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31.
32.
Genetic evidence of closed life-cycles for some coral reef fishes within Taiaro Lagoon (Tuamotu Archipelago, French Polynesia) 总被引:2,自引:0,他引:2
Taiaro Lagoon has no permanent or regular connection with the ocean (ingress is restricted to episodes of high sea-level
and/or strong wave action) raising the question of how fish populations with normally dispersive larvae are maintained inside
this lagoon. We compared the genetic population structures of two coral reef fishes, Acanthurus triostegus and Chaetodon ulietensis, present on both sides of the atoll rim to determine whether there is evidence of reproductive isolation. Genetic surveys
showed that the lagoonal and oceanic populations were statistically different at five loci (AAT
*
-3, GDA
*, HPD
*, MDH
* and SDH
*) in A. triostegus and three loci (PGI-2*, IDH
* and PGD
*) in C. ulietensis, producing high F
st values of 0.055 and 0.021, respectively. Our genetic and demographic data on these species suggest that both may be completing
their life-cycles inside the lagoon, which leads us to question the common assumption that coral reef fishes require oceanic
conditions for larval development.
Accepted: 28 August 1997 相似文献
33.
34.
External chemical signals used by scleractinian corals to recognize suitable substrata for larval settlement and metamorphosis were identified from crustose coralline red algae (CCA). A fragment of coral rubble with CCA induced larval metamorphosis of the scleractinian coral Pseudosiderastrea tayamai. A natural inducer and compounds that enhanced its effect in larval metamorphosis were isolated from the methanol extracts of coral rubble with CCA. A bromotyrosine derivative, 11-deoxyfistularin-3 (10− 7 M) isolated from the CCA, induced the metamorphosis of P. tayamai larvae (27.5 ± 24.0%). In the presence of fucoxanthinol (10− 9 M) and fucoxanthin (10− 9 M), the percentage of metamorphosis induced by the bromotyrosine derivative was further enhanced to 87.8 ± 13.0 and 88.4 ± 17.8%, respectively. Both carotenoids are also found in the coral rubble with CCA. These results suggest that bromotyrosine derivative and carotenoids have a synergistic effect in the metamorphosis of P. tayamai larvae. The synergistic effect provides a higher selectivity for recruitment than a single-component natural inducer for recognizing suitable substrata for larval metamorphosis. Thus, the effect might offer a survival advantage for benthic marine invertebrates. 相似文献
35.
Tettamanti G Grimaldi A Casartelli M Ambrosetti E Ponti B Congiu T Ferrarese R Rivas-Pena ML Pennacchio F Eguileor Md 《Cell and tissue research》2007,330(2):345-359
We have analyzed midgut development during the fifth larval instar in the tobacco budworm Heliothis virescens. In prepupae, the midgut formed during larval instars undergoes a complete renewal process. This drastic remodeling of the
alimentary canal involves the destruction of the old cells by programmed cell-death mechanisms (autophagy and apoptosis).
Massive proliferation and differentiation of regenerative stem cells take place at the end of the fifth instar and give rise
to a new fully functioning epithelium that is capable of digesting and absorbing nutrients and that is maintained throughout
the subsequent pupal stage. Midgut replacement in H. virescens is achieved by a balance between this active proliferation process and cell-death mechanisms and is different from similar
processes characterized in other insects.
This work was supported by FAR 2006 (University of Insubria) to G.T., by a MIUR-FIRB-COFIN grant (no. RBNE01YXA8/2004077251),
and by the Centro Grandi Attrezzature (University of Insubria). 相似文献
36.
Distributions of mosquito larvae likely are a consequence of multiple factors, although two commonly studied factors (quality
of the larval environment and the terrestrial matrix in which these habitats reside) have rarely and simultaneously been varied
in the field to understand distributions of larvae. We monitored aquatic containers of two leaf detritus levels within a forest,
prairie, and industrial habitat across five months to understand the temporal and spatial colonization of aquatic invertebrates
in Northcentral Illinois, USA. Data were collected monthly on mosquito populations and the composition of other invertebrates
colonizing containers. Overall, six species of mosquitoes colonized containers, with Culex restuans and Aedes triseriatus having the highest relative abundances. There were strong seasonal abundance patterns for these two mosquito species, with
the dominant species changing over time in the forest habitat. The responses of other mosquito taxa were more variable, with
abundances reflective of either the terrestrial matrix or larval habitat quality. High detritus containers supported the highest
abundances of most species encountered, regardless of habitat. Non-mosquito taxa were less common numerically, but analyses
suggested that some taxa, such as syrphid larvae, often co-occurred with mosquitoes. Nested subset analysis indicated communities
were strongly nested, and that both habitat type and detritus level were important in explaining nested patterns of aquatic
invertebrates. Our data show that both the larval habitat and the surrounding terrestrial matrix shape patterns of container
mosquitoes, and that other container invertebrates vary in similar ways as mosquitoes.
Handling editor: K. Martens 相似文献
37.
Kaplan RM Vidyashankar AN Howell SB Neiss JM Williamson LH Terrill TH 《International journal for parasitology》2007,37(7):795-804
Ivermectin and moxidectin are closely related avermectin/milbemycin anthelmintics and available data suggest that side resistance occurs with these two drugs. However, moxidectin remains effective against many species of ivermectin-resistant worms due to its higher potency. The larval development assay (LDA) is routinely used to diagnose ivermectin resistance in Haemonchus contortus but laboratory diagnosis of moxidectin resistance is hampered by the lack of any validated in vitro tests. The objective of this study was to measure the relative susceptibility/resistance of H. contortus to moxidectin on goat farms in Georgia, and to validate the DrenchRite LDA for detecting resistance to moxidectin. Fecal egg count reduction tests (FECRT) were performed at five different moxidectin dose levels and DrenchRite LDAs were performed in duplicate on nine meat goat farms in Georgia, USA. To improve our ability to make inferences on the relative levels of resistance between farms, FECRT data were first analysed using a linear mixed model, and then Tukey's sequential trend test was used to evaluate the trend in response across dose levels. LDA data were analysed using log-dose logit-response and probit models. Using these statistical results, we were able to rank the nine farms from the least to the most resistant, and to develop a set of criteria for interpreting DrenchRite LDA results so that this assay can be used to diagnose both clinically apparent moxidectin resistance, as well as sub-clinical emerging resistance. These results suggest that our novel approach for examining these types of data provides a method for obtaining an increased amount of information, thus permitting a more sensitive detection of resistance. Based on results of the LDA, moxidectin-resistant farms had resistance ratios, compared with an ivermectin-sensitive farm, ranging from 32 to 128, and had resistance ratios of 6-24 compared with an ivermectin-resistant/moxidectin naive farm. Moxidectin resistance was diagnosed both in Haemonchus and Trichostrongylus on almost half of the farms tested, despite this drug only being used on these farms for 2-3 years. 相似文献
38.
We have conducted a preliminary study of tidal and diurnal variations in the distribution of dominant larval and juvenile
fishes in the Chikugo River inlet (Ariake Bay, Kyushu, Japan) to determine whether selective tidal stream transport (STST)
occurs. Larval and juvenile fish were collected from the mesohaline zone of the Chikugo River inlet during spring 2002. Temperature,
salinity, depth, and current velocity were measured. Larval and juvenile abundance were compared among four tidal conditions,
flooding tide, high tide, ebbing tide, and low tide, and between day and night. A total of 12 families, 15 species, and 5,577
individuals were collected. Temperature did not vary significantly with tidal conditions whereas salinity, depth, and current
velocity varied significantly. Salinity also was correlated significantly and positively with depth. The abundance of most
of the fishes was correlated positively and significantly with salinity and depth. Lateolabrax japonicus, Trachidermus fasciatus, Acanthogobius hasta, and other gobiid larvae (Gobiidae spp.) were significantly more abundant during high tide; in contrast, Coilia nasus and Neosalanx reganius were most abundant during low tide. The abundance of most of the fishes was higher during high tides at night than during
the day, indicating the existence of STST, which may be strategically associated with ascending progress to upstream nursery
areas. 相似文献
39.
Due to its intermediate complexity and its sophisticated genetic tools, the larval brain of Drosophila is a useful experimental system to study the mechanisms that control the generation of cell diversity in the CNS. In order to gain insight into the neuronal and glial lineage specificity of neural progenitor cells during postembryonic brain development, we have carried an extensive mosaic analysis throughout larval brain development. In contrast to embryonic CNS development, we have found that most postembryonic neurons and glial cells of the optic lobe and central brain originate from segregated progenitors. Our analysis also provides relevant information about the origin and proliferation patterns of several postembryonic lineages such as the superficial glia and the medial-anterior Medulla neuropile glia. Additionally, we have studied the spatio-temporal relationship between gcm expression and gliogenesis. We found that gcm expression is restricted to the post-mitotic cells of a few neuronal and glial lineages and it is mostly absent from postembryonic progenitors. Thus, in contrast to its major gliogenic role in the embryo, the function of gcm during postembryonic brain development seems to have evolved to the specification and differentiation of certain neuronal and glial lineages. 相似文献
40.
AFLP markers were used to investigate the population genetic differentiation among populations of Sebastes schlegelii from China and Japan. A total of 405 bands were amplified for 180 individuals from 9 populations by 3 pairs of selective primers. S. schlegelii exhibited high Nei's gene diversity with an average value of 0.29 for all populations. No significant genealogical branches or clusters corresponding to sampling localities were detected by UPGMA tree. The results of AMOVA analysis and pairwise FST values showed no genetic divergence among different geographic populations. The result of STRUCTURE demonstrated all populations of S. schlegelii examined in the study shared one single gene pool. 相似文献