Intertidal distribution of infauna in a central California lagoon: the role of seasonal blooms of macroalgae

This study examined the roles of seasonal blooms of green algae, Ulva expansa (Setchell) Setchell et Gardner, and biotic disturbance by burrowing ghost shrimp, Callianassa gigas Dana, and foraging rays, on the intertidal distributions of a phoronid, Phoronopsis viridis Hilton, and a tellinid bivalve, Macoma nasuta (Conrad). Algal removal experiments in 1984 and 1986 demonstrated that heavy seasonal algal cover in the lower zone significantly reduced the abundances of both Phoronopsis and Macoma. Growth of Macoma transplanted into the algal zone was significantly lower in plots with algal cover than in plots regularly cleared of algae. Algal cover did not significantly affect early recruitment of either Phoronopsis or Macoma. Neither ghost shrimp nor rays appeared to reduce the abundances of phoronids or clams, although ray disturbance did result in a significant increase in the proportion of phoronids regenerating dorsal body parts. These results indicate that seasonal algal blooms are capable of producing discrete patterns of infaunal distribution in intertidal sedimentary habitats.     

THE EFFECT OF A HORN SNAIL ON ULVA EXPANSA (CHLOROPHYTA): CONSUMER OR FACILITATOR OF GROWTH?1

To determine whether California horn snails are more likely to be consumers or facilitators of Ulva expansa (Setch) S. & G. growth in estuaries, we conducted manipulative experiments that evaluated algal growth and the movement of N between the water column, algal tissue, and, in the second experiment, sediments. Algae grew poorly in the absence of sediments, drawing on their own sequestered N supplies (3.5% of dry weight reduced to <2%) and N released by snails and by depleting inorganic N in the water column. There was no evidence of consumption when snail densities ranged from 0 to 900.m^?2 (0, 3, 6, and 9 per aquarium), as algal growth was similar for all snail densities, and snail lengths did not increase during the 21–d experiment. when sediment was provided, N was depleted in the sediment and enhanced in the algal tissue. As in the first experiment, the water column was depleted of inorganic N and enriched with organic N, mostly in the dissolved form. Because both snails and macroalgae often dominate the shallow waters of southern California's lagoons and estuaries, our evidence that the snails are primarily facilitators of algal growth (via transfer of N from sediments to the water column) suggests that snails may play an important role in both food web and N dynamics.     

扩张莫尼茨绦虫(圆叶目:裸头科)精子的扫描结构

自Gresson 1962在Nature上报道了绦虫的精子发生及结构以来,至今已报道了近70种绦虫的精子结构。法国Justine（1991,1995,1998）对寄生动物的精子结构有较深人的研究,并对寄生扁虫的精子结构及其系统学意义有相关综述,对绦虫精子的系统学特征研究中,概述了11个目、43属、56种真绦虫精子结构的相关信息,不仅从精子的结构,而且从精子的发生过程来研究其系统意义,归结出真绦虫的一些共源性状如：绦虫的成熟精子中缺乏线粒体并且存在冠状体结构;     

Biosynthesis of ribosome-inactivating proteins from callus and cell suspension cultures of Mirabilis expansa (Ruiz &Pavon)

 Callus and cell suspension cultures from the little known Andean crop Mirabilis expansa were developed and maintained on Murashige and Skoog medium supplemented with 2,4-dichlorophenoxyacetic acid (1 mg/l) and kinetin (0.1 mg/l). Callus and cell suspension cultures were screened with antibodies raised against ME1 (27.5 kDa) and ME2 (27 kDa), two ribosome-inactivating proteins (RIPs) previously found in roots of M. expansa. A 29-kDa protein found in callus and cell suspensions reacted strongly with ME1 antibodies. The 29-kDa protein, named MEC, was purified to homogeneity by ammonium sulfate precipitation and cation exchange perfusion chromatography. Amino acid N-terminal sequencing revealed close homology between MEC and ME1. The MEC amino acid sequence examined was highly conserved among RIPs from widely different sources. This new RIP was immunolocalized to the cell walls of callus and cell suspension cultures. Received: 20 August 1999 / Revision received: 10 December 1999 / Accepted: 21 December 1999     

Sulla posizione sistematica di Euphrasia marchesettii Wettst

Abstract

On the systematic position of Euphrasia marchesettii Wettst. B. marchesettii Wettst. is generally considered as a hybrid between E. kerneri Wettst. and a not well mentioned species of subsect. Angustifoliae. Some ecological and phenological observations rouse a doubt on this interpretation and suggest the hypotesis that E. marchesettii may have a common origin with E. kerneri. Its differentiation could be possibly due to specialization in wet communities. A morphometric study was carried out to compare E. marchesettii with its possible ancestors out of subsect. Ciliatae and Angustifoliae. The results of this study show that the highest morfological affinity of E. marchesettii is with E. kerneri; consequently it should be included in subsect. Ciliatae.     

Experimental studies on the cadmium accumulation in the cestode Moniezia expansa (Cestoda: Anoplocephalidae) and its final host (Ovis aries)

The tapeworm Moniezia expansa and naturally infected sheep were investigated with respect to their cadmium accumulation. Cadmium chloride (CdCl₂, 0.2 g) was added to 10 ml of distilled water and administered orally to the sheep every day for a period of 1 week. The cadmium content of M. expansa was lower than that in the liver tissues of sheep, although this difference was not significant. The highest mean cadmium concentrations were found in the liver of sheep infected with M. expansa (24.5 ± 11.5 mg kg⁻¹ dry weight). The mean cadmium concentration measured in M. expansa was 21.5 ± 19.2 mg kg⁻¹ dry weight, which was 31 and 1.5 times higher than levels determined in the muscle and kidney of the host, respectively, but 0.9 times lower than levels determined in the liver of host. Sheeps with M. expansa infection always had higher cadmium concentrations in the tissues (with the exception of the blood) than their uninfected conspecifics.     

扩张莫尼茨绦虫(绦虫纲:圆叶目)卵黄细胞发育的超微结构

用透射电镜观察了扩张莫尼茨绦虫(Moniezia expansa)卵黄细胞发育的全过程。扩张莫尼茨绦虫卵黄细胞发育的规律为：(1)细胞体积不断增大;(2)质、核比不断增加而核体积几乎不发生改变,核表面从规则变为不规则,再由不规则变为规则,核内出现染色质浓缩成小块再分散的发育变化过程;(3)线粒体逐渐增多,发育不断完善;(4)粗面内质网及高尔基复合体出现由少到多,发育不断完善,再由多到少不断退化的变化;(5)由高尔基复合体组装的电子致密的小卵黄囊不断融合,至卵黄细胞成熟时仅有一卵黄囊,占据细胞大部分体积[动物学报49(2)：256—261,2003]。     

扩张莫尼茨绦虫(圆叶目:裸头科)精细胞分化、精子形成及精子形态

本项研究应用光学显微镜、扫描和透射电子显微镜,观察了扩张莫尼茨绦虫的精细胞分化、精子形成全过程及精子的精细结构。扩张莫尼茨绦虫的精细胞分化过程为：1)初级精原细胞主要发生于幼节的睾丸滤泡中;2)次级精原细胞发生不完全分裂形成16个细胞一簇的初级精母细胞群,以共同的中央细胞质相连;3)初级精母细胞的特征为细胞核中出现联会复合体结构;4)紧接着的第二次成熟分裂,产生64个由中央细胞质相连的细胞核较小的精细胞。精子形成始于精细胞中分化区的形成,成熟精子缺乏线粒体,具有质膜和冠状体、1—4个领域排布的质膜下皮层微管,细胞质中存在电子致密的颗粒状物质,具一个不规则形态的细胞核,具有“9 1”类型的轴丝构造,缺乏轴丝周围鞘。从精子的纵切面上可将精子区分为5个区段(Ⅰ一Ⅴ区)。在精子形成过程中,中心粒基部出现螺旋形小根结构在寄生虫中为首次报导;成熟精子具有游离鞭毛,在绦虫中为首次发现[动物学报49(3)：370—379,2003]。     

转化生长因子β1免疫反应阳性物在扩展莫尼茨绦虫体内的分布

用免疫组化SABC法研究了转化生长因子 β1免疫反应阳性物在扩展莫尼茨绦虫成熟体节内的分布。结果表明 :转化生长因子免疫反应阳性物广泛分布于扩展莫尼茨绦虫成熟体节内。扩展莫尼茨绦虫成熟体节的组织结构包括被膜与实质两部分 ;实质被肌层分为外部的皮质与内部的髓质 ,在皮质内有节间腺、肌细胞、神经细胞、排泄 (焰 )细胞等 ;髓质内主要是卵 ,包于卵外的生殖管道 ,以及管道间的连结组织。免疫组化染色显示节间腺、被膜、卵及子宫壁呈强阳性着色 ,光密度测定结果分别为 0 2 70 5± 0 0 80 4 ,0 2 4 5 5± 0 0 4 17,0 4 6 38± 0 0 6 0 3,0 0 373± 0 0 6 13。皮质区与髓质区均有弥散阳性反应产物。表明转化生长因子在扩展莫尼茨绦虫体内广泛分布 ,介导虫体生长及实现其适应寄生生活