Observations on the larval development of Mystus macvopterus (Bleeker): Bagridae

From June to July 1988, larvae of Mystus macropterus (Bleeker) were obtained by artificial propagation of spawners collected from the Jialing River, China. Larvae grown in water temperatures ranging from 26 to 29°C were fully developed at approximately 20 days. The newly-hatched larvae measured 6.0–7.5 mm t.l. , exceeding the dimensions of any known newly-hatched larvae of freshwater catfishes indigenous to China. Five days after hatching, when the larvae were 11.4 mm t.l. and the prolarval stage was complete, exogenous feeding commenced. Twelve days after hatching, at 18.4 mm t.l. , the yolk sac disappeared, organogenesis was almost complete and the juvenile period began. At 20 days post-hatching, at 23.0 mm t.l. , the lateral line system had formed and the juveniles resembled the adults with respect to all external features, which signalled the end of thejuvenile period. Comparison of the larval development in eight species ofeconomic freshwater catfishes shows that the most significant aspect of the larval development of M. macropterus is the sustained (6–7 days) mixed nourishment period and the early differentiation of organs, which enhances the survival rate of the larvae.     

Developmental analysis of the evolutionary origin of vegetative propagules in Mimulus gemmiparus (Scrophulariaceae)

Mimulus gemmiparus (Scrophulariaceae), a rare endemic of Colorado, has a novel life history that depends on an unusual method of vegetative reproduction. The plants are functionally annuals; however, reproduction is asexual via propagules that have been termed gemmae. The morphological identity and the evolutionary antecedent of these propagules are unclear. We approached this problem through comparative developmental analyses of M. gemmiparus and the presumed progenitor species, Mimulus guttatus. In M. gemmiparus there are two meristems initiated in the axil of each leaf primordium. The distal meristem has the potential to produce either a lateral branch or a flower, and the proximal meristem becomes a vegetative propagule (the gemma) that is ultimately surrounded by an expanded, ensheathing petiole. The first leaves of the propagules are thickened and are the site of nutrient storage. Consequently, these propagules can be characterized morphologically as brood bulbils. Mimulus guttatus also has two meristems in each leaf axil; however, the proximal meristem typically remains dormant and serves no function in the life history of this species. Based on architectural and developmental correspondence, we hypothesize that the propagule of M. gemmiparus is homologous to the proximal meristem of M. guttatus. Comparative analysis shows that evolution of the bulbil has involved both the incorporation of features present in shoots of M. guttatus and the acquisition of novel features.     

中国新纪录种长须拟鳠记述及拟鳠属评述(英文)

记述采自中国广西壮族自治区的北伦河鲿科鱼类1新纪录种,长须拟鳠Mystus gulio(Hamilton,1822)。新纪录种为1小型鲿科鱼类,其主要形态特征如下:背鳍Ⅱ,7;胸鳍Ⅰ,8;腹鳍条11～13;脊椎骨数29～31;胸鳍和背鳍棘后缘呈锯齿状;脂鳍基长不及臀鳍基之半长;眼睛圆形且中等大;尾鳍深叉状,上叶稍长于下叶;上颌须末端达腹鳍基中部。拟鳠属Mystus与其近缘属拟鳠Hemibagrus种类的眼前缘与后鼻孔的距离明显大于两鼻孔间距,为这两属区别于鲿科其他属的形态特征之一。鳠属种类的脂鳍基都较长,一般为臀鳍基的2倍; 拟鳠属种类的指鳍基长度变化较大,或大于臀鳍基长,或短于臀鳍基长; 脂鳍基长度不宜用于鉴别拟鳠属和鳠属。但两属的枕骨和囟门沟的形态差异显著,拟鳠属种类的枕骨宽大,囟门沟短;鳠属种类的枕骨窄小,囟门沟长;该类特征可用于鉴别两属物种。     

诱导大鳍鱯和长吻鮠排卵过程中血清GTH水平的变化

繁殖期从嘉陵江收集性成熟的大鳍■ 和长吻 野生亲鱼,用Ｌｉｎｐｅ方法（即ＬＨＲＨ－Ａ加多巴胺Ｄ２受体拮抗剂地欧酮）或传统的ＬＨＲＨ—Ａ加脑垂体的方法进行催产,定时取血样,用放射免疫方法测定催产过程中血清ＧＴＨ水平的变化,进一步证实鲇形目鱼类ＧＴＨ的分泌受到下丘脑分泌的促性腺激素释放激素ＧｎＲＨ和多巴胺的双重调节;排卵和产卵也是以血清ＧＴＨ的急剧升高为先导的,而最终能否排卵还有赖于血清ＧＴＨ峰是否超过“排卵阈值”。尽管催产后的大鳍 和长吻 雄鱼血清ＧＴＨ水平也有一个高峰出现,但血清ＧＴＨ水平升高幅度都大大低于雌鱼,这种现象在硬骨鱼类可能具有普遍性。     

Population structure of the Southeast Asian river catfish Mystus nemurus

A total of 143 microsatellites were isolated from Mystus nemurus using a 5' anchored polymerase chain reaction technique or the random amplified hybridization microsatellite method, the first set of microsatellite markers developed for the Southeast Asian river catfish. Twenty polymorphic microsatellite loci were used as markers for population characterization of M. nemurus from six different geographical locations in Malaysia (Perak, Kedah, Johor, UPM, Sarawak and Terengganu). The number of alleles per locus ranged from 2 to 11 with 6.3 as the average number of alleles per locus. Characterization of the populations showed relatively high levels of genetic variation compared with previous studies using allozyme markers. The highest genetic similarity was found between Perak and Kedah, while the highest genetic distance was found between Terengganu and Kedah. The majority of clustering was in accordance with geographical locations and the histories of the populations. Microsatellite analysis indicated that the Sarawak population might be genetically closer to the Peninsular Malaysian populations than has been previously shown by other molecular marker studies.     

Within and between generation phenotypic plasticity in trichome density of Mimulus guttatus

Mimulus guttatus (yellow monkeyflower) frequently produce glandular trichomes, a trait that may resist herbivory. Constitutive production of trichomes is variable both within and among populations of M. guttatus and most of this variation is genetic. This study demonstrates that damage on early leaves can induce increased trichome production on later leaves, a plastic response that is likely adaptive. Moreover, this study shows that this induction can be maternally transmitted, increasing trichome density in progeny before they experience herbivory. This transgenerational response must involve a yet undescribed epigenetic mechanism. These experiments also show genetic variation among plants in the capacity for both within and between plant generation induction. Despite the clear evolutionary importance of variation in constitutive and induced herbivory-resistance traits, few other studies have noted genetic variation in both within a plant species.     

大鳍促性腺激素分泌调控的研究

用非洲鲶鱼促性腺激素放射免疫测定方法测定了科鱼类样品中的促性腺激素含量。用这种方法和鲤鱼促性腺激素β亚基放射免疫测定法测定大鳍同一批血清样品结果也相当吻合。通过注射促黄体素释放激素类似物和／或多巴胺的Ｄ２受体拮抗剂地欧酮后,定时取样测定血清促性腺激素含量,证明大鳍促性腺激素的释放同时受到下丘脑分泌的促性腺激素释放激素和多巴胺的双重调节。但是,多巴胺只能抑制由促性腺激素释放激素诱导的促性腺激素分泌,而不能直接抑制基础的促性腺激素分泌,这与非洲鲶鱼相似而与金鱼和鲤鱼等鲤科鱼类明显不同。     

大鳍鳠鱼体能量密度及其预测模型

于2000年11月至2001年10月由嘉陵江收集野生大鳍鳠成鱼100尾,其中冬季(12月)、春季(3月)、繁殖前(6月)、繁殖后(8月)、秋季(10月)雌雄各10尾。测定了这10个样本的鱼体能量密度及生化组成。统计分析结果表明：鱼体各生化成分含量,能量密度的性别间差异在各个季度均不显。在雌性群体中,秋季样本的蛋白质含量(16．23％),脂肪含量(5．84％),干物质含量(26．67％)和能量密度(6．14kJ／g)显高于其余各样本的相应指标。春季样本中鱼体脂肪含量和能量密度最低(2．39％,4．55kJ／g)。在雄性群体中,秋季样本的蛋白质含量(16．34％)与能量密度(5．85kJ／g)最高;春季样本中脂肪含量(1．3l％)、干物质含量(22．49％)、能量密度(4．16k．J／g)最低。各样本能量密度均分别与干物质和脂肪含量呈显的直线相关关系。通过协方差分析,将雌性群体中冬季、春季、秋季以及繁殖后样本共4个样本的能量密度与干物质含量的公共回归方程作为以干物质含量(D)预测大鳍鳠雌性群体在非繁殖期能量密度(E)的预测模型：E=-5．573 0．437D;将繁殖前雌性样本的能量密度与干物质含量的回归方程作为预测大鳍鳠雌性群体在繁殖期的能量密度的预测模型：E=-0．605 0．250D;将冬季、春季、秋季以及繁殖后雄性4个样本的能量密度与干物质含量的公共回归方程作为预测大鳍鳠雄性群体在非繁殖期的能量密度的预测模型：E=-6．046 0．456D;将繁殖前雄性样本的能量密度与干物质含量回归方程作为预测大鳍鳠雄性群体在繁殖期的能量密度的预测模型：E=-3．64 0．366D。     

Effect of hydrogen sulphide on liver somatic index and Fulton's condition factor in Mystus nemurus

The growth rate and liver somatic index were significantly ( P <0.05) lower in Mystus nemurus exposed to hydrogen sulphide compared to controls. These differences increased with corresponding increases in hydrogen sulphide concentrations. No significant differences ( P >0.05) in Fulton's condition factor were detected between the exposed fish and the controls. The results revealed that liver somatic index is a more sensitive indicator of hydrogen sulphide toxicity compared to Fulton's condition factor.