Effect of temperature on sex ratio in guppy Poecilia reticulata (Peters 1860)

In this study, the effect of temperature on survival and sex ratios of guppy Poecilia reticulata (Peters 1860) was investigated. Treatments of 19, 21 and 22.5°C low and 29, 32 and 35°C high water temperature were used on fry and gravid females for 11 days after parturitions and several days starting from the 16th day after first parturition until second parturition respectively. The high water temperature treatments caused the death of gravid females. Survival rates of heat‐treated fry were generally decreased with increasing and decreasing temperature. The sex ratios of the progenies from survived gravid females were not differed from a balanced sex ratio (P>0.05). The proportion of females increased gradually with decreasing temperature and the proportion of males increased gradually with increasing temperatures rather than having a threshold response in heat‐treated fry. However, mortality of heat‐treated fry was high; it is most likely that our results were biased by sex‐dependent mortality, which were also revealed by corrected sex ratios of the treatment groups and progeny testing of some individuals. These results suggest that a major gene linked to X‐chromosome could be responsible for resistance and sensitivity to both high and low temperature.     

Dietary supplementation with the microalgae Parietochloris incisa increases survival and stress resistance in guppy (Poecilia reticulata) fry

Dietary enrichments with the arachidonic acid (ARA)‐rich microalga, Parietochloris incisa, on the survival of guppy (Poecilia reticulata) fry were examined. Diets were applied via Artemia enrichment to fish from two commercial farms for 34 and 36 days of experimental period (trials 1 and 2, respectively). In trial 1, Artemia nauplii were enriched with dry biomass of whole algal cells at 0 (control), 0.1, 0.2 and 0.4 mg mL^?1. Fry fed with Artemia enriched with 0.4 mg mL^?1 demonstrated the lowest mortality rates (24% and 1% in farms 1 and 2, respectively) compared with controls (36% and 13% in farms 1 and 2, respectively). In trial 2, fry were fed with Artemia, enriched with whole algal cells (0.4 mg ml^?1), algal hexane extract (HE; containing primarily ARA‐rich triacylglycerols and β‐carotene; 0.19 mg ml^?1) or the extraction residue (0.28 mg ml^?1). Acute stress (5 min air exposure) was applied after 18 days. The lowest mortality was recorded in the whole alga‐fed group (av. 26% and 2.6% in farms 1 and 2, respectively), with a slightly, but not significantly higher mortality in the HE‐fed group (av. 29% and 6.2% in farms 1 and 2, respectively). Elevated lysozyme was associated with the reduced mortality. Overall, the use of P. incisa as a dietary supplement for guppy fry during their first month of life enhanced their survival and stress resistance.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

DNA markers for estimation of inbreeding depression and heterosis in the guppy Poecilia reticulata

Molecular markers have significant potential for use in precise breeding programmes in aquaculture. This paper reviews the use of DNA markers to estimate inbreeding depression and heterosis in the guppy Poecilia reticulata. Full‐sib matings revealed that inbreeding causes declines in survival and salinity tolerance, but not in undwarfism, growth and high water temperature tolerance, indicating the effects of inbreeding differ among fitness‐related traits. Salinity tolerance was used to quantify the level of inbreeding depression and heterosis because the trait is strongly sensitive to inbreeding and shows a linear decrease with an increase in inbreeding coefficient. A positive correlation was observed between heterozygosity at microsatellite loci and salinity tolerance among 17 guppy populations. This indicates that heterozygosity estimated from microsatellites is a useful indicator for the estimation of inbreeding depression, suggesting that overall heterozygosity is important for fitness‐related traits that show inbreeding depression. Use of DNA markers to estimate the amount of heterosis in various strain combinations was examined using diallele and reciprocal crosses among four domestic strains. The amount of heterosis differed among the strain combinations and correlated with Nei's genetic distance measured by microsatellites and also by dissimilarity using random amplified polymorphic DNA (RAPD) analysis. This indicates that microsatellite and RAPD markers are useful for estimating the amount of heterosis in various strain combinations, further suggesting that the amount of heterosis depends on the genetic differences between the strains. The present study showed that DNA markers are useful tools for estimating inbreeding depression and heterosis in guppy breeding.     

Using attraction to light to decrease cannibalism and increase fry production in guppy (Poecilia reticulata Peters) hatcheries. II: the effects of light and cannibalistic adults

Predation of newborn fish by cannibalistic adults is a major cause of fry loss in guppy breeding tanks. The efficacy of using light to attract newborn guppies into a safe area, thereby reducing the cannibalism rate, was evaluated in aquaria. The aquaria were divided using small‐mesh netting into a section with adult fish and a safe section without adults, above which a light source was installed to attract the newborns. Both, the presence of cannibalistic adults and the light, increased the number of newborns in the safe section. The effect of the cannibals was pronounced during the day, and the effect of light seemed to be more pronounced at night. The presence of light significantly decreased cannibalism rate after 30 min, but not 16 h after the introduction of newborns. When tested with cannibalistic adults that have not been fed for 5 days prior to testing, cannibalism rate was higher and the effect of light on reducing cannibalism was evident both 30 min and 16 h after the introduction of newborns. The results demonstrated the potential efficacy of using white light in reducing cannibalism and increasing fry yields in guppy hatcheries.     

Effects of different commercial diets on growth performance,health and resistance to Tetrahymena sp. infection in guppies,Poecilia reticulata (Peters)

The effects of feeding guppy fry, Poecilia reticulata (Peters), different commercial diets from BernAqua [MeM (R = Regular, O = Ornamental and P = Premium) and experimental feed (EF] and Ocean Nutrition (ON) on growth was tested for 57 days. Health status and resistance to Tetrahymena infection were analysed at the end of the trial. The highest growth was obtained in fish fed MeM Regular and MeM Premium (mean final weights of 427 and 417 mg respectively). Fish fed EF had a significantly higher rate of spinal deformity (12.7%) than all other feeding groups (3.05% or less). Histological analysis revealed the accumulation of liver glycogen and/or lipid in fish from all feeding groups; fat accumulation in the abdomen was most pronounced in the EF and MeM Regular‐fed fish, and muscle dystrophy was observed in ca. 50% of the fish from all feeding groups except the MeM Ornamental‐fed group. The highest mortality following Tetrahymena infection occurred in fish fed EF (87%) and the lowest mortality in the MeM Ornamental‐fed fish (58%). Mortalities in all other feeding groups ranged between 69% and 76%. In summary, MeM Ornamental feed provided a moderate weight gain, no muscle dystrophy, negligible deformity and the greatest resistance to parasitic infection.     

Urbanisation affects the diet and feeding selectivity of the invasive guppy Poecilia reticulata

The process of urbanisation is increasing the frequency and magnitude of fluctuations in the availability of food resources for fish. In this study, we investigated whether the diet and prey selected by the guppy Poecilia reticulata reflect the different levels of urbanisation using the total area of impervious surface soil as the metric. Rural streams (low percentage of urbanisation—LPU) and urban streams (high percentage of urbanisation—HPU) were sampled during both the rainy and dry seasons. The hypothesis tested was that the diet and selective behaviour differ spatially and seasonally between LPU and HPU streams. Among the analysed items, seasonal significant differences were only observed in HPU streams. In LPU streams, the trophic spectrum was wider, and a higher diversity of prey was selected. In HPU streams, the diet richness was lower with a dominance of Chironomidae, and there was also less variability in selected prey. Ephemeroptera and Trichoptera were always avoided, but Coleoptera were avoided only in LPU, while Oligochaeta were avoided in HPU streams. Thus, the diet and prey selected by P. reticulata were different between LPU and HPU streams, and this species has potential to compete for food with the native fauna in a wide variety of environmental conditions and available resources. Therefore, this dietary flexibility probably offers competitive advantages when colonising and establishing in a new habitat.     

Effect of Echinacea purpurea on growth and survival of guppy (Poecilia reticulata) challenged with Aeromonas bestiarum

The effects of Echinacea purpurea supplementation on growth performance, nutrient utilization, body composition and disease resistance were studied in the ornamental fish Poecilia reticulata. Five diets were used, each differing in Echinacea content (0 g kg^?1 diet – control, 5 g kg^?1 diet – group 1, 10 g kg^?1 diet – group 2, 20 g kg^?1 diet – group 3, 30 g kg^?1 diet – group 4 and 60 g kg^?1 diet – group 5), and the fish were fed twice daily at a rate of 30 g kg^?1 body weight per day for 67 days. The gain in the body weight and the condition factor were significantly increased in groups 2‐5, whereas specific growth rate and feed conversion ratio were significantly increased in the supplemented groups (P < 0.05). Cumulative mortalities after challenge infection with the fish pathogen Aeromonas bestiarum were the lowest in the groups supplemented with Echinacea. Log‐rank tests showed significant differences between the supplemented groups 1, 2, 3, 4 and 5 and the control group (P = 0.0074, P = 0.0075, P = 0.00507, P = 0.00001 and P = 0.00001, respectively). The results of this study indicate that Echinacea improves body weight gain and resistance against challenge infection in fish.     

Tetrahymena sp. infection in guppies, Poecilia reticulata Peters: parasite characterization and pathology of infected fish

Tetrahymena sp. infection was diagnosed in guppies imported from Singapore. The parasite was isolated (Tet-NI) and optimally cultured in vitro in RM-9 medium. Cytological analyses [silver-staining and scanning electron microscopy (SEM)] revealed a pyriform-shaped, 64 × 41-μm holotrich ciliate without caudal cilium, containing a macro-nucleus (18.25 × 16.83 μm) and micro-nucleus (5.73 × 5.40 μm). Wet-mount examination and histological analyses of fish exposed to the parasite by co-habitation, immersion and infection by i.p. (intra-peritoneal) and i.m. (intra-muscular) injection revealed numerous ciliates on the skin, and in the gill and caudal fin blood vessels. Ciliates surrounded internal organs, the peri-orbital region of the eye, and were observed inside developing guppy embryos. Some muscle necrosis was associated with infection, but little or no inflammatory response. Immersion, co-habitation and i.m. injection caused relatively high infection rates and levels in the skin and tail, and lower infection in the gill blood vessels and internal organs; i.p. injection caused higher infection in the gill blood vessels and internal organs. Co-habited fish had relatively high infection levels in the hind-gut sub-mucosa. This is the first report of controlled systemic infection by Tetrahymena sp.     

Using attraction to light to decrease cannibalism and increase fry production in guppy (Poecilia reticulata Peters) hatcheries. I: phototactic reaction and light colour preference

A substantial proportion of newborns are lost in guppy hatcheries to cannibalism by the broodfish although small‐mesh baskets, which allow passage to small fry only and provide a predation‐free area, are used in breeding tanks. If newborn guppies are attracted by light, illuminating the small‐mesh baskets might enhance aggregation of newborns in the mesh basket and thus mitigate cannibalism effect. In this study, light attraction and light colour preference in newborn guppies were investigated. Testing the attraction to white, blue, green and red LED lights revealed attraction to each of these light types in newborns, but no significant attraction in adult females. Both newborns and adult females exhibited reduced mobility under red LED light. In a preference experiment in which all light colours were presented simultaneously, newborns were most attracted to the white light (52.0% of the newborns) and least attracted to the red light and darkness (6.8% and 6.7% of the newborns respectively). These results support the potential efficacy of using white light to attract newborns into the baskets in guppy breeding tanks and reduce cannibalism effects.     

不同投饵率对花鳗鲡黑仔苗生长的影响

实验设置1.0%,1.5%,2.0%,2.5%,3.0%五个不同投饵率水平,在水温30℃的条件下,选取同一种饲料,对规格为3.67±0.30g的花鳗鲡黑仔苗进行40d的生长实验。结果表明,投饵率对花鳗鲡黑仔苗的相对增重率、特定生长率、饲料转化率均有显著性影响（p〈0.05）,花鳗鲡黑仔苗生长的适宜投饵率是2.0%;在此投饵率下,花鳗鲡黑仔苗的饲料转化率为（47.39±1.17）%,特定生长速率为（1.08±0.03）%/d,相对增重率为（52.49±1.04）%,存活率为100%。     

Rhabdomyosarcoma in the Japanese medaka, Oryzia latipes (Temminck & Schlegel) and guppy, Poecilia reticulata Peters

Abstract. Three cases of skeletal muscle neoplasms occurring in two small fish species used in carcinogen tests are reported. The cases illustrated a wide range of histologic patterns, and consisted of a well-differentiated juvenile type, a well-differentiated pleomorphic type and a poorly differentiated pleomorphic type. A rhabdomyosarcoma with juvenile type features developed in the Japanese medaka, Oryzias latipes , exposed to 0·5 ml/1 of the solvent dimethylformamide. A pleomorphic type rhabdomyosarcoma occurred in one medaka and in one guppy, Poecilia reticulata , exposed to the carcinogen methylazoxymethanol acetate. These cases indicate the potential for skeletal muscle cells in medaka and guppy to become neoplastic but, because the tumours occurred at a low frequency, there may not necessarily be a chemical aetiology.     

Short-term dietary supplementation with the microalga Parietochloris incisa enhances stress resistance in guppies Poecilia reticulata

Two trials were conducted to determine the effects of dietary enrichments with the microalga Parietochloris incisa , rich in arachidonic acid (ARA), on stress resistance in guppies Poecilia reticulata . The microalga was added to commercial diets as a neutral lipid (NL) extract and its fractions or as broken cells. Experimental diets were applied for a period of 14 days. In trial 1, commercial diets were supplemented with NL (containing 25 mg ARA and 0.11 mg β-carotene g⁻¹ feed), its triacylglycerol (TAG) fraction (containing 25 mg ARA g⁻¹ feed and no β-carotene) and the β-carotene fraction (containing 0.11 mg carotenoid g⁻¹ feed and minute amounts of ARA). Neutral lipid-fed fish demonstrated the highest resistance ( P <0.05) to osmotic stress (32-ppt NaCl), followed by fish fed with diets supplemented with TAG and β-carotene alone, which were more resistant than control ( P <0.05). In trial 2, fish fed diets supplemented with higher levels of broken alga (26.1 mg ARA g⁻¹ feed) were more resistant ( P <0.05) to stress as compared with fish fed lower ARA (16.3 mg g g⁻¹) or an unsupplemented control diet. We suggest a dietary supplementation with broken P. incisa cells to enhance stress resistance in guppies before a stressful event.     

Effect of ammonia-N on growth and feeding of juvenile Macrobrachium rosenbergii (De-Man)

Survival rate, growth and feed intake were determined for late juveniles (4.31 ± 0.18 g) of river prawn Macrobrachium rosenbergii in freshwater with total ammonia‐N (NH₃‐N+NH₄‐N) concentrations of 0.015 (control), 0.5, 1.0 and 1.5 mg L⁻¹ for 60 days at pH 7.53 ± 0.04 and temperature 24.0 ± 2.5°C. Survival rate was significantly (P<0.05) lower (54 ± 4.2–70 ± 5.4%) for total ammonia concentrations from 0.5 to 1.5 mg L⁻¹ [0.0139–0.0419 mg L⁻¹ of unionized ammonia (NH₃)]. Growth (0.026–0.030 g day⁻¹ range) of the prawns did not differ for the different NH₃ levels but were significantly (P<0.05) lower compared with control (0.056 g day⁻¹). Feed intake rates also diminished significantly (P<0.05) from 77.60 ± 2.45% at control (0.015 mg L⁻¹ NH₃‐N) to 48.69 ± 2.13% at 1.5 mg L⁻¹ NH₃‐N (0.0419 mg L⁻¹ of unionized NH₃).     

Replacement of fish meal with two fermented soybean meals in diets for rainbow trout (Oncorhynchus mykiss)

The present study investigated the effect of fish meal (FM) replacement with fermented soybean meal (FSM) on growth and feed utilization of rainbow trout. Two FSM products, FSM1 (more fermentation with more small peptide and acid than FSM2) and FSM2 were used to replace 20%, 40% and 60% of FM in control diet (250 g/kg FM), respectively (FSM1‐20, FSM1‐40, FSM1‐60, FSM2‐20, FSM2‐40 and FSM2‐60). Then the seven diets were fed to rainbow trout (18.1 g) for 8 weeks. Weight gain (WG), feed conversion ratio (FCR) and digestibility of crude protein and dry matter showed no significant difference among the groups of FSM1‐20, FSM1‐40, FSM2‐20, FSM2‐40 and the control, but WG significantly decreased and FCR increased when 60% FM was replaced by both FSMs (p < .05). The replacement of 40%, 60% FM resulted in lower villus height than the control (p < .05), and intestinal protease activity was lower in FSM2‐40, FSM2‐60 and FSM1‐60 groups than the control group (p < .05). In addition, the activity of alkaline phosphatase and superoxide dismutase increased with increasing levels of FSM (p < .05). In conclusion, dietary fish meal could be replaced by 40% with both FSMs without adverse effects on growth and feed utilization of rainbow trout based on an eight weeks feeding trial.     

Simultaneous effect of sex and dose on efficacy of clove oil,tricaine methanesulfonate, 2‐phenoxyethanol and propofol as anaesthetics in guppies,Poecilia reticulata (Peters)

We studied the simultaneous effect of sex and dose on anaesthesia efficacy to estimate, if possible, the lowest effective dose (LED) for clove oil, tricaine methanesulphonate (MS‐222), 2‐phenoxyethanol (2‐PE) and propofol in mature guppies. LED is the lowest dose needed to reach A5 stage in a mean time of 3 min, with mean recovery (R5) time of 5 min. We used four doses/anaesthetic: 25, 50, 75 and 100 mg/L for clove oil; 120,140,160 and 180 mg/L for MS‐222; 800, 1,000, 1,200 and 1,400 mg/L for 2‐PE, and 7.50, 8.25, 10.00 and 11.25 mg/L for propofol. Each dose was tested on 10 females and 10 males. Morbidity, mortality and behavioural changes were checked on two control groups (10 males and 10 females/group). Sedation (A3), A5 and R5 times were recorded. Significant interactive effect dose*sex on A5 time was found for each anaesthetic agent (p_dose*sex < .05). Except for MS‐222 (p_dose*sex = .284), significant interactive effect dose * sex on R5 time was found (p_dose*sex < .05). A5 time in females tended to be greater than in males, but, in general, R5 times were longer in males. Body size differences between males and females could explain these differences in MS‐222 on A5 time and for clove oil, 2‐PE and propofol on R5 time. No dose simultaneous meet LED′s conditions relating to both A5 and R5 times; therefore the lowest doses inducing A5 in a mean time of 3 min could be a safe guideline for anaesthetic procedure in both male and females.     

An evaluation of potential diets for the culture of postpueruli spiny lobsters Panulirus argus (Palinuridae)

Provision of a suitable feed is paramount for the ongoing success of spiny lobster culture. This study compared and evaluated the performance of seven diets for first instar juvenile spiny lobster Panulirus argus [5–6 mm carapace length (CL)] based on growth rates, survival, and feed conversion ratio. Results demonstrated that a seafood-based juvenile formulation produced the fastest growth rate (3.49% weight gain day⁻¹ and 0.90% CL increase day⁻¹ over a 28-day period). These growth rates were also reflected by a low feed conversion rate (3.04) for this formulated feed. Similar results were also obtained for juveniles fed a frozen seafood diet, however, frozen brine shrimp, Artemia salina (both enriched and un-enriched), frozen enriched mysis shrimp, a dry pellet, and a meal-based juvenile formulation did not produce consistent growth rates. Survival rates ranged between 38% and 85% and demonstrate that juvenile lobsters have better likelihoods of survival in captive culture environments compared to the wild. Although further nutritional refinement is recommended, the results from this research have significant implication for the possible expansion of juvenile spiny lobster growout to a larger scale.