Larval Dry Weight Research Articles

Food selection and digestion characteristics of Atlantic halibut ( Hippoglossus hippoglossus) larvae fed cultivated prey organisms

The aim of the present study was to investigate the pattern of food selection by larvae of Atlantic halibut fed Brachionus plicatilis and different size classes of Artemia franciscana, including short-term enriched (ST) A. franciscana nauplii. A second aim was to study the digestibility of different size classes of A. franciscana by halibut larvae. The larvae did not show any significant preference for B. plicatilis or nauplii of A. franciscana during the first 2 days after initiating first feeding at 285 day degrees. From day 3 and onwards, they selected significantly ( P<0.05) for A. franciscana. When offered different size classes of A. franciscana, from newly hatched nauplii to juveniles as long as 4.8 mm, they selected positively for newly hatched A. franciscana (<0.60 mm) up to day 20 (3.0–3.5 mg dry weight larva −1), when they suddenly started to select positively for larger A. franciscana. From the larval dry weight of 4.0 mg (after day 20), they selected significantly for A. franciscana in the size class 1.20–1.39 mm. However, the larvae ingested A. franciscana shorter than 0.60 mm during the whole live feed period, independently of the availability of larger prey items. The ST A. franciscana nauplii, which is the most commonly used live feed size for halibut larvae, was apparently slightly less digested than the other size classes. It is suggested that this difference in digestion ability was a result of the very high lipid content of the ST A. franciscana compared to that of juvenile A. franciscana and newly hatched A. franciscana. Based on the selection and digestibility results the feeding regime for halibut larvae should consist of newly hatched nauplii, eventually together with B. plicatilis, the first week. Thereafter two weeks with ST A. franciscana nauplii and then a switch to 3-day-old A. franciscana juveniles for the rest of the live feed period.

Fluctuating life-history parameters indicating temporal variability in metal adaptation in riverine chironomids

Adaptation to toxicants in animal populations is influenced primarily by two counteracting forces. First, the intensity and duration of peak concentrations of toxicants is responsible for the actual level of selection pressure on the population. Second, the process of adaptation can be disrupted by gene flow as a result of crossings with nontolerant individuals. These counteracting forces were analyzed in riverine insects in which we expected that the level of metal adaptation is subject of considerable fluctuations, due to variable dilution of metals and a variable transport of nontolerant individuals in river water. To this purpose, the stability of metal adaptation in different Chironomus riparius populations was analyzed during a 5-month period in a heavily polluted lowland river. This was examined by measuring mortality, larval dry weight, and accumulation of zinc under laboratory conditions. The results showed that in midge populations originating from metal-contaminated field sites several life-history parameters (like control mortality and growth response under cadmium exposure) of the laboratory reared F1 generations showed considerable temporal variation. In addition, the presence of metal-adapted midge populations was indicated on several occasions on the metal-exposed field sites. Reference populations on the other hand, showed stable life history patterns throughout the sampling period, and no signs of metal adaptation were found. These observations showed that the actual level of metal adaptation varies considerably, both in time and space. Adaptation to metals in riverine chironomids, therefore, should be looked on as a highly dynamic process.http://link. springer-ny.com/link/service/journals/00244/bibs/37n2p175.html

Costs and Benefits of Mating in the Grasshopper Chorthippus parallelus (Caelifera: Acrididae)

Fitness consequences of different levels of mating benefits, viz., (1) virgin, (2) seldom mated, (3) free mating chances with the same male throughout the female's life span, and (4) free mating chances with three males always offered, were investigated in female meadow grasshoppers Chorthippus parallelus. No differences among the treatments were apparent in egg number per pod, total egg number per female, and hatching success of larvae. Seldom-mated females had offspring with the heaviest average larval dry weight. We did not find costs of mating in terms of reduced female longevity and residual dry weight between the treatments.

Larval development of hoplias cf. Lacerdae (Pisces: Erythrinidae) and delayed initial feeding effects

Larval development of Hoplias cf. lacerdae was studied under laboratory conditions. After hatching, ontogenetic changes were recorded on food-deprived larvae in 12-hour intervals. Mouth opening occurred after 2.5 days and notochord terminated flexure in 6.5 days. Notochord length increased at a constant rate until complete yolk absorption (13,5 days). Larval dry weight and body height diminished gradually up to 21 days after hatching, when all starved larvae died. Every 12 hours after yolk absorption, groups of larvae (n=15), were separeted, and fed with Artemia nauplii for 10 days. The point-of-no-return (when 50% of larvae were unable to feed or to assimilate ingested food after delayed feeding), was not apparent in this species.

Egg Size and Viability and Seasonal Offspring Production of Young Atlantic Cod

Abstract Experiments monitoring the egg and larval production of captive northwest Atlantic cod Gadus morhua indicated that first-time spawners perform poorly compared to second-time spawners. They breed for a shorter period, produce fewer egg batches, exhibit lower fecundity, and produce smaller eggs with lower fertilization and hatching rates; moreover, their larvae are less likely to hatch in environmental conditions favorable for survival. Batch-average egg diameters of first-time spawners underwent a continuous rapid decline between initial and terminal batches, whereas second-time spawners commonly exhibited a parabolic curve (slight increase followed by a decrease). Seasonal composite hatching rates of all eggs spawned by first- and second-time spawners were 13 and 62%, respectively. Larval production per maternal gram was an order of magnitude greater for second-time than for first-time spawners (200 versus 20 larvae/g). Batch-average egg diameter declined 11% and larval dry weight declined 29% fr...

Larval condition and vulnerability to predation: an analysis based on mixed-prey experiments

Many recent studies in larval fish ecology measure larval nutritional condition (e.g., RNA/DNA ratios), with the ultimate goal of assessing future survival probabilities. Larvae of intermediate or poor condition are generally considered to be more vulnerable to predators than larvae in good condition. The objective of our study was to experimentally test whether larvae in poor condition have lower relative survival rates when exposed to a predator. We conducted mixed-prey experiments with larval capelin (Mallotus villosus) on days 6, 8, and 10 posthatching by putting 75 fed and 75 starved larvae in 38-L containers with (treatments) and without (controls) predators (juvenile lumpfish, Cyclopterus lumpus). There were no significant differences in the mean condition (RNA/DNA ratios) or dry weights of larvae recovered from controls and treatments. These results suggest that RNA/DNA ratios are not useful indicators of vulnerability to predation for larval capelin.

Serum composition of Aedes aegypti (Diptera: Culicidae) larvae and the production of an oviposition repellent are influenced by infection with the entomopathogenic digenean Plagiorchis elegans (Trematoda: Plagiorchiidae), starvation, and crowding.

Subjecting Aedes aegypti (L.) larvae to conditions that induced the production of oviposition repellency also reduced their wet and dry weights and the concentration of total serum carbohydrates, amino acids, and proteins. Thus, infection with metacercariae of the entomopathogenic digenean Plagiorchis elegans (Rudolphi), starvation for 7 d, or crowding for 2 d reduced larval dry weights by as much as 32, 20, and 23%, respectively, and wet weights by 20, 14, and 11%, respectively. Total serum carbohydrates declined by as much as 36, 21, and 29% for infected, starved, and crowded larvae, respectively, amino acids by 39, 48, and 44%, and protein concentrations by 72, 63, and 62%, respectively. Repellency dilution titers were correlated inversely with movement of the mouth parts and gut. Incubation of infected, starved, and crowded larvae in 0.01 g/liter glucose greatly reduced the level of repellency of their waters, whereas adding glucose to repellent waters had only minor effects. Results indicate that the induction of repellency is associated strongly with nutritional depletion effects.

Interannual variations in condition indices of larval Norwegian spring-spawning herring

The sea water temperature off the Norwegian coast was lower in 1994 than in 1992 and 1993. RNA/DNA ratios of Norwegian spring spawning herring increased with increasing larval dry weight all years, except for larvae sampled south of 62°N in 1994. The RNA/DNA ratios indicated that each year, only a small portion ( 0.7%) of the larvae were starving. RNA/DNA ratios and temperature were negatively correlated in 1992, but in other years no significant correlations were found. Residuals of In RNA v. In DNA and In W v. Ls were poorly correlated in all years, but residuals of In RNA v. In DNA and In DNA v. In W were negatively correlated in all years. Principal component analysis showed that the RNA/DNA ratio and DNA (% of weight) were correlated with different axes. Abundance data for herring at the early larval and 0-group stages in 1992–1994 indicated higher mortality in 1994 compared with the other years. The data do not indicate that average larval condition was poorer in 1994 than in other years. However, the variability in larval condition was higher in 1994 than in other years, and the condition of later larval stages was relatively lower in 1994 than in other years.

Effects of salinity on yolk sac larvae of Atlantic halibut ( Hippoglossus hippoglossus L.)

Larvae of Atlantic halibut ( Hippoglossus hippoglossus L.) were transferred to nine different salinities (range 20–42 ppt) immediately after hatching, or to five different salinities (range 24–39 ppt) at day 30 post-hatching (p.h.) The experiments were terminated 49 days p.h. (at 5 °C); i.e. at first feeding. When newly-hatched larvae were introduced to different salinities, the highest survival rates (69–90%) were obtained at 27–32 ppt. A high yield of normally developed larvae was only obtained within a limited range of salinities (29–34 ppt). Thirty-day-old larvae tolerated a wider range of salinities than newly-hatched larvae, and only larvae transferred to the highest salinity (39 ppt) exhibited significantly reduced survival and yield of functional larvae. Myotomal height, larval dry weight and yolk volume were little influenced by the rearing salinity in either experiment. The buoyancy of halibut larvae was influenced both by the rearing salinity and by larval age.

Effects of temperature on yolk sac larvae of Atlantic halibut ( Hippoglossus hippoglossus L.)

Larvae of Atlantic halibut were incubated at five different temperatures (4, 6, 8, 10 and 12 °C) from hatching onwards (Experiment 1), and at 4 °C for a period of 0, 10, 20, 30 or 40 days before the temperature was increased to 6 °C or 8 °C (Experiment 2). Both experiments were terminated at time of first feeding, 230 day-degrees (d °) after hatching. In Experiment 1, larval survival was significantly lower at 12 °C, and the yield of normally developed larvae dropped significantly when larvae were incubated at 6 °C or higher. When larvae were incubated for different periods at 4 °C (Experiment 2), the number of days at 4 °C had a significant effect on larval survival and the frequencies of functional larvae, jaw deformations and yolk sac oedema, while the temperatures in the second period (6 °C or 8 °C) had no significant effect on the same traits. Frequency of normally developed larvae increased with increasing number of days at 4 °C while the survival rate tended to decrease with increasing number of days at 4 °C. Myotomal height, larval dry weight, yolk sac volume and feeding incidence were less influenced by the incubation temperature in both experiments. The results demonstrated that the development of abnormalities like gaping jaws and yolk sac oedema in halibut yolk sac larvae can be associated with high temperatures and presence of different temperature tolerances at different developmental stages.

The effect of gut contents on dry weight estimates of Chironomus tentans larvae: Implications for interpreting toxicity in freshwater sediment toxicity tests

AbstractGut contents have long been recognized as a potentially important source of bias in studies concerned with estimating contaminant body burdens in benthic macroinvertebrates. In this study, we show that gut‐associated, inorganic material may also lead to significant overestimates of weight in Chironomus tentans larvae in sediment toxicity tests and thus influence statistical interpretation of effects on growth with this organism. Two methods were evaluated regarding their potential to correct for the proportion of larval dry weight contributed by gut contents: purging and determination of ash‐free dry weight (afdw). Each method was assessed in a series of 10‐d growth tests using (1) clean sand and clay substrates with a restricted particle size distribution (mean particle size: 8, 146, 218, 306, 448, and 592 μm), and (2) sediments collected from both clean and contaminated field sites encompassing a wide range in particle size distribution. Both purging and afdw determination resulted in significant reductions in the dry weight of larvae in most substrates &lt;306 μm and in the field‐collected sediments. In these treatments, 7–59% of the dry weight of fourth instar larvae was comprised of inorganic material contained within the digestive tract. Sediment organic carbon was also important; the contribution of gut contents to larval dry weight in a highly organic (23.6%) sediment was only 7.9% despite a small particle size distribution (mean = 149 μm). Correction for ingested material changed the rank order of treatment means in all tests and reduced the number of statistically significant outcomes for many treatment comparisons. Both methods reduced variability (lower standard deviation) associated with mean dry weight estimates, although variability was generally greater with purging than with the afdw method. Based on the results of this study, we recommend that afdw, not dry weight, be used to determine the weight of C. tentans larvae in 10‐d and life‐cycle tests with this organism.

Balsam Fir Foliar Chemistry in Middle and Lower Crowns and Spruce Budworm Growth, Development, Food and Nitrogen Utilization

The impact of current-year foliage from the middle or lower crown section of balsam fir trees on larval growth, development, nitrogen, and food utilization was studied with laboratory rearing experiments, gravimetric analyses, and foliage chemical analyses. Pupal dry weight, pupal nitrogen weight, and total development times were not affected by feeding on current-year foliage from either the middle or the lower crown section. However, the nutritive and, particularly, allelochemical profiles were significantly different between crown levels and influenced spruce budworm food utilization, depending on development stage. Newly molted fifth instars feeding since post-diapause on middle crown foliage had lower dry weight and nitrogen weight than those fed lower crown foliage. This apparently resulted from the high monoterpene content in the mid-crown foliage. At the end of the fifth instar, however, insects from both crown levels had similar larval dry weights and nitrogen weights. Larvae fed middle crown foliage compensated with several mechanisms that led to increased relative nitrogen accumulation rate (RNAR) including increased efficiencies of conversion of ingested and digested nitrogen (ECIN, ECDN). Sixth-instar development time was nearly two days shorter for larvae fed middle crown foliage compared to those fed lower crown foliage. A higher relative consumption rate (RCR) due to the high content of two phagostimulatory components (soluble sugars and β-pinene) may account for reduced sixth-instar development time. Larvae from the middle crown section had higher relative growth rates (RGR) and RNAR than those from the lower crown. Pupal development time was also longer in the lower crown. The existence of spruce budworm flexibility to adapt to foliar biochemistry variations by developing compensatory mechanisms enables larvae to exploit the whole tree crown.

Larval Growth Patterns in the Aesop Shrimp Pandalus Montagui

Larvae of the Aesop shrimp Pandalus montagui Leach (Decapoda: Caridea: Pandalidae), were reared in the laboratory at 5 different temperatures (6, 9, 12, 15, and 18°C), and their growth patterns were analyzed in terms of molting frequency, size increments (total length, TL, carapace length, CL), and increase in larval dry weight (W). Pandalus montagui passed through 6 zoeal and 2-5 decapodid stages. While 2 of the latter occurred consistently (obligatory stages), up to 3 additional (facultative) decapodid stages were passed before metamorphosis to the first juvenile. Molting occurred at regular intervals, with little interstage variation, so that the instar number could be described as a linear function of the time of development, with an increasing molting frequency at increasing temperatures. A nonlinear relationship (power function) was found between average intermolt duration and temperature; this regression was linked with data for water temperatures measured during the spring near Helgoland (southern North Sea), in order to predict the approximate duration of larval development and peak settlement in the field. From instar I-VIII, larval size increased as a linear function of the number of molting cycles, but no significant growth and no further morphological changes were observed in later (facultative) larval stages. The morphometric relationship between TL and CL remained linear throughout larval development, with an increasing trend in the TL:CL quotient. W increased exponentially with the number of instars, and as a power function of larval size. The overall patterns of larval development and growth in P. montagui are compared with those known from other pandalid species and in other caridean shrimps.

Case Features of Caddisfly Larvae (Sericostoma selysi) as Related to Water Velocity and Potential to Drift

ABSTRACT Variation in case characteristics of larvae of Sericostoma selysi (Pictet 1865) as related to water velocity and resistance to passive entry into the drift was investigated in the field. Larvae from river sections of different current velocity (low: 0.30–0.35 m·s−1 and high: 0.60–0.65 m·s−1) were collected. Case and larval dry weight were weighed; frontal and lateral surface areas of the cases were also measured. Larvae from high-speed waters had heavier and narrower cases than those from the low-speed waters. We believe that this is an adaptation in response to water velocity, which enables larvae living under conditions of high velocity to resist the drag forces of moving water.

The significance of growth in Chironomus tentans sediment toxicity tests: Relationship to reproduction and demographic endpoints

AbstractIn the Chironomus tentans 10‐d growth test, changes in larval growth relative to sediment contamination are often ascribed ecological relevance by assuming that such changes become manifest at the population level through effects on reproductive output even though the relationship between growth and reproduction is poorly understood. The objective of this study was to evaluate the relationship between growth and reproduction in C. tentans and to use these data in a demographic model to predict the growth and size of a theoretical population. Growth was manipulated by varying food supply (0.29, 0.33, 0.38, 0.42, 0.46, and 0.5 mg/individual per d). The test was initiated with 12 newly hatched larvae per replicate and carried through one complete generation. Larval growth and survival were determined at 20 d, and reproduction was monitored daily during emergence. Food supply did not significantly affect survivorship at any life stage; survival of larvae at 20 d, pupae, and adults exceeded 83%, while survival of larvae in the reproduction replicates exceeded 65%. Both larval and adult dry weight declined significantly with a reduction in food supply. Total emergence was reduced at the lowest feeding level only, whereas the rate of emergence declined at food supplies below 0.42 mg/individual per d. Based on the relationship between larval and adult dry weight, a minimum larval tissue mass of between 0.5 and 0.6 mg dry weight/individual appears to be necessary before emergence can take place. The number of eggs/female declined significantly with a decrease in food supply below 0.42 mg/individual per d. Above this level (corresponding to larval dry weight of ∼ 1.5 mg/individual), the addition of more food had no effect on reproductive output. Fecundity (number of daughters/female) and expected number of progeny declined linearly with reduced food supply. Application of the data in a demographic model showed that the growth and predicted size of a population would decline significantly with a decline in larval growth and reproductive output. These results demonstrate that changes in growth, positive or negative, can be used to make meaningful predictions regarding reproduction and population dynamics in the midge C. tentans.

Effects of prey density on the growth and mortality of weakfish Cynoscion regalis (Bloch and Schneider) larvae: Experiments in field enclosures

Weakfish larvae ( Cynoscion regalis (Bloch and Schneider)) were reared in large enclosures (1.4 m 3) deployed near adult spawning grounds in Delaware Bay, USA. Larvae were fed wild zooplankton, and experimental prey levels encompassed naturally occurring densities (10, 100 and 1000 prey items 1 −1). Separate experiments were conducted for early-stage and late-stage larvae in 1990, and the late-stage experiment was repeated in 1994 using an improved statistical design. In 1990, there was a trend toward elevated growth rates with increasing prey levels. For early-stage larvae, larval notochord lengths ( NL) varied with prey density and ranged from 3.65 to 4.30 mm. Larval dry weight ( W) also varied with prey density and ranged from 39.5 to 61.3 μg. Calculated growth rates varied accordingly. Growth among late-stage larvae followed a similar trend, and NL ranged from 4.65 to 5.25 mm, while W ranged from 73.7 to 139.7 μg. In the repeated late-stage experiment (1994), a nested ANOVA showed significant effects of prey level on growth. Notochord length (4.33 mm) and dry weight (72.3 μg) were significantly depressed at the lowest prey density. Rates of instantaneous mortality were variable among individual enclosures and were not related to prey density in either year. Our results differ from previous field enclosure studies, which have shown little effect of prey density on the growth of larval fish. By contrast, our data indicate that low food levels may result in depressed growth rates among weakfish larvae in nursery areas like Delaware Bay. These lower growth rates may lead to an increased duration of larval development, potentially culminating in high mortality from increased exposure to predation or from advection from suitable juvenile habitats.

Metal‐supplemented diets alter carbohydrate levels in tissue and hemolymph of gypsy moth larvae (Lymantria Dispar, lymantriidae, lepidoptera)

AbstractLarvae of Lymantria dispar were exposed to two concentrations each of Cd, Pb, Cu, and Zn from hatching to day 3 of the fourth instar. The metals were applied via artificial diet (wheat germ diet); two control groups were reared on either an uncontaminated artificial diet (C) or on a natural diet (oak leaves, EF). High‐pressure liquid chromatography (HPLC) was employed to analyze the hemolymph carbohydrates, whereas body glycogen and glucose were determined enzymatically. The results were analyzed with respect to diet‐specific differences (oak leaves versus wheat germ diet) and metal exposure compared with the uncontaminated artificial diet. Hemolymph trehalose levels were higher in oak leaf‐reared individuals than in those fed on the wheat germ diet (p &lt; 0.01), whereas the opposite applied to the body glycogen and free glucose levels (p &lt; 0.01). The average trehalose value of the control (C) (4.3 mg/ml) was reduced by metal contamination, dependent on both the metal itself and the concentration (Cd, Cu, Zn; 1.4–3.3 mg/ml). Sorbitol was not detected in the hemolymph of EF specimens, whereas it occurred in all artificial diet‐fed groups. Metal‐ and dose‐dependent differences in the hemolymph sorbitol levels were observed in the treatment groups, but not in the controls. Glycogen content increased in the low concentration of Cd, Pb, and Cu, whereas a decrease was observed for the low Cd and both Zn concentrations. Tissue free glucose was enhanced only in three of the metal groups. Generally, fresh and dry weights of larvae were reduced in all groups except the high Cu‐contaminated one. The results may indicate that mass outbreaks of an important forest pest insect like L. dispar may be facilitated in metal‐contaminated areas because parasitization success of antagonistic species may decline due to deterioration of nourishment within the metal‐stressed host.

Effects of bioturbation by tube‐dwelling chironomid larvae on oxygen uptake and denitrification in eutrophic lake sediments

1. Oxygen uptake and denitrification were determined in two bioturbated sediments from a eutrophic lake in southern Sweden. In laboratory mesocosms, an organic profundal sediment was incubated with Chironomus plumosus L. and a sandy littoral sediment with an organic‐rich top layer was incubated with Polypedilum sp. Both species of chironomid are sediment tube‐dwelling.2. Oxygen consumption, expressed per gram of larval dry weight, was enhanced to the same extent by the larvae in both sediments. Measurements of the respiration rate of individual larvae revealed that the respiration per gram dry weight of the smaller Polypedilum sp. was more than three times higher than that of C. plumosus.3. Denitrification was measured using the ‘nitrogen isotope pairing’ technique. In the organic sediment, denitrification of nitrate from the water phase (dw) and denitrification of nitrate from coupled nitrification (dn) were each correlated with the biomass of C. plumosus. In the sandy sediment, dw was correlated with the biomass of Polypedilum sp., while dn did not show any correlation with Polypedilum sp.4. Oxygen uptake in the organic sediment was increased by a factor of 2.5, dw 5‐fold and dn 2.5‐fold at a biomass of 10 g m–2 dry weight of C. plumosus. The same biomass of Polypedilum sp. in the sandy sediment resulted in a 2‐fold stimulation of oxygen uptake and a 3‐fold stimulation of dw, while dn was not affected. These differences in stimulation between oxygen uptake and denitrification by the larvae in the sediments suggest that the stimulation pattern cannot be explained by simple extension of the sediment surface. The burrows evidently reduce the distance between the nitrate source in the water column and the denitrifiers in the anoxic zones.5. This study indicates that bioturbation by macrofauna elements can have a great impact on denitrification in lake sediments, and that different organisms can influence nitrogen turnover in specific ways.

Relationships betweenDendroctonus micans Kug. (Coleoptera: Scolytidae) survival and development and biochemical changes in Norway Spruce,Picea abies (L.) Karst., phloem caused by mechanical wounding

The bark of Norway spruce trees,Picea abies (L.) Karst., was wounded to produce areas of bark with differing biochemical characteristics. Adults and larvae ofDendroctonus micans Kug. were inserted into these trees at points around the wounds. Larval survival was higher, larval dry weights were higher, and adults were more likely to oviposit at sites around the wound that had higher phloem moisture contents. Larvae showed higher survival and dry weights in phloem with low terpene contents. Adults oviposited in phloem with lower stilbene glucoside contents. Phloem moisture differed at sites around the wound compared with that at a control site away from the wound, and the nitrogen content of entire bark cores was higher above wounds than at control sites away from the wounds. Phloem moisture correlated with the nitrogen content of entire bark. Phloem terpene contents correlated with each other, as did the stilbene contents. Associations between the host exploitation pattern ofD. micans and the biochemistry of the host phloem are discussed in relation to preselection by adults of sites suitable for larval development.

A method for estimating larval life spans of aseasonal aquatic insects from streams on Bougainville Island, Papua New Guinea

1. The larval life spans of twelve species of aseasonal aquatic insects (eight Trichoptera, three Ephemeroptera, one Odonata) were investigated in two tropical streams with near constant water temperatures.2. Life spans were estimated from equations relating larval life span to the ratio between cohort production (estimated from the size–frequency technique) and annual production (estimated from regressions in the literature).3. Life spans varied from 40 to 250 days and were positively correlated with maximum larval dry weight (r = 0.73, P &lt; 0.001). Ephemeroptera had the shortest larval life spans (40–110 days), Trichoptera intermediate (95–185 days) and Odonata the longest (250 days).