Laid Egg Masses Research Articles

The breeding biology of the black‐crowned night‐heron (Nycticorax nycticorax) and the little egret (Egretta garzetta) at the Huleh Nature Reserve, Israel

The breeding biologies of the black‐crowned night‐heron (Nycticorax nycticorax) and the little egret (Egretta garzetta) were studied in the mixed heron breeding colony at the Huleh Nature Reserve, Israel, from 1977 to 1980. Both studied species have resident (30%) and migrating populations. The colony consisted of about 3,000 pairs of seven breeding species nesting in 5‐7 highly synchronous mixed species sub‐colonies from mid‐March to mid‐September. Mean time‐lapse between initiation of two sub‐colonies is 20.45 days. Mean duration of egg‐laying within a sub‐colony is 12.45 days and of hatching is 12.38 days. Nests are built each year mainly with papyrus stems and there are significant differences among little egrets, night‐herons and cattle egrets in their tendency to use different nesting material. Mean clutch size was 3.41 for little egrets and 2.97 for night‐herons, while the most frequent clutch size was three in both species (54.9% and 68.5%, respectively). Mean fresh laid egg masses were 27.15 g and 31.33g for little egrets and night‐herons, respectively. The variability in egg mass within a clutch was significantly smaller (on average 12 times and 7 times for little egrets and nightherons, respectively) than between clutches. Incubation of each egg lasts 21.6 days in little egrets and 21.1 days in night‐herons. Mean egg mass loss during incubation was 14.6% and 13.8% for little egrets and night‐herons, respectively. Hatching success is 90.2% (n= 177) in little egrets and 92.4% (n= 258) in night‐herons, and hatching order is related to laying order in both species. Hatchling's mass at hatch ranged from 13‐26 g (n= 34), 74.8% of initial egg mass for little egrets and 19‐29 g (n= 30), 73.8% of initial egg mass for night‐herons. Chick development rates were studied in nature and in captivity. In both species there is a linear correlation between a chick's age and its body dimensions. Chicks reach adult dimensions at about one month and fledge at the age of 35‐42 days. Fledged chicks disperse during the first year up to 50‐60km from the colony. Survival rates for chicks up to the age of 28 days are 69.9% and 56.6% for little egrets and night‐herons, respectively. The main mortality factor for eggs and chicks is probably predation by avian predators. Data on minimum longevity, 10‐11 years for little egrets and 7‐8 years for night‐herons, were obtained from resightings of tag‐marked individuals. Long‐term monitoring and study of the structure and breeding parameters of a regionally important colony in relation to known environmental effects are an essential tool for conservation and management plans for colonial species.

Partial Characterization and Biological Activity of a Metamorphic Inducer of the Dorid Nudibranch Adalaria proxima (Gastropoda: Nudibranchia)

Partial Characterization and Biological Activity of a Metamorphic Inducer of the Dorid Nudibranch Adalaria proxima (Gastropoda: Nudibranchia)

Predation of Chilo suppressalis (Walker) eggs by the black cricket Metioche vittaticollis (Stal)

Metioche vittaticollis (Stal) is an important predator of rice insect pests, including several defoliators and stem borers. Little information is available about its role in suppressing pest populations. We studied the predation of M. vittaticollis using striped stem borer (SSB) eggs as prey in insect cages. Freshly laid egg masses of SSB were glued to leaves of 35-d-old TN1 rice plants at densities of 80, 160, 240, 320, and 400 plant -1 . These plants were enclosed individually in 11-cm-diam and 55-cm-high cylindrical mylar cages. One M. vittaticollis, starved for 12 h, was released for each test plant. Fourth-instar larvae and adult male and female crickets were caged individually with the eggs, and the experiment was replicated 10 times. After 24 h of exposure, the number of eggs consumed at each stage was recorded. Consumption rate per day at each stage of M. vittaticollis was determined.

UTILIZATION AND DEGREE OF DEPLETION OF EXOGENOUS SPERM IN THREE HERMAPHRODITIC SEA HARES OF THE GENUS APLYSIA (GASTROPODA: OPISTHOBRANCHIA)

Two series of experiments were conducted to examine the utilization of exogenous sperm and their degree of depletion in three hermaphroditic sea hares, Aplysia kurodai Baba, 1937, A. Juliana Quoy & Gaunard, 1832, and A. parvula Guilding in MOrch, 1863. The first series of experiments was designed to determine whether one mating is enough for female partners to receive sufficient sperm to fertilize at least one egg mass. For this purpose, isolated individuals were mated as females once with conspecific individuals and the viability of their subsequent eggs was examined. When successfully inseminated, individuals of all the three species received enough sperm to fertilize at least one egg mass, and they continued to lay 3.6–8.5 viable egg masses. However, 10–36% of the matings by these sea hares did not result in any viable egg production by the female partner, indicating that these matings did not involve sperm transfer Such matings without sperm transfer tended to be shorter than matings with successful sperm transfer The second experimental series was conducted to examine whether sperm depletion actually occurs or not in field-caught adults. For this purpose, adult individuals caught in the field were allowed to lay eggs under isolated conditions without mating All the individuals of A. kurodai and A. juliana stored enough sperm to fertilize at least one egg mass. However, in A. parvula, 23–33% of individuals laid egg masses containing non-viable eggs at their first spawning after isolation, indicating that these individuals were depleted in exogenous sperm

Ineffective Maternal Care of a Subsocial Bug against a Nymphal Parasitoid: a Possible Consequence of Specialization to Predators

AbstractIn the subsocial bug Elasmucha putoni, females lay egg masses on leaves of fruit‐bearing wild mulberry trees. Parent females invariably remained straddling their offspring until the offspring moulted to the second instar on natal leaves. Thereafter, the females usually settled on the stem of shoots which harboured second‐or‐later‐instar nymphs feeding on fruit or aggregating on leaves, and faced toward the base of the shoot. To evaluate the effectiveness of maternal attendance on parasitism of nymphs by a braconid wasp, I divided the boughs of each mulberry tree into two experimental groups: a single bough which was isolated from the others by Tanglefoot treatments and on which guarding females were removed from broods before the second instar, and other boughs on which broods were left intact as controls. The experiments showed that nymphal parasitism was not affected by the presence of females. The position and orientation of females attending second‐or‐later‐instar nymphs is probably effective for detecting predators approaching the nymphs by walking along the stem; however, this posture may prevent the females from detecting parasitoids, which fly and land directly on plant parts close to the nymphs. The ineffectiveness of the females in providing defence against the parasitoid is possibly associated with a specialization of the attending posture to pedestrian predators: a parental defensive behaviour specific to these predators may make the offspring more vulnerable to the parasitoid.

Predation and parasitism on eggs of two pod‐sucking bugs,Nezara viridulaandPiezodorus hybneriin soybean

Abstract Cohorts of newly laid egg masses of two pod‐sucking bugs, Nezara viridula and Piezodorus hybneri (Hemiptera: Pentatomidae), were exposed to naturally occurring predators and parasitoids on soybean in unsprayed fields at four sites in Northern Sumatra. The fate of the young stages was recorded until the late first instar, before the nymphs start to disperse and feed. Partial life tables showed that mortality of N. viridula until the late first instar was 50–87%, of which 18–65% occurred during the egg stage and was mainly caused by predation; 2–26% of the eggs died of parasitism. P. hybneri which was present at only two sites, showed a 73–89% mortality until the late first instar, of which 69–85% was during the egg stage and, again, mainly caused by predation; 15–24% of the eggs died of parasitism. To evaluate the role of individual egg predator species in the field, we conducted hourly observations of exposed egg masses of the two pests. Dolichoderus sp., Solenopsis geminata (Hymenoptera: Formici...

Oviposition, Fecundity, and Body Size of a Pestiferous Midge, Chironomus crassicaudatus (Diptera: Chironomidae)

Field-caught gravid female Chironomus crassicaudatus Malloch in central Florida laid egg masses mostly in the morning at onset of photophase in the laboratory. Fifty-seven percent of these females laid a second egg mass in their adult life. Number of eggs averaged 1,338 and 245 per mass in the first and second mass, respectively. Average egg incubation period was 2 d, with initiation and cessation of egg hatch occurring at 1.5 and 5 d after oviposition, respectively. Relationship of body size and fecundity of female C. crassicaudatus was studied by measuring wing length and examining number of eggs per mass and parity. Body size of nulliparous and of parous females had a significant linear relationship with dry body weight. Larger females had a significantly higher number of eggs per mass and percentage parity than small females.

Recognition and avoidance of previously laid egg masses by the oblique-banded leafroller (Lepidoptera: Tortricidae)

Investigations were conducted on oviposition by laboratory-reared oblique-banded leafrollers, Choristoneura rosaceana Harris. In paperbag oviposition chambers, females deposited their egg masses in a significantly nonrandom, uniform manner in 16 of 20 replicates. Inpetri dish oviposition chambers, gravid females were exposed to egg masses recently deposited by other females. As determined by the magnitude of the mean direction vector of the second egg mass in relation to the first, females detected and avoided egg masses laid by other females. In addition, they avoided waxed paper from which a recently oviposited egg mass had been removed. This phenomenon is most likely due to a pheromone laid down with each egg mass.

Effects of Female Size, Mate Size, and Number of Copulations on Fecundity, Fertility, and Longevity of Nezara viridula (Hemiptera: Pentatomidae)

For once-mated female Nezara viridula L., size (width across the pronotum at the humeral angles) was positively correlated with fecundity (total lifetime egg production), size of the largest egg mass (number of eggs), and longevity (days as adult). Mate size was positively correlated with fecundity since females mating larger males lived longer and laid egg masses at a higher rate. Females mating larger males were less likely to lay infertile egg masses (all eggs unfertilized). Mate effects suggest size-dependent sperm and nutrient transfer to the female during copulation or reduced risk of contagion for females mating larger males. For multiply mated females, fecundity was positively correlated with both longevity and the number of matings. Thus, in the wild, females may be selected to mate with larger males and to mate repeatedly, patterns observed in previous field studies.

Host age and host selection byTrichogramma nubilale

Selection byTrichogramma nubilale (Ertle & Davis) for different aged egg masses ofOstrinia nubilalis (Hubner) was examined by separating components of parasitism. FemaleT. nubilale were exposed to egg masses of 2 different ages (freshly laid egg masses versus 1, 2, 3 or 4 day old egg masses), and the age of the initial egg mass inspected, number and percent of eggs and egg masses parasitized, and the emergence rate of pharate parasitoids was recorded. When there was a large difference in age between young and old egg masses, ♀♀ inspected initially more young egg masses (>2 days difference), parasitized a greater percent of young egg masses (>2 days difference), and parasitized more eggs/parasitized egg mass in young egg masses (>3 days difference) than old egg masses. Females did not discriminate between host age when hosts were similar in age. Successful emergence of parasitoids was greater from younger eggs than older eggs, although emergence was better from one-day-old eggs than from fresh eggs. These results imply that when the hosts were sufficiently different in age, ♀♀ were attracted to younger egg masses more than older egg masses, and they tended to remain ovipositing for longer periods of time on younger egg masses than older egg masses. Moreover, ♀♀ appeared to prefer to oviposit in hosts in which their young are more likely to complete development.

Oviposition site selection by Mansonia mosquitoes on water lettuce

Abstract. 1. Viable Mansonia egg masses occur in nature on both the upper and under surfaces of Pistia stratiotes (L.) leaves. Upper‐surface masses were from Mansonia dyari Belkin, Heinemann & Page, but lower‐surface oviposition was attributable to both M. dyari and M. titillans Walker.2. Upper‐surface egg masses were often out of water but were concentrated near a wet‐dry stain line on the leaf. Lower‐surface masses were laid underwater within 3 mm of the leaf edge, except for those oviposited through fenestrations caused by insect damage.3. Oviposition varied seasonally and masses were most numerous between August and December when water lettuce plants were large and crowded. Egg masses were clumped on plants and leaves and concentrated on mature or mature‐old leaves that subtended mean angles of 28–34° from the horizontal.4. On intact plants in cages, M. dyari laid egg masses on both leaf surfaces in approximately the same proportions as observed in nature. On detached leaves floating flat on the water, M. dyari laid all masses on under surfaces.5. At 20 and 25°C, egg development of M. dyari required 17.4 and 8.8 days (means), these being significantly longer than the mean times for M. titillans. Some larvae from eggs that hatched in the absence of water survived 72 h in the eggshell.6. Upper‐surface oviposition by M. dyari may be an adaptation to the crowded growth of water lettuce, the mosquito's favoured host plant, whose leaves are largely out of water. Leaf ageing and subsidence cause submergence of most upper‐surface eggs by the time of hatching.

Control of Elm Leaf Beetle Larvae and Eggs with Spray Oils, 1988

Abstract Evaluations were made of Scalecide foliar spray oil for control of elm leaf beetle eggs and larvae. Larval evaluations were made by counting larvae on 5 branch terminals/treatment on 24 Jun. Foliar applications were made immediately following the count by spraying until run-off. Very hot, dry conditions existed at the time of treatment. At 4 DAT, the marked terminals were counted again. Mortality was corrected by using Abbott’s formula. Evaluations of spray oils against egg stages were done in a similar manner. Twelve recently laid egg masses for each treatment were marked and sprays were applied 28 Jul. After all eggs had hatched, egg masses were removed and examined in the laboratory.

Studies on survival, biological activities and behavior of Biomphalaria glabrata, the host snail of schistosomiasis, submitted to increased hydrostatic pressure: a technique.

To study changes in survival, in biological activities and behavior of planorbids submitted to increased hydrostatic pressure, we developed a technique using two transparent chambers and a hydraulic piston. The apparatus permitted renewal of the liquid medium without substantial variations in pressure, thus eliminating excretion products and maintaining the desired O2 level and thereby permitting us to evaluate the effects of pressure independently of the occurrence of anoxia. Pressure was maintained without any contact of the liquid medium with compressed air, a situation which reproduced with relative fidelity what occurs in nature and assured the presence of the same amounts of gases in the two observation chambers (Control and Experimental). Biomphalaria glabrata was found to be able to survive at least 48 hours when submitted to 49.02 x 10(4) Pa (equivalent to a water depth of 48.8 m), continuing to lay egg masses and showing few behavioral changes when compared with the control group.

Alkylphosphonates as unique compounds in the metabolism of the schistosomal vector Biomphalaria glabrata.

Examination of intact freshly laid egg masses of the schistosomal snail vector Biomphalaria glabrata by both 31P nuclear magnetic resonance spectroscopy and colorimetric phosphorus analysis indicated that 98% of the phosphorus in the egg masses was present in the form of alkylphosphonic acids. At least 87% of the total phosphorus originally present was comprised of 2-aminoethylphosphonic acid. During 11 days of embryonic development, alkylphosphonate-phosphorus decreased from 98% to 50% of the total phosphorus, indicating a possible role for phosphonate-phosphorus in the embryonic nutrition of these snails. Considering the relative uniqueness of the alkylphosphonates in nature, the very high concentration of these compounds in freshly laid eggs, and the reduction in their amount during embryonic development, the anabolic and catabolic pathways of alkylphosphonates may serve as sites for highly specific analogues in the control of these schistosomal vectors.

The life histories of Limnephilus externus Hagen, Anabolia bimaculata (Walker), and Nemotaulius hostilis (Hagen) (Trichoptera, Limnephilidae) in a pond in southern Alberta, Canada

Limnephilus externus and Anabolia bimaculata are caddisflies that typically inhabit temporary pools, while Nemotaulius hostilis is a species that inhabits permanent pools. In a permanent pond with a fluctuating water level, both groups could be accommodated. The temporary-pool species laid egg masses on the ground above the water level in late summer. Larvae hatched in the autumn but remained in the masses until submersed by the rising water in the spring. Larvae grew at rates faster than those for any permanent-water trichopteran studied to date. Limnephilus externus adults emerged through August and underwent a 1-month reproductive delay. Anabolia bimaculata adults emerged through July, but showed no signs of a reproductive delay. By contrast, N. hostilis oviposited on riparian vegetation and larvae entered the water on hatching in August. Larval growth rates approximated those of other detritivorous shredders found in permanent waters. Over 75% of adult emergence occurred in 1 week at the end of May and adults underwent a reproductive diapause of slightly over a month's duration. The metabolic cost of high water temperatures on cool-adapted limnephilid caddisflies is postulated as the driving force behind the evolution of reproductive diapause in this family.

Cytophysiological study of neurosecretory and pheromonal influences on sexual development inOphryotrocha puerilis(Polychaeta, Dorvilleidae)

Summary Prominent secretory nerve endings are found at the posterior margin of the supraesophageal ganglion in the protandric polychaete, Ophryotrocha puerilis. Solitary juveniles developing as primary males, and then as females, accumulate neurosecretory material in the nerve endings which thereby swell and become filled with granules. Females maintained in mass culture have similar terminals, whereas in secondary males (males which had been females before), these axon terminals are very small and contain no material. When such males are isolated, they accumulate neurosecretory material within the nerve endings and become females. When formerly isolated females are put together, their stores of neurosecretory material are rapidly discharged. Subsequently they lay egg masses and switch to the male state. These effects are mediated by a pheromone released during social contact of formerly isolated females. The complexity of the relationship between neurosecretory activity and sexual state is indicated by t...

Larval Allatectomy and Reduced Oviposition of the Gypsy Moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae)1

The effects of larval and pupal allatectomies on egg production by the female gypsy moth, Lymantria dispar (L.), are compared. Correlation analysis showed that the weight of an egg mass reflects the egg number in it. On the average, allatectomies performed on female 6th instars caused an 89% reduction in wet weight of egg masses subsequently laid. Similar surgeries performed on prepupae and early pupae caused insignificant reduction in the weight of egg masses. Allatal reimplantation into a 6th instar restored the ability to lay egg masses of normal weight. Since larval allatectomy did not greatly change ovarian wet and dry weights, results suggest that the loss of the corpora allata affects ovulation and oviposition rather than ovarian development.

Structure and biodegradation of the polysaccharide components of egg masses isolated from snails of an Ampullarius species

A polysaccharide preparation, isolated from egg masses deposited by snails of an Ampullarius species, was purified via precipitation with Cetavlon in the presence of sodium borate, and found to contain d-galactose and a smaller proportion of d-glucose, and to have two components with sedimentation coefficients of 10 S and 40 S. A polysaccharide, isolated from freshly laid egg masses, was highly branched and was shown to contain nonreducing α- d-glucopyranosyl and β- d-galactopyranosyl end-groups, and 3,6-di- O-substituted β- d-galactopyranosyl residues. One or more of the polysaccharide components was a d-glucopyrano- d-galactopyranan with non-reducing α- d-glucopyranosyl end-groups (1→4)-linked to β- d-galactopyranosyl residues. The polysaccharide preparations, obtained from freshly laid egg masses and from those that were left for 10 and 15 days after being laid, were structurally different from each other. With the passage of time, progressive diminution of the 10 S component and the proportion of d-glucose in the polysaccharide took place, suggesting that each constituent was consumed preferentially by the snail embryos as an energy source.

2-Aminoethylphosphonic Acid Metabolism During Embryonic Development of the Planorbid Snail Helisoma

In freshly laid egg masses of Helisoma sp., more than 95 percent of the phosphorus is found in alkylphosphonic acids, as determined by phosphorus-31 nuclear magnetic resonance spectroscopy. These compounds are metabolized during embryonic development, as shown by differential acid hydrolysis and experiments with phosphorus-33-labeled phosphoric acid. Further, nuclear magnetic resonance spectroscopy indicates phosphonic acid involvement in related snail families, including the schistosomal vector Biomphalaria glabrata.

Olfactory responses of the adult screw-worm after removal of the antennae, mouthparts, tarsi, and legs.

The removal of certain appendages or segments from adult Cochliomyia hominivorax (Coquerel) and subsequent tests of oviposition, response to baited and unbaited traps, and response to screw-worm-infested wounds of sheep showed that the more important olfactory receptors are situated on the antennae and mouthparts. Removal of only 1 appendage did not reduce egg production drastically, but when both the antennae and mouthparts were removed only 21% of the flies laid egg masses (compared with 93% for the controls). Little oviposition occurred when the “antennaless” (lies were separated from the egging medium; also these flies did not discriminate between baited and unbaked traps, nor were they able to locate screw-worm-infested wounds on sheep. Flies having only 1 antenna removed were able to locate baited traps and infested wounds, but not nearly so well as normal flies. Flies with excised mouthparts responded like normal flies to baited and unbaked traps. The precise location of the receptors was not determined, but the results indicate the necessity of using intact specimens for attractant or behavioral studies.