Effects on growth and reproduction of the coral Stylophora pistillata by the mutualistic damselfish Dascyllus marginatus

Although coral dwelling fishes are common on coral reefs, the nature of their effect on the host corals is poorly understood. The present study, conducted in the Gulf of Eilat (Red Sea) between July 1989 and August 1990, demonstrated that the branching coral Stylophora pistillata (Esper) benefits, in two components of coral fitness, from the presence of the damselfish Dascyllus marginatus (Rüppell), an obligate coral dweller. The growth rate of damselfish-inhabited corals was significantly higher than that of corals without damselfish. This was observed, using two growth assessment methods, in long-term (>7 mo) comparisons between: (1) corals where the damselfish were experimentally removed versus corals with unaltered fish groups; and (2) naturally inhabited versus non-inhabited corals. The presence of damselfish did not affect the coral's specific (per surface area) reproductive output, whether it was assessed by the number of female gonads per polyp or by the number of planulae released cm^-2 surface area d^-1. However, the more rapid increase in branch size in damselfish-inhabited corals resulted in an apparent increase in the total reproductive output, with age, in growing corals. These findings demonstrate that the association between the damselfish D. marginatus and its host coral, S. pistillata, is mutualistic.     

水稻精细胞差异表达基因RSG6的克隆和抗体制备

选用在水稻精细胞和二细胞花粉的差减文库中获得的在精细胞中表达量显著增强且可能代表新基因的EST之一 (BF4 75 2 0 7)为探针 ,筛选水稻精细胞cDNA文库 ,得到一全长为 1176bp的序列 ,其开放读码框编码 2 81个氨基酸 ,与已知蛋白质无明显同源性 ,属于一新发现的基因 ,GenBank登录号为AF4 4 2 4 90 .这是第 1次从高等植物精细胞中分离到的全长基因 .RT PCR结果证明该基因在根、叶、二细胞花粉、成熟花粉、授粉子房和精细胞中均有表达 ,但在精细胞中的表达量要高得多 ,是精细胞差异表达基因 .将此基因命名为RSG6 (ricespermgene6 ) .将RSG6的编码区克隆到表达载体pQE30上 ,构建重组质粒 .经IPTG诱导后 ,在E .coliM15 (pREP4 )中表达出了N端融合了 6×His的融合蛋白 .用纯化的融合蛋白免疫家兔 ,制得高效价、高特异性的抗体     

Comparative growth and mortality of Bonamia ostreae -resistant and wild flat oysters, Ostrea edulis, in an intensive system. I. First year of experiment

Since the early nineteen-seventies, the parasitic protozoans Marteilia refringens and Bonamia ostreae have consistently deleteriously affected the French production of Ostrea edulis (Linné). Purification and inoculation of B. ostreae that were achieved in the late nineteen-eighties allowed a selection program to be initiated. Two O. edulis strains, S85 and S89, were raised that displayed significant resistance to B. ostreae in the field. Growth was monitored to ensure that the resistant strains grew at a rate comparable to that of controls, using two crosses between the first generation of S89 and the second generation of S85 (G1G2), and between the first generation of S89 and wild oysters (G0G1). Growth and mortality were monitored for seven consecutive months in an intensive open circulating system at the IFREMER station of Bouin (Vendée, France). A Chapman-Richards model of growth revealed that the two “resistant” crosses grew significantly better than two controls from Quiberon Bay (Brittany), an area in which B. ostreae is endemic, and Palavas (Mediterranean Sea), where oysters are less infested by this parasite. The asymptotic values for growth curves ranged between 27.2 and 28.2 g for G1G2 and G0G1 vs 21.0 and 22.8 g for the controls. There was a similar trend in mortality, with G1G2 (11.8%) surviving better than the three other populations (from 28.7 to 57.5%). B. ostreae was not detected during the experiments and mortalities were attributed to feeding conditions that were not optimal, reinforced by gametogenesis and high temperatures during the summer. It is suggested that the better performance of G1G2 and G0G1 resulted from their increased resistance to stress. Received: 10 March 1997 / Accepted: 4 August 1997     

Gonadal structure and population characteristics of the protogynous goby Coryphopterus glaucofraenum

Protogynous hermaphroditism has been reported in two gobiid species within the genus Coryphopterus, including C. nicholsi from the temperate northeastern Pacific and C. personatus from the Caribbean. In a third species from the Caribbean, C. glaucofraenum, experimental groups were established and gonad structure of experimental individuals (collected off the southwest coast of Puerto Rico between February 1985 and June 1987) was subsequently examined histologically to determine the sexual pattern. Protogyny was confirmed in C. glaucofraenum. Sex change was either initiated or completed, typically by the largest female, in all-female groups held for 10 to 40 d. Ovarian, transitional, and testis structure were similar to that of C. nicholsi and C. personatus. No preformed testicular tissue was evident in the ovary proper and ovarian features were not retained in the sex-changed testis beyond the newly transformed stage. Secretory accessory gonadal structures associated with the testis and which develop at the time of sex change arose from precursive tissue masses associated with the ventral portion of the ovarian wall in the region of the common genital sinus. The rapid development and onset of function in these structures, generally preceding that of the associated developing testis, suggest that they may play an important role in sex change events and in advertising new male status. Based on observed similarities of ovarian, transitional and secondary testis structure in three protogynous Coryphopterus species, including one species isolated since the last closing of the American landbridge, it is probable that protogyny is an ancestral condition in this genus.     

Aluminum neurotoxicity in mammals

Although aluminum comprises a large percentage of the Earth's crust, it is excluded from body tissues, and especially from the central nervous system. When aluminum is experimentally introduced to the central nervous system, several neurotoxic effects are observed:i.e. neurofibrillary changes, behavioral and cognitive deficits and enzymatic and neurotransmitter changes, as well as certain types of epileptic seizures.The localization of relatively high levels of aluminum in Alzheimer disease, Guamanian amyotrophic lateral sclerosis and Parkinsonism-dementia has led to the implication of aluminum as a pathogenic factor in these diseases. Recent studies have shown that microtubule-associated proteins are part of the paired helical filaments which make up the intraneuronal neurofibrillary tangle. Other studies have identified the protein making the vascular and neuritic (senile) plaque amyloid and located the gene responsible for this protein to chromosome 21.Our electron microprobe analysis studies have not found the levels of aluminum or silicon in either the neurofibrillary tangles or amyloid cores reported elsewhere, nor have the levels of aluminum been elevated in approximately one half of the tangles and plaque cores examined to date.     

Variations de quelques facteurs estimatifs de la biomasse,et en particulier de l'ATP,chez plusieurs algues marines planctoniques

ATP, carbon, and nitrogen content, and cell volume have been measured in 7 marine algae in culture. Intraspecific differences are negligible during the phase of exponential growth; interspecific differences in ATP and carbon content are slight during this phase compared with those observed in the same cultures between the exponential and senescent phases. As the interspecific differences agree well with those reported for algae in situ, this leads the authors to believe that the greater part of the biomass in situ is always in a state of physiological youth. ATP content is higher in diatoms, and seems linked with silica shell synthesis. In non-silicified species, there is a significant correlation between the ATP: plasma ratio and the division rate, although the cellular volumes are quite different. In the author's opinion, ATP content allows a good estimation of biomass to be made, as well as, under controlled conditions, a suitable estimation of primary productivity; however, because of their high silica content, diatoms should be considered separately from other phytoplankters.     

Hydrodynamic and towing characteristics of a modified model of the Clarke Jet Net

In a series of studies to develop an effective high speed plankton sampler, hydrodynamic research was carried out on a modified model of the Clarke Jet Net. A theoretical analysis of the motion of the sampler was made using an IBM 7040 computer, and test tows were made in an experimental ship tank and at sea. To maintain the roll angle of the sampler at approximately zero, a v-shape bridle was applied. A pair of towing holes should be selected for the particular range of towing velocity. The calculated longitudinal stability seemed good in all the cases examined. Towing tests in the ship tank at 2 to 3 m/sec revealed sufficient stability. The motion of the sampler at speeds higher than 3 m/sec can be assumed from hydrodynamic coefficients derived from the ship tank experiment. Towing-cable characteristics, assumed by computation, indicated that about 500 m at 6 kt and 1,000 m at 12 kt should be paid out to lower the sampler down to 100 m. The effect of the sampler on the cable is found only adjacent to it and is almost negligible beyond 50 m from it in depth. Results of sea tests at 6 and 9 kt confirmed the stability of the sampler. Examination of the catch suggested that the present model can be used, with some modifications, for the quantitative and qualitative sampling of large zooplankton.Contribution No. 231 from the Seikai Regional Fisheries Research Laboratory, Nagasaki.