The production dynamics and trophic basis of 7 dominant species of chironomids were investigated in the area of a second-order river of the Hanjiang River basin, in central China from June 2003 to June 2004. The results showed that Tvetenia discoloripes was by far the most abundant chironomid, dominating the overall standing stock of the taxa. In terms of life cycle, Chaetocladius sp., Eukiefferiella potthasti and T. discoloripes developed 1 generation a year, whereas Microtendipes sp. and Pagastia sp. developed two, while Pentaneura sp. and Polypedilum sp. developed three. T. discoloripes was the most productive chironomid with 120.305 8 g/m2.a, Pentaneura sp. and E. potthasti had relatively high production values of >17 g/m2.a, and the rest were <10 g/m2.a. All the production temporal variation tended to follow biomass patterns. T. discoloripes, Chaetocladius sp. and Pagastia sp. concentrated most of their production in winter, whereas E. potthasti, Pentaneura sp. and Polypedilum sp. had relatively higher production throughout the year. Only Microtendipes sp. had a production that peaked in summer. The overlap in temporal distribution of production among the chironomid species was generally high (>0.5), especially for filter-collectors Microtendipes sp., Chaetocladius sp., Chaetocladius sp., T. discoloripes and Pagastia sp. All species except Pentaneura sp. consumed a large portion of amorphous detritus, constituting more than 90% of their diets, and contributing nearly 90% to their secondary production. All the 7 chironomids represent obvious adaptation to local highly variable climate in summer and autumn in life cycle pattern, production dynamics, and food type.
Mayflies constitute a major part of macroinvertebrate biomass and production in lotic ecosys- tems, and play an important role in material cycle and energy flow. There are more than 250 species of may- flies in rivers and streams of China. In order to learn their ecological functions, an investigation on life cycle, production and trophic basis of dominant species of mayflies in a second-order branch of Hanjiang River basin, Hubei, China was carried out during June 2003 to June 2004. The results showed that the dominant mayfly species Epeorus sp. and Caenis sp. developed two generations per year; in term of Epeorus sp., pupation mainly occurred in spring and then from late summer to early autumn, while Caenis sp. pupated in spring and autumn. The abundance and biomass of the Epeorus sp. population peaked twice (1 226 ind/m2, 3.142 5g/m2) in April and June. Caenis sp. also had two peaks (307ind/m2, 1.590 g/m2), but in February and June. Cohort production and cohort P/B ratio of Epeorus sp. were 161.009 g/m2 wet weight and 7.7, respectively, and an- nual production and P/B ratio were 267.46g/m2.a wet weight and 15.4, respectively; cohort production and P/B ratio of Caenis sp. were 26.7995g/m2 wet weight and 4.7, its annual production and P/B ratio were 53.60 g/m2.a wet weight and 9.4, respectively. For Epeorus sp., the proportions contributing to secondary production of the main food types were: amorphous detritus, 33.46%; fungi, 10.83%; vascular plant detritus, 1.80%; dia- toms, 53.90%; for Caenis sp., the proportions were 70.79%, 6.90%, 3.52% and 18.77%, respectively.
Starvation metabolism is one of the important parts of respiration for normal activities of chironomids. During April 1996 to March 1997, the relationships of starvation metabolism and tempera-ture, body weight of two common chironomids in Biandantang Lake were carefully investigated. The re-sults showed relationship between starvation metabolism (R, mgO2/ind.d) and body weight (Ww, mg wet wt) was: Chironomus plumosus, lgR=-2.573+1.021lgWw (5℃), lgR=-2.710+1.354lgWw (10℃), lgR= -1.824+0.823lgWw (15℃), lgR=-1.364+0.442lgWw (20℃), lgR=-2.763+1.517lgWw (25℃); and Tokuna-gayusurika akamusi, lgR=-2.390+0.752lgWw (5 ℃ ), lgR=-1.978+0.710lgWw (10 ℃ ), lgR=-1.676+ 0.648lgWw (15℃), lgR=-1.517+0.650lgWw (20℃), lgR=-2.434+1.290lgWw (25℃). Relationship of starvation metabolism and temperature (T, ℃) was: C. plumosus, R = -0.051 + 0.021T -0.0006T2 ; T. akamusi, R= -0.051 + 0.021T -0.0006T2. The complex relationship of the three parameters was: C. plu-mosus, R=0.0098Ww0.3882e0.1068T; T. akamusi, R=0.0012Ww1.1936e0.0711T. With the above regressions, the estimated annual starvation metabolisms of the two chironomid species in Biandantang Lake were: C. plumosus, 24.2791 kJ/m2.a; T. akamusi, 8.7864 kJ/m2.a, respectively. This provides a firm foundation for the comparative study of bioenergetics of the chironomids.
大型底栖动物在河流生态系统中发挥着重要作用,2003年6月至2004年6月间对汉江流域2级河流——黑竹冲河大型底栖动物群落优势种类的生产力进行为期1周年的调查研究,结果表明,主要优势种杂色特维摇蚊(T veten ia d iscolorip es G oet-ghebuer)和波特真开氏摇蚊(E uk ieff eriella p otthasti L ehm ann)的生活史均为1年1代。杂色特维摇蚊种群现存量在1年中出现1次峰值,波特真开氏摇蚊则出现3次。采用龄期频率法(instar-frequency m ethod)测算的周年生产量分别为:杂色特维摇蚊,120.3058g/(m2.a),P/B为10.5;波特真开氏摇蚊,17.7554g/(m2.a),P/B为11.4。两种摇蚊的生产量动态在时间上重叠程度较大,比例相似性系数达0.63,重叠现象主要发生在冬春季节。杂色特维摇蚊前肠内含物中,无形态碎屑、真菌和硅藻所占平均比例为95.81%,0.52%和3.67%;对生产量的贡献率分别为87.56%,2.38%和10.06%;波特真开氏摇蚊前肠内含物中,无形态碎屑、真菌和硅藻所占比例分别为93.48%,0.68%和5.84%,对生产量的贡献率分别为:81.71%,2.97%和15.32%。
