Fecundity of the three-spined stickleback, Gasterosteus aculeatus (L.)

The number of eggs spawned by female three-spined sticklebacks Gasterosteus aculeatus (L.) was highly correlated with the size of the fish expressed either as total length or as weight after spawning. There were no significant correlations between the size of the eggs measured either as wet weight per egg or as dry weight per egg, and the size of the fish. Nor were there significant correlations between the calorific value of the eggs and the length or weight of the fish. Regressions relating egg production to the length and the weight of the fish are given. These results and an analysis of previous studies on the fecundity of the stickleback suggest that variations in fecundity are primarily a reflection of variation in the size of the fish at maturity, and that this size is related to the race of the stickleback and to environmental conditions such as food supply which influence the growth of sticklebacks.     

The effect of size of food ration on egg production in the female three-spined stickleback, Gasterosteus aculeatus L.

The effect of food level on the egg production of three-spined sticklebacks was studied experimentally. High food levels increased the percentage of fish that matured, and the weight of the fish at maturity. Weight at maturity was positively correlated with the number of spawnings, the mean number and the weight of eggs produced per spawning. Food level had no effect on the size of the eggs, whether size was expressed as wet or dry weight per egg. Fish on the highest food level spawned at shorter intervals than fish at the lower levels. A preliminary model of the effect of food supply on recruitment to a stickleback population is nresented.     

Assessment of egg quality and realised fecundity of whiting Merlangius merlangus L. in captivity

Potential predictors of egg quality were assessed in whiting Merlangius merlangus L. permitted to spawn in a tank from which eggs were collected. These included fertilisation rate, the proportion of viable buoyant eggs, egg diameter, and egg wet and dry weights; all were influenced by temporal effects and were negatively correlated with days from start of spawning. The spawning period was protracted, from February to June. Mean daily egg production per female was 2.74 ± 2.43 g and 2338 ± 2075 eggs, equivalent to 14.6 ± 13.1 g kg^?1 day^?1 female^?1. Egg diameter was 1.21 ± 0.04 mm, egg wet weight 1.20 ± 0.21 mg, dry weight 0.10 ± 0.02 mg, and mean fertilisation rate and hatching rates were 76.8 and 73.3%, respectively. The incubation period ranged from 72 to 80 degree days and was dependent on temperature (x) and described by the equation y = 25.92 e^?0.1219x. Realised fecundity was also assessed to determine if this gave a more accurate measure of reproductive potential, and this was compared with potential fecundity estimated from predictive regressions on fish length from fisheries data. Realised egg production of 20 females of 185 g mean weight and 256 mm fork length was 4 444 360 (95% CL 4 093 961–4 743 018), similar to predicted seasonal egg production based on gravimetric fecundity measurements of wild caught fish.     

Subsidies for production of Chironomus calligraphus larvae (Chironomidae,Diptera) in the laboratory

The objective of this study was to evaluate the effect of temperature, type of mineral substrate, and type and amount of feed on the growth of Chironomus calligraphus as a subsidy for the production of Chironomus larvae to feed the fish. Egg production was evaluated at 22, 25, and 28?°C on fine (0.074–0.210?mm), or silty sand (0.002–0.250?mm), and no mineral substrate as control. For larval production, 0.10, 0.20, and 0.30?mg/larvae of fish feed, poultry feed, or turkey manure were used as food. The highest number of egg masses was produced when mineral substrates and 25?°C were used, but the higher number of eggs/mass was registered in the control. Therefore, the total number of eggs and hatched larvae produced was the same in the presence or in the absence of mineral substrates (p?>?0.05). The best results for survival and growth were recorded for larvae reared with fish or poultry food. The increase in the amount of feed was correlated with weight gain only for larvae fed with poultry feed, with no reduction in survival.     

Patterns of variation in size of Boat-tailed Grackle Quiscalus major eggs

Boat-tailed Grackle Quiscalus major eggs averaged 8^.09 g wet weight. Mean egg weight represented 8 05 % of female body weight. Based on egg weight, Grackle eggs have a shorter incubation period than the general passerine pattern.
Egg weight varied significantly with sequence of laying and between clutches in both two-egg and three-egg clutches. Last laid eggs weighed less than first laid eggs. The mean weight of the first two eggs laid in three-egg clutches did not differ from the mean egg weight of two-egg clutches. The average clutch of two and three eggs weighed 16.33 g and 24.16 g, respectively.
Mean egg weight varied between study colonies and with season. Grackles at East Lake laid eggs that weighed less than grackles at either Alligator Lake or North Lake. Eggs laid during March averaged less than eggs laid later in the season. The locality variation reflects the different timing of nesting between sites rather than food abundance. As nutrient provisioning increases with an increase in egg weight, the seasonal change in egg weight probably reflects improved feeding conditions for the female. This suggests that selection favours beginning laying before reserves of the female are sufficient to lay the largest egg possible.
The size of the young at hatching was correlated with egg size. Newly hate had young averaged 79.6% of fresh egg weight. Egg weight did not determine the probability of hatching or starvation of the young. Females do not appear to adjust egg size facultatively depending on the sex of the young. Eggs producing males and females did not vary significantly in weight, whether comparisons were made within or between clutches.     

Limitation of reproduction by feeding condition in a carabid beetle,Carabus yaconinus

1. Effects of the amount of food consumed on reproduction of the carabid beetle, Carabus yaconinus B., were studied in the laboratory by rearing beetles at different food levels, and the feeding and oviposition rates in the field were estimated on the basis of the relationships between the amount of food consumed, body weight and egg production obtained in the experiment.
2. The maximum amount of food consumed was 150 mg of minced beef per day. The number of eggs laid per day and the mean body weight increased with an increase in the amount of food consumed. High mortality occurred only when the beetles consumed less than 25 mg of minced beef per day.
3. The ratio of current body weight to the minimum one just before death by starvation, W/W_min, was used for the estimation of the rates of food consumption and egg production. The relationships between mean W/W_min ratio, the amount of food consumed and the number of eggs laid per day were clarified.
4. The relationships between ovary states (ovary weight and the number of mature eggs in the ovary) and W/W_min ratio were examined for the females caught in the field. Females with higher values of W/W_min ratio had more mature eggs.
5. The amount of food consumed by females in the field during the reproductive period was estimated to be 50–70% of the maximum value attained in the experiment and the estimated rate of oviposition was 45–59% of the maximum rate attained in the experiment.

     

Observations on effects of feeding level on growth and reproduction in haddock, Melanogrammus aeglefinus (L.) in captivity

Individual haddock, Melanogrammus aeglefinus (L.) were maintained at different feeding levels in an aquarium from November until the completion of spawning. The mean duration of spawning was 33.2 days (range 19–59) during which an average of 16.6 (range 10–25) batches of eggs were produced. The size and dry weight of the eggs declined during the spawning period. Egg production and feeding level were correlated positively. There was some suggestion that when female haddock received low rations (< 5 kcal day^-1) a lower proportion spawned, and the dry weights of the eggs were lower compared with females on high rations (> 13 kcal day ^-1). The relation between daily growth in wet weight, g, and daily surplus energy intake, kcal, was: G =(0.295 E )— 0.328. When food energy is restricted, haddock appear to achieve a balance between somatic growth and reproduction.     

Effect of spawning number and ration on reproductive performance of the batch-spawning three-spined stickleback Gasterosteus aculeatus

An experiment quantified the effect of food ration and spawning number on the breeding season reproductive performance of batch-spawning, female three-spined sticklebacks Gasterosteus aculeatus . Individually housed females were maintained on fixed rations of 2, 4, 8 or 16% of their initial postspawning mass of live enchytraeid worms from immediately after their first spawning until they ceased spawning. Number of spawnings correlated positively with ration. Total breeding season reproductive investment (total wet mass of eggs produced as a percentage of initial postspawning female mass) ranged from 38% at the 2% ration to 147% at the 16% ration. At the lower rations, postspawning mass, batch fecundity and wet and dry masses of the batch declined over successive spawnings, with the rate of decline inversely related to ration. At the highest ration, there was no decline in batch fecundity and postspawning mass increased over successive spawnings. Mean reproductive investment per inter-spawning interval was higher at the highest ration, but at all rations declined over successive spawnings. Mean reproductive effort per inter-spawning interval (wet mass of eggs spawned as a percentage of the wet mass of food consumed over the inter-spawning interval) was inversely related to ration. At the higher rations, reproductive effort showed no trend over successive spawnings. Neither spawning number nor ration had a systematic effect on egg diameter, wet mass per egg, dry mass per egg or total lipid content of the eggs. If the rate of food intake was insufficient, although batch fecundity declined, the main adjustment was a reduction in the number of spawnings in the breeding season.     

Effect of food limitation on food consumption and reproductive allocation by adult milkweed bugs, Oncopeltus fasciatus

Male/female pairs of adult milkweed bugs, Oncopeltus faciatus were offered reduced food rations (100 mg milkweed seeds/week, 50 mg seeds/week, and 25 mg seeds/week) at 232C, 14L : 10D photoperiod. The high rate of food consumption normally occurring during the teneral period (first 8 days posteclosion) and subsequent food consumption were reduced on both reduced rations. Initial fresh weight was lost by bugs on both reduced rations and their weekly fresh body weight tended to remain less than bugs on the 100 mg seeds/week ration.Normal onset of egg production (about 3 weeks posteclosion) was delayed 6 weeks and normal length of a female's life (13–14 weeks) was increased 7–8 weeks on the 25 mg seeds/week ration. Rate of egg production exhibited a linear decrease with decrease in food ration on both reduced rations due to an increased interclutch interval, while fresh egg weight, duration of egg stage, number of eggs/clutch and percentage of clutches containing fertile eggs were little affected.Gross egg production efficiency (efficiency of conversion of ingested food into eggs = dry mg egg production × 100/dry mg food ingested) was high on both the 100 and 50 mg seeds/week rations (27.9% and 21.1%, respectively) and low (7.7%) on the 25 mg seeds/week ration. These data are discussed in the context of the reciprocal interaction between nutrient intake and egg production.     

Daily ration of juvenile Coregonus lavaretus (L.) fed on living zooplankton

Juvenile whitefish, Coregonus lavaretus (L.), wet weight 0.04 to 5.2 g, from Lake Constance were kept at 10, 12 and 16° C water temperature, respectively and fed with living zooplankton. The experimental duration lasted 72 to 120 h. Daily rations were defined as the amount of zooplankton remaining subtracted from the amount of zooplankton added after a 24 h interval. The mortality of the zooplankton was determined in parallel experiments without fish. Relative daily ration (zooplankton weight/fish weight) v. fish weight increased up to a fish dry weight of approximately 0.12 g and then decreased steadily. The maximum daily ration was about 270% of fish body wet weight (wet/wet) corresponding to 75% of body dry weight (dry/dry), respectively. In fishes of a dry weight higher than 0.12 g (wet weight 0.65 g) a significant difference in food intake was found between 12 and 16° C. The specific growth rate ranged from nearly 0 up to 33% per day. No correlation was found between daily ration and specific growth rate.     

The biochemical composition and calorie density of the walleye pollock <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> in the Sea of Okhotsk

In tissues of the walleye pollock Theragra chalcogramma the dry matter content averages 18.5%. The lipid content of the raw material is 0.7%, the protein content is 15.3%, carbohydrates are 0.6%, and ash is 1.3%. The average calorie density is 940 cal/g wet weight and 5080 cal/g dry weight. The dry matter content of gonads varies within 14.9–28.0% in females and 14.5–17.0% in males. The lipid content of the raw material is 0.9–3.0% in females and 1.3–1.8% in males; the protein content is 10.2–21.5% and 10.7–13.4%, respectively. The calorie density of female gonads is 702–1537 cal/g wet weight and 4426–5482 cal/g dry weight; for the male gonads it is 760–960 cal/g wet weight and 4952–5641 cal/g dry weight. The dry matter content of the liver varies within 42.2–62.2% for females and 34.4–62.4 for males. The lipid content of the raw material is 25.6–44.5% for females and 16.6–41.3% for males; the protein content is 6.3–9.8% and 8.1–12.3%, respectively. The calorie density of the liver in females varies within 2918–4601 cal/g wet weight and 6370–7395 cal/g dry weight; in males it is 2291–4357 cal/g wet weight and 6392–7492 cal/g dry weight. The minimum calorie density of the liver is observed in juvenile pollock: 963 cal/g wet weight and 2045 cal/g dry weight. The dry-matter content of feces in different size groups varies within 15.0–18.4%. Values of the average lipid content of raw material range from 1.1 to 1.6%; the protein content is from 1.8 to 3.8% and carbohydrates are from 0.9 to 1.4%. The calorie density of feces from variously-sized walleye pollock varies within a narrow range, from 308 to 362 cal/g wet weight. The energy equivalent ranges, depending on body size, from 259 to 2377 cal. The share of energy concentrated in the somatic (muscle) tissue of variously-sized walleye pollock during ontogenesis constitutes 56.5–93.9%; in female gonads it is 0.9–26.6%; in male gonads it is 0.4–7.3%, in the female liver it is 7.9–27.2%, and in the male liver it is 5.7–26.9%. The amount of energy (cal), concentrated in the female liver and gonads is on average 1.5 and 3 times as high as that in the male liver and gonads, respectively. The maximum total energy loss (15–30%) in mature walleye pollock of various-sizes occurs in the spawning period, during the transition from the maturity stage 5 to stage 6. The total amount of energy accumulated during the lifecycle from small juveniles (<17 cm) to very large individuals (>60 cm) averages 1964 kcal for females and 1465 kcal for males. The difference in the amount of energy is explained by the fact that oogenesis requires more energy than spermatogenesis.     

The relationship between fecundity and fertility in the mouthbrooding cichlid fish Tilapia leucosticta

The development of fry in the mouth of the female mouthbrooder Tilapia leucosticta Trewavas is described. The egg production by fish of various lengths is plotted and a curvilinear regression for standard and total length fitted. The number of eggs produced is approximately equal tothe square of the total length in centimetres of the parent fish. The brood numbers of 460 femalesare plotted against length, and linear regressions for mean brood number and mean fry number fitted. The relationship between the expressions for numbers of fry brooded and egg production gives anestimate of brooding efficiency that decreases with increasing parent length. Individual female fish show signs of reripening and the timing of this process is estimated from gonad state and from the length of fry brooded in the mouth. The relationship between fecundity (egg production) and fertility (fry brooded) is considered and the effect of maturation size, growth rate and spawning frequency assessed.     

Feeding behaviour of cod (Gadus morhua) in relation to spawning

The food consumption and egg production of 26 adult (13 female and 13 male) Atlantic cod ( Gadus morhua ) were monitored during prespawning, spawning and postspawning periods. Females spawned from late January to mid-April. Feeding activity occurred from December to early January and ceased for females, on average, 36 days (15–54 days) before the onset of spawning. The duration of spawning by females was, on average, 42 days (10–61 days) and feeding was suppressed by both sexes during the first three-quarters of each female's spawning period. Mature females went, on average, 70 days or 19% of the year without eating. An abrupt increase in feeding activity, particularly by females, occurred during the last quarter of spawning or shortly after the release of the last egg batch (on average, feeding started again after 91% of a female's eggs had been released or 82% of egg batches). Females consumed greater quantities of food than males during both winter and postspawning feeding periods. During spawning, females lost, on average, 29% of their body weight and males 14%. Fecundity ranged from 0.75 to 3.97 million eggs per female. The volume of eggs produced by four individual females (range = 1285–5995 ml in four to 11 batches) ranged from 99 to 195% (mean 150%) of a female's postspawning body volume. Six immature cod fed throughout the experimental period and gained, on average, 8% of initial body weight. Laboratory results were supported by stomach fullness index values of Georges Bank cod exhibiting different maturity states.     

Nuptial food gifts influence female egg production in the scorpionfly Panorpa cognata

Abstract.  1. Before copulation, male Panorpa cognata scorpionflies offer females a salivary secretion, which is consumed by the female during copulation. It has previously been demonstrated that this nuptial food gift functions as mating effort by increasing male attractiveness and by increasing ejaculate transfer during copulation.
2. In this study, the effect of saliva consumption on female reproductive output was investigated, and thus the possibility that nuptial food gifts also serve as paternal investment. The experimental design enabled the effect of nuptial gift consumption to be disentangled from other possible effects of multiple mating or increased copula duration.
3. The results showed that saliva consumption increases female egg production by on average 8% (4.5 eggs) per consumed salivary mass, whereas mean egg weight was not influenced.4. These results have important implications for the evolution and maintenance of both male nuptial gifts and female polyandry in this and other species.     

Morphometry and diet of Mormyrus rume in the Lekki lagoon,Nigeria

Aspects of the biology of Mormyrus rume (Cuvier and Valenciennes) in Lekki lagoon were investigated. This included the length-weight relationship, condition factor, food and feeding habits and the fecundity of the fish species. The major fishing methods employed for collecting the 225 specimens were castnetting and setnetting. The total lengths ranged from 15.0 to 24.9 cm while the standard lengths ranged from 13.0 to 23.0 cm. The body weights also ranged from 26.2 to 99.3 g. The fish exhibited isometric growth in the lagoon. The mean condition factor obtained was 1.20. The condition factor generally decreased with increase in individual sizes. The major food items were detritus and plant parts. The population of males was significantly higher than the females. The gonadosomatic index showed that M. rume in the Lekki Lagoon uses an average of 7.89% of its body weight in egg production. Fecundity ranged from 741 to 6000 eggs with an average of 2991 eggs per female.     

The relationship between fecundity and fertility in the mouthbrooding cichlid fish Tilapia leucosticta

The development of fry in the mouth of the female mouthbrooder Tilapia leucosticta Trewavas is described. The egg production by fish of various lengths is plotted and a curvilinear regression for standard and total length fitted. The number of eggs produced is approximately equal to the square of the total length in centimetres of the parent fish. The brood numbers of 460 females are plotted against length, and linear regressions for mean brood number and mean fry number fitted. The relationship between the expressions for numbers of fry brooded and egg production gives an estimate of brooding efficiency that decreases with increasing parent length. Individual female fish show signs of reripening and the timing of this process is estimated from gonad state and from the length of fry brooded in the mouth. The relationship between fecundity (egg production) and fertility (fry brooded) is considered and the effect of maturation size, growth rate and spawning frequency assessed.     

Fecundity, lifespan and egg mass in butterflies: effects of male-derived nutrients and female size

1. Effects of larval reserves and nutrients received as adults on fecundity and lifespan in female Danaus plexippus (the Monarch Butterfly) were measured to determine the relative importance of different sources of nutrients for reproduction and somatic maintenance.
2. Egg-laying lifespan was correlated with female size but not with the amount of male-derived nutrients or adult food concentration.
3. Lifetime fecundity was higher when females received a large first spermatophore, but was not affected by female size when lifespan was controlled or by adult food concentration.
4. At the end of their lives, females contained unlaid eggs and retained, on average, 88% of their initial mass. This proportion was unchanged in two years, although mean egg-laying lifespan varied from 22·5 to 28·7 days.
5. Egg mass decreased over the female lifespan, and was correlated with female size.
6. These results suggest that larval reserves are more important for somatic maintenance than adult income, but that the protein-rich nutrients received from males contribute to egg production. This supports theoretical predictions and empirical studies of other Lepidoptera showing that larval reserves are less likely to affect fecundity when the adult income can contribute substantially to egg production.     

Comparison of feeding efficiency, development time and survival of Tasmanian eucalyptus leaf beetle larvae Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae) on two hosts

The native Eucalyptus leaf beetle Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae) has become a pest of the introduced, plantation species, Eucalyptus nitens Maiden in Tasmania, Australia. However, in the field it prefers to oviposit on the Tasmanian native species, E. regnans F. Muell. This laboratory study found that the performance of C. bimaculata larvae was superior on foliage of E. nitens compared with E. regnans . Larval development was 4 days shorter on E. nitens than on E. regnans foliage. Total food consumption per larva and relative consumption rates were about 30% lower while relative growth rates and weight of emergent adults were more than 25% higher on E. nitens than E. regnans . Efficiency of conversion (ECI) of fresh food into larval wet weight was 0.26 on E. nitens compared with 0.14 on E. regnans . Mortality of larvae feeding on E. nitens (23%) was only one third of that on E. regnans (69%), a result of high first instar mortality on E. regnans . Although the amount of foliage consumed per larva was lower on E. nitens (0.23 g vs 0.32 g), the differential mortality meant that the amount of E. nitens consumed per egg batch was 60% more than that of E. regnans . If these results occurred in the field, then the same monitored population of C. bimaculata eggs may result in heavier defoliation of plantation E. nitens than of E. regnans . These data show that the reported oviposition preference of C. bimaculata for E. regnans in the field cannot be explained by selection of host factors related to superior larval performance.     

Food utilization and metabolic efficiency in larval and adult house crickets

The most rapid growth of the fat body, ovaries and residual body occurred only at the time of maximal feeding, which was the time of highest metabolic rate. Larvae ceased feeding before the next moult and lost weight. Adult females did not cease feeding and never lost weight. Mated females maintained a high feeding rate that corresponded to a constant oviposition rate with no gonotrophic cycles. Virgin females maintained a lower feeding rate and maintained fully mature eggs in a viable state for life.Growth during the last larval stadium was entirely somatic and characterized by a great accumulation of a lipid rich (65%) fat body. Net growth during the first 10 days of adult life was entirely gonodal, because the small amount of residual body growth was matched by the amount of fat body loss. However, since the residual body was 60% protein and the fat body was 60% lipid, some of the somatic protein growth had to come from the diet and some of the fat body lipid went for ovarial growth.The 20% dietary protein was more than sufficient for all somatic and ovarial growth, and some protein was catabolized for energy. The amount of uric acid in larval faeces accounted for almost all protein catabolism, but in adult females half of the catabolized protein nitrogen did not appear in the faeces. With only 5% dietary lipid both larvae and adults had to synthesize additional lipids from carbohydrates to supplement absorbed lipids for growth demands. Almost all absorbed and synthesized lipids were used for somatic growth in the larvae and for ovarial growth in the adults, because the per cent of food calories used for growth greatly exceeded the per cent dry weight of food used for growth. Based on the calories and dry weight of available fuel, almost all energy production was based on carbohydrate oxidation. Some carbohydrate was used for lipid synthesis but very little was used for growth.Probably the absorption efficiency (72%) and growth efficiency (28%) was the same for both the last instar larvae and virgin females because they ate exactly the same food. However, the larval metabolic efficiency (42%) was higher than that of females (37%), which indicated that more of the absorbed food was converted to tissue during larval growth (somatic) than during adult growth (ovarial).Of the dry weight of food eaten during the last larval stadium, 30% was egested, 32% was oxidized, 28% appeared as growth, and 10% was condensed to lipid and became part of the 28% growth. Of the dry weight of food eaten during the first 10 days of adult life, 27% was egested, 41% was oxidized, 25% appeared as growth, and 6% was condensed to lipid.     

Growth and Energy Demand of Meloidogyne incognita on Susceptible and Resistant Vitis vinifera Cultivars

Food (energy) consumption rates ofMeloidogyne incognita were calculated on Vitis vinifera cv. French Colombard (highly susceptible) and cv. Thompson Seedless (moderately resistant). One-month-old grape seedlings in styrofoam cups were inoculated with 2,000 or 8,000 M. incognita second-stage juveniles (J2) and maintained at 17.5 degree days (DD - base 10 C)/day until maximum adult female growth and (or) the end of oviposition. At 70 DD intervals, nematode fresh biomass was calculated on the basis of volumes of 15-20 nematodes per plant obtained with a digitizer and computer algorithm. Egg production was measured at 50-80 DD intervals by weighing 7-10 egg masses and counting the number of eggs. Nematode growth and food (energy) consumption rates were calculated up to 1,000 DD based on biomass increase, respiratory requirements, and an assumption of 60 % assimilation efficiency. The growth rate of a single root-knot nematode, excluding egg production, was similar in both cultivars and had a logistic form. The maximum fresh weight of a mature female nematode was ca. 29-32 μg. The total biomass increase, including egg production, also had a logistic form. Maximum biomass (mature adult female and egg mass) was 211 μg on French Colombard and 127 μg on Thompson Seedless. The calculated total cost to the host for the development of a single J2 from root penetration to the end of oviposition for body growth and total biomass was 0.535 and 0.486 calories with a total energy demand of 1.176 and 0.834 calories in French Colombard and Thompson Seedless, respectively.