留言板

尊敬的读者、作者、审稿人, 关于本刊的投稿、审稿、编辑和出版的任何问题, 您可以本页添加留言。我们将尽快给您答复。谢谢您的支持!

姓名
邮箱
手机号码
标题
留言内容
验证码

2004年  第25卷  第3期

显示方式:
研究论文
To date,there still is lack of a general consensus regarding the phylogenetic relationships of three living orders of amphibian among herpetologists.The most widely accepted hypothesis is the monophyletic origin in the class Amphibia,which proposed a sistergroup relationship between Caudata and Anura (the Batrachia hypothesis) to the exclusion of the Gymnophiona.However,the phylogenetic relationship among living amphibians is still a controversial issue.The complete nucleotide sequence of the mitochondrial genome of Fejervarya limnocharis was detailedly compared with those of 6 other amphibians.The nucleotide sequences of 22 tRNA encoded by 7 amphibians mitochondrial genomes were combined and aligned to the homologous sequences of the 11 veterbrate taxa.Teleosts selected as outgroup,the phylogenetic analyses results show that MP and ML trees all strongly support the monophyly of living amphibians with respect to other living tetrapods and favor a sister group relationship for caecilians and urodeles.Robustness of our results was confirmed by high bootstrap support of all nodes in the trees.This result contradicts the Batrachia hypothesis,and is consistent with Bolt s hypothesis (1991) basing on the morphological data.The result was also supported by previous molecular studies based on the data from mitochondrial and nuclear rRNA genes.In addition,the reason for our result inconsistent with previous works and the shortcomings of phylogenetic analyses based on the complete mitochondrial genomes were also discussed.
In order to study the effect of weak noise on the sound signal extraction of mouse (Mus musculus Km) inferior collicular (IC) neurons from environments,we examined the changes in frequency tuning curves (FTCs) of 32 neurons induced by a weak noise relative to 5 dB below minimum threshold of tone (reMT-5 dB) under free field stimulation conditions.The results were as follows:1) There were three types of variations in FTCs,sharpened (34.4%),broadened (18.8%),and unaffected (46.9%),nevertheless,only the alteration of sharpened FTCs was statistically different.2) Sharpness of frequency tuning induced by a reMT-5 dB noise was very strong.Q10 and Q30 of FTCs were increased by (34.42±17.04)% (P=0.026,n=11) and (46.34±22.88)% (P=0.009,n=7).3) The changes of inverseslopes (Iss,kHz/dB) between high (Ishigh) and low (Islow) limbs of FTCs were dissymmetry.The Ishigh of FTCs decreased markedly (P=0.046,n=7),however,there was little change (P=0.947,n=7) in Islow.Our data revealed for the first time that the weak noise could sharpen frequency tuning and increase the sensitivity on the high frequency of sound signal in IC neurons of mouse.
We investigated nest-site characteristics and reproductive season changes of horned larks (Eremophila alpestris) and small skylarks (Alauda gulgula) during three periods from Apr.to Sep.in 2000-2002 at Haibei Alpine Meadow Ecosystem Research Station,the Chinese Academy of Sciences,in northern Qinghai Province.Nests of horned lark (n=27) and small skylark (n=43) were used to eximined nest-site characteristics.We used stable isotopes to determine the dietary contributions ratio of raise nestling,and compare nest-site characteristics and overlap degree of diet of horned lark and small skylark.The result shown:1)there was significantly difference between the exoteric degrees of nests in horned lark and small skylark (P<0.01),which were 92.16% and 34.61%,respectively.2)the number of distance to nearest structural element of horned lark (0.07±0.26) was significantly lower than that of small skylark (2.57±1.19)(P<0.01).3)the vegetation height and the percentage of vegetation cover of nest-site of small skylark were significantly higher than those of horned lark(P<0.01).4)the food resource,reproductive season length and reproductive frequency largely overlapped in these two species.There is a balance between cost and benefit of horned lark and small skylark in nest-site selection.It is possible that predation and thermal consideration have guided the evolution of nest-site selection of two species,and the coexistence mechanism of them is nest-site differentiation.
Phylogenetic relationships of 8 genera of Megophryidae (Anura) were discussed based on 25 partial sequences of mitochondrial 16 S rRNA gene.Maximum likelihood,maximum parsimony,and neighbor joining analyses were performed on the dataset.The ingroup was divided into two major clades,Clade 1 and Clade 2,on the gene tree.Clade 1 included Megophrys,Brachytarsophrys and Atympanophrys,while Leptolalax,Oreolalax,Scutiger,Leptobrachium and Vibrissaphora belonged to Clade 2.This met the result of morphological study.It was primarily estimated that the divergence age of two clades occurred 14.2-18.7 million years ago.The topology of Clade 1 did not support Megophrys to be a monophyletic group.In Clade 2,Leptolalax was believed to be a valid genus and was the taxon that occurred much early.
Flush distance,how close one can get to a bird before it flushes,reflects the adaptation of birds to human intrusion.A larger flush distance indicates a lower adaptation to human intrusion.To examine the patterns of the adaptation of birds to human intrusion and its influencing factors,9 dominant and widely-distributed species were selected among 42 species surveyed in Hangzhou,China from September 2002 to January 2003.Based on the differences in vegetation type,building index and disturbance degree,habitats were divided into 5 categories:building areas,urban woodlots,western mountains,ponds and farmlands.Four variables reflecting biological traits of birds (body size,activity height,migratory status,conspicuousness) and one habitat variable (visibility of observation point) were selected to examine their influence on flush distance.We found that:1)The degrees of human intrusions in 5 habitats were significantly different.2)There were significant differences in the flush distance of 9 species among different habitats.Generally,the flush distance was negatively associated with human intrusion.3)The analysis of bivariate correlation showed that flush distance was positively associated with body size and the visibility of observation point,but it was negatively associated with activity height.However,there was no significant association between the flush distance and the conspicuousness of birds.Our results indicated that most species had adapted to human intrusions to some extent,and that the birds with larger body,or those occurred in the habitats with higher visibility or closer to the ground had relatively lower adaptation to human intrusions.
The K value of negative binomial distribution less affected by density was chosen to describe the spatial and temporal patterns of the natural population of Cicadulina bipunctella (Mats) at three elevations.Spatial distribution information of the population showed either clumped (aggregated) or uniform patterns during the period of maize growth.The population of C.Bipunctella distributed uniformity (K<0) at the last twenty days in April,and spatial aggregation (K>0) in May,then dispersal (K<0) from the first ten-day period to the middle ten days of June and aggregation (K>0) again from the last ten-day period of June to the first ten-day period of July.The high elevation had the highest degree of aggregation in May,followed by the low elevation from the last ten-day of June to the first ten-day of July according to the K values.Based on the coefficients of Taylors power law and Iwaos M*-X regression,the degree of aggregation of the high elevation and the middle elevation were higher than the low elevation during the whole period of maize growth.
A blind loach Triplophysa tianeensis sp.nov.(Holotype:KIZ 200301003,59.2 mm SL) has been recognized on basis of collections from an underground river of Hongshuihe in Tiane County,Guangxi,China,January 2003.Triplophysa tianeensis is closely related to T.gejiuensis,T.shilinensis,T.aluensis and T.nandanensis.It can be distinguished from T.gejiuensis and T.shilinensis by following characters:posterior end of pelvic fin not reaches anus vs.reaches;branched caudal fin rays 16 vs.14-15.Triplophysa tianeensis can be further identified from T.aluensis by following characters:dorsal fin origin at the middle point of the body vs.dorsal fin origin closer to snout tip than to caudal fin base;dorsal fin origin posterior of pelvic fin origin vs.dorsal fin origin anterior of pelvic fin origin;anus very close to anal fin origin vs.anus some distance from anal fin origin.Triplophysa tianeensis is most closely related and sympatric to T.nandanensis,but it can be easily distinguished from T.nandanensis by following characters:branched dorsal fin ray 7 vs.8,branched dorsal fin ray 9 vs.10-11;branched pelvic fin ray 6 vs.7;distal margin of dorsal fin truncate vs.emarginate;dorsal fin origin posterior of pelvic fin origin vs.anterior of.Furthermore,T.tianeensis has more prominent cave-dwelling features than T.nandanensis:eye highly degenerated,eye diameter 16.8-32.8 (25.0) times in head length vs.eye small but not degenerated,eye diameter 4.7-9.0 (7.5) in head length;without pigment on body and fins in large individuals vs.with densely cloudy blotches on head and body and with spots on fins.
To better understand stable isotope enrichment and metabolism of small mammals and to provide alternative for their dietary information analysis,a controlled feeding experiment was conducted on plateau pikas (Ochotona curzoniae) with mixture of flours of corn (C4 plant),millet (C4 plant) and mung bean (C3 plant).Muscles of back legs were collected from plateau pikas for stable isotope analyses after 40 days artificial feeding.The results demonstrated that stable carbon and nitrogen isotopes showed great variations after introduction of artificial food.Stable carbon isotope ratios of treatment groups became less negative compared with the control [(-19.05±0.09)‰ to (-24.66±0.42)‰] and showed great differences (t=-31.528,df=6,P=0.000).Stable nitrogen isotope ratios of treatment groups were a little bit positive compared with the control [(3.61±0.32)‰ to (3.28±0.13)‰] (t=1.427,df=7,P=0.197).Fractionations of stable carbon and nitrogen isotopes between plateau pikas muscles and their diets were 4.73‰ and 2.79‰ respectively.Introduction of C4 food had strong effect on stable isotope metabolism (especially for stable nitrogen isotope) of plateau pikas.Turnover rate of stable carbon and nitrogen isotopes for plateau pikas might be much more than forty days as respected.
We examined mitotic chromosomes of three newly found members of the Drosophila obscura species group,D.luguensis,D.dianensis and D.limingi from Yunnan and compared their karyotypes to those of respective related species.D.luguensis possessed a diploid number of 12 chromosomes,comprising 3 pairs of metacentrics (V-shaped),2 pairs of acrocentrics (rod-like) and 1 pair of micro-chromosomes (dot-like).Both the X and Y were metacentrics.D.dianensis and D.limingi possessed a diploid number of 10 chromosomes,comprising 1 pair of large V-shaped,1 pair of moderate-sized V-shaped,2 pairs of submetacentric (J-shaped) chromosomes,and 1 pairs of dot-like chromosomes,with their X chromosomes were J-shaped and Y chromosomes were short rod-like ones.Based upon the results of chromosomal comparisons,geographic information of the sinobscura subgroup,as well inter-specific phylogenetic relationship deduced elsewhere,D.luguensis was considered to retain an ancestral form of the karyotype within this subgroup.The present observations have also implied that D.sinobscura (2n=12:2V,1J,2R,1D) might have derived from a sub-lineage of a pre-"sinobscurahubeiensis" lineage by pericentric inversion of moderate-sized metacentric autosomes and D.hubeiensis (2n=10:4V,1D) from another sub-lineage of the same lineage by centric fusion of 2 pairs of acrocentric autosomes.Similar chromosomal changes of centric fusion,centric fission and/or pericentric inversion might have occurred during the course of species divergences between D.dianensis and D.subsilvestris (2n=12:3V,2R,1D),an European member closely related to D.dianensis,and between D.limingi and D.tsukubaensis (2n=12:3V,2R,1D),an East Asian member near to D.limingi.
Total RNA was isolated from pituitary of grouper (Epinephelus coioides),and SMART cDNA was synthesized from 50ng RNA.Two genes in the growth hormone/prolactin family were cloned from SMART cDNAs plasmid library.The growth hormone (GH) cDNA contains 938 bp and encodes 204 amino acids (aa).The prolactin (PRL) cDNA contains 1429 bp and encodes 212 aa.The deduced aa sequences of grouper GH,PRL and SL were compared with those of other eight species.Average genetic distances and a dendrogram showing the hierarchical structure of affinity among different nine fishes were implemented in Mega 2 and CLUSTAL W1.64 b.Branch and bound strap analysis (1000 replicates) were performed and the degree of support for particular nodes were produced.The three phylogenetic trees drawn from the whole aa sequence of GH,PRL and SL were almost identical,Epinephelus coioides,Perca flavescens,Sparus aurata and Paralichthys olivaceus were clustered into one group,Oncorhynchus keta and Oncorhynchus mykiss were clustered into one group,Carassius auratus and Ictalurus punctatus were clustered into one group,while Anguilla japonica alone was clustered into another group.Alignment of the deduced aa sequence and the phylogenetic tree based on GH/PRL/SL showed the same clustering as the present hierarchy of fish and a higher conservation of SL than GH and PRL among various fish species is suggested in this text.Although there is only 24%-31% identity between the three hormones overall,the C-terminal region shows a higher identity.Grouper SL appears to be more closely related to GH (30.8%) than to PRL (25.6%),which is slightly more than the identity of GH to PRL (24.1%).
In order to study the effects of n-3 highly unsaturated fatty acids (n-3 HUFA) content in broodstock diets on the reproductive performance and seasonal changes of plasma sex steroids levels,five groups of Plectorhynchus cinctus female broodstocks were respectively fed a natural diet composed of trash fish (D5) and four artificial formulated diets containing 0.16% (D1),1.27% (D2),2.36% (D3) and 3.47% (D4) of n-3 HUFA,during the whole reproductive cycle.Their fecundity,egg and larval quality were evaluated,and the levels of plasma sex steroids were monthly monitored.It was found that the eggs production/kg of female,fertilization rate of eggs,larval survival and length at mouth-opening stage of both D2 and D3 group were equivalent to those of D5 group;however,those of D1 and D4 group were significantly lower than D5 group.Dietary n-3 HUFA content showed no obvious influence on the seasonal change pattern of plasma 17β-estradiol (E[2]) and testosterone (T).However,the plasma E[2] and T levels in gonad developmental and mature seasons of D1 and D4 group were significantly lower than those of D5 group.Dietary n-3 HUFA content also displayed some influence on E[2] and T production by in vitro ovarian follicles.Little basic E[2] production was observed by ovarian follicles of D4 group.Human chorionic gonadotropin (HCG,100 IU/mL) stimulated E2 and T production by ovarian follicles of D2-D5 group;however,ovarian follicles of D1 group had no response to HCG.The results suggest that the optimum n-3 HUFA requirements in broodstock diet of P.cinctus range between 1.27% and 2.36%,deficient or high dietary n-3 HUFA content may have negative effect on reproductive performance of broodstocks;n-3 HUFA may affect the reproductive performance by influencing the production of sex steroids.
The tegument and exoskeleton structure and the cement glands activities of female pleopod in different physiological stages of Eriocheir sinensis were investigated by histological method.The results show that the pleopod tegument consists of epicuticle,exocuticle,endocuticle and epithelial cells.The epithelial cells often connect firmly to cement gland.Cement gland tubules come across the exoskeleton.In different physiological stages (youth,maturation,spawning,and abortion),the pleopods of Taihu spawning crab and Wenzhou local crab have some significant differences,which mainly shows in the ratio and the array of epicuticle,exocuticle,endocuticle and epithelial cells,the amount and the distribution of the setae pockets,the substance in the setae pockets and the cement glands secretion aperture.Also,the cement glands activities and the open gates of the setae pockets are related to the egg attachment.The histological structure of pleopod between Taihu spawning crab and Wenzhou spawning crab is different,which the cement glands and mucus of Taihu spawning crab are much higher than those of Wenzhou spawning crab.The analysis shows that the abortion of Eriocheir sinensis closely relate to the histological structure of pleopod,and the development and activity of cement gland.
The embryonic development course of Alligator sinensis was divided into 28 stages,based upon observations on 150 A.sinensis embryos at varied embryonic day,according mainly to their external morphology for early stages of embryos,such as body torsion,brain vesicles,sensory organs morphology,limbs,branchial arches,facial processes,heart,skin and etc,and chiefly to the histological differentiation of their organs for late stages of embryos.It was found that the embryonic day of A.sinensis was relatively in accordance with that of A.mississippiensis for each of early 20 stages and was different for late 8 stages presumably due to a different staging method.It was suggested that histological index about organ differentiation should be introduced into the late stages determination for embryonic development of alligator and crocodiles,so as to make an agreement in staging method and to provide with basic documents and objective references for subsequent studies on developmental biology of alligators and crocodiles.