Origin of the v. portae and variability of its tributaries in laboratory animals. III. The laboratory rat (Rattus norvegicus var. alba)

The authors studied the origin of the v. portae and the variability of its tributaries in 30 adult laboratory rats (Rattus norvegicus v. alba) after injecting blue-dyed latex into the venous bed. In 21 cases (70.0%) the v. portae was formed from three tributaries. In 18 of these cases (60.0%) they were the v. mesenterica cranialis, v. lienalis and v. pancreaticoduodenalis cranialis. In eight cases the v. portae was formed from four or five tributaries and in only one case was it formed from two--the v. mesenterica cranialis and v. lienalis. In 21 cases (70.0%) the v. gastrica sinistra was a tributary of the v. lienalis. It collected blood from the anterior and posterior surface of the stomach and sometimes originated as far away as the curvatura major ventriculi. A v. cardiaca was present in all 30 cases (100%). As a rule (in 28 cases, i.e. 93.3%), it was a tributary of the v. gastrica sinistra. There was likewise a v. pylorica in every case; most frequently this united with the v. pancreaticoduodenalis cranialis, but was also connected with other veins in the vicinity. A v. pancreaticoduodenalis cranialis was always present. In 22 cases (73.3%) it was an independent tributary of the v. portae. In 11 cases (36.7%), there were no vv. gastroepiploicae or equivalent vessels and blood from the stomach was drained mainly by the v. gastrica sinistra. A v. gastroepiploica dextra was present in 11 cases (36.7%), mostly as a tributary of the v. lienalis; in two cases (6.7%) there was a v. gastroepiploica sinistra and in six cases (20%) the place of these veins was taken by vv. gastricae as tributaries of the v. lienalis. In 21 cases (70.0%) the v. lienalis was joined by the v. gastrica sinistra. In 22 cases (73.3%) inter-organ anastomoses between the spleen, stomach and pancreas were found. A v. pancreaticoduodenalis caudalis was always present and in 20 cases (66.7%) it was an independent tributary of the v. mesenterica cranialis. A comparison of the origin of the v. portae and the organization and variability of its tributaries in the rat, cat and guinea pig shows that, in agreement with their position in the zoological system and their mode of life, there was greater similarity between the rat and the guinea pig as regards practically all the veins examined.     

The v. portae of the domestic cat and variability of its tributaries

In the domestic cat the v. portae originates as a thick venous trunk below the liver through confluence of the v. gastrica sinistra, v. lienalis and v. mesenterica cranialis. It was formed in this way in 19 cases, i.e. in 63.3%. Among the aberrations found in the other cases, the most frequent was a common trunk for the v. gastrica sinistra and v. lienalis (6.7%). In 26 cases (86.6%), the v. gastrica sinistra was an independent tributary of the v. portae. A single v. lienalis was found in 27 cases (90.0%). Inter-organ anastomoses were found in the region of the v. lienalis. In 29 cases (96.7%) they connected the cranial part of the spleen with the fundus ventriculi. Inter-organ venous anastomoses between the caudal part of the spleen and the pancreas were found in four cases (13.4%). These anastomoses came from within the spleen and joined the veins of the stomach or the pancreas. In 14 cases (46.6%) the v. mesenterica cranialis originated as the v. colica dextra or v. caecalis. In nine cases (30.0%), in the concavity of the small intestine we found two trunks forming the v. mesenterica cranialis-one from the caecum and the other from the ileum and jejunum. Lastly, in five cases (16.7%) the v. mesenterica cranialis started only from the ileum and jejunum. The most frequent first tributary-in 19 cases (63.3%)-was a venous trunk of varying length formed by union of the v. mesenterica caudalis and the v. colica media, which started in 11 cases (36.7%) as the v. colica dextra.(ABSTRACT TRUNCATED AT 250 WORDS)     

Veins of the large intestine, stomach and pancreas of the domestic cat and their variability

Most frequently - in 19 cases (63.3%) - the v. colica media was a tributary of a trunk, formed together with the v. mesenterica caudalis, which emptied into the v. mesenterica cranialis. In two cases (6.7%) it emptied independently into the v. mesenterica cranialis. In 25 cases (83.3%) the v. mesenterica caudalis arose from the rectum and, at colon ascendens level, acquired one or more vv. colicae sinistrae. In six cases (19.8%) the v. colica dextra opened into the v. ileocolica and in eight cases (26.7%) it was the initial tributary of an independent v. ileocolica which joined the v. mesenterica cranialis directly. The drainage of venous blood from the stomach is organized as follows: the fundus region is connected to the v. lienalis by means of inter-organ anastomoses. The curvatura minor is drained by means of the v. gastrica sinistra. Venous blood from the region of the curvatura major ventriculi flows partly into the v. lienalis (by way of the vv. gastroepiploicae or small veins) and partly into the v. gastrica sinistra. Drainage of venous blood from the pancreas: a v. pancreaticoduodenalis cranialis was present in 16 cases (53.3%) and a typical v. pancreaticoduodenalis caudalis was found in 12 cases (40.0%). Simultaneous formation of both vv. pancreaticoduodenalis, with a possible incidence of small venous efferents to the v. lienalis, was observed in only nine cases (30.0%). In 21 cases (70%), blood from the region of the flexura duodenojejunalis was drained by the last v. jejunalis; in other cases it drained into the vv. pancreaticoduodenales.(ABSTRACT TRUNCATED AT 250 WORDS)     

Variability of branching of the a. coeliaca (truncus coeliacomesentericus) in the guinea pig (Cavia aperea f. porcellus)

The authors studied branching of the a. coeliaca (the truncus coeliacomesentericus) in a group of Peruvian short-haired guinea pigs, with special reference to its variability. After the animals had been anaesthetized, their arterial bed was injected with red-dyed latex, fixed and dissected. In all 30 guinea pigs (100%), blood was supplied to the unpaired organs of the abdominal cavity by a truncus coeliacomesentericus arising from the aorta abdominalis at fundus ventriculi level. In 53.3% of the cases, the truncus coeliacomesentericus divided into a truncus gastrolienalis sending out an a. gastrica sinistra and an a. lienalis, and to a truncus hepatomesentericus which split up into an a. hepatica communis and a. mesenterica cranialis. An a. coeliaca (tripus Halleri) was found in only one guinea pig (3.3%), as a branch of the truncus coeliacomesentericus. In the remaining cases, the truncus branched in the most varied ways. The a. gastrica sinistra was most frequently (60%) a branch of the truncus gastrolienalis. In 21 cases (70%) there was a single a. gastrica sinistra and in nine cases (30%) it was doubled. In 29 cases (96.7%) the a. hepatica communis arose from the truncus hepatomesentericus. The classic type of division of the a. hepatica communis to an a. hepatica propria and an a. gastroduodenalis was observed in every case (100%). In 100% of the cases, the a. hepatica propria terminated in a r. dexter and a r. sinister to the liver. An a. cystica, as a direct branch of the a. hepatica propria, was formed in 28 cases (93.3%). In every case (100%) the a. pancreaticoduodenalis cranialis was a branch of the a. gastroduodenalis. An a. gastrica dextra was recorded in only eight cases in the series (26.7%)--in 23.3% as a branch of the a. hepatica propria and in 3.3% as a branch of the a. cystica. Duplication of this artery was found in one case (3.3%). An a. lienalis was found in 28 cases (93.3%), as a direct branch of the truncus gastrolienalis; in two cases (6.7%) it was doubled. An a. gastroepiploica sinistra and a. gastroepiploica dextra were present in 100% of the cases. Inter-organ arterial anastomoses were found in 22 guinea pigs (73.3%)--between the spleen and the stomach (36.7%), between the pancreas and the stomach (10%), between the stomach, spleen and pancreas (10%) and, in the remaining cases, as various combinations of these connections.(ABSTRACT TRUNCATED AT 400 WORDS)     

Variability of ramification of the a. mesenterica cranialis in the domestic rabbit (Oryctolagus cuniculus f. domestica)

The authors studied the ramification of the a. mesenterica cranialis and its variability in 30 domestic rabbits (Oryctolagus cuniculus, f. domestica, breed New Zealand White). The animals were anaesthetized and red-dyed latex was injected into their arterial bed via the thoracic aorta. In every case (100%), the a. mesenterica cranialis was an independent trunk arising from the abdominal aorta 1.5-2 cm caudally to the origin of the a. coeliaca. We did not observe a truncus coeliaco-mesentericus in our material. In 17 cases (56.7%), the a. pancreaticoduodenalis caudalis was the first branch of the a. mesenterica cranialis. In 28 cases (93.3%) it formed a thick trunk which divided into two main branches to the aboral part of the duodenum and the caudal part of the pancreas respectively; in two cases (6.7%), the a. pancreaticoduodenalis caudalis was duplicated. In only two cases (6.7%), the first branch of the a. mesenterica cranialis was the a. colica media. The a. mesenterica cranialis then divided into two thick trunks to the intestine - the truncus jejunalis and the truncus ileocaecocolicus. Single aa. jejunales branched off successively from the arching truncus jejunalis. The truncus ileocaecocolicus led in a caudal direction and broke up, as a rule, into three arteries supplying the ileum, the caecum and the colon transversum. In 17 cases (56.7%), 1-6 aa. jejunales arose directly from the trunk of the a. mesenterica cranialis and 13-21 from the convexity of the arch of the truncus jejunalis. In 13 cases (43.3%), all the aa. jejunales found (11-23) were branches of the truncus jejunalis. On the mesenteric side of the jejunum, the aa. jejunales forked and formed an arcade from which small branches led to the intestine. In the rabbit we always observed only one arcade; more complex systems were not formed. A truncus ileocaecocolicus, whose branching was characterized by marked variability, was found in all 30 cases (100%). Division of this trunk to an a. ileocaecalis, a. caecocolica and a. colica dextra was observed in only four cases (13.3%). In every case, extensive anastomoses with branches of the a. colica dextra and a. colica sinistra were formed. In general, it can be claimed that the arterial bed of the a. mesenterica cranialis is highly variable. Since little attention has been paid in the literature to variability of the ramification of this artery in different species of mammals, the authors will concentrate, in their next studies, on a detailed investigation of the arterial bed of the abdominal cavity, and of its variability, in further laboratory animals.     

The blood supply of the stomach

156 abdominal preparations were explored by arteriography, corrosion and dissection. The stomach is vascularized by four well-anastomosed main arteries: the arteria gastrica dextra and sinistra and the arteria gastroepiploica dextra and sinistra. Other important vessels include: the arteria gastroduodenalis, the arteriae gastricae breves for the upper half of the greater curvature, a posterior gastric artery (36%), an accessory left gastric artery (12%) and an arteria supraduodenalis. The main vessels give rise to some very specific collaterals, e.g. the omental arteries that may form an omental arcade (44%), supra- and infra-pyloric branches, retroduodenal branches, rami cardiaci, esophagei and tuberales and an accessory left hepatic artery. The gastroduodenal artery always arises at a fixed point.     

Similarities in zooplankton community between River Drawa and its two tributaries (Polish part of River Odra)

Zooplankton communities were studied in a river and its tributaries with different hydrological, biological and physico-chemical conditions. Small similarities were noted in the zooplankton community (mostly Rotifera) between a tributary characterised by a regular bed and the river. No influence of a tributary with an irregular bed and variable water flow was noted on the zooplankton of the river it joined. It was concluded that the tributaries had very little influence on the zooplankton community in the river which they joined. The most probable reasons for this were the predatory behaviour of fry, escape of zooplankton into the river vegetation and therefore not carried down by the river current, and reproduction of zooplankton in slack waters, small floodplains and densely vegetated riparian zones of the main river.     

Systematisation of the arteries in the splenic hilus

156 abdominal preparations were explored by arteriography, corrosion and dissection. Within the meanders of the splenic artery a basic pattern can be traced. The division of the artery can easily be summarized by introducing the term of a truncus lienogastroepiploicus. The short gastric arteries are always present, and usually they are longer and more important than may appear from their name. In nearly half of the preparations (52%) an artery for the extremitas lienalis posterior is found; an artery for the extremitas lienalis anterior is very exceptional. A posterior gastric artery can be identified (36%) but it must be distinguished from several other vessels. The arteria colli pancreatis (for the neck of the pancreas) is a constant vessel that may have a superior (usually arteria lienalis) or an inferior origin (arteria mesenterica superior). It commonly supplies the transverse pancreatic artery and often the prepancreatic arcade. The arteria corporis pancreatis, too, is a constant artery. The pancreatic tail is thoroughly irrigated by usually more than one arteria caudae pancreatis. An important part of the greater curvature is not accompanied by the left gastroepiploic artery, but is supplied by the arteriae gastricae breves.     

Non-direct homing behaviours by adult Chinook salmon in a large, multi-stock river system

Two non-direct homing behaviours, overshoot of natal tributaries and temporary non-natal tributary use, were evaluated for 5150 radio-tagged spring–summer Chinook salmon Oncorhynchus tshawytscha from 40 populations in the large Columbia River system. Over 7 years, 2–44% (mean = 15%) of individuals within each group temporarily entered presumed non-natal tributaries. In addition, many Chinook salmon from lower river tributaries initially travelled 3 to >250 km upstream in the main-stem river beyond confluences with presumed natal tributaries before returning to the natal sites ('overshoot'). Both overshoot and temporary tributary use behaviours declined exponentially with increasing distance from the natal tributary. Non-direct homing also increased later in the season as water temperatures rose and was associated with hatchery origin in some cases. The behaviours may reflect a mix of active searching for olfactory cues from natal sites, behavioural thermoregulation and orientation challenges in a large-river migration corridor transformed by dams and reservoirs. While anadromous salmonid homing is generally accurate and precise, these results indicate that route finding can be non-direct, potentially increasing energetic costs and harvest risks during migration.     

澜沧江梯级开发下鱼类支流生境替代效果

作为干流高坝水电开发导致鱼类生境丧失的一种补偿措施,支流替代生境近年来被广泛应用于受工程影响河段的土著鱼类保护,但替代支流发挥怎样的保护效果及干流对其的影响仍不清楚。以实施了澜沧江梯级生境替代的支流基独河与罗梭江为研究对象,并选择了邻近的对照支流,通过对鱼类调查数据的分析对比,揭示了各支流鱼类种类组成与群落结构的差异特征,初步阐明了梯级开发下鱼类支流生境替代效果以及干流工程建设对其的影响。结果表明：澜沧江支流替代生境对干流鱼类具有明显的保护作用,支流生境修复后鱼类物种丰富度明显提高,罗梭江土著鱼类、特有鱼类物种数分别增加了12种、7种,基独河则是7种、2种,替代生境能为澜沧江土著鱼类、部分濒危特有鱼类和洄游鱼类提供完成生活史的关键栖息地。干流对支流生境替代保护有着重要影响,罗梭江、基独河与邻近干流鱼类群落的Bray-Curtis相似性分别为21.76%、10.73%,支流河口段保持“河相”是支流生境替代保护效果可持续的关键。综合考虑生境替代保护的效益与投入,建议今后开展此类保护措施时优先选择库尾河相区的支流。     

Spontaneous Bleeding in Pancreatitis Treated by Transcatheter Arterial Coil Embolization: A Retrospective Study

Background/Objectives

A rare, but life-threatening complication in pancreatitis is a spontaneous bleeding from intestinal vessels with or without previous formation of (pseudo-) aneurysms. And yet, the optimal diagnostic and therapeutic strategies remain unclear.

Methods

We performed a retrospective analysis of all patients with pancreatitis and intraabdominal bleeding at a German tertiary referral center between January 2002 and December 2012.

Results

Bleeding occurred in <1% (14/3,421) of patients with pancreatitis. Most involved vessels were arteria lienalis, arteria gastroduodenalis, and arteria pancreaticoduodenalis. All bleedings could be stopped by transcatheter arterial coil embolization. Recurrent bleeding after coil embolization occurred in 2/14 (14%) patients.

Conclusions

In cases of intraabdominal hemorrhage in patients with pancreatitis, transcatheter arterial coil embolization should be considered as the first interventional procedure.     

Seasonal movements and tributary-specific fidelity of blue sucker Cycleptus elongatus in a Southern Plains riverscape

This study used acoustic telemetry and a multistate Cormack–Jolly–Seber model to determine the seasonal movement patterns of blue sucker Cycleptus elongatus from 2015 to 2017. Several hypotheses were ranked using AIC_c, and it was determined that the movement patterns of blue suckers in a mainstem reach below a hydropower dam (i.e., tailwater) differed from those of blue suckers tagged in the major tributaries (perennial with stream order >3). This study estimated a low probability (≤0.13) blue suckers would leave the tailwater reach at any time during the study. Conversely, blue suckers tagged in the major tributaries had a high probability (≥0.88) of leaving after the spawning season (February–May). Blue suckers tagged in the major tributaries displayed a high probability (0.83) of returning to the tributaries in the spawning season of 2016 when discharges were high. Blue suckers also had a higher probability of fidelity to the tributary where they were tagged (0.65) rather than straying to different tributaries (0.18). The majority of tagged blue suckers that strayed selected the only undammed tributary in the study area. In 2017, spring discharges were low, and the probability of blue suckers returning to any major tributary was low (0.19), with little difference in the probability of displaying site fidelity (0.10) vs. straying (0.09).     

Using parentage analysis to estimate rates of straying and homing in Chinook salmon (Oncorhynchus tshawytscha)

We used parentage analysis based on microsatellite genotypes to measure rates of homing and straying of Chinook salmon (Oncorhynchus tshawytscha) among five major spawning tributaries within the Wenatchee River, Washington. On the basis of analysis of 2248 natural‐origin and 11594 hatchery‐origin fish, we estimated that the rate of homing to natal tributaries by natural‐origin fish ranged from 0% to 99% depending on the tributary. Hatchery‐origin fish released in one of the five tributaries homed to that tributary at a far lower rate than the natural‐origin fish (71% compared to 96%). For hatchery‐released fish, stray rates based on parentage analysis were consistent with rates estimated using physical tag recoveries. Stray rates among major spawning tributaries were generally higher than stray rates of tagged fish to areas outside of the Wenatchee River watershed. Within the Wenatchee watershed, rates of straying by natural‐origin fish were significantly affected by spawning tributary and by parental origin: progeny of naturally spawning hatchery‐produced fish strayed at significantly higher rates than progeny whose parents were themselves of natural origin. Notably, none of the 170 offspring that were products of mating by two natural‐origin fish strayed from their natal tributary. Indirect estimates of gene flow based on F_ST statistics were correlated with but higher than the estimates from the parentage data. Tributary‐specific estimates of effective population size were also correlated with the number of spawners in each tributary.     

Arterial vascularization of the tail of the pancreas with special reference to the relation of the tail and body vessels

The cauda pancreatis has a characteristic pattern of vascularization. Among the big arterial stems surrounding it, up to 4 arteries, 'caudal arteries', nourish the arterial system of the cauda. These stems originate especially in the Arteria gastroepiploica sinistra and in the lower main splenic branch of the Arteria lienalis. The vascular relations between corpus and cauda can be of different kinds. Five basic types of relations can be identified: type I: the cauda is supplied exclusively by caudal arteries; type II: at least one caudal artery anastomoses with the vessels of the corpus; type III: the cauda is supplied both by the caudal arteries and by vessels of the corpus (non-anastomosing); type IV: combined forms of blood supply by caudal arteries and corpus arteries by way of anastomoses and non-anastomosing vessels are found; type V: the cauda is supplied exclusively be vessels stemming from the corpus. In each of these five types, individual vessels supplying the cauda can assume the function of a terminal vessel.     

Immunity to Onchocerca lienalis microfilariae in mice. II. Effects of sensitization with a range of heterologous species

The model of Onchocerca lienalis microfilariae (mff) injected into CBA and T.O. strains of mice has been used to examine immunity to skin-dwelling microfilariae following exposure to a range of species of helminths. Mice which had received a primary infection with O. cervicalis mff were significantly resistant to challenge with O. lienalis mff (58% reduction relative to challenge controls). Immunization with the uterine contents (eggs and mff) of O. lienalis, O. gutturosa or O. volvulus conferred equivalent levels of protection against challenge with O. lienalis mff (66 to 75%). Similar results were obtained with immunizations in mice that employed either fresh or freeze-killed eggs of O. gutturosa. Significant reductions in the recoveries of O. lienalis mff were also demonstrated following the intraperitoneal implantation of adult male worms of O. gutturosa (30 to 52%), the adults of either sex of Dipetalonema viteae (60%), or after infection with Trichinella spiralis (27 to 81%). Infections with the trematode, Schistosoma mansoni, had a negligible effect on mff recoveries. It is concluded that partial resistance in mice to Onchocerca mff may be stimulated by factors, yet to be determined, that are neither stage nor species-specific.     

Effect of Thymol on the spontaneous contractile activity of the smooth muscles

Effects of Thymol on the spontaneous contractile activity (SCA) have been found in in vitro experiments with circular smooth-muscle strips (SMAs) from guinea pig stomach and vena portae. Thymol was found to possess an agonistic effect on the alpha(1)-, alpha(2)- and beta-adrenergic receptors. Its spasmolytic effect is registered at doses higher than 10(-6)M. Thymol in a dose of 10(-4)M inhibits 100% the SCA of the SMAs and reduces the excitatory effect of 10(-5)M ACH to 35%. It is assumed that Thymol has an analgesic effect through its action on the alpha(2)-adrenergic receptors of the nerve cells. By influencing the beta-adrenergic receptors in the adipose cells, it is possible to induce increased synthesis of fatty acids and glycerol, which is a prerequisite for increased heat release.     

Effects of increased flow in the main stem of the River Rhine on the invertebrate communities of its tributaries

1. We hypothesised that increased flow in the main stem of the River Rhine would influence the invertebrate communities of its tributaries and therefore investigated the invertebrate fauna of six tributaries over 2 years. 2. We collected quantitative invertebrate samples at three sites in each tributary: in the tributary mouth (influenced by Rhine water whenever flow in the Rhine exceeded mean annual level), in the zone reached by average floods (return period 1.5 years) in the Rhine (average flood level sites), and immediately upstream of the range of extreme Rhine floods (reference sites). Samples were taken in spring, summer and autumn of each year, at different flow levels of the Rhine. We also compared substratum composition at the three sites. 3. Tributary mouth sites had the finest substratum, the lowest total invertebrate density and the lowest taxon richness. At average flood level and reference sites, these three parameters were similar. 4. Taxa known to prefer larger rivers were mostly confined to the tributary mouth sites, and species preferring upland streams dominated at the average flood level and reference sites. 5. Multivariate analyses confirmed the influence of the Rhine on the tributary mouth sites. Invasive invertebrate species, which usually appear only in the Rhine itself, were found at the tributary mouth sites but not further up in the tributaries. 6. Our study shows that increased flow in the main stem of the Rhine influenced substratum composition and invertebrate communities at the tributary mouth sites. These results imply that the relationship between the main stem of a river and its tributaries is not one‐way (from tributary to main stem), but rather a two‐way interaction.     

Onchocerciasis in British cattle: a study of Onchocerca gutturosa and O. lienalis in North Wales

Onchocerca gutturosa and O. lienalis infections in British cattle were studied by examination of cattle post-mortem originating from North Wales and Cheshire (north west England). In 463 adult animals, the microfilarial (mf) prevalence was 28.5%. In 95.3% of the mf infected animals, gravid worms could not be found at either the ligamentum nuchae or the gastro-splenic omentum. Dermal mf at the head were identified as O. gutturosa on the basis of their highly significant association with the presence of gravid O. gutturosa at the ligamentum nuchae, which were found in only 3.2% of cattle. Mfs were isolated from different skin sites and from adult worms and a minimum of 10 mfs from each isolate were examined for width and acid phosphatase (AP) staining pattern. The width of O. gutturosa dermal mf was less than 4 micron (4 isolations), narrower than that of putative O. lienalis mf isolated from umbilical skin of cattle without evidence of O. gutturosa, which were in 20/22 isolations greater than 4 micron wide. The dermal mf were also distinguished on the basis of different AP staining patterns which, for each species, correlated closely with that of hatched intrauterine mf from their respective adult female worms. Based on the criteria of morphology and AP staining patterns the mf species prevalences in the survey population were estimated as O. lienalis 24.1% and O. gutturosa 2.2%, with a further 2.2% of cattle infected with both species. The results indicate that the predilection site of adult O. lienalis is not the gastro-splenic omentum. In North Wales, the distribution of the two species was different; O. lienalis was widely distributed in all cattle rearing areas both lowland and upland, whereas O. gutturosa was largely restricted to valleys close to major rivers.     

Geometry of biodiversity patterning: assemblages of benthic macroinvertebrates at tributary confluences

We assessed whether tributaries in upland catchments (=watersheds) affected assemblages of benthic macroinvertebrates in mainstems, as has been reported in northern hemisphere systems. Eight confluences of small to medium streams (stream orders 1–4, 2.2–10.8 m wide) were studied in the Acheron River basin in Victoria, Australia. For each confluence, two transects were sampled at each of five zones relative to the confluence: two zones upstream in the mainstem, one zone upstream in the tributary, one zone at the confluence and one zone downstream in the mainstem. Surveys were conducted in both high-flow and low-flow conditions. In mainstems, there was no change in macroinvertebrate density, taxonomic richness or functional feeding group composition downstream relative to upstream of the confluences. While tributaries statistically had distinctive benthic macroinvertebrate assemblages compared to mainstems, these distinctions were small. In low flows, densities in tributaries were substantially lower than in mainstems, but densities during high flows were more similar (albeit only about one-third as high as in low flow) in tributaries and mainstems. An inverse pattern was evident for taxonomic richness, where richness in tributaries and mainstems was similar in low flows but was greater in mainstems than in tributaries in high flows. We found little evidence of tributary effects in macroinvertebrate assemblages in this basin, which is at odds with some previous results from other continents. To explain this divergence, we suggest a conceptual model outlining factors that control variation in effects of tributaries on assemblages of benthic macroinvertebrates in mainstems.     

丹江口库区滩涂与入库支流植被与土壤种子库: 水传播潜力探讨

为了探索库区滩涂与入库支流土壤种子库与植被的关系, 以及物种通过水传播扩散的潜力, 对丹江口库区内4条支流及其入库滩涂的地表植被和土壤种子库进行了调查。结果显示, 支流地表植被和种子库的物种多样性高于库区滩涂, 汉江库区滩涂和支流的地表植被与种子库均有较高的物种相似性。DCA排序和TWINSPAN聚类可以明显地将支流的植被和种子库样方与滩涂的植被和种子库样方分到不同的样方组, 结合物种排序图可以清楚地发现, 流入汉江库区支流的植被和种子库的物种组成与滩涂的植被和种子库的物种组成有密切联系。汉江库区滩涂0-15 cm的土层内都有种子萌发, 而丹江库区种子库中只有狗牙根(Cynodon dactylon)一种植物, 且仅存在于0-5 cm土层。研究结果表明, 繁殖体通过支流向滩涂的水传播作用对植被建立有积极贡献。