FINE STRUCTURE OF ZOOSPOROGENESIS, ZOOSPORE GERMINATION, AND EARLY GAMETOPHYTE DEVELOPMENT IN CLADOPHORA SURERA (CLADOPHORALES, CHLOROPHYTA)

The fine structure of zoosporogenesis, zoospore germination, and early gametophyte development in Cladophora surera Parodi et Cáceres were studied. Zoosporogenesis started with simultaneous meiosis in all nuclei of apical initial cells. The resulting haploid nuclei duplicated in turn by successive centric, closed mitoses. Then, each initial cell divided into two short zoosporangia. Numerous vacuoles appeared around each sporic nucleus. The delimitation of uninucleate zoosporocytes occurred by cytokinetic furrows produced by the coalescence of tiny, clear vesicles, without microtubules. Final shape of the zoospore resulted from gradual expulsion of vacuoles from the cell body. Mature biflagellate zoospores exhibited a conspicuous apical papilla containing fine granular globules, the basal apparatus, and a microtubular "umbrella" formed by numerous cortical microtubules that ran backward the length of the cell body. The chloroplast showed a conspicuous eyespot. The zoosporangial wall disorganized at the pore through which the zoospores were liberated. Zoospores settled on a substrate by their anterior papilla secreting an adhesive. Germination involved retraction of the apical papilla, loss of the "umbrella" microtubules and eyespot, and the lateral absorption of the entire flagellar apparatus, i.e. basal apparatus plus axoneme, into the cytoplasm. Early gametophyte development involved the synthesis of a thin, young cell wall, the development of outer peripheral vacuoles, the appearance of the marginal reticulate chloroplast, and the formation of the first central vacuoles derived from abundant endoplasmic reticulum. Close to the plasmalemma ran longitudinally oriented cortical microtubules. Eventually, the germling developed an achlorophylic, elongated rhizoidal portion.     

COMPLEX COLONY STRUCTURE IN SOCIAL INSECTS: II. REPRODUCTION,QUEEN-WORKER CONFLICT,AND LEVELS OF SELECTION

Differences in colony structure between two populations of the forest ant, Myrmica punctiventris, have had dramatic consequences on allocation to growth and reproduction. A population in Vermont, in which colonies have a single, once-mated queen, shows no evidence of inbreeding or population subdivision and has allocated 25% of sexual reproduction to males in two consecutive years. In contrast, for a population in New York that is facultatively polygynous, we have evidence of microgeographic genetic structure and inbreeding, and the populationwide allocation ratio was extremely male-biased. Additionally, the Vermont population allocated much more energy to sexual reproduction than did the New York population. Detailed analysis of data from the Vermont population, within which colonies undergo a seasonal cycle of expansion to multiple nesting sites (polydomy), gave strong evidence of queen-worker conflict over male allocation and indicated that workers are winning that conflict. Finally, we used contextual analysis to find that fertility selection operates almost exclusively at the level of the individual nest rather than at the higher level of the multinest colony.     

鼎湖山针阔叶混交林的第一性生产力研究

本文应用“树木收获法”和“气体分析法”,结合凋落物收集数据,综合测定了鼎湖山针阔叶混交林中的各种群第一性生产力以及群落的光。进一步综合分析表明,该群落的叶面积指数为１１;生物量为２６１ｔ·ｈｍ￣（－２）;总生产力约为１１７．６ｔ·ｈｍ￣（－２）·ａ￣（－１）,光能利用效率为１２％;第一性生产力为２０．９ｔ·ｈｍ￣（－２）·ａ￣（－１）。由于该群落是南亚热带演替系列中间阶段的代表性类型,因而本研究结果有助于了解本地带植被动态过程生产力发展规律和对能量的利用状况。     

ULTRASTRUCTURE OF VEGETATIVE ORGANIZATION AND CELL DIVISION IN THE UNICELLULAR RED ALGA DIXONIELLA GRISEA GEN. NOV. (RHODOPHYTA) AND A CONSIDERATION OF THE GENUS RHODELLA1

This study suggests that the genus Rhodella be restricted to that set of features currently observed only in Rhodella maculata Evans and Rhodella violacea (Korn-mann) Wehrmeyer, that a new genus Dixoniella be established to accommodate the unicellular red alga, Rhodella grisea (Geitler) Fresnel, Billard, Hindák et Pekár-ková, and that Rhodella cyanea Billard et Fresnel be further studied for probable reclassification. These conclusions are based on ultrastructural comparisons of Dixoniella grisea with published information on the genus Rhodella. The presence of thylakoids in the pyrenoid, a peripheral encircling thylakoid in the chloroplast, a dictyosome/nuclear envelope association, and the lack of a specialized pyrenoid/nucleus association in D. grisea separate this alga from the genus Rhodella. Cell division in D. grisea is not demonstrably different from that in Rhodella, although the unusually well-defined material of the presumptive microtubule organizing center (MTOC) made it possible to follow the development and behavior of the MTOC to a greater degree than in previously studied red algal cells. The surprising amount of conformity in cell division characters between D. grisea and the genus Rhodella prompted a comparison of cell division characteristics in all red algal unicells studied to date. All unicells show a remarkable degree of similarity except for differences in interzonal spindle length, dissimilarities in size of the nucleus-associated organelle (NAO), and the unusual NAO of Porphyridium purpureum (Bory) Drew et Ross.     

GROWTH, PRIMARY PRODUCTIVITY, AND NITROGEN FIXATION POTENTIAL OF NODULARIA SPP. (CYANOPHYCEAE) IN WATER FROM A SUBTROPICAL ESTUARY IN THE UNITED STATES

Nodularia is a halotolerant, filamentous, dinitrogen-fixing cyanobacterium that forms massive blooms in some coastal oceans, estuaries, and saline lakes worldwide. Although the genus is globally distributed, its blooms are sporadic and appear to be confined to certain water bodies. Blooms are frequently associated with phosphorus enrichment; therefore Nodularia may benefit from increased anthropogenic nutrient loading to coastal waters. We studied the potential for Nodularia to grow in the nitrogen-limited Neuse River Estuary (North Carolina, U.S.A.) with laboratory growth experiments in Neuse River Estuary water and by examining physico-chemical data from the estuary. Analysis of nutrients (nitrogen and phosphorus), salinity, and temperature data from the Neuse River Estuary between 1994 and 1998 revealed that suitable conditions for Nodularia prevailed during the summer of each of these years for time spans ranging from 1.5 to 5 months. Growth of two laboratory strains in Neuse River Estuary water was as fast or slightly slower than in artificial growth medium, as long as the culture inoculum had phosphorus reserves. Phosphorus addition did not stimulate growth of already phosphorus-sufficient inocula. Phosphorus starvation of the inoculum before the experiment decreased growth rates in the estuarine water unless additional phosphorus was supplied. Although phosphorus addition had a stimulatory effect on dinitrogen fixation and productivity, the effect differed for the two Nodularia strains. Results suggest that growth of Nodularia in North Carolinian estuaries is possible, and that such growth would be phosphorus-limited at times. Phosphorus availability may determine the times and locations for potential establishment of Nodularia in this and similar estuarine ecosystems.     

中华猕猴桃和美味猕猴桃自然居群遗传结构及其种间杂交渐渗

 利用9对SSR引物对中华猕猴桃（Actinidia chinensis）和美味猕猴桃（A. deliciosa）两近缘种的5个同域分布复合体和各自1个非同域分布居群进行了遗传多样性、居群遗传结构的分析以及种间杂交渐渗的探讨。结果表明：1）两物种共有等位基因比例高达81.13%,物种特有等位基因较少（中华猕猴桃：13.27%,美味猕猴桃：5.61%）,但共享等位基因表型频率在两近缘种间存在差异,而且与各同域复合体中两物种样本的交错程度或间距存在关联;2）两种猕猴桃均具有极高遗传多样性,美味猕猴桃的遗传多样性（H_o＝0 .749, PIC＝0.818）都略高于中华猕猴桃（H_o＝0.686,PIC＝0.799）;3）两猕 猴桃物种均具有较低的Nei’s居群遗传分化度,但AMOVA分析结果揭示种内异域居群间（F_ST=0.091 5）和同域复合体种间（F_ST=0.111 5）均存在一定程度的遗传分化;中华猕猴桃居群遗传分化（G_ST=0.086; F_ST=0.212 1）高于美味猕猴桃（G_ST= 0.080;F_ST=0.142 0）;4）同域分布复合体两物种间的遗传分化（G_ST=0.020）低于物种内异域居群间的遗传分化（中华猕猴桃：G_ST=0.086; 美味猕猴桃：G_ST=0.080）,同域复合体物种间的基因流（N_m＝7.89 -29.75）远远高于 同种异域居群间（中华猕猴桃：N_m =2.663; 美味猕猴桃：N_m=2.880）; 5）居群UPGMA聚类揭示在同一地域的居群优先聚类,个体聚类结果显示多数个体聚在各自居群组内,但各地理居群并不按地理距离的远近聚类,这与Mantel相关性检测所揭示的居群间遗传距离与地理距离没有显著性相关的结果一致。进一步分析表明两种猕猴桃的遗传多样性和居群遗传结构不仅受其广域分布、远交、晚期分化等生活史特性的影响,同时还与猕猴桃的染色体基数高 (x=29)、倍性复杂和种间杂交等因素密切相关,其中两种猕猴桃的共享祖先多态性和同域分布种间杂交基因渗透对两猕猴桃的居群遗传结构产生了重要影响。     

GOBIID FISHES OF THE GENUS GLOSSOGOBIUS IN THE LIMPOPO SYSTEM: A FIRST RECORD AND A RANGE EXTENSION OF G. CALLIDUS (SMITH, 1937)

Summary

Recently, a specimen of Glossogobius callidus was collected in the Marico Oog, a major source of the Limpopo River in the western Transvaal. This locality is some 1500 km from the river mouth. Earlier taxonomic confusion of Glossogobius giuris and G. callidus has resulted in the omission of G. callidus from identification keys published before 1979. As a result, that species has not been recorded from the Limpopo system. A previously published record of G. giuris from that system, at a locality about 950 km from the sea, is now shown to be based on a misidentification of G. callidus specimens.