Molting Frequency Research Articles

Transcriptomic analysis and transgenerational effects of ZnO nanoparticles on Daphnia magna: Endocrine-disrupting potential and energy metabolism

The widespread application of zinc oxide nanoparticles (ZnO NPs) has raised concerns over the adverse effects on aquatic species. In this study, transcriptomic analysis was applied to evaluate the chronic toxicity of ZnO NPs on the freshwater invertebrate Daphnia magna and the intergenerational effects were then further investigated. Parent daphnia (F0) were exposed to ZnO NPs at 3, 60, and 300 μg L−1 for 21 days. ZnO NPs significantly inhibited the reproduction (first pregnancy and spawning time, total number of offspring) and growth (molting frequency and body length) of F0. Here, differentially expressed genes (DEGs) involved in lysosomal and phagosome, energy metabolism and endocrine disruption pathways were significantly downregulated. Furthermore, disruption on the transport and catabolic processes probably resulted in the particle accumulation. The inhibited pathways related to energy metabolism may partially account for the body length, molting and reproductive restriction. The suppression of growth and reproduction may attribute to the down-regulation of insulin secretion and ovarian steroidogenesis pathways, respectively. Partial recovery of growth and reproductive inhibition in F1 – F3 descended from the F0 generation exposure did not support constant transgenerational effects. This study unravels the molecular mechanisms and transgenerational consequences of the toxicity of nanoparticles on Daphnia.

Sustainable development of antarctic krill environmental resources based on system dynamics

Abstract Antarctic krill mainly inhabit the Antarctic Ocean, not far from Antarctica, especially the Weddell Sea, where krill is dense. Marine fisheries have reached new levels, but the topic of sustainable use of marine fishery resources is far from reaching the required levels. In order to study the sustainable development of the Antarctic krill environment, this paper studies the living environment and applicability of Antarctic krill based on system dynamics, and provides some references for the sustainable development of marine resources. Mentioned the use of case analysis method, literature analysis method and other methods to collect data, build a Model, and read and analyse a large number of related literatures through the literature survey method. The experimental results proved that the salinity has a significant effect on the survival rate of Antarctic krill (p < 0.05). When the salinity is 34, the molting frequency reaches its maximum value, which is 70 %. It is concluded that the ability of Antarctic krill to adapt to gradual changes in salinity is stronger than that of sudden changes in salinity, and the suitable salinity for survival is 30-42. With 34 as the basic salinity, when the salinity rises within a certain range, the molting rate of krill will increase, and as the salinity decreases, the molting rate will gradually decrease. This shows that improving the environmental resources of Antarctic krill is an effective method for improving salinity.

TINGKAH LAKU LOBSTER PASIR (Panulirus homarus) YANG DIPELIHARA PADA SHELTER BERBEDA

Efforts are being made to reduce the high rate of cannibalism by using shelters in their maintenance of cages. Shelters are needed as a hiding place for moulting of lobsters, as well as expanding the living area. The aims of this study was to determine the behavior of spiny lobster including the frequency of molting and the level of cannibalism. This research took place in July–October 2021, at the Vocational School, IPB University. The design used in this research was a completely randomized design (CRD) using 4 treatments and 3 replications. The treatments in this study consisted of rearing of lobster with box-hole brick shelter (A), rearing of lobster with round hole brick shelter (B), rearing of lobster with pipe shelter (C) and rearing of lobster without shelter (K). The molting frequency of lobsters reared with box-hole shelters tended to be higher (60.0%) than other treatments but not significantly different (P>0.05). The percentage of cannibalism in lobsters reared without shelters / control (47.67%) tended to be higher than lobsters reared in batako shelters.

Antagonistic effects of copper and microplastics in single and binary mixtures on development and reproduction in the freshwater cladoceran Daphnia carinata

The combined effect of microplastics (MPs) and other contaminants such as trace metals is largely unknown although MPs can act as a vector for other contaminants. The present study investigated the impact of a single and mixture of MPs and a common trace contaminant, copper (Cu) on the Australian freshwater cladoceran Daphnia carina . No acute value was recorded when D. carinata was exposed to clear polyethylene size of 1–10 μ m with the concentration ranging from 5, 25, 50, 100, 200 and 300 mg/L during 48 h of exposure. D. carinata showed a tendency to utilize MPs from the surrounding environment to prolong their life when the food was scarce. When D. carinata were exposed to environmentally relevant concentrations of Cu: 1 and 3 μ g/L or MPs concentration of 0.25 and 1 mg/L for 21 days, no effects on reproduction was recorded. The impacts of Cu and MPs on molting frequency in the mixture treatments were less than in the single contaminant treatments. D. carinata juveniles were more sensitive to Cu than the adults regardless of the presence or absence of MPs. The findings highlight the importance of clarifying the interaction between traditional and contaminants of emerging concern for effective risk assessment. • Microplastics (MPs) could prolong the survival of D. carinata when food was scarce. • Reproduction in D. carinata was not affected by exposure to MPs and Cu individually. • D. carinata juveniles were more sensitive to Cu than adults. • Effects of Cu on moulting of D. carinata was smaller in the presence of MPs.

The success on pre-mating molt of immature female mud crab (Scylla tranquebarica) reared at different depth in concrete tank

Cannibalism is one of the obstacles event in the mud crab breeding program. Placement of the prospective broods communally in a container waiting for coupling and mating to occur naturally often leads to fights each other that cause limb defects and even death. Fail in providing optimal environmental conditions in a controlled container also often results in prolonged period of premating-molt and spawning. This study aims to prepare female mud crab broods separately from males placed at different depth in the water column to see the success of premating-molt and mating process. The early inter-molt phase of immature female crabs that heading premating-molt stage were randomly selected from crab sellers in the local market with the following initial data: CW 100 ± 3.4 mm, CL 65.6 ± 2.5 mm, and BW 154.2 ± 16.6 g. Each of 30 available crabs was inserted in separate crab-box after then 10 crab-box placed at each different depth of 0, 70 and 140 cm respectively in an outdoor concrete tank. At the same time, three male broodstock weighing >350g were placed individually in a 0.5 ton fiberglass tank in the hatchery building. The newly molted female in crab-box were immediately transferred to the male tank to mate. The response to growth, molting time, molting frequency, success of mating and spawning to the depth treatment were recorded during the study. The results showed that the rearing of crabs at different depths did not show any significant differences (P>0.05) in growth and molting time, but the molting frequency and survival rate at 70 cm depth were better than other depth treatment.

Potential of methyl fernesoate isolate from the Cyprus extract in prospective broodstock of shrimp (Penaeus monodon. Fab)

Cyprus rhizoma is reported to have methyl fernesoate compounds that are identical to Juvenil hormone III, some researchers have used it as a natural pesticide to control insect populations, whereas in aquaculture, especially in crustacea Juvenil hormone (methyl fernesoate) can stimulate the activity of other hormones such as ecdysterone and serotonin which play a role in the regulation of metamorphosis and maturation of both male and female gonads. The research activities carried out consisted of two stages including isolation of methyl fernesoate compounds from rhizomes of Cyprus sp through extraction, maceration, and purification of these compounds using appropriate organic solvents, then the application of Cyprus sp extracts to prospective black tiger shrimp through injections at a dose of 0,100, and 150 ug / g BW, and ablation of the eyestalk as a positive control. The study was conducted using a completely randomized design (CRD) method with 5 treatments and 2 replications. Observations made include molting frequency, gonadal maturity level, number and diameter of eggs, and measurement of the rate of development of vitellogenesis through a molecular approach with RT-PCR technique using primary vitellogenin F, R and β-Actin F, R. The observation of molting frequency showed the highest molting frequency in the treatment of 150 ug / g BW that is 15 times during maintenance, while the parent shrimp that had the highest gonad maturity was in the treatment of 100 ug / g BW as much as 75%. The results of the measurement of the rate of development of vitellogenesis through a molecular approach with PCR technique using the vitellogenin primers F, R, and β-Actin F, R showed a positive development in the broodstock shrimp treated with Cyprus sp.

Effects on Life-History Traits of Hypogastrura viatica (Collembola) Exposed to Imidacloprid Through Soil or Diet.

Collembola (springtails) are important members of soil communities worldwide by contributing to degradation of organic matter. In nature, Collembola might be exposed to the neonicotinoid insecticide imidacloprid, which is fairly persistent in soil. We exposed the widespread Hypogastrura viatica to imidacloprid through soil or food and monitored the animals during exposure and a post exposure period. We recorded effects on life-history traits affecting individual fitness, that is, mortality, behavioral activity, several reproduction traits, and molting frequency. Exposure through soil led to a concentration-dependent mortality, while the mortality from dietary exposure possibly reflected reduced feeding activity. The body burden of imidacloprid in the Collembola did not differ between treatments. We found no sign of recovery in behavioral activity following exposure in either experiment. The egg production of H. viatica was not significantly affected by imidacloprid at 0.01 mg/kg dry soil but showed a tendency to reduce number of eggs per batch and reduced hatching success. At higher concentrations, reproduction was close to, or completely, stopped. The molting frequency decreased during exposure, while in the post exposure period, we saw milder effects at the highest concentrations, suggesting elimination through molting or reduced toxic response as a result of reduced feeding activity. Overall, H. viatica was more sensitive to imidacloprid than previously studied Collembola, which highlights the importance of considering species sensitivities when risk-assessing soil environments.Environ Toxicol Chem 2021;40:3111-3122. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

RNA interference shows that Spook, the precursor gene of 20-hydroxyecdysone (20E), regulates the molting of Macrobrachium nipponense

The aim of this study was to explore the function of the Mn-Spook gene, which was found in the ovary transcriptome of the Oriental river prawn (Macrobrachium nipponense). The Spook gene, which is the precursor gene of 20-hydroxyecdysone (20E), plays an important role in the process of molting in many arthropods, but its function in M. nipponense is unclear. We cloned the full-length Mn-Spook gene from the ovary of M. nipponense and found that it had the same conserved domains as the P450 gene of the Halloween family of genes. The Mn-Spook gene was highly expressed in ovary and gill tissue during the breeding period. During ovarian development, Mn-spook gene expression was highest at the nearly-ripe stage, and it also was highly expressed in the zoea developmental stage. Cellular localization analysis showed that Mn-Spook signals accumulated in the cytoplasmic membrane and nucleus of oocytes. Finally, we used RNA interference to evaluate the function of the Mn-Spook gene. Compared with the control group, in vivo injection of Mn-Spook dsRNA effectively downregulated the expression of Mn-Spook and the content of 20E. The molting frequency of M. nipponense in the experimental group also was significantly inhibited. These results demonstrated that the Mn-Spook gene played an important role in the molting process of M. nipponense.

Dietary gamma-aminobutyric acid (GABA) supplementation increases food intake, influences the expression of feeding-related genes and improves digestion and growth of Chinese mitten crab (Eriocheir sinensis)

Animal growth performance is determined by food intake, digestion and nutrient absorption and the complex central and peripheral nerves may regulate the quantity of food intake. This study evaluates the effects of gamma-aminobutyric acid (GABA) supplements in purified diets on the growth performance, food intake and digestive ability of juvenile Chinese mitten crab Eriocheir sinensis, and the possible mechanism of neuromodulation. A total of 1200 juvenile crabs (0.77 ± 0.02 g) were fed with six diets supplemented with graded GABA levels (0, 40, 80, 160, 320 and 640 mg/kg dry matter) for 8 weeks. Each diet group had five replicates, and each replicate had 40 crabs in a tank (100 × 80 × 60 cm). The weight gain, specific growth rate, molting frequency, and the activities of digestion (α-amylase, trypsin and lipase) and absorption (Na+-K+-ATPase and γ- glutamyl transferase) enzymes were significantly increased by moderate dietary GABA supplementation compared with the 0 mg/kg GABA supplementation group. Furthermore, the food intake of juvenile E. sinensis was significantly increased with moderate dietary GABA supplementation compared with the 0 mg/kg GABA supplementation group. The qRT-PCR results showed that the expression of the orexigenic neural signal-related genes was significantly up-regulated, and the anorexigenic neural signal-related genes were significantly down-regulated in the cranial ganglia, thoracic ganglia and intestine tissues. Meanwhile, the expressions of the main genes involved in taste modulation and reward regulation were significantly up-regulated, whereas the expression of genes related to punishment regulation was significantly down-regulated in cranial ganglia and thoracic ganglia. Two-slope broken-line regression analysis of specific growth rate and weight gain against the dietary GABA levels showed that dietary GABA at the optimal dietary level was 84–89 mg/kg, and this level can improve growth performance, food intake, digestion and absorption in juvenile E. sinensis. GABA might act as an orexigenic neural signal or work with other appetite-related nerve signals to promote food intake by participating in regulating the satiety circuit and the reward circuit.

Light intensity impacts on growth, molting and oxidative stress of juvenile mud crab Scylla paramamosain

An 8 weeks regression study was performed to test the effects of increasing light intensities from darkness to 30 W m−2 on growth performance, molting, antioxidant capacity, and gene expression of molting and apoptosis-related genes in Scylla paramamosain. No significant differences were found in survival rates between treatments (ranging from 71.7 to 87.3% at the end of the experiment). However, weight gain and specific growth rate over the study period displayed a curvilinear response to light treatments with peak values in crabs exposed to 10 W m−2. Linear (BLM), quadratic (BQM), and 4-parameter saturation kinetic (4-SKM) models show the optimal light intensities for SGR were 12.98, 18.27, and 11.36 W m−2, respectively. The light intensity did not appear to impact molting. However, crabs reared in darkness showed significantly reduced molt frequency (3.51 ± 0.16) and extended intermolt intervals compared to other treatments. Melatonin levels in the eyestalks were significantly higher in crabs exposed to darkness (502.52 ± 56.24 pg mL−1) than light intensities of 10–30 W m−2 (413.50 ± 32.38 and 384.99 ± 15.56 pg mL−1). Cortisol levels were significantly lower in the 0 and 5 W m−2 groups. Light intensity significantly impacted the activity of antioxidant enzymes, with crabs showing a significant increase in total antioxidant capacity (T-AOC) under 10 W m−2, catalase (CAT), and superoxide dismutase (SOD) under 15 W m−2 and lower malondialdehyde (MDA). Gene expression of the molt-inhibiting hormone (MIH) was downregulated in eyestalks from crabs exposed to 10 W m−2 compared to darkness and 20–30 W m−2. Expression of apoptosis-related genes did not show clear light intensity trends. Taken together, these results suggest light intensity can impact S. paramamosain growth, molting, stress levels, and antioxidant capacity. As such, light regimes used in crab farming should be carefully considered to optimize productivity and welfare.

Effects of Two Different Macroalgae (Ulva lactuca and Jania rubens) Species on Growth and Survival of Red Swamp Crayfish (Procambarus clarkii) as Feed Additive

The effects of dietary supplementation of two different macroalgae Ulva lactuca and Jania rubens on the growth performance, survival and feed conversion ratio of juvenile red swamp crayfish juvenile (Procambarus clarkii) were investigated. Red swamp crayfish with an average total length of 56.2±6.67 mm and an average weight of 3.77±0.2 g were placed at tanks (10 crayfish at each tank) and offered diets 8 weeks. Different levels of macroalgae were added to commercial sea bass feed, and no seaweed was used as a control group. It was observed that crayfish fed with 10% feed had higher growth performance (in terms of length and weight) than those fed with 15% diet and control group (P<0.05). The lowest feed conversion rate was observed in juvenile crayfish fed with 15% feed (P<0.05). The highest survival rate was 50.0% at group fed with 15% feed, followed by 46.66% (control group) and 43.33% (10% diet groups), respectively. This study showed that there was no statistical difference in survival rate among treatment groups (P>0.05). However, the frequency of molting was mostly observed in the group fed with 10% diet. Therefore, the results showed that seaweed (Ulva lactuca and Jania rubens) could be used as a supplement for red swamp crayfish diet (Procambarus clarkii) at 10% to improve growth performance with no adverse effects on feed efficiency or survival rate.

Development, growth and allometry in a cohort of the tarantula Grammostola vachoni (Araneae: Theraphosidae)

Spiders are perfect model for developmental stage and growth studies because the juvenile period is broken into instars. Theraphosidae family, are largest and longest-lived spiders and females continue to grow and molt over the sexually mature stage is reached. However, their development and growth are still unknown. Thus, our objective was describe in detail the development of the juveniles of Grammostola vachoni until reaching the adulthood, estimate the growth of somatic and spermathecae dimensions, and analyze any possible allometric relation between the spermathecae and body size during the development. The mortality of individuals was 10.7% per year; and both sexes molted between once and twice by a year with a peak in the molt frequency in the third year of life. The intermolt interval was similar between sexes and tended to increase during development. The spermathecae appeared in the immature females more frequently in the 8th molt (4.03 years) and males reached adulthood frequently at the 11th molt (7.03 years). Both sexes had similar growth percentage (38%) and its was constant throughout their whole development. In contrast, the spermathecae growth percentage was 98% and always was higher than the percentage of body growth. The somatic characters did not show any differences between females and males. The spermathecae measurements showed positive allometric growth related to the body size. The results of our study completes the baseline biology information about the development, growth and its relationship, aspects mostly unknown in tarantulas.

Evaluation of mealworms (Tenebrio molitor) meal as an alternative protein source for narrow‐clawed crayfish (Pontastacus leptodactylus) juveniles

An eighty-day feeding study was performed to investigate the effects of mealworm meal (Tenebrio molitor) on the growth, survival and moulting frequency of juvenile Narrow-clawed crayfish (Pontastacus leptodactylus). Three dietary treatment groups with triplicate were fed with a fish meal-based without MW (control diet: MW0), two diets with 50% (MW50) and 100% (Mw100) of fish meal substitution with MW respectively. P. leptodactylus juveniles (11.0 ± 0.05 mm, mean ±SE and 0.011 ± 0.002 g, mean ±SE) were randomly stocked into nine flow-through tanks with a density of 30 crayfish per tank and reared for 80 days. Crayfish fed with MW50 mealworm meal showed positive effects on weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), apparent net protein utilization (ANPU), moulting frequency (MF) and feed conservation ratio (FCR), but lower survival rate (SR) as compared to the other diet groups. Protein and lipid contents of the whole body of the crayfish fed with replacement diet (MW50) were found to be higher than those of the other two diet groups (p<0.05). However, the MW100 diet slightly increased the moisture and ash contents of the crayfish. Our observation indicated that the addition of a 50% mealworm meal in the diet of P. leptodactylus juveniles improved the growth performance of the crayfish without causing any adverse effects. Therefore, T. molitor meal can be considered as an alternative animal source of protein for the narrow-clawed crayfish juveniles.

Parameters of equations for group growth of golden king crab &lt;i&gt;Lithodes aequispinus&lt;/i&gt; in the northern Okhotsk Sea

Growth of golden king crab in the northern Okhotsk Sea is considered. Parameters of von Bertalanffy growth equation were estimated using SLCA method (Shepherd's length composition analysis): the asymptotic carapace widthW∞was 252.0 mm for males and 165.3 mm for females; the growth rate K was 0.081 and 0.130, respectively. Relative increment per molt for males with carapace width of 116-154 mm was estimated as 11.6 % for the carapace width and 10.9 % for the carapace length. Directly determined (by tagging) dependence of males molt frequency on their size was approximated by logistic curve of molting probability with the threshold of 164 mm carapace width for 50 % probability of annual molt. Mean probability of annual molt for recruits was estimated as 87 %, for pre-recruits — as 92 %. Taking into account the data on increment per molt and annual molt probability, the growth curve for males had the parameters:W∞= 296 mm andK= 0.073. The age of recruits was estimated as 9 years by SLCA approach and as 8 years on the results of tagging. The growth equations parameters were determined for the first time for golden king crab in natural habitat in the Russian waters. These results could be used in models and for theoretical studies of Crustacean life history.

Effect of dietary egg yolk lecithin levels on survival, growth, lipid metabolism, and antioxidant capacity of early juvenile green mud crab Scylla paramamosain

This study investigated the effects of different dietary egg yolk lecithin levels (with 0% (EL0), 1% (EL1), 2% (EL2), 3% (EL3), and 4% (EL4) EL supplementation) on survival, growth, lipid metabolism, and antioxidant capacity of the early juvenile green mud crab (Scylla paramamosain). Total of 420 crabs (initial weight 8.14 ± 0.30 mg) were randomly assigned into five experimental groups (with 3 replicates). At the end of the eight-week culture experiment, the highest survival (92.86 ± 4.52%) was obtained in EL3 group. Significantly higher growth performance (final body weight (FBW), weight gain (WG), and specific growth rate (SGR)) was also observed in the EL3 group, and there was no significant difference from the EL2 group. The highest molting frequency (MF) and transcription level of ecdysone receptor (EcR) gene were also obtained in EL2 group suggested that EL could increase the MF of early juvenile S. paramamosain by up-regulating the mRNA expression of EcR and ultimately promote its growth. In addition, the higher body lipid composition along with increased EL levels suggested that EL could promote lipid absorption and disposition in S. paramamosain. Compared with other crabs, the crabs in EL2 group had significantly higher ∑n-3/∑n-6 ratio. The highest transcription level of fatty acid binding proteins (FABPs) gene also observed in EL2 group. Furthermore, the crabs in EL4 group had significantly lower transcription level of fatty acid synthase (FAS) gene. This result implied that feeding of EL supress the fatty acids synthesis but induce fatty acid transport genes in S. paramamosain. In the hepatopancreas, the content of thiobarbituric acid reactive substances (TBARS) decreased significantly with the dietary EL addition. Meanwhile, significantly higher superoxide dismutase (SOD) activity was observed in the EL2 and EL3 groups. This indicated that dietary EL improved the antioxidant capacity of S. paramamosain. According to the polynomial regression analysis of SGR, 2.56% dietary EL level could achieve the maximum growth of early juvenile S. paramamosain.

Influences of dietary vitamin D3 on growth, antioxidant capacity, immunity and molting of Chinese mitten crab (Eriocheir sinensis) larvae

This study investigates the effects of vitamin D3 (VD3) on growth performance, antioxidant capacity, immunity and molting of larval Chinese mitten crab Eriocheir sinensis. A total of 6,000 larvae (7.52 ± 0.10 mg) were fed with six isonitrogenous and isolipidic experimental diets with different levels of dietary VD3 (0, 3000, 6000, 9000, 12000 and 36000 IU/kg) respectively for 23 days. The highest survival and molting frequency were found in crabs fed 6000 IU/kg VD3. Weight gain, specific growth rate, and carapace growth significantly increased in crabs fed 3000 and 6000 IU/kg VD3 compared to the control. Broken-line analysis of molting frequency, weight gain and specific growth rate against dietary VD3 levels indicates that the optimal VD3 requirement for larval crabs is 4825–5918 IU/kg. The highest whole-body VD3 content occurred in the 12000 IU/kg VD3 group, and the 25-dihydroxy VD3 content decreased with the increase of dietary VD3. The malonaldehyde content was lower than the control. Moreover, the superoxide dismutase activity, glutathione peroxidase and total antioxidant capacity of crab fed 6000 IU/kg VD3 were significantly higher than in control. Crabs fed 9000 IU/kg showed the highest survival after 120 h of salinity stress, and the relative mRNA expressions indicate vitamin D receptor (VDR) is the important regulatory element in molting and innate immunity. The molting-related gene expressions showed that the response of crab to salinity was self-protective. This study would contribute to a new understanding of the molecular basis underlying molting and innate immunity regulation by vitamin D3 in E. sinensis.

Evaluation of silver nanowires (AgNWs) toxicity on reproductive success of Daphnia magna over two generations and their teratogenic effect on embryonic development

This study assessed the reproductive toxicity of silver nanowires (AgNWs) in Daphnia magna over two consecutive generations. An acute immobilization test was conducted according to the ΟECD 202 guidelines. To perform reproductive toxicity tests in both F0 and F1 generations, the animals were exposed to different concentrations of AgNWs (0, 0.4, 2, 10, and 50 µg L−1) and pyriproxyfen (0.4 µg L−1), as a positive control, based on the ΟECD 211 principles. Overall, AgNWs were acutely toxic to D. magna with EC50 value of 0.063 mg L−1. Compared to the control groups, AgNWs disrupted reproductive performances of D. magna through increasing the egg development time and time to production of first brood as well as decreasing the total offspring production and molting frequency in both F0 and F1 generations. After exposure to AgNWs, the number of male neonates and non-reproductive females increased in the F0 generation, whereas just male neonates raised in the F1 generation. Moreover, AgNWs caused several congenital anomalies including underdeveloped antennae, 2nd antennae, malpighian tube, rostrum, sensory bristles, tail spine, and malformed eyes. Together, AgNWs could disrupt reproductive health of D. magna, and these types of bioperturbations could dramatically change the good health state of aquatic ecosystems.

Interaction and effects of graded levels of dietary phytic acid on the moulting performance, whole body mineral composition and availability on the freshwater prawn Macrobrachium rosenbergii

The presence of anti-nutritional factors such as phytic acid (PA) in a number of potentially useful plant ingredients has been a major impediment to their use as replacements for fishmeal in aquafeeds. This study builds on an earlier studying investigating the growth performance and nutrient utilisation in the juvenile Malaysian giant river prawn, Macrobrachium rosenbergii exploring the effects and interactions of dietary PA with minerals on growth (somatic tissue). Additionally, the study set out to determine the changes in whole-body mineral composition and also on muscle tissues and the carapace, when different levels of PA were included within the diet. The hypothesis under test was that PA, as a mineral-binding agent by chelating di- and trivalent cations inhibits mineral availability. To explore this, effects of graded levels of PA (i.e. 0.26–control, 6.48, 11.28, 16.53, 21.45 and 26.16 g PA kg−1) on the moult frequency and mineral availability in juvenile M. rosenbergii (mean initial carapace length of 6.22 ± 0.52 mm; mean initial weight of 0.20 ± 0.01 g; n = 20 per replicate) fed over a period of 140 days were determined. The levels of PA assessed in this feed trial had no major detrimental effects on moult frequency. Negative effects (p < 0.05) of high PA levels (i.e. 21.45–26.16 g PA kg−1), however, were found on the whole-body phosphorus concentration. An increasing trend, although not significantly so, was recorded for the calcium content in the whole-body and carapace with increasing PA inclusion. Significant changes (p < 0.05) were observed in the levels of zinc, copper, potassium and sodium in the carapace, particularly in the prawns fed the diet containing 11.28 g PA kg−1, which suggests that the specific minerals were either selectively utilised or retained in the carapace. These changes may have a serious impairment hence caution should be exercised to ensure that the anti-nutritive effects of PA are minimised.

Ocean freshening adversely affects the food detection ability of the gammarid amphipod Haustorioides koreanus

Anthropogenic CO2 emissions to the atmosphere have increased not only air temperature, but also precipitation, which has intensified freshening of the sea surface in some parts of the ocean. As a result, many regions, including the Yellow Sea, have been confronted with a decrease in salinity. In this study we investigated the effects of low salinity on the number of dead individuals and behaviour of Haustorioides koreanus, a gammarid amphipod living in the upper and sandy regions of the tidal flats of the west and south coasts of South Korea. The experiment was conducted over 32 days with four different salinity conditions: 30 (control), 27, 24 and 21psu (n=8 each). Although the number of dead individuals, the moulting frequency and burrowing and swimming behaviours of H. koreanus did not significantly differ, the time taken for food detection was increased significantly by low salinity (21psu). A decrease in the speed of food detection suggests that low salinity can reduce the amphipod’s ability to detect chemical cues.

Dietary phospholipid alleviates the adverse effects of high-lipid diet in Chinese mitten crab (Eriocheir sinensis)

An 8-week feeding trial was conducted to investigate the impacts of dietary phospholipid (PL) on growth, antioxidant status and lipid metabolism of Eriocheir sinensis juveniles (0.53 ± 0.01 g) fed four diets including high lipid (13%, HL) and low lipid (8%, LL) and each lipid level containing either high PL (5%, HP) or low PL (1%, LP). Final weight, weight gain, specific growth rate and molting frequency in the HL-LL group were lower than those in the HL-HP group. Compared with the HL-LP group, the enzymatic antioxidant activities increased and hepatopancreatic malondialdehyde content decreased in the HL-HP group. In addition, the high dietary PL significantly suppressed the accumulation of lipid in the hepatopancreas and the whole-body induced by high lipid diets. Quantitative real-time PCR showed that the dietary PL reduced excessive lipid deposition in the hepatopancreas through promoting lipid oxidation and exportation as well as inhibiting lipid absorption and synthesis at the transcriptional level. This study indicates that high dietary PL could promote lipid utilization in E. sinensis fed a high-lipid diet by optimizing lipid metabolism to improve growth performance.