Origin of the Regeneration Blastema in Polychaete Annelids

Since the early part of this century, controversy has surroundedthe origin of the cells ot the regeneration blastema in annelids.Cells of the epidermis and reserve mesodermal cells have eachbeen thought to form the entire blastema. With increasing frequency,it is being suggested that in numerous polychaetes each layerof tissue in the regenerate arises from the corresponding oldgerm layer. Evidence presented here from experiments utilizingtechniques of radioautography, histochemistry, X-irradiation,and electron microscopy in addition to histological observationlargely supports the last hypothesis. In the light of recentexperiments, it appears that the new epidermis and gut arisefrom the corresponding old tissue. The formation of the mesodermcannot yet be generalized, but reports indicate that it mayarise from dedifferentiated muscle cells, cells of the peritonealepithelium, and free coelomocytes.     

Vitellogenin concentrations in the haemolymph and ovaries of Ixodes scapularis ticks during vitellogenesis

The vitellogenin and vitellin concentrations in the haemolymph and ovaries of Ixodes scapularis females were determined using a double sandwich enzyme-linked immunosorbent assay. The level of vitellogenin in the haemolymph began to increase just prior to tick detachment from the host and continued to increase until 2 days after detachment. There was a slight decrease in the vitellogenin level 4 days after detachment, but a second peak was observed approximately 5 days after oviposition. Subsequent to oviposition, the vitellogenin levels in the haemolymph quickly decreased. The concentration of vitellogenin in the haemolymph ranged from 1.55 to 11.48 g l^-1 during the period after dropping from the host through oviposition. The concentration of vitellin in the ovaries began to increase as the female began rapid engorgement (0.03 mg per female) and declined after oviposition (0.1 mg per female).     

Effects of Copper on the Burrowing Behavior of Estuarine and Coastal Invertebrates,the Polychaete Nereis diversicolor and the Bivalve Scrobicularia plana

Alterations of the burrowing behavior of two benthic invertebrates living in intertidal mudflats, the polychaete Nereis diversicolor and the bivalve Scrobicularia plana, were studied in individuals exposed to soluble copper. The design of the contamination procedure took into account the results assessing the influence of some natural factors potentially able to influence burrowing (artificial vs. natural sediment, lighting, size of the shell for bivalves). Animals were exposed for 4 d to concentrations ranging from 25 to 150 μ g Cu l^{? 1}. At the end of exposure, the burrowing kinetics in clean sediment were determined after 1 and 2 d, then the animals were frozen until acetylcholinesterase (AChE) activity determination. Even at the lowest tested concentrations, copper caused hypoactivity in organisms belonging to both species studied. Behavioral impairments were not related to AChE activity inhibition. Metabolical or physiological disturbances could be the cause of these impairments. Concentrations affecting burrowing behavior were below those responsible for lethality in these species.     

Development of monoclonal antibodies for monitoring Aedes atropalpus vitellogenesis

Monoclonal antibodies to a mixture of Aedes atropalpus and A. aegypti soluble yolk proteins were produced by hybridomas between the fusion of P3X63.653 myeloma cells and splenocytes of immunized BALB/c mice. Ascites fluid collected from mice innoculated with cloned hybridoma cells contained high specificity and affinity to the soluble yolk proteins of both Aedes species. Seven different hybridoma lines produced antibodies with specificity to both A. atropalpus and A. aegypti and one cell line produced antibodies monospecific to A. aegypti soluble yolk proteins. Monoclonal antibodies specific to A. atropalpus vitellin and vitellogenin were characterized by a combination of gel electrophoresis, western blotting and immunohistochemical staining. An indirect double antibody sandwich enzyme-linked immunosorbent assay was developed using a mixture of the seven hybridoma antibodies to A. atropalpus vitellin for monitoring vitellogenin levels in individual mosquito haemolymph samples. With this procedure, the peak period of vitellogenin synthesis in A. atropalpus was found to be 18 to 30 h after adult eclosion.     

Temporal events of gypsy moth vitellogenesis and ovarian development

Abstract The vitellogenic period of gypsy moth ovarian development starts on day 3 of the pupal stage and continues through adulthood. During this period, rapid increases occur in follicle size, protein content, and wet weight of the ovary. Patency is observed on day 3 of the pupal stage.
Pre-vitellogenic follicles are formed in the last larval stadium. Newly formed follicles detach from the germarium on day 4, and increase rapidly to 140 per ovariole at the end of the last larval stadium. The pre-vitellogenic follicles are uniformly around 50 um in diameter. No vitellogenin is incorporated into the oocytes until the pupal stage.
Polyacrylamide gel electrophosesis (PAGE) in the presence of sodium dodecylsulphate (SDS) analysis of male and female haemolymph samples and vitellogenic ovaries demonstrates the presence of two female-specific subunits of vitellogenin of 180 kD and 160 kD. These proteins are detected only in haemolymph and ovarian extracts of vitellogenic females. The molecular weight of the native protein determined by size exclusion chromatography is approximately 400–420 kD.
A highly sensitive double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed to monitor the temporal changes in vitellogenin titre in haemolymph. Vitellogenin production starts on day 2 of the last larval stadium, reaching a maximum level by day 6 of the last larval stadium, and decreasing in the late pupal stage as vitellogenin was internalized into the oocytes. This is the first report of vitellogenin production occurring in the larval stage of a holometabolous insect. The fact that vitellogenin production and uptake occur during different stages of development in the gypsy moth, opens up some interesting questions concerning the underlying regulatory mechanisms controlling each process.     

Polychaete zonation and its relation to algal distribution down a vertical cliff in the western Mediterranean (Italy): a structural analysis

The zonation of polychaetes down a vertical cliff (0–5 m in depth) at Cape Romito, Leghorn, Italy, was investigated. The structural organization of the community changed with depth. A community typical of photophilic environments was found in the superficial zone (0–2 m), while in the deeper zone (3–5 m), a more diversified community characterized by species typical of sciaphilic environments was present. At the surface (0 m) the community was very poor in species and individuals and thus probably corresponds to the midlittoral fringe. In fact, some species typical of the midlittoral zone were found. This distribution pattern was constant for samples taken in February and August 1985. The distribution of polychaetes was closely related to that found for macroalgae. It is hypothesized that algae condition the substratum and that this is the main factor responsible for the zonation of polychaetes.     

Effects of starvation on the vitellogenesis,ovarian development and fecundity in the ectoparasitoid,Nasonia vitripennis (Hymenoptera: Pteromalidae)

A female‐specific protein, vitellogenin (Vg), and its corresponding egg vitellin (Vt) are identified in the ectoparasitic wasp Nasonia vitripennis. Both native Vt and Vg have a molecular mass of about 350 kDa, which is composed of two subunits of approximately 190 kDa and 165 kDa under reducing and denaturing conditions (sodium dodecyl sulfate—polyacrylamide gel electrophoresis). An indirect sandwich enzyme‐linked immunosorbent assay developed with both monoclonal and polyclonal antibodies against N. vitripennis Vt. Vg was first detected in the hemolymph on the 10th day after parasitism, and was first observed in oocytes on the 12th day. In adults deprived of food, the highest hemolymph Vg level occurred at the time of adult eclosion and the highest level of Vt in ovaries was found at 30 h after eclosion. In contrast, feeding adults with 20% sucrose resulted in the reduction of Vt uptake by ovaries and the extension of life span, but had little effect on Vg production. Deprived of hosts, starvation of female wasps had no significant effects on ovariole growth and oocyte maturation before the wasps died. However, starvation of female wasps supplied with hosts accelerated the wasps laying progeny into hosts, but resulted in a decrease of total progeny production by comparison with wasps fed with 20% sucrose.     

Carcinogenesis: Evolution of concepts

Cancer is considered as an unintended consequence of internal imperfection of multicellular organisms: Darwinian evolution “does not foresee the future and does not plan for it”, it is forced to handle only anything that it has at a given moment “at hand”, which makes inevitable compromises and restrictions. In this case, there are a number of founding dogmas including mutagenesis as the main driving force of carcinogenesis; the environment as the main source of mutagenic effects; tumor monoclonality; cancer cell multistage transformation as Darwinian process of successive mutation—selection cycles. Recent discoveries complicate, supplement, and sometimes transform into an opposite fixed concepts. As a result, a new “image” of carcinogenesis is formed as a biological phenomenon whose conservation is indicative of its evolutionary utility.     

Oogenesis in the Polychaete Dipolydora commensalis

Oocytes of the polychaete Dipolydora commensalis develop in the gonad, in close contact with the wall of the genital blood vessel, up to the late stages of vitellogenesis. At the blood vessel wall, between the neighboring vitellogenic oocytes, and sometimes on the apical surface of the oocytes, there are flattened follicular cells. However, no continuous, well-expressed gonad envelope is found. Oogenesis is asynchronous. Gametes at all developmental stages, from oogonia to late vitellogenic oocytes, occur in the gonad. Dividing oogonia vary from 6 to 10 m in diameter. RNA, proteins, glycogen, and lipids accumulate in the oocytes during vitellogenesis. The breakdown of the oocyte germ vesicle occurs in the gonad. Before spawning, gametes accumulate in the coelom and reach 80–90 m in diameter, at which point a new generation appears in the gonad.     

In vivo stimulation of vitellogenesis in Aedes aegypti with juvenile hormone,juvenile hormone analogue (ZR 515) and 20-hydroxyecdysone

Decapitated blood-fed Aedes aegypti mosquitoes do not undergo normal oöcyte maturation. Topical application of 1.25 ng JH analogue (ZR 515) or 250 ng JH-I restored ovarian development in 70–80% of the treated females. The rate of vitellogenin synthesis in these animals was 80% of normal blood-fed controls.When ligated abdomens were treated, 125 pg ZR 515 or 12.5 ng JH-I were sufficient to restore ovarian development in 80% of the animals. The rate of vitellogenin synthesis in these animals was 70% of normal blood-fed controls. On the other hand, injection of 1.25 μg 20-hydroxyecdysone was needed to restore ovarian development and vitellogenin synthesis in decapitated and abdominally ligated females.These experiments indicate that JH concentrations closer to the physiological norm than 20-hydroxyecdysone, can restore ovarian development and vitellogenin synthesis in vivo.     

Comparative Analysis of Hox Gene Expression in the Polychaete Chaetopterus: Implications for the Evolution of Body Plan Regionalization

The Hox genes are widely regarded as candidates for involvementin major evolutionary changes in body plan organization. Weexamine Hox gene expression data for several taxa, in relationto recent work on the polychaete annelid Chaetopterus. The workin Chaetopterus shows the basic conservation of colinearityof anterior expression boundaries seen in other groups. It alsoreveals novel patterns including early expression in the larvalgrowth zone and later formation of posterior boundaries thatcorrelate with morphological transitions in the polychaete bodyplan. The polychaete gene expression pattern is compared withthose of Hox gene homologs in other taxa to reveal differencesthat represent evolutionary changes in Hox gene regulation betweenlineages. Correlations between Hox gene expression differencesand morphological differences are examined, focussing on a numberof cases in which posterior Hox gene expression boundaries correlatewith morphological transitions. Differential regulation of theseposterior expression boundaries is proposed as a possible mechanismfor changes body plan regionalization.     

Origin and release sites of a hormone stimulating oviposition in the stick insect Clitumnus extradentatus

In the stick insect, Clitumnus extradentatus, a hormone stimulating oviposition, produced in type-A neurosecretory cells is located in the thoracic and anterior abdominal ganglia. At the end of the photophase, this neurohormone is stored in neurohaemal areas associated with segmental nerves. During the scotophase, the neurohormone is released into the haemolymph and acts on the genital tract, triggering nocturnal oviposition. The oviposition stimulating hormone is not species-specific.     

凡纳滨对虾卵母细胞卵黄发生的超微结构

利用电镜研究凡纳滨对虾卵母细胞卵黄发生的全过程。结果表明 :凡纳滨对虾卵黄的发生是双源性的。卵黄发生早、中期是内源性卵黄大量合成的阶段 ,卵黄发生中、后期则以外源性卵黄的合成为主。内源性卵黄主要由内质网、线粒体、核糖体、溶酶体、高尔基器等多种胞器活跃参与形成。其中数量众多的囊泡状粗面内质网是形成内源性卵黄粒的最主要的细胞器 ;部分线粒体参与卵黄粒的合成并自身最终演变为卵黄粒 ;丰富的游离核糖体合成了大量致密的蛋白质颗粒并在卵质中直接聚集融合成无膜的卵黄粒 ;溶酶体通过吞噬、消化内含物来形成卵黄粒和脂滴 ,且方式多样 ;高尔基器不直接参与形成卵黄粒。外源性卵黄主要通过卵质膜的微吞饮活动从卵周隙或卵泡细胞中摄取外源物质来形成     

Later stages of regeneration in the Polychaete, Nephtys

The sequence of events in posterior regeneration of the polychaete, Nephtys, has been examined in histological preparations from the fifth day to the end of the third week after amputation, that is from the time when wound healing is complete until several new segments are differentiated. The pygidium forms and begins to differentiate prior to segmentation. The first indication of each new segment is the appearance of a large pair of segmental blood vessels which arise from the vascular complex in the gut wall. Associated with these are fibroblasts, the anlagen of the new septum. Epidermal derivatives develop subsequently, appearing first ventrolaterally, close to the regenerating nerve cord. The mitotic rate appears to be highest prior to the period of maximum segment formation. Visible cell differentation follows, and subsequent growth of segments is primarily by cell enlargement. It appears likely that the blood-vascular system associated with the gut and the regenerating nerve cord, both of which are disproportionately large in the regenerate, are important for the initiation of new segments.     

The first tomopterid, a polychaete from the Carboniferous of Scotland

Briggs, Derek E. G. & Clarkson, Euan N. K. 1987 07 15: The first tomopterid, a polychaete from the carboniferous of Scotland.
The first known example of a fossil tomopterid, Eotomopteris aldridgei , is described from the Lower Carboniferous of Granton, Edinburgh. The head bears tentacular cirri, and the trunk preserves evidence of at least 20 pairs of parapodia. The polychaete is associated with other soft-bodied and lightly skeletalized organisms including crustaceans, conodonts, an additional chordate, and branching structures which resemble hydroids. It is similar to living tomopterids and was probably pelagic. This discovery indicates that these polychaetes were well established by the early Carboniferous and probably before.     

Patterns of polychaete recolonization in Queensland subtropical estuaries following severe flooding

Quantitative sampling of macrobenthos and fouling organisms in the estuarine reaches of the Calliope River and Auckland Creek, Gladstone, Australia has been conducted since November 1974, and includes the recovery period (1974–1981) following severe flooding (and flood-induced scouring) in December 1973/January 1974. Changes in numbers of the 18 most abundant species of benthic polychaetes and one encrusting serpulid (Ficopomatus uschakovi) are examined. Numbers of F. uschakovi settling on fouling panels showed a regular seasonal pattern, with a late summer maximum and a winter minimum throughout this period. The total numbers of individuals for all taxa in benthic samples followed a clear colonization pattern, with super-imposed seasonality; plateau densities were reached five years after flooding. Total numbers of the 18 most abundant polychaetes showed a similar recolonizational pattern including the seasonal variation.Generally, those species of polychaetes with similar trophic strategies displayed similar patterns of abundance throughout the period:(i) The suspended detritus feeders (F. uschakovi, Branchiomma sp., Lysilla pacifica, Amaena trilobata and Terebellides stroemi) formed a constant proportion of the population; (ii) Mobile surface detrital feeders (Glycera americana, Nephtys mesobranchia, Lumbrineris sp., Sthenolepis sp. and Poecilochaetus serpens) initially formed a high proportion of the population which diminished with time; (iii) The stationary surface detrital feeders (Magelona dakini, Paraprionospio sp., Isolda pulchella and Pseudopolydora kempi) initially formed a low proportion which increased to a maximum four to five years after flooding and subsequently declined; (iv) The sole surface deposit feeder examined (Leitoscoloplos normalis) had two peaks — in early 1975 and 1978; (v) The subsurface deposit feeders (Cossura sp., Sternaspis scutata, Euclymene sp. and Mediomastus sp.) initially formed a small proportion increasing continuously to become the most abundant group at the end of the period. It is suggested that these changes reflect changes with time in the substrate since theflood-induced scouring of these estuaries, particularly the gradual accumulation of detrital material, and the changing availability of food for the different trophic groups.