摘要:

The timing of final maturation and competence for fertilization of oocytes from individuals ofNereis (Neanthes) virenswas investigated. In the first experiment, one group was decerebrated and the other was not. Both groups were placed into a long-day photoperiod (LD 16:8). The oocytes from the decerebrated animals became fertilizable and successfully developed to the larval stage in advance of the other group. In the second experiment one group was maintained in long-day and the other in short-day photoperiod (LD 8:16). The oocytes from the animals exposed to long-day photoperiod became fertilizable in advance of those maintained in short-day photoperiod. These results indicate an influence of external photoperiod on the final stages of oocyte maturation resulting in advanced fertilizability and successful larval development.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652441

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

As a first detailed approach towards the fine structure of the eggshell in members of the family Arctiidae (Hexapoda: Lepidoptera), deposited eggs ofUtetheisa ornatrixfrom the subfamily Arctiinae are described. Scanning electron microscopy revealed that the eggs are dorso-ventrally depressed spheres and attached with the flattened basal pole to the surface of the food plant. At the upper pole, cross- or star-shaped micropyles occur at the center of a small zone characterized by high reticulation consisting of straight, polygonally arranged elevations of the chorion. The flanks are not reticulated and possess aeropyles in their upper portions, but are smooth in their lower part. The architecture of the chorion was studied using transmission electron microscopy. It is ca. 4 μm thick in the upper flank, but decreases to ca. 1.1 μm at the base. The values are at the lower end of the spectrum found in the Lepidoptera. The chorion has an elaborate substructure in the upper flank, but assumes a homogenous texture towards the base. The entire surface is covered by mucous secretions that are very prominent around the transition from the flanks to the bottom. A highly sculptured and thick chorion may be interpreted as an effective protective device for the developing embryo. The eggs ofU. ornatrixare smooth over wide areas and possess a thin chorion. This may mean that the eggshell plays only a minor role in the protection against predators and parasites. Indeed, the work of others has shown that the eggs ofU. ornatrixare protected through large amounts of pyrrolizidine alkaloids that they receive from their mothers. We assume that with this chemical defense in place, an elaborate eggshell can be dispensed with in the moth.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652442

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The α-galactoside binding lectin fromArtocarpus hirsutainhibits growth and has anti-fertility activity onTribolium castaneum(Herbst) (Coleoptera: Tenebrionidae) (red flour beetle). Postembryonic development was affected to a significant level when freshly hatched first instar larvae ofT. castaneumwere fed on a lectin-treated diet at 0.5% (w/w) concentration. Although larval survival till the tenth day did not differ significantly, larval weight did. Similarly, time taken for pupation, percentage pupation, time taken for adult emergence and percentage adult emergence were adversely affected. Larval-pupal intermediates comprised 11% and pupal-adult intermediates comprised around 50% of the treated population after 30–35 days. Finally, the F1 breeding pairs completely failed to reproduce successfully since the female adults from the breeding pairs were unable to lay a single egg.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652443

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Sperm transfer in Conchostraca LeptestheriidaeLeptestheria dahalacensisRüppel, 1837, a strictly amphigonic species, occurs due to the production in males of an extremely primitive structure. This structure, analogous to spermatophores present in most Crustacea, may be observed in the lumen as thin strips of crystalline material. Shortly before mating, sperm produced in the gonads are released together with the crystalline fibres that serve as a net which helps keep the sperm compact and adherent to the male's body. The surface and shape of the so-called spermatophore is described. Mating time is partly dependent on the degree of adherence of the spermatophore to the female's body. The origin and conformation of this primitive structure is assessed in terms of its significance as an adaptive mechanism.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652444

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The pattern of brood production was analyzed in the grass shrimpPalaemonetes pugio.Determination of patterns of brood production as successive (spawning after each molt) or alternate (spawning after every other molt) was made by observations on individual females paired with males in the laboratory over a four-month period. A pattern of successive parturial (spawning) molts was the most common pattern. However, in a majority of these successive parturials, the ovary of the female was not mature at hatching of embryos from a previous brood. There was a delay of 10–11 days, during which ovarian maturation took place, between embryo hatching and the next (parturial) molt. This pattern of “slow successive” parturials does not result in the truly continuous brood production which occurs in many caridean species, i.e., spawning of a new brood within 1–2 days after hatching of a previous brood. However, there was a relatively low percentage of females in which the ovary was mature at embryo hatching. These latter females did have a parturial molt after only 2 days (“fast successive” parturial). In the “alternate” pattern, more frequent later in the 4-month observation period, hatching of embryos was followed by a non-parturial (without spawning) molt within 2 days, followed by an intermolt period of 10 days during which ovarian maturation occurred prior to the next (parturial) molt. The interval between spawns was similar in the “slow successive” and “alternate” parturial molt patterns (22–23 days) compared to a much shorter one (14–15 days) in the “fast successive” parturials. Examination of reproductive females from field samples indicated that the spawning pattern observed in the laboratory was that which occurs in natural populations in southern Louisiana. Although brood production inP. pugiois not truly continuous, the relatively short interspawn intervals observed still allow production of several broods during the breeding season.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652445

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In order to obtain basic data on mechanisms controlling starfish development, we examined the effects of the inhibition of RNA synthesis on the development of the starfish,Asterina pectinifera.Embryos were treated with formycin A in three ways: (a) Continuous treatment starting at various stages, (b) treatment for various lengths of time following 1-methyladenine (1-MA) administration and (c) pulse treatment for 2h at various stages. Results indicated that: (1) embryos treated with formycin A from the beginning of 1-MA treatment arrested as early blastulae; (2) treatment with formycin A inhibited rotation, hatching and vegetal plate formation depending on when they were treated; (3) treatment with formycin A from mid- to late-blastula stage inhibited gastrulation; (4) treatment with formycin A from late blastula to early gastrula stage prohibited mesenchyme differentiation, mesenchyme migration, and coelomic pouch formation depending on the time of treatment. Developmental arrest was reversed by the addition of uridine and cytidine.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652446

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The ultrastructure of spermatozoa and spermiogenesis inPolydora neocaecais described. Most morphological features and measurements of cellular components of the spermatozoa are similar to previously studied members of the genusPolydora.However, early spermatids contain finely granular chromatin which becomes finely fibrillar in late spermatids and uniformly electron-dense in mature spermatozoa. Fibrillar chromatin morphology has not been reported within the Spionidae and may represent a species-specific trait or a previously unrecognized transient developmental process. Spermatozoa ofPolydora neoceacaexhibit an elongate, cylindrical nucleus and a bullet-shaped acrosome that contains channels of electron transparent material. No microtubules are associated with nuclear elongation. The basal body of the axoneme occupies a short implantation fossa in the nucleus. The middlepiece contains 6–10 mitochondria closely aligned with the axoneme. Platelets, presumably carbohydrate storage bodies, are found along the nucleus and middlepiece. Additional electron-dense granules occur in the cytoplasm of the middlepiece.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652447

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A comparative analysis was carried out of reproductive mode, larval development pattern, and larval growth rate under identical conditions of three members of theCapitella capitataspecies complex:Capitellasp I from New York, US,Capitellasp M from shallow hydrothermal vents off Milos, Greece, andCapitellasp S from an intertidal flat on Sylt, Germany. In addition, three populations from salmon farms,CapitellaK (Kilmelford, Scotland),CapitellaCm andCapitellaCt (Cranford, Ireland), are described for the first time. Three development patterns were observed: planktotrophic (CapitellaK and Ct populations), lecithotrophic (Capitellaspp I, M and Cm populations), and direct development (Capitellasp S). Experiments with planktotrophic larvae from theCapitella Kpopulation at different temperatures, in the presence and absence of light and with several kinds of substrate were not successful in inducing settlement, although differences in the duration of larval survival were observed. Overall, major differences in reproductive modes and larval development patterns were observed among representatives of different species and populations reared under identical culture conditions. In contrast, such modes and patterns are consistent across generations. Whereas larval type and developmental mode appear to be determined largely by genetic factors, environmental conditions have an important influence on the timing of key developmental processes, such as settling and growth.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652448

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Lygocoris pabulinusfemales are polyandrous under laboratory conditions (Groot et al., 1998). As the insect mating system affects sexual communication and thus sexual behavior as a whole, we studied sperm transfer, storage and displacement inL. pabulinus.To be able to fully understand these processes, detailed information on the female reproductive tract is essential. Therefore, we first studied the female genitalia in detail. The bursa copulatrix consists of four plates, and a spermatheca is connected anteriorly to the bursa. At copulation a spermatophore is formed in the spermatheca. The spermatophore is compartmentalized, consisting of a sperm-containing portion, a large sperm-free portion and a mating plug. After 24 h the spermatophore has partially disintegrated. The mating plug is still intact but reduced in size. Sperm are found throughout the spermatheca and in the median and lateral oviducts where fertilization most likely takes place. The amount of male-derived substances transferred to females during first matings was ca. 5.2% relative to male body weight. To understand the effects of matings on the sexual communication, we determined sexual attraction of mated females at long and close range. At long range females were unattractive for only 1–2 h after mating, while they remained attractive at close range. Mated males were not attracted to virgin females for 2 h after mating, and only 23% of the tested males mated again within 24h. Together, these results suggested a high paternal investment that may affect reproductive output. To determine if this is the case, and hence if multiple matings affect fecundity and/or longevity, we conducted two oviposition experiments. From these experiments no positive effects on total fecundity or longevity in multiply mated females were apparent.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652449

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652450

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor