摘要:

Spermatogenesis and ecdysteroids were studied in male-destined fourth instar nymphs of the tickOrnithodoros parkeri. Feeding stimulated spermatogenesis. Elongated spermatids appeared well before epicuticle deposition and continued to be formed until after ecdysis. Ecdysteroid titers were measured by RIA in individual ticks that were categorized according to the stage of spermatogenesis. The titer was low at the spermatogonial stage, increased as the number of primary spermatocytes increased, and reached a small peak at the time when many cells reached late prophase of meiotic division I. HPLC-RIA analysis tentatively demonstrated the presence of only 20-hydroxyecdysone and ecdysone at that time. Then the titer dropped to a low level as soon as the elongated spermatids appeared at the distal pan of the testis. A second and larger peak of ecdysteroids appeared during the continuous formation of the elongated spermatids. However, this peak was obviously correlated with epicuticle deposition.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672428

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The objectives were to characterize the ovarian development and hemolymph vitellogenin concentrations during the reproductive cycle in the freshwater prawn,Macrobrachium rosenbergii. The ovaries ofM. rosenbergiiwere classified into five developmental stages, and the ovarian histology of each stage was characterized. The ovarian stages correlated closely with the gonadosomatic index, the oocyte diameters, and the characteristics of ovarian histology. Sequential bleeding at 3-day intervals from each of seven prawns was also conducted for at least two reproductive cycles. Vitellogenin concentrations in the hemolymph were measured with a validated enzyme-linked immunosorbent assay. Vitellogenin concentrations in the hemolymph showed similar profiles in the 18 reproductive cycles tested in these prawns. Vitellogenin concentrations increased in the hemolymph of prawns in the early stages of ovarian development (stage I or 11) and were maintained at high levels until stage V. Hemolymph vitellogenin concentrations fell abruptly during (or just prior to) oviposition and remained at low levels until the embryos hatched or were removed. There was not a close correlation between ovarian stages and the concentrations of circulating vitellogenin.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672429

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The ovariuterus of the scorpionLeiurus quinquestriatusconsists of three longitudinal tubes with five tubes interconnecting them. Oocytes of various sizes are situated on very short pedicles on the ventral side of the ovariuterus tubes. About 50 of either large or small oocytes could be observed under the dissecting microscope. Smaller ones (less than 50 pm in diameter) could only be recognized using a scanning electron microscope or in microscopic sections. Such means also allowed the identification of scars left by shrunken pedicles following parturition. The entire ovariuterus of a female was screened under SEM, and all visible oocytes were counted. In females kept at 25°C, growth and maturation of the small oocytes were accelerated, markedly increasing the number of large oocytes. Moreover, a large number of small, yellow, degenerated oocytes was noticed in these females.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672430

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Food preferences (flavor and size) by two echinoderm plutei,Paracentrotus lividusandArbacia lixula, were studied in two experiments. These included selection between polystyrene spheres (flavored and non-flavored) of different sizes in short-term (15 min) feeding experiments and selection among food algae of varying sizes in long-term (24 h) feeding experiments. Clearance and ingestion rates change during larval ontogenesis and are dependent on the size and the quality of available particles. In general, clearance rates were higher for larvae fed on a mixture of three sizes of polystyrene spheres or algae than for those fed separate foods. Young larvae (4- and 6-arm stage) had a higher clearance rate with larger-sized spheres (18.5 μm) and larger-sized algaProrocentrum micans(26.0 μm). For older larvae (8-arm stage with rudiment), the preference was divided between medium- and larger-sized particles. Retention capability of small-sized spheres (2.9 μm) and algae(Isochrysis galbana), compared to the other sizes of particles, was very low during all experiments. When different sizes of spheres and algae were offered separately,Arbacia lixulalarvae ingested larger-sized particles at great rates throughout development. YoungParacentrotus lividuslarvae ingested larger-sized spheres at greater rates than other sizes of particles. During older larval stages, mediumsized spheres are ingested preferentially. In mixtures of different-sized particles, mediumsized spheres and algae are generally captured first. For young larvae clearance and ingestion rates increased when spheres were treated with a filtrate ofCriscosphaera elongataalgae. Young larvae select particles on the basis of their quality and size; as larvae grow, particle selection is size dependent.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672431

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

During the reproductive cycle oocytes ofMacrobrachium rosenbergiifemales grow in diameter from 20 μm to 650 μm, while the gonado-somatic index increases from 0.2 to 8.0. SDS-PAGE polypeptide profiles of the cytosolic fraction from ovaries in various stages were studied. Specific vitellin bands were identified by immunoblotting.In vitrosynthesis of protein was measured by TCA precipitation and autoradiography of SDSPAGE separated polypeptides. Incorporation of [35S]-methionine and cysteine was highest in animals having an oocyte diameter of 50–150 pm and lower in pre-vitellogenic ovaries (20–50 μm). The lowest synthesis was found in late-vitellogenic ovaries (300–500 μm). Most of the incorporation was found in non-vitellin polypeptide bands. These results suggest the existence of an extraovarian source of vitellogenin inM. rosenbergii.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672432

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Seasonality of reproduction ofRoweia stephensoni, Pseudocnella sykionandNeostichopus grammatuswas compared using gonad indexes, gonadal tubule diameters, egg diameters and the abundance of spermatozoa in tubules from January 1992 until August 1993. All three species were dioecious and the populations studied did not deviate from a 1:1 sex ratio. Body sizes at first sexual maturity were 2.5–2.9 cm3forR. stephensoniandP. sykionand 3.0–3.9cm3forN. grammatus.The gonads ofR. stephensoniandP. sykionconsisted of a group of unbranched tubules of equal diameter, with males having more tubules of a smaller diameter than females. By contrast, the gonad ofN. grammatusconsisted of two tufts of multiple branched tubules. All three species had annual reproductive cycles, and inR. stephensoniandP. sykiongametogenesis occurred from March 1992 until August/September 1992, and gonad maturity was maintained until spawning in January 1993. By contrast, inN. grammatusgametogenesis occurred from July 1992 until September 1992, and gonad maturity was maintained until spawning in December 1992/January 1993. InR. stephensoniandP. sykiongonads never completely regressed whereas inN. grammatusgonads regressed after spawning.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672433

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The hyaline spheres (HS) in auricularia ofStichopus japonicusconsist of extracellular material in which solitary cells are present. This extracellular material can be stained by dyes for lipids. There are no membranes or other structural elements in HS. The cells within HS are most probably responsible for secreting the extracellular material. HS are not embryonic inductors of the ciliary rings which appear during metamorphosis. They probably store nutrients which permit larvae to complete metamorphosis successfully, but this remains to be established.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672434

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Male accessory reproductive glands (MARG), testis (including its sheath) and abdominal integument along with adhering fat body were cultured invitroto determine their ability to synthesize ecdysteroid during the first 10 days of adult development. Ecdysteroid synthesis by MARG was highest on day 2 (0.180 ng/mg) while the testis showed a peak on day 5 (0.436 ng/mg). In the testis, the sheath is mainly responsible for ecdysteroid synthesis. Ecdysteroid is also synthesized by the abdominal integument with adhering fat body, and peak activity is observed on day 8 (0.50 ng/mg). A time-course study showed that ecdysteroid synthesis increased linearly in all tissues over a 24-h incubation period. However, little storage of ecdysteroid occurred in the tissues.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672435

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

When their hostLineus ruberis hyperinfested, numerous male and femaleIntoshia lineihaving reached sexual maturity leave the host spontaneously to lead a period of free life in seawater during which sexual reproduction occurs. The latter involves a mating process which leads to internal fertilization. The fertilized ova give birth to embryos then, 24 h later, to swimming ciliated larvae which, once out of the female parasite, constitute infecting agents.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672436

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672437

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor