ovulation rate and produce sufficient eggs in the Asian catfish Clarias macrocephalus . In June 1990, injection of 0.05 or 0.10 μg LHRHa/g body weight (BW) + 1 μg PIM/g resulted in 100% ovulation, while only 80% of gravid catfish injected 0.025 μg LHRHa + 1 μg PIM/g ovulated. Most of the eggs stripped from 6 out of 8 control fish were not mature. Fertilization and hatching rates of LHRHa + PIM-induced fish (75–90% and 39–51%, respectively) were higher than those of control fish (36–39% and 0–1% respectively). In August and September 1990, at gravid catfish ovulated after injection of 0.05–0.10 μg LHRHa + 1 μg PIM/g BW. However, only 20% of the fish given 0.025 μg LHRHa/g + 1 μg PIM/g BW in August ovulated. No eggs could be striped from any of the control fish in August and September 1990. Techniques developed in this study, showed a simple and effective way of spawning captive catfish, C. macrocephalus . A simultaneous intramuscular injection of 0.05 μg LHRHa + 1 μg PIM/g and stripping of eggs at 16–20 h post-injection have been tested to yield high ovulation, fertilization and hatching rates.     

Isolation and characterization of microsatellites in the Asian walking catfish Clarias macrocephalus

Microsatellite loci were characterized in the walking catfish, Clarias macrocephalus, random clones from a small genomic library using a (GT)₁₅ probe. Primers for DNA amplifications using polymerase chain reaction (PCR) were designed and synthesized for 23 loci. Twelve loci were polymorphic, with the number of alleles ranging from two to 13 alleles per locus. Developed microsatellite primers should prove useful for population studies and genetic mapping of the walking catfish.     

Effect of dietary carbohydrate-to-lipid ratios on growth and feed utilization in Chinese longsnout catfish (Leiocassis longirostris Günther)

An 8‐week growth trial was carried out in a semi‐recirculation system at 26 ± 0.5°C to investigate the optimal dietary carbohydrate‐to‐lipid (CHO:L) ratio for carnivorous Chinese longsnout catfish (Leiocassis longirostris Günther). Triplicate tanks of fish were assigned to each of five isocaloric and isonitrogenous diets with different carbohydrate‐to‐lipid ratios (0.75, 1.48, 1.98, 2.99 and 5.07). The results showed that a higher specific growth rate (SGR) and feed rate (FR) were observed in the fish fed diet ratios of 1.98 CHO:L (P < 0.05). Overloading dietary carbohydrate (5.07 CHO:L ratio) caused skeletal malformations. Apparent digestibility of dry matter (ADC_d) significantly increased with dietary CHO:L ratio (P < 0.05), while significantly higher apparent digestibility of protein (ADC_p) and apparent digestibility of energy (ACD_e) was observed only in the 1.98 CHO:L group (P < 0.05). Whole body contents of dry matter, lipid and energy significantly increased as the CHO:L ratio decreased (P < 0.05). The hepatosomatic index (HSI) was highest at 1.98 CHO:L ratio (P < 0.05). Highest dietary CHO:L ratio resulted in lower liver glycogen, liver lipid, plasma glucose and plasma triacylglycerol (P < 0.05), whereas there was no significant difference in plasma total cholesterol (P > 0.05). High dietary CHO:L ratio caused pathological changes in fish morphology and liver histology. Based on maximum growth, the optimal carbohydrate‐to‐lipid ratio was 1.98 for Chinese longsnout catfish.     

Dietary and seasonal effects on the dorsal meat lipid composition of Japanese (Silurus asotus) and Thai catfish (Clarias macrocephalus and hybrid Clarias macrocephalus and Clarias galipinus)

The effects of dietary lipids and seasonal variation on the lipids of wild and cultured catfish (Japanese catfish, Silurus asotus; Thai catfish, Clarias macrocephalus and hybrid Clarias macrocephalus x Clarias galipinus) were determined by analysis of the lipid content and fatty acid composition of their dorsal meat. The predominant fatty acids of dorsal meat were 16:0, 18:1n-9, 18:2n-6, 20:4n-6 (arachidonic acid, AA), and 22:6n-3 (docosahexaenoic acid, DHA). The DHA content in the diet of Japanese catfish was higher than that in the diet of Thai catfish, and this was reflected in the dorsal meat of the Japanese catfish, which had a remarkably high percentage of DHA compared with the meat of the Thai catfish. Cultured Japanese catfish had a higher percentage of 18:2n-6 than Thai fish and a lower percentage of AA in winter than in summer season. There were also seasonal variations in the percentage of n-6 fatty acids in Japanese catfish. In summer, the fatty acid composition of the cultured Japanese catfish was similar to that of the wild catfish. These fatty acid changes in the lipid classes, triacylglycerol, phosphatidylcholine and phosphatidylethanolamine were similar to those observed for total lipids. These results indicate that the percentage of DHA in the dorsal meat of catfish is influenced by dietary fatty acid, and it may be that it can be increased in cultivated fish by administering a diet containing a large amount of DHA.     

Viability of catfish (Clarias macrocephalus, Gunther) eggs fertilized at varying post-ovulation times

HCG-induced (dose: 2 iug⁻¹ body weight) ovulated eggs of catfish ( Clarias macrocephalus ) remained viable for artificial fertilization up to 10 h post-ovulation without apparent significant loss in fertility. At 12 h post-ovulation viability decreased significantly, showing little or no hatching at 20 h. A limit of 10 h between ovulation and egg-stripping was suggested for this species at an ambient temperature of 26–31° C.     

Superficial neuromasts of the flatfish Peltorhamphus novaezeelandiae (Günther)

Examination using light and transmission electron microscopy showed that each superficial neuromast of the New Zealand sole, Peltorhamphus novaezeelandiae , consists of a typical sensory epithelium lying between two epidermal lappets. The neuromasts occur both singly and in rows over the head and along and above the lateral-line on the body. As well as variation in the shape of the lappets and the size of the organs from different areas of the fish, there is a marked difference between their distribution on the left and right sides. It is suggested that the lapperts may improve the directional sensitivity of the neuromasts, or alternatively, that their function may be purely protective. The possibility is discussed that variation in the size and form of the organs reflects functional differences.     

Growth and morphological development of laboratory-reared larval and juvenile bighead catfish Clarias macrocephalus (Siluriformes: Clariidae)

Morphological development in laboratory-reared larval and juvenile bighead catfish Clarias macrocephalus is described. Body length (BL) of larvae and juveniles was 3.4 ± 0.3 (mean ± SD) mm just after hatching, reaching 11.3 ± 1.0 mm by day 16, and 24.2 ± 2.8 mm by day 40. Overall aggregate fin ray numbers (except for caudal fin procurrent rays) attained full complements by 15.2 mm BL. Gill buds appeared on day 0, those of barbels (four pairs) and primordial nostrils on day 1, and pectoral fins on day 3. All larvae began feeding by day 3. Conical teeth were observed on day 7. Notochord flexion began on day 2, the yolk being completely absorbed during days 7–9. Melanophores were scarce at hatching, increasing with growth to cover almost the entire body except the ventral surface of the abdominal cavity. Proportions of head length, pre-anal length, body depth, eye diameter, and maxillary barbel length became relatively constant after yolk absorption, those of snout length and upper jaw length increasing until ca. 12–13 mm BL and decreasing thereafter. Suprabranchial organ started developing in postflexion larval stage larger than ca. 11.0 mm BL (day 16), and air-breathing was suggested to be functional at that time.     

An anomalous specimen of Rhamdia guatemalensis (Günther, 1864)

In March of 1984 an immature Rhamida guatemalensis (Günther, 1864) lacking the right pectoral fin (Fig. 1) was captured in the Sangregado sector, Arenal Dam, Guanacaste, Costa Rica (10°28' N, 84°46'W) The body colouration and morphometric characteristics were as described for this species (Bussing 1966; Zúñga, 1980). X-ray examination revealed the absence of the radial bones and the fin rays of the right peoctoral fin. External examination of the tegument of this region showed no scars or evidence of accidental loss of the appendage, indicating that the fin had never developed.
Morphometric data from this abnormal specimen are: total length, 14.25 cm, standard length, 11.98cm; maximum height of body, 22.35 cm; maximum width of body, 2.40 cm, caudal peduncle width, 1.27 cm; head length, 3.00cm.     

Blood and other possible inflammatory cells in the sparid Acanthopagrus australis (Günther)

The peripheral blood cells of Acanthopagrus australis include erythrocytes, elongated and rounded thrombocytes, lymphocytes, neutrophils and monocytes. The ultrastructure of lymphocytes, neutrophils and monocytes is described. Type 1 cells with characteristic elongated, eosinophilic granules and type 2 cells with rounded, apparently labile granules are common in the gill filaments and do not increase or decrease significantly in abundance in ectoparasite-infested gill filaments. Extravascular neutrophils tend to be more evident in pathologic tissue. Lymphocytes and the macrophage-like type 3 cells are the most abundant infiltrating cells in pathologic gill tissue. Apart from ultrastructural and histochemical data, granule length and width are sufficient criteria to distinguish between the neutrophil, type 1, type 2 and type 3 cells.     

Structure-function studies of five natural, including catfish and dogfish, gonadotropin-releasing hormones and eight analogs on reproduction in Thai catfish (Clarias macrocephalus).

Five distinct forms of gonadotropin-releasing hormone (GnRH) and their analogs, six of which are newly designed, were used to study reproduction in Thai catfish, Clarias macrocephalus. Determination was made for the percentage of fish that ovulated within 16-18 h; the percentage of eggs fertilized; and the percentage of larva that hatched and survived for 7 days. The results show, firstly, that natural chicken GnRH-II, which is identical with catfish GnRH-II, was significantly more effective at a dose of 300 micrograms/kg than the control injection for the induction of ovulation. Dogfish GnRH at the same dose was also significantly more effective than the control, but was not significantly different from chicken (catfish) GnRH-II for ovulation induction. The novel catfish GnRH-I, mammalian GnRH and salmon GnRH were not effective at 100, 150 or 300 micrograms/kg in Thai catfish. Secondly, 5 of 8 analogs of GnRH at a dose of 20 micrograms/kg resulted in a significantly higher percentage of ovulating fish compared with the control fish. Among these five analogs, the most effective were the two analog forms of chicken GnRH-II (D-Arg6,Pro9 NEt and D-Nal6,Pro9 NEt), followed by the salmon GnRH analog (D-Arg6,Pro9 NEt), a dogfish GnRH analog (D-Arg6,Pro9 NEt) and the mammalian GnRH analog (D-Ala6,Pro9 NEt). Not significantly different from the controls were the two catfish GnRH-I analogs and one of the dogfish (D-Nal6,Pro9 NEt) analogs. The six new analogs had not been previously tested in any animal. Thirdly, the number of fish ovulating was the same whether GnRH was administered in one or two injections.     

瓜实蝇幼虫人工饲料设计及其优化

采用正交试验设计,对瓜实蝇幼虫人工饲料四种主要组成成分南瓜∶玉米粉=1∶1、酵母粉、蔗糖、苯甲酸钠进行优化筛选,以瓜实蝇幼虫的存活率、幼虫历期、老熟幼虫化蛹率、平均蛹重和羽化率作为试验考察指标,筛选出上述4种成分在瓜实蝇幼虫基础人工饲料中的最优量为南瓜∶玉米粉=200 g∶200 g、酵母60 g、蔗糖15 g、苯甲酸钠1.2 g。     

Development of Asian parasitoids in larvae Of Drosophila Suzukii feeding on blueberry and artificial diet

In just a few years, the Asian fly Drosophila suzukii has invaded several continents and has become a very serious pest of many fruit crops worldwide. Current control methods rely on chemical insecticides or expensive and labour‐intensive cultural practices. Classical biological control through the introduction of Asian parasitoids that have co‐evolved with the pest may provide a sustainable solution on condition that they are sufficiently specific to avoid non‐target effects on local biodiversity. Here, we present the first study on the development of three larval parasitoids from China and Japan, the Braconidae Asobara japonica and the Figitidae Leptopilina japonica and Ganaspis sp., on D. suzukii. The Asian parasitoids were compared with Leptopilina heterotoma, a common parasitoid of several Drosophilidae worldwide. The three Asian species were successfully reared on D. suzukii larvae in both, blueberry and artificial diet, in contrast to L. heterotoma whose eggs and larvae were encapsulated by the host larvae. All parasitoids were able to oviposit one day after emergence. Asobara japonica laid as many eggs in larvae feeding in blueberry as in artificial diet, whereas L. heterotoma oviposited more in larvae on the artificial diet and the Asian Figitidae oviposited more in larvae feeding on blueberry. Ganaspis sp. laid very few eggs in larvae in the artificial diet, suggesting that it may be specialized in Drosophila species living in fresh fruits. These data will be used for the development of a host range testing to assess the suitability of Asian parasitoids as biological control agents in invaded regions.     

Cardio-respiratory morphometrics of spangled perch, Leiopotherapon unicolor (Günther, 1859), (Percoidei, Teraponidae)

The heart of Leiopotherapon unicolor comprises 0.135±0.005% of total body weight compared to the average teleost heart size of 0.081±0.002% body weight. The respiratory surface area of 569 mm² g⁻¹ is also much larger than that found in most freshwater fish. The exponent b in the equation Gill Area = a. body wt^b was evaluated at 1.04, whereas the theoretical value for b is only 0.75. It is therefore evident that L. unicolor has an excessively large gill area and a large heart, which facilitate oxygen uptake in hypoxic environments.     

Stocking density‐dependent growth and survival of Asian sun catfish,Horabagrus brachysoma (Gunther 1861) larvae

The aim of the experiment was to evaluate the growth and survival of Horabagrus brachysoma larvae at different stocking densities (3, 7, 13, 20, 27 and 33 larvae L^?1) during their hatchery phase. Total length and wet weight of the larvae consistently decreased (P < 0.05) at the end of 14 and 28 days of rearing as the density increased. The specific growth rate was significantly (P < 0.05) highest at three larvae L^?1 compared to the other five densities. The percent weight gain and survival of larvae was also highest at lowest density. The observation corroborates that catfish larvae can be reared at low densities in stagnant water conditions. Considering the value of larval growth, survival and overall weight gain, the stocking density of seven larvae L^?1 has been identified as the maximum for larval rearing of H.  brachysoma under hatchery conditions.