Individual Wet Weight Research Articles

Influence of larval density, substrate moisture content and feedstock ratio on life history traits of black soldier fly larvae

Performance and body composition of insect larvae depend on quality and quantity of their diet, and on biotic factors such as larval density. Experiments were undertaken to assess the effects of larval density, substrate moisture content and feedstock ratio on larval life history parameters of black soldier fly (BSF) in the laboratory. Four-day-old larvae were separately reared under six different densities (1, 2, 4, 6, 8 and 10 larvae/cm2) and at five substrate moisture content levels (40, 50, 60, 70 and 80%) obtained by moistening feed with fresh water. Five feedstock ratios of 25, 50, 100, 150 and 200 mg of feed per larva per day were also tested. Each treatment had four replicates and used commercial chicken feed as substrate. Results showed that individual larval feed reduction, wet weight, survival rate, body size and body thickness had a negative correlation with rearing densities, while larval development time correlated positively. The increase in substrate moisture content has significantly affected the larval feed reduction, wet weight, development time, body size and body thickness of the larvae. On the other hand, the survival rate was not significantly affected. The larvae subjected to diet 150 mg/larva/day showed a highest individual wet weight (0.19±0.003 g), body size (20.55±0.335 mm) and body thickness (4.982±0.081 mm). Their recorded development time was relatively short (11.25±0.500 days), compared to the other. The larval survival rate was not significantly affected by the feedstock ratio. This study indicates that larval life history parameters of BSF are influenced by the rearing conditions.

Effects of four natural diets on the culture performance and biochemical composition of megalopa of Eriocheir sinensis during desalination period

Frozen copepods, frozen adult Artemia, live rotifers and live Artemia nauplii were used as feed for the megalopa of Eriocheir sinensis during desalination stage to determine the most nutritious and cost-effective feed. The biochemical composition of the four feeds was analysed. Then, the individual wet weight, individual dry weight, survival rate, the cost and the biochemical composition of the megalopa were measured after the desalination. The resulting effects on the metamorphosis ratio and the duration of the megalopa were also assessed. The results showed that the duration of desalinated megalopa to first stage crab for all treatments was approximately 3.5 days, while the metamorphosis rate of the copepod treatment was significantly higher than the other treatments with the value of 96.33 ± 3.79%. In terms of biochemical composition, after desalinization, the moisture content of megalopa in the adult Artemia treatment was the highest, and the total lipid in the Artemia nauplii treatment and rotifer treatment was significantly higher than the other two treatments. The desalinated megalopa from copepod treatment had the highest percentages of DHA (22:6n-3) and EPA (20:5n-3) among the four treatments. The desalinated megalopa from copepod treatment and rotifer treatment had the higher contents of protein. In conclusion, frozen copepods have higher nutritional value for the megalopa during the desalination period. Therefore, feeding the megalopa with copepods can improve the culture performance and megalopa quality, and can also reduce the feed cost during desalination stage.

Looking at the complex relationships between migration behavior and conditional strategy based on energy metabolism in the European glass eel (Anguilla anguilla)

Diadromy in eel is facultative and the diverse propensities in glass eel estuarine migration may lead to a large spatial dispersion, which may has profound influences on the species sex determination. In this study, we sought to clarify the relationship between European glass eel energetics and their pattern of migration behavior, in the framework of the conditional strategy. Marine glass eels were sampled in autumn and spring, stratifying high and low energetic status, respectively. Their migration behavior was determined in experimental installations that mimic tides using a change in water current direction every 6.2 h. When synchronized to the current reversal, glass eels were called active while individuals hiding in the substratum were considered as non-active. Then, for each active fish, a level of swimming activity was determined and both migration behavior and level of swimming activity were correlated to the individual wet weight (used as a proxy of energy stores), standard metabolic rate (relative SMR) and transcriptomic profile of metabolism related genes. Results showed that spring glass eels presented a lower probability to migrate, a lower wet weight and a higher expression of genes involved in energy stress resistance than autumn ones, supporting a conditional strategy based on individual's energy status. However, within each season, no wet weight difference was observed between active and non-active fish. In autumn glass eels, migration behavior was weakly related to relative SMR while in spring, none of the parameters analyzed allows discriminating active and non-active glass eels. The level of swimming activity in active fish was related to their relative SMR in autumn and to their wet weight in spring. Altogether, our results could not validate a conditional strategy but spring glass eels displayed some signs of energy distress and a lower level of swimming activity than autumn ones.

Improving the estimation of deep-sea megabenthos biomass: dimension to wet weight conversions for abyssal invertebrates

Deep-sea megafaunal biomass has typically been assessed by sampling with benthic sledges and trawls, but non-destructive methods, particularly photography, are becoming increasingly common. Estimation of individual wet weight in seabed photographs has been achieved using equations obtained from measured trawl-caught specimens for a limited number of taxa. However, a lack of appropriate conversion factors has limited estimation across taxa encompassing whole communities. Here we compile relationships between measured body dimensions and preserved wet weights for a comprehensive catalogue of abyssal epibenthic megafauna, using ~47,000 specimens from the Porcupine Abyssal Plain (NE Atlantic) housed in the Discovery Collections. The practical application of the method is demonstrated using an extremely large dataset of specimen measurements from seabed photographs taken in the same location. We also collate corresponding field data on fresh wet weight, to estimate the impact of fixation in formalin and preservation in industrial denatured alcohol on the apparent biomass. Taxa with substantial proportions of soft tissues lose 35 to 60% of their wet weight during preservation, while those with greater proportions of hard tissues lose 10 to 20%. Our total estimated fresh wet weight biomass of holothurians and cnidarians in the photographic survey was ~20 times the previous estimates of total invertebrate biomass based on trawl catches. This dramatic uplift in megabenthic biomass has significant implications for studies of standing stocks, community metabolism, and numerical modelling of benthic carbon flows.

Observations on the population characteristics of<i> Apionsoma (Apionsoma) misakianum </i>(Sipuncula: Phascolosomatidae), a new species for the Mediterranean fauna

The present paper deals with the ecology and population characteristics of the sipunculid Apionsoma (A.) misakianum from the Aegean Sea, which is a new record for the Mediterranean Sea. A total of 571 specimens of this species were collected at 25 stations between 41 and 195 m depth. The majority of specimens were found between the depth intervals 101-150 m (46%) and 151-200 m (45.2%). The biometrical parameters such as the trunk length and individual wet weight of the specimens were evaluated using regression and correlation analyses. In addition, the morphological, ecological and distributional features of the species are given and discussed.

The combined effects of temperature and salinity on growth and survival of juvenile mud crabs ( Scylla serrata Forskål)

An experiment was conducted to determine the effects of temperature and salinity on the growth and survival of the mud crab Scylla serrata, and the combined optima for these parameters during the nursery phase. Instar 2 crablets, mean weight 18.43±0.42 mg were individually reared at combinations of temperature (20, 25, 30, and 35 °C) and salinity (0‰, 5‰, 10‰, 20‰, 30‰, and 40‰) for 18 days. Crablets were fed an artificial penaeid diet to satiety each day and at harvest were weighed, and the carapace width was measured. All crablets held at 0‰, regardless of temperature, were dead the morning after stocking and were therefore excluded from any data analysis. Survival was significantly different among treatments due to temperature but not due to salinities between 5‰ and 40‰. The mean survival for the various temperatures were 36.0%, 98.0%, 96.0%, and 94.0% for temperatures of 20, 25, 30, and 35 °C, respectively. Growth, as measured by individual wet weight at harvest, carapace width, instar 3 intermoult duration, and weight-specific growth rate (WSGR percentage per day), was influenced more by temperature than by salinity, although both had significant effects on all parameters examined. Analyses indicate that maximum WSGR of around 16% day −1 was achieved at 30 °C and 10–20‰ salinity. Based on the findings of this experiment, S. serrata juveniles from the Northern Territory of Australia should be reared at approximately 30 °C with salinities in the range of 10–25‰ in order to achieve maximal production.

Lactate dehydrogenase activity in two cirolanid isopods: the relationship with zonation and motility capacity on sandy beaches

[In this paper we report lactate dehydrogenase (LDH) apparent specific activity, in two species of cirolanid isopods that inhabit exposed sandy beaches. LDH has been related to burst swimming capacity and we expected higher activities in Excirolana armata (Dana, 1852) since it occupies lower beach levels and is a stronger swimmer than Excirolana braziliensis Richardson, 1912. LDH apparent specific activity was positively correlated to the logarithm of individual wet weight (p (β = 0) < 0.05), ranging from 4.67 to 22.3 μmol min-1 g ww-1 for E. armata and 0.57 to 7.88 μmol min-1 g ww-1 for E. braziliensis. Slopes differed significantly. LDH activity is reduced at basic pH in both species. Vmax and Km for organisms of more than 0.03 g were higher in E. armata (13.36 μmol min-1 g ww-1 and 0.99 mM, respectively) than in E. braziliensis (3.26 μmol min-1 g ww-1 and 0.17 mM, respectively). These results support the positive allometry of anaerobic enzymatic activity/weight at specific level, and suggest that distribution patterns in these organisms could be related to the physiology of locomotion., In this paper we report lactate dehydrogenase (LDH) apparent specific activity, in two species of cirolanid isopods that inhabit exposed sandy beaches. LDH has been related to burst swimming capacity and we expected higher activities in Excirolana armata (Dana, 1852) since it occupies lower beach levels and is a stronger swimmer than Excirolana braziliensis Richardson, 1912. LDH apparent specific activity was positively correlated to the logarithm of individual wet weight (p (β = 0) < 0.05), ranging from 4.67 to 22.3 μmol min-1 g ww-1 for E. armata and 0.57 to 7.88 μmol min-1 g ww-1 for E. braziliensis. Slopes differed significantly. LDH activity is reduced at basic pH in both species. Vmax and Km for organisms of more than 0.03 g were higher in E. armata (13.36 μmol min-1 g ww-1 and 0.99 mM, respectively) than in E. braziliensis (3.26 μmol min-1 g ww-1 and 0.17 mM, respectively). These results support the positive allometry of anaerobic enzymatic activity/weight at specific level, and suggest that distribution patterns in these organisms could be related to the physiology of locomotion.]

Diet and growth of stocked and wild 0+ pikeperch, Stizostedion lucioperca (L.)

Wild and stocked 0+ pikeperch, Stizostedion lucioperca (L.), were sampled with a purse seine from Lake Oulujärvi, situated at the northern edge of the distribution range of the species. The stocked fry started immediate feeding on 0+ smelt, Osmerus eperlanus (L.) after their introduction into the lake in early August at about 50 mm length, whereas the smaller wild pikeperch fry continued to feed on zooplankton. Individual wet weight of the stocked pikeperch was about six‐fold compared with the wild pikeperch throughout August. The length of the ingested smelt was as on average 50%, and maximum 66%, of the pikeperch length. Wild 0+ pikeperch were too small to forage on 0+ smelt. Predation by older conspecifics on 0+ pikeperch was observed.

Influence of asexual reproduction on the structure and dynamics of Holothuria (Halodeima) atra and Stichopus chloronotus populations of the Great Barrier Reef

To determine the effect of asexual reproduction by transverse fission on the population structure of holothurians, ensities and individual weights of Holothuria atra (JÄÄger,1833)and Stichopus chloronotus (Brandt, 1835)were measured over a 26-month period on near-shore reefs of the Great Barrier Reef. Densities of H.atra (0.01—0.69 individuals m –2 )and S. chloronotus (0.11—1.67) did not increase during periods of intense asexual reproduction, and the density on each reef remained relatively stable.The effect of fission was clearly visible in the weight —frequency distributions of both species. The average individual wet weight in each population declined (H. atra from 105/134 g to 64/94 g in two respective populations;S. chloronotus from 128/302 g to 82/190 g in two respective populations) with the onset of fission in early winter, and more individuals in the weight range of fission products were found. The biomass followed the seasonal trend of the average weights for both species, with minimum values in winter. A conceptual model based on these and previous findings identified five possible factors (mortality, habitat stability, optimum individual size, food availability, larval supply) involved in promoting or repressing transverse fission, and the model indicated the consequences for the population.

The holopelagic life cycle of the deep-sea medusaPeriphylla periphylla(Scyphozoa, Coronatae)

Abstract The life cycle of Periphylla periphylla (Peron & Lesueur, 1809) is described. it is the only known direct development of a coronate scyphozoa, showing a holopelagic life cycle without any sessile stage. It also lacks an ephyra stage that normally precedes the medusa stage and it is the first scyphozoan life cycle with sexual propagation where the planula stage is missing. The morphology and histology in the early development is described and a description of eight well recognised developmental stages, covering the period from egg to young medusa, is presented. A brief comparison of the population structure in 1992 and 1997 in Lurefjorden, Norway shows that there has been a dramatic change. The population in 1992 showed a normal size distribution with a median individual wet weight of 540 g, eggs and stages did not occur in the plankton and there was no significant recruitment. Eggs and larvae were first observed in 1993 and since then they have been present in all seasons. The population therefore showed a bimodal size distribution in 1997, composed of an aid cohort with a median wet weight of 760 g and a new and nume1ically dominating cohort with a median wet weight of 40 g. The abundance and population structure of P. periphylla indicate an exceptionally high age potential for a jellyfish and very low mortality in Lurefjorden.

Salinity tolerance of hatchery-reared postlarvae of Penaeus indicus H. Milne Edwards originating from India

The effect of salinity (S) on growth, survival, total biomass and individual wet weight of Penaeus indicus postlarvae (PL), from broodstock originating from India, but reared through several generations in recirculating systems in Europe, was examined in the laboratory. Hatchery-reared postlarvae (PL7-22) appear to tolerate a wide range of salinities (5–40 ppt S). Although animals tolerate abrupt salinity changes of up to 10 ppt S, transfer from 30 ppt S to 10 and 5 ppt S without acclimation resulted in mass mortalities over a period of 24 h. PLs grown at 25 ppt without acclimation exhibited the best growth and survival between PL7 and PL22 ( P < 0.05). Following a 10-day acclimation period, the postlarvae reared at various salinities (10, 20, 30, 35, 40 and 50 ppt) displayed the best performance (growth, survival, total biomass) at salinities between 20 and 30 ppt from PL20 and PL60 ( P < 0.05). While postlarvae up to PL60 gain resistance to high salinities (40–50 ppt S), lower salinities (10 ppt S) were lethal for the postlarvae after the PL45 stage. In contrast to Red Sea P. indicus, high salinities of 40–50 ppt caused cessation in the growth, and reduced survival and biomass of the Indian postlarvae.

Rearing of European grayling, Thymallus thymallus L., larvae using dry and live food

. European grayling, Thymallus thymallus L., larvae, after hatching, were fed solely on a dry food diet and compared to those fed live zooplankton. After 28 days of rearing at temperatures ranging from 15·0°C to 18·3°C (mean, 16·4°C) fish fed the dry diet reached 0·21 g individual wet weight and 31mm in total length; those fed zooplankton reached 0·13g and 27·5 mm respectively. The survival rate of fish fed the dry diet was higher (56·6%) than that of fish fed the live food (40·7%). Results are discussed in the light of the development of the alimentary tract in the early ontogeny of grayling.

Influence of initial weight during the change from live to compound feed on the survival and growth of four cyprinids

In a series of trials, larvae of common carp ( Cyprinus carpio L.), silver carp ( Hypophthalmichthys molitrix Rich.), grass carp ( Ctenopharyngodon idella Val.) and bighead carp ( Aristichthys nobilis Rich.) were transferred directly from a diet of zooplankton to a dry, compound feed. The dry diet was based on a previously described diet of yeast and freeze-dried animal tissues. Common carp larvae showed the best growth on live zooplankton (46.3 mg individual weight after 14 days) compared to fish fed solely on dry feed (13.8 mg). Transfer of common carp larvae to dry diet when they reached 4.27 mg significantly improved growth, but no dependence was observed on two diets tested. Grass carp larvae grew equally well on live food and on the best compound diet (8.7 mg after 15 days), but fish transferred to dry diet at 4.3 mg showed significantly improved growth. The growth rate, however, depended on the diet (12.9–23.5 mg). Silver carp grew better when fed solely on dry diet (23.5 mg), compared to live zooplankton (15.8 mg after 15 days), but this was due to an insufficient supply of suitable live food. Transfer of fish at 6.8 mg to dry diet improved the growth only slightly, and dependence on the kind of dry diet was observed. Bighead carp larvae showed better growth on live zooplankton (42.2 mg after 15 days) than on the best compound diet (18.6 mg). Fish transferred at 5.6 mg to dry diets showed good growth, but high mortality was observed. It was concluded that common carp larvae are the most “difficult” to raise solely on dry diet, whereas silver carp larvae are the “easiest”. The present study has shown that the transfer of four cyprinids to dry diet improved their growth rate and that the transfer is possible at the individual wet weight of 5–6 mg.

Competition for Food between Two Intertidal Starfish Species and its Effect on Body Size and Feeding

Two predaceous intertidal starfish that overlap broadly with respect to food, space, and time were found to compete for a limited food supply in the San Juan Islands, Washington State. The experiment involved complete removal of a larger (up to 600 g average wet weight) starfish (Pisaster ochraceus) from a small island—reef and addition of them to a second island—reef while a third reef served as a control. In response to Pisaster removal, the mean individual wet weight of the smaller (maximum size = 45 g wet weight) asteroid (Leptasterias hexactis) increased significantly in 15 months. Addition of Pisaster resulted in a significant decrease in Leptasterias size; no change in average Leptasterias size was observed on the control reef. A highly significant inverse correlation between the estimated biomass densities (wet weight/m2) of the two species at 10 areas suggests that competition is widespread and that the species are generally in competitive equilibrium. A major consequence of the small size of Leptasterias is an apparent inability to capture larger prey. Coexistence seems based upon "specialization" by each predator on different—sized prey. Evidently, reduced competition stress results in an increase in Leptsterias's community role as a predator. Conversely, when competition is severe, the community role of Leptasterias appears unimportant.