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1.
In the gonochoric polychaetous annelid Eunice siciliensis Grube, germ cells only develop in the posterior segments of the worm; these segments subsequently differentiate into an epitokous portion separating at maturity from the infertile body part. As in the Pacific and Atlantic palolo worms, the epitokous portions die some hours after spawning. Laboratory investigations revealed that the anterior parts of spawned worms survive and regenerate genital segments. After a period of at least 8 months, paired gonads are developed in these segments. Gonia proliferating later from the germinal tissue are released from gonadal sacs into the coelomal cavities, where gamete development occurs. A reproductive epitokous portion does not mature and separate until the second year of cultivation; it is followed by caudal regeneration. These facts and the observation that only about 50% of the individuals obtained from samples of coralligène were sexually differentiated, led to the conclusion that E. siciliensis probably has a bi-annual reproductive cycle. Caudal regeneration does not depend on the presence of a prostomia hormone. The ability to form posterior regenerates is inherent to the parapodial segments of all body regions, except for mature genital segments. This is also valid for the formation of morphologically different secondary prostomia. However, for initiation and further promotion of gametogenesis and epitokous development, at least one gonadotropic factor originating from the prostomium is required. Neurosecretory cells within the brain suggest this factor(s) to be of neuro-endocrine nature. Specimens developing secondary prostomia were found both under field and laboratory conditions. In several cases, sexual development took place, and even epitokous portions were separated from such individuals. From this it appears that the gonadotropic functions are re-established by the regenerated prostomia in order to ensure reproduction in individuals accidentally deprived of the anterior end. The possible rôle of temperature and light as environmental factors involved in the control of normal and regenerative growth, of sexual development and reproduction is discussed.  相似文献   

2.
Decerebrate, sexually immature juveniles of Ophryotrocha labronica develop into males and females, although the normal ratio observed in intact worms is not attained. Even without the prostomium, primary males split into secondary females and stable males. Stable males and females do not show any reaction after decerebration as far as sexual differentiation is concerned. The females proliferate new sets of oocytes and the males continue spermatogenesis. In a great number of cases, decerebrate secondary females resume spermatogenesis. Amputation of the prostomium induces the development of the k-jaw. Even in small individuals below the size at which the k-jaw normally appears, the change to the k-jaw is induced. Heterospecific transplantations of prostomia from female O. labronica donors to decerebrate O. puerilis hosts revealed that the prostomia of female O. labronica produce and release a substance which completely compensates the lack of the host's own prostomium. Obviously, this ootropic substance is not necessary in all cases for gaining and/or maintaining female differentiation in O. labronica. Although it is produced both in stable females and secondary females, only a portion of the secondary females requires this substance for female differentiation. It is, therefore, presumed that the strength or stability of female differentiation expresses itself by hormone-dependent or independent oogenesis. In crosses with a gonochoristic population of O. labronica, protandric hermaphroditism is restricted to a few descendants. Crossing experiments within the protandric population of O. labronica seem to indicate a genetic component in the degree of protandry and in sex determination.  相似文献   

3.
Like many other benthic infaunal invertebrates, spionid polychaetes often lose portions of their bodies to predators, which affects their activities. Feeding palp loss and tail loss have been studied in several spionids, but the capacity for anterior tissue regeneration has not been compared in different species. The present study examines anterior tissue regeneration in two species, Dipolydora quadrilobata (Jacobi 1883) and Pygospio elegans Claparède 1863, in two laboratory experiments. Tissue removal treatments included removal of palps only, removal of anterior tissue through the first setiger, anterior tissue through the fifth setiger, all anterior tissue through half of the gill-bearing setigers, and all anterior tissue through the last gill-bearing setiger. Regeneration was monitored by capturing images of the worms and digitizing the area of regenerated anterior tissue or counting the number of segments that grew over time. Worms of both species regenerated anterior tissue regardless of the amount removed. Morphogenesis during regeneration followed a similar pattern in these two species regardless of the amount of anterior tissue lost, progressing from wound healing to formation of a recognizable prostomium and peristomium (“head”) by 6 days post-ablation. Palp and setal growth, addition of segments, and formation of nuchal organs and the ciliated food groove followed so that worms appeared to have re-grown “normal,” but smaller, “heads” and palps by 9–12 days following ablation. Over the course of 16 days, worms that lost more segments regenerated less tissue relative to their initial intact size and did so more slowly. There was no significant palp growth during the first 3 days following ablation. Rate of segment addition was directly related to the degree of tissue loss in D. quadrilobata. P. elegans added segments at similar rates whether 50 or 70% of the original segments was removed.  相似文献   

4.
Eunice siciliensis (Grube)1 is a sedentary polychaete with separate sexes; its germ cells develop only in the posterior part of the body. In March and April, females with whitish or even dark-green oocytes, males with only few spermatogonia, and individuals with no germ cells at all were discovered in the “coralligène” of the Banyuls region (European Mediterranean Sea). In august, besides immature and sexually non-differentiated worms, mature individuals of both sexes were captured: females with dark bluish-green oocytes of diameters up to 250μm, and males with milky genital segments containing spermatozoa. Soon after isolation from the substrate, these individuals performed characteristic movements with their posterior body parts, which then autotomized, and released ova and spermatozoa. Evidence is given that the anterior, atokous body parts survive in their tubes in the “coralligène” after separation from the epitokous portions, and regenerate new genetal segments. The development of gametes observed in these regenerated segments indicates the ability of E. siciliensis to reproduce more than once during its lifetime. Not only caudal, but also prostomial regeneration was observed; the formation of a (morphologically different) secondary prostomium appears to be essential for any development of germ cells in worm fragments. E. siciliensis exhibits surprising similarities in habits and in formation of an epitokous form with Eunice viridis (Gray), the “palolo” worm of the South Pacific Ocean, but nevertheless, lacks the prominent criteria of this famous species: the ventral eye spots on each genital segment in males and females, and the paired areas with brown pigmentation on the ventral side of each epitokous segment in the males.  相似文献   

5.
Early development was examined, under various salinities, for two sympatric nereidid polychaetes, Hediste japonica and H. diadroma, which participated in a simultaneous reproductive swarming in an estuary of the Omuta-gawa River in Ariake Sea, Japan. The eggs of both species were isotonic to the medium of 27.5–30 psu salinity. The egg diameter in the isotonic salinity was 180–205 μm in H. japonica, and 130–160 μm in H. diadroma. Successful development of most embryos was observed in a salinity range of 22.5–30 psu in both species, while successful fertilization occurred in wider ranges of salinity, i.e., 10–34 psu in H. japonica and 10 to 30 psu in H. diadroma. In both species, free-swimming larval life started from the indistinct hatching of trochophores out of a jelly layer capsule. The lecithotrophic development appeared to run to the 4-setiger nectochaetes in H. japonica, while to 3-setiger nectochaetes in H. diadroma, resulting in a shorter pelagic larval life in H. japonica. In a comparison of larval morphology among Hediste species, we found a definite negative correlation between the prostomium width, which represents the larval size and depends on egg size, and relative length of chaetae to the prostomium width: the relative length of chaetae was the longest in H. diadroma (with the smallest egg size and long pelagic life), intermediate in H. japonica (intermediate egg size, short pelagic life), and the shortest in H. atoka (largest egg size, no true pelagic life). We also examined the possibility of hybridization between H. japonica and H. diadroma through cross-insemination experiments. The gametes of the two species were reciprocally compatible, and viable hybrid offspring were produced by the laboratory crosses. The hybrid larvae expressed intermediate phenotypes, but with a greater maternal influence in characteristics such as the relative length of chaetae and the lecithotrophic larval duration.  相似文献   

6.
The effects of two fixed photoperiodic regimes on the rate of somatic growth and segment proliferation in the semelparous polychaete Nereis (Neanthes) virens Sars has been investigated. The two photoperiods (16 h light:8 h dark and 8 h light:16 h dark, hereafter LD 16:8 and LD 8:16) were close to the extremes experienced naturally by N. (N.) virens in the course of a year. The experiments were carried out during the ambient winter and all worms (including four-setiger larvae raised out of season) showed elevated feeding, growth and enhanced segment-proliferation rates when reared under LD 16:8, compared to worms reared under LD 8:16. The rate of replacement of lost segments after caudal ablation was also higher under LD 16:8. The number of segments present when the segment proliferation rate had fallen to zero was higher in individuals grown from birth under LD 16:8 compared to those grown under LD 8:16. Feeding activity showed a degree of spontaneous recovery under LD 8:16 from January onwards, but remained lower than under LD 16:8. This difference continued into the following spring, and was not attributable to differences in sexual maturity. We conclude that the rate of feeding in N. (N.) virens and other indicators of somatic growth rate such as rates of caudal regeneration and segment proliferation are directly influenced by the photoperiod, but that the seasonal cycle of growth also includes a circa-annual component modifying the response to static photoperiods according to the time of year. Received: 20 October 1998 / Accepted: 4 February 1999  相似文献   

7.
Three new species of free-living marine nematodes are described from sublittoral sediments in Liverpool Bay, UK. Pselionema longiseta n.sp. (Ceramonematoidea) is closest to P. longissimum Gerlach, 1952, from which it is distinguished by the longer cephalic setae and the larger amphids; Laimella filicaudata n.sp. (Chromadoroidea) is closest to L. longicauda Cobb, 1920, from which it is mainly distinguished by the much greater curvature of the spicules and the longer caudal apophyses of the gubernaculum; Pseudonchus decempapillatus n.sp. (Choanolaimoidea) is closest to P. deconincki Warwick, 1969 and is distinguished by the presence of 10, rather than 13, pre-anal supplements in the male, by the longer cephalic setae, and by the presence of numerous caudal setae.  相似文献   

8.
用不同浓度柠檬醛处理不同部位剪切的蚯蚓,和处理剪切后不同时间段的蚯蚓体段,探讨了柠檬醛对赤子爱胜蚓再生作用的体段、作用浓度和敏感时间段.结果表明,柠檬醛对蚯蚓再生有明显影响,但这种作用依不同体段而异,以体段P7和P25作用最显著,而A25,A90和P60的受柠檬醛影响较小; 柠檬醛影响蚯蚓头部再生,而不影响尾部再生;对再生有影响的柠檬醛浓度为1mmolkg-1, 0. 1mmolkg-1和0. 01mmolkg-1 (土壤),对蚯蚓再生作用的时间为切后0. 5~1d.试验显示,柠檬醛干扰蚯蚓再生头部形成而且还影响再生头尾体轴形成;内源视黄酸在蚯蚓头尾轴再生图式形成中有重要作用. 图4表4参18  相似文献   

9.
The regeneration rate of arms of the infaunal brittlestar Ophiophragmus filograneus was determined in natural and planted beds of the seagrass (Halodule wrighttii) in Tampa Bay, Florida, USA in 1990. Annually, brittlestar densities did not differ on average between the two beds, but they did show marked differences on individual dates. Rates of arm loss could not be determined for the two sites separately, but were estimated for the entire area. Between 52 and 94% of the brittlestars collected showed evidence of arm regeneration. Approximately one-third of those collected were regenerating one arm, with smaller proportions regenerating two or more arms. Regeneration rate was greater overall for individuals that had lost more tissue; however, the rate of soft-tissue regeneration per arm regenerated was significantly greater for those that had lost one arm compared to those that had lost three arms. The rate of soft-tissue regeneration did not differe between individuals from the two seagrass beds, and regeneration rate was lower than reported for other infaunal brittlestars. Skeletal regeneration per arm was similar in both arm-removal treatments. This result supports the hypothesis that echinoderm skeleton is energetically inexpensive and may help to lengthen arms during early regeneration. The rate of skeletal production was three-fold greater in individuals from the planted seagrass than in those from the natural. bed. As increased skeletal regeneration requires some additional energy, this indicates a greater energy expenditure and differential allocation by brittlestars regenerating in the planted seagrass areas.  相似文献   

10.
The occurrence and relative abundance of tissue (arm) regeneration in the ophiuroid, Ophiacantha bidentata (Retzius), was examined in individuals collected primarily among colonies of the deep-water coral Lophelia pertusa off the southeastern United States. Seven deep-water coral sites (384–756 m), located between Cape Lookout, NC, and Cape Canaveral, FL, were sampled in June 2004 using a manned submersible. The presence of regenerative tissue was evaluated by visual inspection of each individual ophiuroid, and the proportion of regenerating arms per individual was examined relative to size of individual, geographic location, and depth of collection. Ophiacantha bidentata, the dominant brittle star collected, commonly displayed signs of sublethal injury with over 60% of individuals displaying some evidence of regeneration. These levels of regeneration rival those reported for shallow-water ophiuroids. Larger individuals (>6.5 mm disc size) had a higher incidence of regeneration than smaller individuals. Size of individual and percent of regeneration were negatively correlated with depth. Although O. bidentata was significantly less abundant in southern versus northern sites, ophiuroid abundance did not appear to be influenced by amount or density of coral substratum. Presence of dense aggregations of O. bidentata indicates that they are an important component of the invertebrate assemblage associated with deep-water coral habitat especially in the northern part of the study area. Assuming that observed frequencies of injury and subsequent regeneration represent predation events then dense ophiuroid aggregations in deep-water coral habitats represent an important renewable trophic resource within these communities.  相似文献   

11.
B. W. Munday 《Marine Biology》1993,115(4):661-668
The boreo-Mediterranean amphiurid Amphiura chiajei Forbes occurs in high numbers (700 individuals/m2) in Killary Harbour, a fjordic inlet on the west coast of Ireland. 99.1% of the adult individuals show signs of arm regeneration, while 0.5% show regeneration of the disc. A study of the phenomenon commenced in November 1987 and continued on a seasonal basis until July 1989. Specimens were collected by SCUBA. The overall mean length of regenerated arm tissue over the 21 mo sampling period was 33.5±6.5 mm. Regeneration points were most common in the proximal and in the distal one-third of each arm. An overall mean of 4.21±0.3 arms per individual showed evidence of regeneration, while biomass assays revealed that regenerated tissue accounted for up to 57.9% of the total body weight. Anthropogenic activity (e.g. bottom trawling) may contribute to regeneration, although sub-lethal predation appears to be the main causitive factor of regeneration. Gut analyses of potential predators at the sampling station revealed that fish species (especially the Pleuronectidae) are particularly implicated. This predation seems to vary seasonally, being greatest in the summer months. Since the larger individuals showed the greatest evidence of arm regeneration, it is assumed that such sub-lethal damage is a persistent experience. Whatever the causality, the population of A. chiajei in Killary Harbour is deemed to be highly resilient.  相似文献   

12.
Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant and has been found to be the predominant perfluorinated chemicals (PFCs) in the environment. In the present study, planarian Dugesia japonica is employed to investigate the toxicity of this compound. The behavioural activity, survival, regeneration and antioxidant enzyme activities of the D. japonica exposed to PFOS were investigated. The results showed that the planarian D. japonica is very sensitive to low concentration pollutants including PFOS and suitable for toxicological bioassays. PFOS has severe toxicity in inducing oxidative stress, regeneration and development toxicity in planarians. The toxicity is indicated by reduced planarian locomotor velocity (pLMV), reduced appearance of auricles in regenerating animals, changed in antioxidant enzyme SOD and CAT activities. The information presented in this study will help elucidating the PFOS-induced toxicity in aquatic organisms.  相似文献   

13.
Y. Achituv 《Marine Biology》1973,18(4):333-336
The distribution of the Mediterranean populations of Asterina wega Perrier is described. Four populations were found to differ in size of animals and regeneration rate. The possible migratory pattern is duscussed.  相似文献   

14.
H. Schmidt 《Marine Biology》1970,5(3):245-255
Anthopleura stellula Ehrenberg 1834, a sea anemone from Eilat, Red Sea, is redescribed in detail and shown to be synonymous with Anthopleura elatensis England 1969. Asexual reproduction by autonomous transverse fission has been observed over a period of 8 months in A. stellula maintained in Mediterranean seawater (37.0 to 37.5 S). Fission always occurs at the same level, below the pharynx, and is followed by an asynchronous regenerative process beginning at the initial point of cleavage. The distal portion of a bisected anemone regenerates a new pedal disc, while pharyngeal formation is induced by the mesenteries of the first-budding directive tentacle in the proximal half; the original oral disc pattern is restored. After regeneration has been completed, the newly formed anemone can similarly engage in transverse fission. The fission process spreads infectionsly. If Bunodactis verrucosa, a Mediterranean anemone, is maintained in the same aquarium with A. stellula then the beginnings of fission followed by dedifferentiation are observed in the Mediterranean species, which does not ordinarily reproduce asexually. A. stellula still exhibits its induced ability to divide transversly if transferred into fresh Mediterranean seawater. When these specimens are exposed to low temperatures (12° to 13°C) for 2 months, fission activity still remains, but for only one division; there is no further fission, and no regeneration of a pedal disc. Abrupt increases in salinity to the salinity level of the Red Sea (40.0 to 41.0) interrupt the fission activity and pedal disc regeneration. A. stellula incised at the level where fission usually occurs promptly undergo transverse fission if cultured with other dividing anemones. However, the other anemones merely exhibit wound healing if the salinity is high. It is thought that fission and regeneration are induced by stimulating substances produced by the anemones during low salinity conditions and that the stimulating substances accumulate in the aquarium water.  相似文献   

15.
The mantle dermal formations (MDFs) ofHypselodoris webbi (D'orbigny, 1839), andH. cantabrica (Bouchet and Ortea, 1980) are globular sub-epidermal structures located in the cephalic and caudal regions. Histologically they consist of an accumulation of vacuolate cells surrounded by a basal lamina and an outer muscular capsule. Chemical analysis ofH. webbi MDFs reveals the presence of high concentrations of longifolin, a well known deterrent furanosesquiterpenoid that had been previously isolated from this species. In the present paper it is demonstrated that the great majority of longifolin accumulated in the mantle ofH. webbi is stored in the MDF vacuolar cells. This finding strongly suggests that such structures act as chemical weapons against predation, mainly protecting vital organs such as the head, rhinophores and gills.  相似文献   

16.
Sublethal predation can be a significant trophic pathway in sediment communities, and the regeneration of damaged tissue affects the activity, growth, and reproduction of prey. A field experiment was conducted 12–18 July 2010 in the Tijuana Estuary, California (+32.56617°, −117.13152°), to measure in situ rates of body growth and palp regeneration of the polychaete Polydora cornuta after simulating sublethal predation by removing 2, 1, or 0 palps from labeled individuals. After 3 days in the field, individuals that had 2 palps removed grew significantly slower than worms that had 0 palps removed; 1-palp worms had intermediate growth. After 6 days in the field, rates of body growth were faster than those of worms recovered after 3 days, with similar trends among the three palp treatments. During the 3-day transplantation, removed palps regenerated to half the initial length of unmanipulated palps. After 6 days, palp lengths did not differ significantly among treatment groups, indicating complete regeneration. The regeneration rate of removed palps was significantly faster than the growth rate of undamaged palps, and palp regeneration rate did not differ significantly between worms that had 1 or 2 palps removed.  相似文献   

17.
Ammonium regeneration and assimilation in eelgrass (Zostera marina) beds   总被引:4,自引:0,他引:4  
Regeneration and assimilation of ammonium in the water column and in sediments of eelgrass (Zostera marina L.) beds of Izembek Lagoon and Crane Cove, Alaska, USA and Mangoku-Ura, northeastern Japan, were investigated by using a 15N isotope dilution technique. In the water column of Mangoku-Ura, ammonium was regenerated at a rate of 12 nmol l-1 h-1 and assimilated at a rate of 74 nmol l-1 h-1. The ammonium regeneration rate in sediments ranged from 2 to 150 nmol g-1 h-1, and with one exception, exceeded ammonium assimilation in sediments (0.3 to 77 nmol g-1 h-1). The ammonium regeneration in the water column was of little significance for the nitrogen supply to the eelgrass bed ecosystem. Net ammonium production (regeneration minus assimilation) in the sediment of Izembek Laggon met nitrogen demand for eelgrass growth, suggesting that ammonium regeneration in the sediments was very important for the nitrogen cycle in the eelgrass bed ecosystem.  相似文献   

18.
Regeneration is a vital physiological process for survival of adult organisms. Bisphenol A (BPA), diethystilbestrol (DES), 17α-ethinylestradiol (EE2), and 17β-estradiol (E2) were examined for their effects on head formation in decapitated freshwater planarians (Dugesia japonica). The median lethal concentration of the test chemicals and the median inhibitory concentration for decapitated planarians and different regenerative endpoints, were determined for 3–7 d of exposure. For planarian head regeneration, the no-observed-effect level of BPA and DES was 0.05 mg L?1 and 1 mg L?1 for EE2 and E2. The effects of BPA, DES, and EE2 on asexual planarian regeneration did not correspond with the order of their estrogenic potencies, suggesting that the effects, at least partially, were due to general toxicity rather than their estrogenicity. In view of the published data on concentrations of xenoestrogens in water bodies versus the nominal levels tested here, this study suggests that the current environmental levels of BPA, DES, EE2, and E2 have no immediate adverse effects on freshwater planarian regeneration.  相似文献   

19.
To measure amounts of tissue lost in natural populations of the burrowing amphiurid ophiuroid Microphiopholis gracillima (Stimpson), individuals were collected from subtidal mud flats in North Inlet, South Carolina, USA, at monthly intervals between February 1985–February 1987 and December 1989–November 1990. Between 20 and 70% of all individuals were regenerating the disc, and 85% of the 2045 arms examined had regeneration scars; >50% had one scar and some arms had up to 4 scars. Fewer individuals were regenerating discs in warmer months, but there was no seasonality in arm-loss frequency. To quantify rates of arm regeneration in the field, individuals which had 1, 2, or 3 arms removed were placed in mud-filled cores in the field in late July and November 1988 and in March and May 1989, and recovered after periods of about one month. Another set of cores was held in a running seawater laboratory during the May 1989 experiment. No regeneration occurred during the cooler times of year (November and March), and rates of regeneration were slower in May (total: 0.13 mg/d; tissue: 0.03 mg/d) than July (total: 0.17 mg/d; tissue: 0.05 mg/d). These rates indicate complete replacement of lost tissue in 100 to 120 d during the growth season. Within experiments, per arm regeneration rates were similar regardless of the number of arms removed. This finding is complicated by small sample size, high variability and low statistical power, but in general individuals which lost 2 or 3 arms regenerated proportionally more tissue than individuals which lost 1 arm. Individuals held in the laboratory regenerated the same amount of tissue but 30% less skeleton than individuals in the field. Sublethal tissue loss is common in this population, and M. gracillima is capable of regenerating at least 50% (each arm=17% of total body weight x 3) of its standing crop in a single growing season. Burrowing brittlestars probably constitute a significant renewable energy source for higher trophic levels in areas where they occur in dense populations.  相似文献   

20.

To develop a novel granular adsorbent to remove arsenic and antimony from water, calcined Mg/Al-layered double-hydroxide (CLDH)-incorporated polyethersulfone (PES) granular adsorbents (PES-LDH) were prepared using a core-shell method having 25% PES in an N,N-dimethylformamide solution. The PES-LDH displayed a spherical hollow shape having a rough surface and the average particle size of 1–2 mm. On the PES-LDH surface, nanosized CLDH (100–150 nm) was successfully immobilized by consolidation between PES and CLDH. The adsorption of Sb(V) by PES-LDH was found to be more favorable than for As(V), with the maximum adsorption capacity of As(V) and Sb(V) being 7.44 and 22.8 mg/g, respectively. The regeneration results indicated that a 0.5 M NaOH and 5 M NaCl mixed solution achieved an 80% regeneration efficiency in As(V) adsorption and desorption. However, the regeneration efficiency of Sb(V) gradually decreased due to its strong binding affinity, even though the PES-LDH showed much higher Sb(V) adsorption efficiency than As(V). This study suggested that PES-LDH could be a promising granular adsorbent for the remediation of As(V) and Sb(V) contained in wastewater.

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