База резюме и ссылок по экологии бентоса

Брюхоногие: распределение

Title: Distribution of Fresh-Water Snails in the Man-Made Oyan

Reservoir, Ogun State, Nigeria

Source: HYDROBIOLOGIA

1999, Vol 416, Iss DEC, pp 181-191

Addresses:

OBAFEMI-AWOLOWO-UNIV, INST ECOL & ENVIRONM STUDIES, IFE, OSUN,

NIGERIA

Fresh-Water Snail; Man-Made Reservoir; Snail Ecology; Snail

Distribution; Tropics; Nigeria

Keywords Plus:

SCHISTOSOMA-HAEMATOBIUM; HABITAT PREFERENCES; WATER SNAILS;

VOLTA LAKE; HOSTS; AREA; TRANSMISSION; OUTBREAK; PATTERNS;

SUDAN

Abstract:

Oyan Reservoir, a typically medium sized man-made reservoir in

southwest Nigeria, were investigated once a month, for 28 months

(August 1990-November 1992). During each monthly visit, seven

stations were sampled for relative snail density, vegetation

cover and physical and chemical properties of the lake water.

Statistical analyses were performed to determine the influence

of these factors on snail abundance and distribution. Seven

aquatic snail species were found in the reservoir, namely

Bulinus globosus, B. forskalii, B. truncatus, Lymnaea

natalensis, Indoplanorbis exustus, Potadoma freethi and Potadoma

moerchi. The relative proportion of these species was 17.6% (B.

globosus), 16.1% (B. forskalii), 0.2% (B. truncatus), 12.9% (L.

natalensis), 23.4% (I. exustus) and 29.8% (both Potadoma spp.

combined) of 28 183 snails collected over the study period. The

seasonal trends of the species were variable but basically

bimodal with peaks in August (rainy season) and

November/December (early dry season). These trends were similar

to the water level and rainfall patterns, suggesting that

seasonal changes in snail density were probably influenced by

these factors. Spatial distribution of each snail species was

similar along each shoreline but significantly different across

the E-W transect. Similar trends occurred for conductivity,

dissolved oxygen and biochemical oxygen demand suggesting that

these factors may have affected snail distribution across

shorelines. Ten species of aquatic vegetation were identified,

six of which correlated positively and significantly with

various snail species. The most important of the associating

vegetation was Impatiens irvingii which correlated with all

snail species and served as an indicator plant for Indoplanorbis

exustus, an introduced snail species in Nigeria.

Брюхоногие

Title: Microhabitat Preferences of Biomphalaria-Pfeifferi and

Lymnaea-Natalensis in a Natural and a Man-Made Habitat

in Southeastern Tanzania

Source: MEMORIAS DO INSTITUTO OSWALDO CRUZ

2000, Vol 95, Iss 3, pp 287-294

Addresses:

SWISS-TROP-INST, DEPT EPIDEMIOL & PUBL HLTH, CH-4002 BASEL,

SWITZERLAND

IFAKARA-HLTH-RES-&-DEV-CTR, IFAKARA, TANZANIA

Author keywords:

Biomphalaria Pfeifferi; Lymnaea Natalensis; Man-Made

Habitat; Microhabitat Preferences; Removal Collecting;

Schistosomiasis; Tanzania

Keywords Plus:

SNAIL INTERMEDIATE HOSTS; BULINUS-GLOBOSUS; URINARY

SCHISTOSOMIASIS; POPULATION-DYNAMICS; IFAKARA AREA;

EPIDEMIOLOGY; HAEMATOBIUM; INFECTIONS; NIGERIA; STATE

Abstract:

Schistosoma mansoni is an important human parasitic disease

which is widespread throughout Africa. As Biomphalaria pfeifferi

snails act as intemediate host, knowledge of their population

ecology is an essential prerequisite towards understanding

disease transmission. We conducted a field study and assessed

the density and microhabitat preferences of B. pfeifferi in a

natural habitat which was a residual pool of a river. Repeated

removal collecting revealed a density of 26.6 [95% confidence

interval (CI): 24.9-28.3] snails/m(2). B. pfeifferi showed

microhabitat preferences for shallow water (depths: 0-4 cm).

They were found most abundantly, close to the shoreline

(distances: 0-40 cm), and preferred either plant detritus ol

bedrock as substratum. Lymnaea natalensis, a snail which may act

as a host for human Fasciola gigantica also occurred in this

habitat with a density of 34.0 (95% CI. 24.7-43.3) snails/m(2),

and preferred significantly different microhabitats when

compared to B. pfeifferi. Microhabitat selection by these snail

species was also investigated in a man-made habitat nearby,

which consisted of a flat layer of concrete fixed oil the

riverbed, covered by algae. Here, B. pfeifferi showed no

preference for locations close to the shoreline, probably

because the habitat had a uniform depth. We conclude that

repeated removal collecting in shallow habitats provides

reliable estimates of snail densities and that habitat changes

through constructions may create favourable microhabitats and

contribute to additional disease transmission.

Пресноводные улитки: конкуренция близких видов.

Volume 96 Issue 2 Page 251-264 - February 2002

Intra- and interspecific competition among coexisting lotic snails

Wyatt F. Cross and Arthur C. Benke

The competitive interactions of two lotic snails, Elimia cahawbensis and Elimia carinifera, were examined in a second-order spring-fed stream. We first demonstrated food limitation in laboratory microcosms where snails grew faster when exposed to enhanced periphyton levels. We then tested the magnitude and relative strengths of intra- and interspecific competition in similar stream and laboratory mesocosm experiments. Treatments were maintained in Plexiglas enclosures over a 7-week period with 0, 1, 2 and 4 ambient biomass of each species alone, as well as mixed species treatments at 2 and 4 ambient. Snail responses to treatments were almost identical in field and laboratory experiments. Growth rates of both species were reduced by increased density of snails indicating strong intra- and interspecific competition among E.cahawbensis and E.carinifera. An analysis of the strengths of intra- and interspecific competition indicated minimal differences for either species, implying a lack of competitive dominance. Although periphyton biomass was generally highest without snails, there was little difference in periphyton biomass and snail production over the four-fold density range, regardless of species composition. These results suggest that E.cahawbensis and E.carinifera are functionally redundant with density-dependent responses in growth rate resulting in similar grazing pressure across a density gradient. This clearly demonstrates that species impact is not necessarily reflected by measures of abundance or biomass, and that secondary production should be considered.

Двустворки: Unionidae

Volume 42 Issue 1 Page 59 - August 1999

Unionid growth patterns in rivers of differing riparian vegetation

Todd J. Morris and Lynda D. Corkum

1.Growth rates were examined as potential controlling agents of unionid

distributions.

2.Analyses of long-term growth in unionid shells revealed two distinct patterns.

Species which dominate rivers with forested riparian vegetation (e.g. Elliptio

dilatata) show slow growth throughout life, whereas species which dominate

grassy rivers (e.g. Pyganodon grandis) show rapid growth during early life and

achieve a smaller maximum size at a younger age.

3.Pyganodon grandis, which occurs in both river types but is much more abundant

in grassy habitats, demonstrates a single growth pattern in both basin types. In

contrast, Lasmigona complanata (Barnes, 1823), which occurs equally in both

basin types, demonstrates two growth patterns which differ depending upon which

river is inhabited. In forested rivers, L. complanata grow slow and steady, whereas

in grassy rivers, these unionids grow faster and achieve maximum size earlier.

4.Short-term transplant studies of P. grandis and E. dilatata confirmed this pattern

of growth for specialist species.

Двустворчатые. Воздействие Corbiculа на сообщество.

Volume 46 Issue 4 Page 491 - April 2001

Воздействие вселения корбикулы на бентос в песчаном водотоке.

The impact of an introduced bivalve (Corbicula fluminea) on the benthos

of a sandy stream

Christine C. Hakenkamp, Suzanna G. Ribblett, Margaret A. Palmer, Christopher M. Swan, Janet W. Reid & Mike R. Goodison

1. The effect of an exotic, burrowing bivalve (Corbicula fluminea) on the benthic

fauna of a sandy-bottomed stream was assessed by field and laboratory

experiments. Corbicula differs from other freshwater, non-native bivalves in that it

both filter- and pedal-feeds and thus has the potential to influence the streambed

community in different ways.

2. In the field, cages were used to vary the abundance of Corbicula in the

streambed. Increasing abundance of Corbicula was negatively associated with the

abundance of benthic bacteria and flagellates but had no apparent effect on other

protists or meiofauna.

3. In the laboratory, we compared the effect of Corbicula on the benthic

community when the bivalves were able both to filter- and pedal-feed with that when

they were able only to filter-feed. Bivalves restricted to filter-feeding were placed in

sediment lacking benthic fauna and organic matter, then the benthos in nearby

natural sediment was compared with the community present when Corbicula was

able to move freely through the sediment and both to filter- and pedal-feed.

Corbicula able to pedal-feed were again associated with a decreased abundance of

benthic flagellates and bacteria, as well as diatoms.

Двустворки: Dreissena

Volume 44 Issue 4 Page 569 - August 2000

Effects of the benthic suspension feeder Dreissena polymorpha on zooplankton in a large river

Jeffrey D. Jack* James H. Thorp

1.We conducted a series of in situ enclosure experiments to assess the impact of

zebra mussels (Dreissena polymorpha) on the plankton of the Ohio River. Adult

mussels were suspended in pelagic enclosures (potamocorrals) at three densities (0,

1000, 2500 mussels per corral) and incubated for 6 days with daily plankton and

physiochemical sampling.

2.The presence of adult zebra mussels was correlated with a shift in composition of

the phytoplankton community and a severe reduction in some rotifers. The effects

of zebra mussels on the larger zooplankton were taxon-dependent, but bacterial

density showed no trend among treatments.

3.Zebra mussels may have significant negative impacts on zooplankton, which may

in turn alter riverine food webs.