Megalopa Research Articles

Effects of Salinity and Ca2+: Mg2+ Ratio on Nutrient Profile, Physiological Responses and Clinical Signs of Penaeus vannamei (Boone, 1931) Reared in Inland Saline Ground Water

Background: A 60-day experiment was conducted to evaluate the combined effect of salinity and Ca2+: Mg2+ ratio on the nutrient profile, physiological responses, and clinical signs of Penaeus vannamei reared in inland saline ground water. Methods: The study used three different salinities viz. T1 (5 ppt), T2 (10 ppt) and T3 (15 ppt) with four different levels of Ca2+: Mg2+ ratios such as 1:1, 1:2, 1:3, and 1:4. A total of 720 healthy post larvae of P. vannamei (mean body weight of 3.70±0.02 g) were stocked (20 shrimp/tank) in 36 circular plastic tanks (100 L capacity each). Each treatment was triplicated following the 3 × 4 factorial design. Result: A significant increase of protein and ash contents and decrease of moisture content were noticed with increasing salinity. The study found no significant difference in the carbohydrate and crude lipid content of P. vannamei. A linear relationship between salinity and serum osmolality was observed which indicated significant increase of osmoregulatory capacity with increasing salinity. The treatment groups fortified with deficient level of Ca2+: Mg2+ ratio showed prominent changes such as abdominal white muscle on dorsal side and muscle cramps. Based on the results, it can be concluded that the better physiological adoption of P. vannamei was observed in 10 and 15 ppt salinities of ISGW fortified with Ca2+: Mg2+ ratio 1:3.

Insights into the wound-healing properties of medicinally important South African Bulbine species – A comparative study

Ethnopharmacological relevanceSouth Africa harbours a large number of Bulbine (Xanthorrhoeaceae) species, which includes ethnobotanically important indigenous species. Traditionally, Bulbine leaves are used by several ethnic groups in South Africa to treat dermatological conditions including wounds, which led to the development of Bulbine-containing cosmetic products. However, scientific evidence is needed to support the claims in treating skin conditions and wound-healing. Aim of the studyThis comparative study was undertaken to investigate the wound-healing properties of five Bulbine species indigenous to South Africa, using in vitro and in vivo models. Materials and methodsFive Bulbine species, B. abyssinica, B. asphodeloides, B. frutescens, B. latifolia and B. narcissifolia were collected from natural populations in the Eastern Cape Province of South Africa. The chemical profiles of the methanol leaf extracts were acquired using ultra-performance liquid chromatography with photodiode array detection in tandem with quadrupole time-of-flight mass spectrometry. The methyl thiazolyl tetrazolium (MTT) assay and maximum tolerated concentration (MTC) assay were used to assess the in vitro and in vivo toxicity of the extracts, respectively. The in vitro scratch assay was employed to monitor cell migration and wound-closure in a HaCaT cell monolayer, following treatment with the plant extracts for 48 h. In vivo wound-healing potential was determined using the zebrafish larvae caudal fin amputation assay, assessed in three-days post fertilization larvae and various concentrations of the plant extracts were tested in both assays to determine the concentration-response effect. Data were analysed using MS Excel® enhanced with the Real Statistics add-in. Results and discussionUsing UPLC-MS, 11 major compounds were tentatively identified in the five Bulbine species. Although the compounds varied between species, all five Bulbine species contained the phenylanthraquinone, knipholone. Kaempferol glucoside was identified in four species, but not in B. abyssinica. The five Bulbine species were non-cytotoxic (cell viability > 80%) towards keratinocytes at all three tested concentrations. However, B. latifolia was toxic towards zebrafish larvae at all the tested concentrations, while the other four species were non-toxic at low concentrations. The results of the scratch assay revealed that B. abyssinica was the most active extract at 100 μg/mL. Compared to the untreated control, wound-closure notably increased by 28% (p < 0.05), 44% (p < 0.01) and 34% (p < 0.05) after 12 h, 24 h and 36 h post-treatment, respectively. Although none of the species achieved 100% caudal fin regeneration by the end of the treatment period, B. frutescens demonstrated the highest regeneration (90%) and most significant difference (p < 0.01) compared to the untreated control. ConclusionThe results revealed that the five Bulbine species have complex chemical profiles, however, they share major compound classes (i.e. phenylanthroquinones and flavonoid analogues) across the species. The study highlights the wound-healing properties of the five species, which is consistent with their traditional use.

Hemp regulates the fitness of corn earworm (Lepidoptera, Noctuidae) and its tachinid (Diptera) parasitoids.

Pest management on hemp is still in its infancy, and biological control options are limited. Helicoverpa zea (corn earworm) is one of the key pests of hemp cultivated outdoors, especially on cultivars grown for cannabinoids and grain. In a three-year study, we assessed the effect of diet on the performance of H. zea and its tachinid parasitoids. Parasitized (bearing fly eggs) and unparasitized (without eggs) H. zea larvae were fed on hemp flowers or an artificial diet. Five tachinid species parasitized H. zea larvae, but the most abundant species were Winthemia rufopicta (68.8%) and Lespesia aletiae (28.3%). Overall, 55.2% of H. zea larvae bearing tachinid eggs died, while the mortality of unparasitized larvae reached 24.7%. The success of tachinids increased by 2-fold when the host larvae were fed on an artificial diet. Our results demonstrated that high protein food (artificial diet), intensity of parasitism, and caterpillar size play a role in the fitness of both the herbivores (H. zea) and its tachinid parasitoids. These findings have important implications for understanding biological control mechanisms and open new insights into the impact of landscape variation on plant-herbivore-parasitoid interactions. This study contains supporting evidence that makes both Winthemia rufopicta and Lespesia aletiae excellent candidates for biological control programs against H. zea, a key pest of hemp in the United States.

Comparative analysis of transcriptomics and metabolomics provides insights into the mechanisms of VPAHPND invasion and hepatopancreatic damage in Litopenaeus vannamei

Acute hepatopancreatic necrosis disease (AHPND) poses significant threats to the global shrimp farming industry; however, its molecular mechanisms remain largely unknown. Previous research has primarily focused on comparisons between infected and non-infected states, limiting our understanding of VPAHPND mechanisms. We integrated transcriptomic and metabolomic analyses to investigate the pathogenic mechanism underpinning AHPND in highly vulnerable post-larvae (PL) stage shrimp. By comparing shrimp infected with VPAHPND, those infected with non-VPAHPND, and uninfected shrimp (controls), we identified different VPAHPND infection responses, including significant cytoskeleton and metabolic reprogramming changes. Specifically, VPAHPND infection disturbed lipid, glutathione, and bile acid metabolism, while a key regulatory factor Farnesoid X Receptor (FXR) in these pathways was down-regulated. These findings suggest that VPAHPND manipulates host metabolism to enhance infectivity, leading to severe and irreparable hepatopancreas damage. Our study highlights the molecular interactions between VPAHPND and shrimp, and provides potential targets to mitigate the impact of AHPND in aquaculture.

Nematodes Can Substitute Artemia in a Co-Feeding Regime for Pacific White Shrimp Post-Larvae Reared in a Biofloc Nursery System.

This study evaluated nematodes as an alternative to live Artemia when provided in a co-feeding regime to Pacific white shrimp (Penaeus vannamei) post-larvae (PL) reared in a biofloc nursery system. A 20-day experiment employing PL11 was performed for an evaluation of four dietary groups: control [C] (fed exclusively with a dry commercial feed); artificial Artemia [AA] (dry feed composed of extracted and processed Artemia cysts and dry commercial feed); live Artemia and dry commercial feed [LA]; and nematodes and dry commercial feed [N] (Panagrolaimus sp. dry nematodes). The diets were provided twice a day, with the remaining six feed provisions being a commercial dry feed for all experimental groups. A biofloc system was chosen as it offers a potentially sustainable approach to intensive shrimp farming. Alkalinity and pH in the [N] group were significantly higher in the last 5 days of the experiment (p < 0.05), likely causing the significantly lower nitrite levels observed in that same group (p < 0.05). Total and volatile suspended solids were significantly lower in the two live feed groups when compared with [C] and [AA] (p < 0.05). Although PL fed the dry diets exhibited higher growth rates (p < 0.05), the [N] and [LA] groups presented significantly higher final survivals (p < 0.05). No differences were found for survival after a salinity stress test (p ≥ 0.05). These results suggest that nematodes can successfully substitute Artemia in a co-feeding regime for P. vannamei PL reared in biofloc nursery systems.

Vertical distribution and tissue selection of Helicoverpa zea (Lepidoptera: Noctuidae) adult oviposition and neonates on soybean with an indeterminate or determinate growth habit.

Helicoverpa zea (Boddie) is a polyphagous pest that can cause serious damage to crops, including soybeans (Glycine max L.). In soybeans with both determinate and indeterminate growth habits, H. zea larvae are more commonly found on leaves compared to blooms, stems, and pods. Past research demonstrated that H. zea adults tend to oviposit near the upper part of the plant canopy in soybeans with a determinate growth habit. However, ovipositional selection on soybeans with an indeterminate growth habit is unknown. We hypothesized that H. zea would oviposit more uniformly throughout the canopy on indeterminate soybean growth habits due to more diffuse reproductive tissue. We planted field and greenhouse experiments with varieties sharing a similar relative maturity (2 maturity group [MG] 5.2 varieties and 2 MG 5.4/5.5 varieties) but with different growth habits. To test oviposition selection, adult H. zea females were allowed to oviposit under field and caged conditions. We counted the number of H. zea eggs and neonates on each plant tissue type from each of 3 equal parts in the plant canopy: upper, middle, and lower. In both experiments, eggs and neonates were most common on leaves at the top of the plant regardless of soybean growth habit. Consequently, ovipositional selection is likely independent of reproductive tissue availability, and patterns of oviposition through the canopy are similar in growth habits. An improved understanding of H. zea ecology in soybeans relative to indeterminate growth habits may improve recommendations for managing this significant pest of soybean.

Development of microbound diet and its application on Macrobrachium rosenbergii larvae and postlarvae

The aquaculture sector actively seeks innovative methods to enhance growth and nutrition in aquatic organisms. Microbound diets (MBDs), known for their finely ground pellets often combined with binders to encapsulate nutrients are gaining prominence. This study aimed to develop an MBD and assess its impact on the growth and body composition of giant freshwater prawn, Macrobrachium rosenbergii larvae and postlarvae (PL) through two feeding trials. Various binders (agar, zein, alginate, carrageenan, and carboxymethyl cellulose) were tested during the development of MBD and were compared with live feed (rotifer). The first feeding trial demonstrated improved larval growth with MBD with agar, reaching an average of Stage XII, compared to those fed the control diet, which only reached Stage IX. The second feeding trial investigated the effect of feeding regimes on giant freshwater prawn PL, consisting of (i) one-time feeding in the morning, (ii) one-time feeding at night, (iii) two-time feeding, (iv) three-time feeding, and (v) four-time feeding. Results showed that two-time feeding had comparable survival rates and growth performance to three-time feeding (survival rate= 43–45 % and weight gain= 0.09–0.11 g), with the best feed conversion ratio in two-time feeding (1.70) and the highest level of highly unsaturated fatty acids (25–26 %) in PL fed one-time and three-time. Overall results suggest that MBD with agar holds promise as a binder with two-time and three-time feeding, enhancing the quality of giant freshwater prawn PL. Further research on extending the duration of the experiment is recommended to assess PL moulting patterns and performance, as varied feeding regimes may significantly impact growth and moulting.

Current status of the global production chain of giant river prawn (Macrobrachium rosenbergii)

Objective: To determine the current state of the global production chain of Macrobrachium rosenbergii, identifying its links and the characteristics of the techniques used. Design/Methodology/Approach: Studies over a period of 20 years (2001-2022) about the production chain of M. rosenbergii were reviewed and analyzed. The information was synthesized in tables and the most relevant production and farming data are offered as an output. Results: The following links of the production chain were identified: production, processing, and commercialization. The Macrobrachium rosenbergii farming and the main technologies used to improve its production are described. Study Limitations/Implications: There is limited systemic information about the M. rosenbergii production chain. The topics addressed the specifics of production, processing, and marketing. Findings/Conclusions: To improve the M. rosenbergii production chain, the following aspects must be guaranteed: the supply of post-larvae (PL) specimens, the development of better monoculture practices, and its integration with other species of commercial importance. The organization of the production chain must also be reviewed, considering its direct and indirect participants.

Effects of stocking density and salinity on the flavour performance and muscle microstructure of black tiger shrimp (Penaeus monodon) post larvae

Effects of stocking density and salinity on the flavour performance and muscle microstructure of black tiger shrimp (Penaeus monodon) post larvae

Antagonistic and enzymatic activities of Bacillus species isolated from the fish gastrointestinal tract as potential probiotics use in Artemia culture.

Probiotics have been used successfully in aquaculture to enhance disease resistance, nutrition, and/or growth of cultured organisms. Six strains of Bacillus were isolated from the intestinal tracts of fish and recognised by conventional biochemical traits. The six isolated strains were Bacillus cereus and Bacillus subtilis using MALDI-TOF-MS technique. The probiotic properties of these Bacillus strains were studied. The tested bacillus strains exhibit antibacterial activity against the different pathogens. The strain S5 gave the important inhibition zones against most pathogens (20.5, 20.33, 23, and 21 mm against Vibrio alginolyticus, Vibrio parahaemolyticus, Staphylococcus aureus, and Salmonella typhimurium, respectively). According to our results, all Bacillus strains have extracellular components that can stop pathogenic bacteria from growing. The enzymatic characterization showed that the tested strains can produce several biotechnological enzymes such as α-glucosidase, naphtol-AS-BI-Phosphohydrolase, esterase lipase, acid phosphatase, alkaline phosphatase, amylase, lipase, caseinase, and lecithinase. All Bacillus strains were adhesive to polystyrene. The adding Bacillus strains to the Artemia culture exerted significantly greater effects on the survival of Artemia. The challenge test on Artemia culture showed that the protection against pathogenic Vibrio was improved. These findings allow us to recommend the examined strains as prospective probiotic options for the Artemia culture, which will be used as food additives to improve the culture conditions of crustacean larvae and marine fish.

Thermal tolerance, development, and physiological impacts of climate warming on zoea larvae of brachyuran crabs

Predicted effects of increasing ocean temperatures, due anthropogenic climate change, might be more challenging for early life history stages owing to reduced thermal tolerance. Thus, determining species responses to the projected climate warming conditions on marine ecosystems is essential to access their vulnerability. Here, we experimentally evaluated the effect of increased temperature on larval survival, development time and metabolic responses of two intertidal crab species (Menippe nodifrons and Ucides cordatus). The metabolic rate (measured as oxygen consumption), ammonia excretion and heartbeat rates were measured in standard fashion way, while the coefficient of temperature was obtained as a measure of organism's sensitivity to temperature increase. Critical thermal maximum and minimum, and thermal safety margins were also obtained. The results indicate a decrease in survival probability and development time for both species, from zoea I to zoea III stage, which was seen in higher extent to larvae of M. nodifrons. There is no significant effect of temperature increase on heartbeats and ammonia excretion rates to both species; however, increases in temperature had a differential effect on metabolic responses of two species. In addition, the critical thermal limits for the larval phase were described for the first time, suggesting that larvae of M. nodifrons are more vulnerable and have lower acclimation capacity to warming waters. Although a high sensitivity in metabolism was seen in U. cordatus, this species demonstrates higher thermal tolerance accompanied by a greater physiological plasticity. Our data emphasize that warming of coastal waters may reduce the larval survival and development time of both species, which can potentially impact its distribution and population size.

Development of an Efficient Fish Feed for Catla catla Post Larvae to Enhance the Survival Rates of Nursery Stages by Using Available Raw Materials

This study aimed to identify a new feed for Catla catla post larvae. There is no suitable feed in Sri Lanka for post-larvae of Indian carp. A complete randomized design was used. Two feeds were formulated using different nutrient compositions with 32 % and 25 % of the fish meal separately. The formulated feeds were used as treatment one and treatment two. Commercial feed was used as the control. Catla catla post-larvae were stocked at a density of 300 post larvae per m2 in nine cement tanks. Growth parameters were measured every two other days. Feeds were formulated according to the nutrient requirement of Catla catla post larvae. Water quality parameters were measured daily to maintain the water quality at the proper level. T-test preformed in Mini tab 16.0. Total body weight and length were significantly different (p&lt;0.05). The survival percentage was higher in T1. Treatment feeds were not affected by the water quality parameters. Catla catla post-larvae show a maximum increase in length, survival percentage and weight in T1. It was concluded that T1 has a good combination of fish meal for Catla catla post-larvae. This study will help in future feed formulation for post-larvae feeds in developing nations.

Effect of light intensity on the survival of European spiny lobster (Palinurus elephas) larvae reared in aquaculture system

Light plays a crucial role in the growth, development, and survival of aquatic organisms. To evaluate the survival of European spiny lobster (Palinurus elephas) larvae in relation to different light intensities (26, 359, and 910 lux, equivalent to 0.35, 4.74, and 12.29 μmol·m−2·s−1, respectively), this study monitored the survival rates of reared spiny lobster from the early instar phyllosoma stages to their metamorphosis into the puerulus stage (111 days after hatching) at the three light intensities. The newly hatched larvae were cultured in 65-L Kreisel tanks with 200 individuals each (three replicates per treatment, i.e., light intensity). Phyllosoma stages I to III larvae showed no significant differences in survival rates under different light intensities. However, light intensity did have a significant impact on the survival rates of phyllosoma stages IV and V as well as the metamorphosis of phyllosoma VI into puerulus. The highest survival rates were observed under high and medium light intensity conditions. At the end of the experiment, the highest mean survival rate for stage VI, the metamorphosis into the puerulus stage, was 42.0 ± 2.52 % under high light intensity. These survival rates for reared pueruli were 84 times higher than those achieved in previous studies. The present study results show promise for the successful implementation of commercial scale rearing protocols for European spiny lobster and have implications for the design of crustacean larvae culture systems.

Feeding rhythm of the zoea larvae of Scylla paramamosain: The dynamic feeding rhythm is not completely synchronized with photoperiod

The feeding rhythm is one of the key factors determining the success of artificial breeding of S. paramamosain. To understand the feeding rhythm of the different zoea larva developmental stages of S. paramamosain, the feeding rate, digestive enzyme activity, and expression of metabolism-related genes were investigated in the present study. The results showed that the S. paramamosain feeding rate has strong diurnal feeding rhythm, being significantly higher at 10:00–14:00 from stages ZI to ZIV. While the feeding rate peaked at 14:00 on Days 10 and 11, the peak shifted to 18:00 on Day 12. The activity of digestive enzymes amylase, pepsin and lipase decreased at night but increased in the daytime, showing a single-phase rhythm similar to that of the feeding rate, suggesting that the digestive enzyme activity was closely associated with the feeding rate during the larval development. Compared to pepsin and lipase, the activity of amylase was the most consistent with feeding rate. In particular, amylase activity peaked at 18:00 on Day 12. Due to its synchronicity with feeding activity, the activity of amylase could provide a potential reference for determining the best feeding time during zoea stages in S. paramamosain breeding. Moreover, the relative mRNA expression of metabolism-related genes SpCHH and SpFAS at most tested points was lower from 10:00 to 14:00, but higher at 18:00 to 6:00 of the next day. On the other hand, the expression patterns of SpHSL and SpTryp were converse to those of SpCHH and SpFAS. Our findings revealed that the S. paramamosain zoea has an obvious feeding rhythm, and the most suitable feeding time was 10:00–18:00 depending on different stages. The feeding rhythm is a critical aspect in aquaculture, influencing a series of physiological functions in aquatic animals. This study provides insights into the feeding rhythm during the zoea development of S. paramamosain, making a significant contribution to optimizing feeding strategy, improving aquafeed utilization, and reducing the impact of residual feed on water environment.

Nursery rearing freshwater prawn, Macrobrachium rosenbergii, in biofloc system integrated with red seaweed, Gracilaria tenuistipitata, at different stocking densities under zero water exchange

This study was conducted to assess the effects of stocking densities on the water quality, survival and growth of the freshwater prawn Macrobrachium rosenbergii postlarvae (PL) cultured in a biofloc system integrated with red seaweed (Gracilaria tenuistipitata). Postlarvae prawns weighing 0.012±0.001 g were stocked at densities of 1,000, 1,500, 2,000, and 2,500 PL/m3, noted as D1, D1.5, D2, and D2.5, respectively. Each density treatment was replicated three times and randomly assigned to 12 plastic tanks of 150 l at a salinity of 10 ppt. Red seaweed was added at a rate of 1.5 kg/m3, and molasses was used as a carbon source to maintain a C:N ratio of 15:1. No water exchange occurred during the 30-day rearing period. Results indicated that water quality parameters, including TAN and NO2-, biofloc volume, total heterotrophic bacteria, and Vibrio spp. counts, increased at higher prawn densities but remained within the appropriate range for prawn performance. Growth rate in weight and survival of prawns decreased as stocking density increased, with D1 and D1.5 showing comparable and significantly higher results compared to D2 and D2.5. Prawn production increased with rising stocking density, with a significant difference among treatments (p&lt;0.05). Furthermore, prawns in D1 and D1.5 exhibited significantly higher feed efficiency than those in D2 and D2.5. These findings suggest that nursery rearing of prawn PL at a density of 1,500 ind/m3 in a biofloc system integrated with red seaweed offers optimal growth and feed efficiency, while maintaining good water quality and conserving water resources.

Molecular Cloning, Characterization, and Expression of a Receptor for Activated Protein Kinase C1 (RACK1) Gene in Exopalaemon carinicauda Zoea Larvae under Aroclor 1254 Stress.

The receptor for activated protein kinase C1 (RACK1) belongs to the typical WD repeat family, which is extremely conservative and important in multiple signal transduction pathways related to growth and development that coordinate the intracellular role of various life activities. As a novel protein with versatile functions, it was found in a variety of organisms. In a previous study, we identified the RACK1 sequence of white shrimp from transcriptome data. In this study, we employed specialized bioinformatics software to conduct an in-depth analysis of EcRACK1 and compare its amino acid sequence homology with other crustaceans. Furthermore, we investigated the expression patterns of RACK1 at different developmental stages and tissues, as well as at various time points after exposure to Aroclor 1245, aiming to elucidate its function and potential response towards Aroclor 1245 exposure. The length of EcRACK1 is 957 nucleotides, which encodes 318 amino acids. Moreover, there were seven typical WD repeats in EcRACK1, which have more than a 96% sequence identity with the RACK1 proteins of Penaeus. The results of tissue expression and spatiotemporal expression showed that it was significantly increased in the II and IV stages, but had a significant tissue specificity in the hepatopancreas, spermary, and muscle tissues of E. carinicauda, adult stage. Compared to the control, EcRACK1 was significantly induced in E. carinicauda zoea larvae exposed to Aroclor 1254 for 6, 10, 20, and 30 d (p < 0.05). These results suggested that EcRACK1 may play an important role in the larval development and environmental defense of E. carinicauda.

Morinda citrifolia fruit extract enhances the resistance of Penaeus vannamei to Vibrio parahaemolyticus infection

Vibrio parahaemolyticus is a gram-negative facultative anaerobic bacterium implicated as the causative agent of several shrimp diseases. As part of the effort to provide biocontrol and cost-effective treatments, this research was designed to elucidate the effect of Morinda citrifolia fruit extract on the immunity of Penaeus vannamei postlarvae (PL) to V. parahaemolyticus. The methanol extract of M. citrifolia was vacuum evaporated, and the bioactive compounds were detected using gas chromatography‒mass spectrometry (GC‒MS). Thereafter, P. vannamei PL diets were supplemented with M. citrifolia at different concentrations (0, 10, 20, 30, 40, and 50 mg/g) and administered for 30 days before 24 h of exposure to the bacterium V. parahaemolyticus. A total of 45 bioactive compounds were detected in the methanol extract of M. citrifolia, with cyclononasiloxane and octadecamethyl being the most abundant. The survival of P. vannamei PLs fed the extract supplement was better than that of the control group (7.1–26.7% survival greater than that of the control group) following V. parahaemolyticus infection. Shrimp fed 50 mg/g M. citrifolia had the highest recorded survival. The activities of digestive and antioxidant enzymes as well as hepatopancreatic cells were significantly reduced, except for those of lipase and hepatopancreatic E-cells, which increased following challenge with V. parahaemolyticus. Histological assessment of the hepatopancreas cells revealed reduced cell degeneration following the administration of the plant extracts (expecially those fed 50 mg/g M. citrifolia) compared to that in the control group. Therefore, the enhanced immunity against V. parahaemolyticus infection in P. vannamei could be associated with the improved hepatopancreas health associated with M. citrifolia fruit extract supplementation.

Intensification of Amazon River Prawn Hatchery

The effects of the intensification on the performance of the Amazon River prawn hatchery carried out in a simple recirculation system were investigated. Newly hatched larvae were stocked in 120 L tanks at 80, 100, 120 and 140 larvae L−1 in a closed recirculating system. The experiment used a randomized block design with five replicates. An exponential equation was adjusted to express the relationship between the stocking density and productivity (postlarvae L−1). The development, larval quality, survival and postlarval (PL) dry weight did not significantly differ among the treatments (p &gt; 0.05). When 80 larvae were stocked, the productivity (54 ± 11 PL L−1) was lower than those at higher densities (p &lt; 0.05). Stocking 120 and 140 larvae L−1 resulted in higher productivities (75 ± 18 and 80 ± 17 PL L−1, respectively) with a lower use of Artemia nauplii to produce each postlarvae (~1200 Artemia nauplii PL−1). The maximum mean M. amazonicum postlarval production estimated by the exponential model was 93 PL L−1. This means that despite the increase in stocking density, productivity tends to stabilize. The results showed that M. amazonicum tolerates high intensification in recirculating hatchery systems based on a crushed shell bed biofilter, and the intensification optimizes Artemia use.

The utilization of brackish water-induced land through a rice-tiger shrimp coculture system

The brackish water-induced lands are abandoned by their owners because the land is unproductive. These lands are adjacent to the pond. This study aims to evaluate the brackish water-induced land through the rice-tiger shrimp coculture system. The land was reconstructed using excavators into 70 % rice fields and 30 % caren for shrimp cultivation. On this land, cultivation was carried out with Irrigated Inbred Rice (Inpari 34) and tiger shrimp (P) and Inpari 35 and tiger shrimp (T). Each treatment is two replicates. Salt-tolerant rice seeds used are varieties of Inpari 34 and Inpari 35 planted on rice fields after seedbeds for 25 days. Post larvae (PL) of tiger shrimp were adapted to a salinity of 7 ppt for 30 days, to be stocked at a density of 4 ind/m2. The growth of rice and tiger shrimp growth and water quality were monitored at a 14-day interval. Production of rice and tiger shrimp was counted at the end of the study. The results showed that salt-tolerant rice varieties Inpari 34 grew from 40 to 108 cm in height and Inpari 35 grew from 43 to 126 cm with production reach 5.060 ± 64.28 and 4.324 ± 19.09 t/ha, respectively, during 105 days of culture period. The survival rate and body weight of tiger shrimp are 20.19 ± 0.43 % and 11.56 ± 2.36 g for Inpari 34 and 20.83 ± 31.26 % and 12.40 ± 2.42 g for Inpari 35 for 65 days culture period, with production estimated 0.176 ± 0.054 (P) and 0.134 ± 0.010 t/ha (T). Inpari 34 and Inpari 35 rice varieties can be cocultured with tiger shrimp on the brackish water-induced land. Rice-tiger shrimp coculture system can be an alternative technology to restore land function that is intrusive by brackish water-induced land and support food security.

Evaluation of Growth Parameters in Post Larvae Catfish in Relation to Feed Types

The aim of this research is to evaluate growth parameters in post larvae catfish in relation to feed types. This study will analyze the trend for length of Claria gariepinus fed on commercial feed, maggot and zooplankton; analyze the trend of weight of Claria gariepinus fed on commercial feed, maggot and zooplankton; analyze the relationship between length and weight and; make forecasts for the length and weight of the fish fed on the specified feed types. Artificial reproduction of African Catfish (C geriepinus) was carried out using the hypophysation technique. Brood stocks were selected from centrally located parent stock holding ponds. Males and females were conditioned in separate ponds. The brood stocks were fed with 20% crude protein formulated feed, acclimatized for three weeks, then transferred into the hatchery holding tanks between 240 Celsius and 270 Celsius to stimulate ovulation after injecting the females with 0.5ml of ovalin. Fertilized eggs were incubated in continuous flow of water until hatching was completed. A commercial starter feed consisting of 8% ash, 6% fiber, 12% NFE, 1.5% calcium, 1.6% sodium, 1.5% phosphorous and sufficient amount of essential vitamins was administered to the larvae. Larvae were randomly distributed into 45 plastic tanks in a flow-through system at a density of 500 fish per tank. Fifteen fries were randomly selected from each holding tank and measurements on weight and length collected daily. Time series analysis and regression analysis were applied in the study. It was found that the length and weight of post larvae fed on mixed zooplankton was consistently lower than the other treatments. The length and weight of the fish fed on the three feed types were successfully modeled and forecasts made for future five periods while the relationship between length and weight was found to be significant on a linear regression model. This certainly adds value as the weight of post larvae catfish is measure with less difficulty and without causing injury or stress to the fish than measurement of length.