Showing papers on "Larva published in 1984"

Anuran size at metamorphosis: experimental test of a model based on intraspecific competition

Abstract: Size at metamorphosis and length of larval period are often, but not invariably, cor- related within cohorts of larval anurans. Collins (1979) proposed intraspecific competition as one causative agent for such a correlation in nature, and this hypothesis was supported by observational data. This study reports the results of an experimental test of that hypothesis. Isolated larvae were reared at one of two food levels (high or low) and, during the period in which metamorphosis occurred, were maintained at either constant per capita food levels, or at increasing per capita levels designed to mimic effects of continual release from scramble-type, exploitative competition. Low food levels decreased average larval growth and average size at metamorphosis and increased average length of larval period. A reduced level of food had no effect on the relative variation in length of larval period. Only "competitive release" affected the relative variation in size at metamorphosis. All four treatments displayed a positive correlation between size at metamorphosis and length of larval period, but only in the combination of low food levels and competitive release was the correlation more than barely significant. Size at metamorphosis displayed a positive allometric relationship to length of larval period in the low food-release treatment, and a negative allometric relationship in the other three treatments. These results support Collins' (1979) model for intraspecific competition as one causative mech- anism for such relationships. Certain aspects of these results support each of two distinct models for the timing of amphibian metamorphosis, but the data as a whole do not fit well with either model.

Pheromonal Control of Metamorphosis in the Pacific Sand Dollar, Dendraster excentricus.

Abstract: Competent larvae are induced to undergo metamorphosis by sand from a sand dollar bed or an aqueous extract of the sand. Gel permeation chromatography and high-performance liquid chromatography of the extract yielded a 980-dalton peptide that will induce metamorphosis between 10(-6) and 10(-5) molar. Extracts of whole adults and gonads were also able to induce metamorphosis, and adults can condition substrates to induce metamorphosis. Therefore, the initiation of metamorphosis in Dendraster excentricus is controlled by a pheromone released by adult sand dollars.

Relationship between growth, differentiation, and length of larval life for individually reared larvae of the marine gastropod, crepidula fornicata

Abstract: Larvae of the gastropod Crepidula fornicata were reared individually through spontaneous metamorphosis in clean glass containers at constant temperatures ranging from 15°C to 29°C; each larva was examined daily. Growth rates were determined from periodic measurements of individual shell length. Differentiation rates were estimated as (days to development of gill rudiments)-1 and as (days until shift from larval to adult shell geometry)-1. Growth ceased abruptly in a majority of the larvae in each treatment, over the size range 900-1100 µm shell length. Larvae continued to ingest phytoplankton during this period, and growth resumed at a normal rate following spontaneous metamorphosis. An inverse correlation was observed between rates of larval growth and length of larval life through spontaneous metamorphosis; faster-growing larvae generally had shorter larval lives than did slower growing larvae. Individual growth rate (µm/day) prior to competence was significantly correlated with rate of individual diffe...

Effect of deer reduction on abundance of the deer tick (Ixodes dammini).

Abstract: To evaluate the role of deer in regulating the abundance of the deer tick (Ixodes dammini) we attempted to treat with acaricide, but eventually removed, about 70 percent of deer from Great Island, Cape Cod, Massachusetts. Deer were captured in box traps, a corral, an entanglement net, and with rifle-fired tranquilizer. Failure of these attempts, combined with ineffective acaricides, led us to deer destruction begun in fall 1982. Larval tick abundance on mice was monitored before and after deer removal. We concluded that deer removal, to the extent accomplished, did not markedly reduce the abundance of the tick. Reduced abundance of deer may not result in reduced abundance of immature ticks if deer removal follows the period of adult tick feeding, or if intensity of infestation per deer increases, or if other mammals substitute as suitable hosts. Reduced tick abundance may be delayed if unattached immature ticks survive more than one year.

Inter- and intraspecific larval competition in Aphidius smithi and Praon pequodorum (Hymenoptera:Aphidiidae).

Abstract: Superparasitism and multiple parasitism of the pea aphid, Acyrthosiphon pisum (Harris), by the solitary hymenopterous parasites Aphidius smithi Sharma & Subba Rao and Praon pequodorum Viereck were studied in the laboratory. In intraspecific competition, an older larva usually eliminated a younger one; exceptions to this rule depended on the relative age difference and developmental stage of the competitors. In interspecific competition, P. pequodorum was intrinsically superior to A. smithi, regardless of the latter's age. The stage of host parasitized and the number of competing larvae had no significant effect on the outcome of the contest. A. smithi females discriminated against aphids previously parasitized by a conspecific female or by P. pequodorum, the degree of oviposition restraint increasing with the time between ovipositions. P. pequodorum females attacked aphids already parasitized by A. smithi, regardless of the age of the Aphidius larva, but avoided oviposition when the aphid contained a Praon larva or embryo. The rate of embryonic development is shown as a major factor in contest-type competition between first-stage larvae.

Aerial Versus Aquatic Oxygen Consumption in Larvae of the Clawed Frog, Xenopus Laevis

Abstract: Tadpoles of Xenopus laevis Daudin can extract oxygen from both air and water. When these larvae have access to air, aerial oxygen uptake averages 16.6% of total oxygen consumption in normoxic water, and increases to 100% of net oxygen consumption in hypoxic water. Neither anaerobiosis nor increased buccopharyngeal ventilation occur in response to hypoxia. If tadpoles are prevented from surfacing to breathe air, they can maintain normal oxygen consumption through aquatic respiration alone in normoxic water, but not in hypoxic water. Unlike air-breathing larvae, exclusively water-breathing larvae respond to aquatic hypoxia by increasing their buccal pumping rate and by accumulating lactate. Even though Xenopus larvae can survive without air for many days, aerial respiration is necessary for other functions: tolerance of hypoxia, normal feeding, locomotion and buoyancy regulation.

Cuticle: Formation, Moulting and Control

Abstract: The relative rigidity of the arthropod exoskeleton makes it impossible for body size to increase continuously during the postembryonic development of these animals. Once they have hatched from the egg, they grow in steps, passing through a variable number of (larval) stages (Fig. 1 a). Apart from a few exceptions, there are between 3 and 10 such stages in the arachnids, 3–20 in the crustaceans, and 3–10 in the insects. In many cases a metamorphosis stage intervenes (some crustaceans; holometabolous insects) (Fig. 9b, c).

Development and growth in larval and juvenile Hyas coarctatus (Decapoda, Majidae) reared in the laboratory

Abstract: Duration of development in the larval and early juvenile stages H. coarctatus was studied in relation to temperature, and compared at extreme (18 and 6 °C) than at intermediate (9 to 15 °C) temperatures. The results were used to estimate the duration of development from hatching to the third crab stage in the field. Settling and metamorphosis was predicted to occur mainly during June. Biomass increased exponentially during larval development. Juvenile growth was also exponential and was maximum at 9 degree C, and minimum at 18 and 6 °C.

Temperature Threshold and Degree-Day Accumulation Required for Development of Postdiapause Sugarbeet Root Maggots (Diptera: Otitidae)

Abstract: Developmental, emergence, and survival rates of the postdiapause larva of the sugarbeet root maggot, Tetanops myopaeformis (Roder), were determined at various constant temperatures. The lower temperature threshold for development was determined by the x-intercept method (9.6°C)and the least variability method (7.6°C). An overall threshold temperature for third-instar larva-to-adult development was estimated to be 8.6°C. Present and past emergence records were compared to degree-day accumulations using this threshold and maximum and minimum air temperatures. Prediction of adult emergence in the spring was greatly improved over use of the Julian date. A difference of up to 3 weeks for 50% emergence between years on a Julian date scale was reduced to just 30 degree-days on a degree-day scale using the determined base temperature. Time of 50% emergence occurred at ca. 200 degree-days.

Egg, larva, and pupa of Lexiphanes saponatus (Coleoptera: Chrysomelidae: Cryptocephalinae)

Abstract: The immature stages of Lexiphanes saponatus (Fabricius) are the first members of Nearctic Cryptocephalinae to be described as well as to be studied. The egg is coated with oblique ornamentations as in other Cryptocephalinae. The larva shows several resemblances with that of the Palearctic genus Suffrianus from which it is distinguished mainly by its large papillate frontal setae. The pupa resembles in general those of Chlamisinae but bears very distinctive projections on the seventh and ninth abdominal segments. The life cycle of L. saponatus is also very interesting. Unlike most other cryptocephaline larvae which live in the leaf litter and are unable to climb on plants, the larva of L. saponatus moves easily on its host plant (Cassandra calyculata) and mimics perfectly the plant buds, becoming almost invisible to the human eye. Although me information is incomplete, it is evident that L. saponatus overwinters in the larval stage, in the first or second instar. It is not known if the larva completes its development during the following warm season or overwinters twice as in other Cryptocephalinae.

Metamorphosis of a protein

Abstract: All insects appear to have a transport lipoprotein in the hemolymph (blood) that is responsible for moving hydrophobic materials through aqueous compartments. This has been called lipophorin because it is believed to be a reversible transport shuttle. Since most insects undergo some degree of metamorphosis from larval stages to the adult, the need to transport hydrophobic materials or the nature of these materials may change in the course of the life span. This is especially marked in the case of the holometabolous insects – those which undergo drastic change of form, e.g. caterpillar-pupa-adult moth. We have found that lipophorin undergoes a molecular metamorphosis paralleling that of the insect.

The biology of Hyperaspis jucunda (Col.: Coccinellidae) an exotic predator of the cassava mealybug Phenacoccus manihoti (Hom. Pseudococcidae) in southern Nigeria.

Abstract: The biology ofHyperaspis jucunda (Muls.) was studied at 27°C and the incubation period averaged 5.1 days. The 1st, 2nd, 3rd and 4th larval instar averaged 2.5; 2.8; 3.4 and 5.0 days respectively. Larval development was completed in about 13.8 days while it took 7.1 days for the pupae. The total developmental time averaged 26.4 days. Mean longevity was 100 and 101 days for males and females respectively. The premating period was 19–24 h while the preoviposition period averaged 6.3 days. The generation cycle (egg to egg) averaged 32.8 days. The oviposition period was about 93 days during which an average female laid 456 eggs.

Biology and temperature responses of Chelonus Kellieae and Chelonus phthorimaeae (Hymenoptera: Braconidae) and their host, the potato tuberworm, Phthorimaea operculella (Lepidoptera: Gelechiidae)

Abstract: Comparative studies were conducted on the biologies and population growth potentials of Chelonus phthorimaeae Gahan, an indigenous North American parasite, and C. kellieae Marsh, an imported parasite from Costa Rica. Both species are primary, solitary, egg-larval endoparasites of the potato tuberworm, Phthorimaea operculella (Zeller). Eggs of both species are hymenopteriform. In the laboratory, superparasitization was noted within the host egg; however, a single parasite larva develops within the haemocoel of the host larva. The parasite larva emerges before host pupation and constructs a silken-white cocoon within that of the host. There are three larval instars, the first being caudate-mandibulate, later becoming vesiculate-mandibulate. The second and third are mandibulate, with the third possessing spines and setae. The pupae are exarate. Developmental time from egg to adult female emergence is 22 days and 26 days for C. phthorimaeae and C. kellieae, respectively, at 26.7±1°C, 50% RH. Morphology of the immature stages and host relationships are presented. Parasitization of P. operculella by each species resulted in reduction of the size of the fourth instar host larvae. Optimum number and age of host eggs for maximum production of parasite progeny was 150 host eggs, 0-24 hours old, for C. phthorimaeae, and 50 host eggs, 0-24 hours old, for C. kellieae. Neither species host feeds nor are a carbohydrate source and free water prerequisites for progeny production. Females of both species require a carbohydrate source and free water for greatest longevity. Observations of the mating behavior disclosed males are polygamous and females monogamous. The mating ritual, searching, and ovipositional behavior are described. Both species are arrhenotokous with virgin and mated female C. kellieae producing approximately equal numbers of progeny, while mated female C. phthorimaeae produced a greater number of progeny than did virgin female C. phthorimaeae. Chelonus phthorimaeae and C. kellieae exhibited a preovipositional period of 2 hours and 4 hours, respectively, prior to production of female progeny.

Immature Stages of Leptopilina boulardi (Hymenoptera: Eucoilidae), a Protelean Parasite of Drosophila spp. (Diptera: Drosophilidae)

Abstract: Leptopilina boulardi (Barbotin et al.), a larval parasitoid of Drosophila spp., possesses a stalked egg, eucoiliform first- and second-stage larvae, and hymenopteriform third-, fourth-, and fifth-stage larvae, followed by a pupal and pharate adult stage. Host age at oviposition significantly affects parasitoid development, whereas host development is in turn affected by the presence of the parasitoid larva and host age when parasitized. The fact that, regardless of sex, adults from hosts parasitized within a 2-h period emerge over 5 days suggests that a density-independent component influences development time.

Effect of Bacillus thuringiensis var. israelensis on a genetically-defined population of black flies (Diptera:Simuliidae) and associated insects in a montane New Hampshire stream.

Abstract: A small, undisturbed stream in central New Hampshire was treated for 1 min with a 10 ppm suspension of Bacillus thuringiensis var. israelensis (B.t.i.) to determine the effect on an outlet-breeding black fly population and associated nontarget aquatic insects. The black fly larval population was eliminated and susbsequent adult black fly biting activity reduced near the treatment site although weather conditions may also have contributed to an observed decrease in biting activity. Some Chironomidae were killed by B.t.i. but they were not abundant enough to adequately assess impact on their populations. Temporary increases in the drift of two Ephemeroptera and two Trichoptera species were observed following treatment. Increase in rate of drift was inversely related to increase in distance from the treatment point. Slight increases in observed drift of three Plecoptera species could not be attributed directly to the B.t.i. treatment. No direct mortality caused by B.t.i. was observed in any stream insects studied except black fly larvae and some Chironomidae.

Effect of the Entomogenous Nematode Nemplectana carpocapsae on the Tachinid Parasite Compsilura concinnata (Diptera: Tachinidae).

Abstract: The entomogenous nematode Neoaplectana carpocapsae and its associated bacterium, Xenorhabdus nematophilus, could not infect the pupal stage of the tachinid Compsilura concinnata through the puparium. N. carpocapsae had an adverse effect on 1-, 2- and 3-day-old C. concinnata larvae within the armyworm host in petri dish tests. All 1-day-old larvae treated with nematodes died in their hosts, whereas 61% and 69% of 2- and 3-day-old larvae treated with nematodes, respectively, died. However, the survivors developed to adults. Nine to thirty-seven percent of adult tachinids which emerged from nematode-treated soil (50 nematodes/cm ~) were infected with N. carpocapsae. The nematode adversely affects C. concinnata directly by the frank infection of the tachinid and indirectly by causing the premature death of the host which results in tachinid death. The tachinid Compsilura concinnata par- asitizes a large number of lepidopterous insects (1). Its biology has been studied by Culver (3) and Fusco et al. (5). The adult is larviparous, and more than one larva may emerge from a host. The parasitized host becomes moribund in 3-4 days, but the tachinid larva does not emerge until the 7th day. After emergence, the larva forms a puparium in the soil or on any convenient surface such as silken webs or bark crev-

Influence of temperature and temperature shifts on the development of chiton larvae, Mopalia muscosa

Abstract: Summary Larvae of the mossy chiton, Mopalia muscosa, were reared either at 10–12°C or 16°C throughout larval development, or were reared at one of the two temperatures for about 400 h (17 days) and then transferred to the other temperature for the remainder of larval development. Temperature regime was found to influence developmental rate, maximum duration of planktonic existence and incidence of spontaneous metamorphosis. The effect of temperature on length of larval life may reflect exploitation of a finite nutritional source by these lecithotrophic larvae. More rapid development was correlated with shorter larval life. The effect of temperature on incidence of spontaneous metamorphosis probably does not have a nutritional basis. In 3 of the 4 treatments, at least 80% of the larvae eventually died, although some larvae metamorphosed spontaneously in all of the treatments. Approximately 50% spontaneous metamorphosis was attained in the fourth treatment, in which larvae initially were reared at the coole...

Relationships of Larval Rearing Variables to Fly Attraction and Oviposition Responses in the Screwworm, Cochliomyia Hominivorax (Diptera: Calliphoridae)

Abstract: Responsiveness of gravid screwworm flies, Cochliomyia hominivorax , in oviposition and olfactometer bioassays was examined in relation to mean larval weight, mean pupal weight, and survival to the pupal stage in the larval rearing groups that supplied the test females. Weights were not of value for predicting adult behavior in bioassays, but the percentage of insects surviving from egg to pupal stage was positively and linearly correlated with oviposition and attraction responses (r2 = 0.48 and 0.57, respectively). Rearing data compiled over a 21-month interval that included the period of behavioral testing were used to establish that the correlations most likely arose from inadequate control over variables that operated prior to the pupal stage and affected both screwworm survival and the subsequent behavioral responsiveness of surviving insects. Survival in larval groups did not vary with parental age at oviposition or with the temperature at which parental insects had been held as pupae, but circumstantial evidence suggested that composition of the larval starting diet affected survival and adult behavior.

The immature stages of culicoides henryi lee and reye (diptera: ceratopogonidae)

Abstract: The larva and pupa of Culicoides henryi are described and earlier larval and pupal keys amended to include this species. Estuarine habitats are confirmed as the breeding sites. Copyright

CRITERIA FOR CONDITION EVOLVED FROM ENCLOSURE EXPERIMENTS t?ITH COD LARVA POPULATIONS

Abstract: Oiestad, V., 1984. Criteria for condition evolved from enclosure experiments with coG larva populations. In: E. Dahl, D.S. Danieissen, E. Moksness and P. Solemdal (Editors) , The Propagation of Cod Gadm morhua L. FlGldevigen rapportser., l, i984: 213-229. A number of experiments have been carried out with cod larvae in mesocosms at variable feeding conditions. Larval growth and survival has been monitored beyond metamorphosis, and in some of the experiments large subpopuiations of emaciated cod larvae have been identified. A methodology for developing criteria for larval condition of general application to cod larvae is suggested based on measurements of standard length, dry weight and myotome height with age determined from the classification of yolk sac resorption.

The larval morphology and ecology of a new species of Melanotrichia from Hong Kong (Trichoptera: Xiphocentronidae)

Abstract: Melanotrichia serica sp n from Hong Kong belongs to the M chichupala‐group, and is shown to be closely related to the two other Chinese species in the genus The Japanese genus Tsukushitrichia is synonymized with Melanotrichia, and Kibuneopsychomyia tanzawaensis Kobayashi is transferred to Melanotrichia The presumed larva of M serica, from a forest stream, is very similar to those of Xiphocentron and Abaria thus confirming the larval characteristics of the family As well as the morphological description, observations are made on the tube structure and feeding habits of the larva, and on the head capsule width of the five larval instars This is the first larval description of an oriental xiphocentronid, and of the genus Melanotrichia

Aldrin epoxidase activity in final instar 'Spodoptera litura' (F.) larvae

Abstract: The ability to epoxidise aldrin to dieldrin was used to monitor mixed function oxidase activity in crude homogenates of midgut, fatbody and carcass of final instar larvae of 'Spodoptera litura' (F.). Activities were much higher in the midgut than in the other tissues. Activity was determined on a mg protein, larva, and mg larva basis. No significant differences in any of these activities were observed in fatbody and carcass during the assay period. With midgut, on a mg protein and mg larva basis, activity was similar throughout the feeding stages of the instar. Larvae assayed during the postfeeding period had the lowest activity. On a larva basis, activity was highest during the middle period of the instar.