STUDIES ON THE GIANT KELP,MACROCYSTIS. II. REPRODUCTION

Neushul , M. (U. Washington, Seattle.) Studies on the giant kelp, Macrocystis. II. Reproduction. Amer. Jour. Bot. 50(4): 354–359. Illus. 1963.—The reproduction of Macrocystis pyrifera was studied in the sea and in the laboratory. The estimated minimum time needed for the completion of the sexual life history of Macrocystis pyrifera in La Jolla, California, is from 12 to 14 months. Young sporophytes begin fruiting when they have from 4 to 8 stipes and a somatic frond weight of from 8 to 10 kg. The behavior of abscised sporophylls in laboratory tanks, as well as their morphology and coloration, strongly suggests an interrelationship between the translocation of photosynthetic products and fructification.     

对自然杂志发表的一篇文章的评注

最近自然杂志(Nature,432:383—386,2004)发表了Chengetal.的文章,首次报道了胡氏贵州龙的生育模式、性双形和可能胎生的证据,这无疑是非常重要的,但认为产胡氏贵州龙的竹杆坡组的时代为中三叠世,这与近年来牙形刺的研究结果不符。牙形刺的研究已充分证明竹杆坡组的时代为晚三叠世的早期(卡尼期)(王成源等,1998;Chen&Wang,2002),比以前认为的时代要晚出现大约一千万年。     

5. BIRDS ON RIETFONTEIN FARM,LOOP SPRUIT VALLEY

Randall, R. M. &; Randall, B. M. 1981. Roseate Tern breeding biology and factors responsible for low chick production in Algoa Bay, South Africa. Ostrich 52:17-24.

Roseate Terns Sterna dougallii were studied in 1977 on St Croix Island, Algoa Bay, South Africa. They are winter breeders in Algoa Bay and remain away from the breeding islands until about three weeks before the first eggs are laid. Full breeding dress is usually attained by the time the chicks hatch, when red appears on the culmen. Reasons are given for regarding the red culmen as an intraspecific aggressive signal. Nest density was 0,2/m² with a mean nearest neighbour distance of 0,66 m ± 0,27 m. Mean size of first clutches was 1,32 eggs, of replacement clutches was 1,03 eggs. Eggs measured 42,1 mm (39,8-44,5 mm) x 30,1 mm (28,6-31,5 mm). In clutches of two eggs, first eggs had significantly larger volumes than second eggs. Incubation took about 25 days and one of the pair did most of the incubating. Rearing took less than 28 days and all the terns had left the island a week after the last chick first flew. Human disturbance, gull predation, intraspecific aggression, and rain were factors contributing to the low production of 33 flying young in 1977. An estimated production of 79 flying young was calculated as necessary to maintain the population of 74 breeding pairs.     

重庆地区鲫外寄生车轮虫形态分类学研究及一新种的描述(英文)

在对重庆地区进行鱼类寄生虫学的调查过程中,从鲫鳃表获得3种隶属于车轮虫属Trichodina Ehrenberg,1830的外寄生车轮虫,其中含一新种,短棘车轮虫Trichodina brevicirra sp.nov,其典型的鉴别性特征为其短细的齿棘。另外两种车轮虫分别为沃玛车轮虫Trichodina ngoma Van As&Basson,1992与网状车轮虫Trichodina reticulata Hirschman&Partsch,1955;沃玛车轮虫为亚洲新记录种。文章对网状车轮虫的3种群进行了详尽的比较讨论研究,尽管该三种群间存在着细微的种群内差异,但网状车轮虫的典型特征则显而易见地存在于三种群间,即为附着盘中央具有8-16个球状或卵圆形的中央颗粒。       

鲫鱼寄生车轮虫一新种的研究

本文记述了寄生在鲫鱼(Carassius auratus)体表和鳃上一种新的车轮虫(Trichodina carassii sp.nov.),虫体直径70(54.6—80.4)μm,附着盘直径58(51.6—67.2)μm,齿环直径32(27.0—36.2)μm,齿体25—30个,齿环中央有7—14个旧齿体残余物形成的颗粒结构。大核马蹄形。小核短杆状,在大核一端的外侧,其位置略有变动。口沟390—400°。齿钩镰刀状,齿棘较直,侧面具有若干个缺刻,末端钝圆或平截,近锥体的后方有一个不太明显的小突起。       

COLONIZING PLANTS ON THE PUMICE PLAINS,MOUNT ST. HELENS,WASHINGTON

Initial colonization on the devastated Pumice Plains on the northern flank of Mount St. Helens, Washington, was monitored in two large grids seven seasons after the eruptions of 1980. The Pumice Plains is composed primarily of deep pumice, but contains a few large mudflow channels and numerous small erosion gullies. Over 45% of 1,600 10 by 10 m quadrats (Willow Spring site) and over 35% of 875 quadrats (Lupine Patch site) were devoid of vascular plants. The most common species were the weedy natives, Anaphalis margaritacea and Epilobium angustifolium, as well as Lupinus lepidus var. lobbii, a native with poor dispersal usually found at subalpine elevations. The first two species invaded by long-distance dispersal; a few individuals of the latter somehow established by 1981 from surviving rootstocks or seeds, and dense populations have developed from these survivors. Other species are typically found at low densities in favorable microsites. Species richness averaged 1.03 per 100 m² at Willow Spring and 1.82 at Lupine Patch. There are 32 species at Willow Spring and 26 at Lupine Patch. Species richness was concentrated in sites with high soil moisture and where topographic irregularities permitted accumulation of seeds. Colonists are an unusual mix of natives, drawn from an array of open habitats, and introduced weeds originating in fields and clearcuts at lower elevations. Colonizing species are primarily herbaceous, perennial, and wind-dispersed, though seedlings of woody “climax” species occur. Three distributional patterns are recognized: hydrophiles, found near streams; facultative hydrophiles, concentrated in wet sites but successfully colonizing upland sites; and species distributed at random or in xeric sites. We predict that the course of succession will continue to be slow and herbs-dominated. Patches of Lupinus lepidus at present do not appear to facilitate colonization. Colonists will continue to be rare and be confined to favorable microsites for several years.     

CYTOGEOGRAPHIC STUDIES ON NORTH AMERICAN ASTERS. I. RANGE SURVEYS OF VIRGULUS ADNATUS,V. CONCOLOR,V. GEORGIANUS,V. GRANDIFLORUS,V. NOVAE-ANGLIAE,V. OBLONGIFOLIUS,V. PATENS,AND V. WALTERI

Chromosome number determinations from 118 populations of eight species of the aster genus Virgulus are reported for the first time. Based on these counts and literature reports the geographic distributions of diploids and tetraploids in V. concolor, V. novae-angliae, V. oblongifolius, and V. patens have been determined. In the first three species, diploids were widely distributed, while tetraploids were more restricted. In V. patens, diploids were restricted to the southwestern portion of the species’ range, while tetraploids were found throughout the range. Both V. adnatus and V. walteri were found only at the tetraploid level throughout their ranges. Two other species with restricted distributions were consistently found to be high level polyploids: V. georgianus with 2n = 50, V. grandiflorus with 2n = 60. The following new combinations are listed: Virgulus georgianus (Alexander ex Small) Semple; Virgulus subsect. Brachyphylli (Torr. & Gray) Semple; and Virgulus sect. Polyliguli (Semple & Brouillet) Semple.