Fine Detritus Research Articles

Xenochironomus ceciliae (Diptera: Chironomidae), a new chironomid species inhabiting freshwater sponges in Brazil

Chironomids living inside freshwater sponges are scarcely known, particularly in the Neotropical region where most of them are to be described. Here, male and female adults, pupa and 4th instar larva of Xenochironomus ceciliae sp. n., living in freshwater sponges of the Parana River (Brazil) are described. The larval labrum with its several densely setose or combed structures somewhat resembling the filtering structures of simuliid larvae and the predominance of fine detritus in the larval gut contents, may indicate that the larvae of Xenochironomus ceciliae sp. n. are collector-filterers and they might be favored by the aquifer systems of the sponges.

Bacterial biomass on fine detritus particles in a woodland stream of Hokkaido, Japan

AbstractBacterial biomass on four different size fractions of benthic fine particulate organic matter (FPOM) was measured throughout a year in a woodland stream in Hokkaido, Japan. Bacterial biomass per ash free dry mass (AFDM) of the FPOM was significantly different among the four size fractions, while the biomass per unit surface area of FPOM was not. Annual mean of bacterial biomass per particle mass positively correlated to the surface area per mass in the four size fractions. In addition, negative correlation was found between the C:N ratio and bacterial biomass per AFDM in FPOM when all fractions were pooled. There was also negative correlation between C:N ratio and the surface area per particle mass in the four size fractions. The difference of bacterial biomass on FPOM among the size fractions could be ascribed to surface area and/or C:N ratio of FPOM, although these effects were not separately evaluated in the present study.

Life history patterns and dietary changes of several caddisfly (Trichoptera) species in a northern Spain stream

Life history patterns of Lepidostoma hirtum, Sericostoma selysii, Hydropsyche pellucidula and Hydropsyche siltalai were investigated for a year in the Aguera stream (northern Spain). All four species showed univoltine life cycles, low synchronisation of larval development, and extended periods of hatching and flight. Young larvae of all four species showed a quick development from summer to autumn probably due to favourable climatic and hydrological conditions. High flows in winter and spring reduced densities presumably by drift. Additionally, food habits of these species, plus those of large individuals of Potamophylax latipennis, Rhyacophila relicta, R. denticulata and R. eatoni were examined. Gut contents indicated changes in diets with development in the four species whose life history was determined. In general, fine detritus was the main food component for early instars, while other food types increased in importance in more developed instars. L. hirtum and S. selysii showed mainly a detritivorous trophic character, their diet shifting from fine detritus in early instars to coarse detritus in late ones. Coarse material in L. hirtum guts increased from 0% at first to 74 % at IVth instar, and in S. selysii from 48 % at first to 95 % at VIIth instar. The hydropsychids H. pellucidula and H. siltalai showed a varied diet, dominated by fine detritus in early instars, but incorporating more than 25 % of animal material in late instars. Large individuals of P. latipennis fed mainly on coarse detritus (95.8 % of the diet). R. relicta and R. denticulata late instars showed a carnivorous diet, with up to 75 % of animal material. On the other hand, with 51.4 % of fine detritus, 30.8 % of animal material and 15 % of coarse plant detritus, R. eatoni seemed to be more omnivorous. Chironomids and baetids were the most frequent prey items in Hydropsyche and Rhyacophila guts. All these results indicate the generalist feature of most studied species from a trophic point of view.

Trichoptera remains from early Holocene river deposits in the Great Belt, Denmark

Analyses of a sediment core from the Great Belt documented the local presence of fluvial deposits. The sediments consisted of silt, clay, sand and organic detritus and they contained macroscopical remains of a mixture of terrestrial, telmatic, lacustrine and fluvial plants and animals. Most noteworthy was the abundance of remains of caddis fly larvae, totalling at least 24 species, which were dominated by fluvial species. Thus, filter‐feeding hydropsychids made up approximately 95% out of 1496 identified specimens, the dominating species being Hydropsyche contubernalis and H. pellucidula. The present‐day requirements of the recorded species point to a fairly fast‐flowing river, at least locally, with areas of stones (some with moss growth) and gravel, but also to more slowly‐flowing parts with sand, fine and coarse detritus. This river may have been considerably larger than any present‐day Danish river. It appears that the fluvial deposits formed locally in connection with flooding of the area south of the core position. AMS radiocarbon dating shows that the sequence was deposited very rapidly during the early Holocene, about 10650 to 10250 cal. years BP. The occurrence of the lentic Leptocerus tineiformis points to a climate at least as warm as today.

Strontium Isotopes, Age, and Tectonic Setting of Cambrian Salinas along the Rift and Transform Margins of the Argentine Precordillera and Southern Laurentia

The Argentine Precordillera generally is interpreted as a fragment of continental crust and sedimentary cover that was rifted from the Ouachita embayment of southern Laurentia in Cambrian time. Synrift sedimentary successions in the northern part of the Precordillera and in the Birmingham graben of southern Laurentia include thick evaporite deposits. Analyses of strontium isotopes indicate that the evaporites are of late Early Cambrian age, consistent with biostratigraphic correlations. Variations in strontium ratios indicate that these Early Cambrian salinas had a persistent base of marine water and that contributions from meteoric runoff varied through time and with location. The stratigraphic and isotopic data suggest a depositional setting of restricted circulation within a system of extensional fault blocks. The salinas occupied graben blocks that were connected to marine circulation and that intermittently received meteoric runoff carrying fine detritus and radiogenic strontium from horst blocks of continental crust. The evaporites in the Precordillera show less meteoric influence than the evaporites in the Birmingham graben, which was far inboard from the continental margin of southern Laurentia. These relationships are consistent with continental rifting in Early Cambrian time, extension of continental crust, and deposition of synrift sediment in graben blocks that were partially open to marine circulation.

Seasonal availability of resources and habitat degradation for the western tree-hole mosquito, Aedes sierrensis.

The nutrient base of aquatic tree-hole communities is derived from leaf litter, benthic detritus, and water flowing down the tree trunk (stemflow water). Previous studies in eastern North America with the mosquito, Aedes triseriatus, have identified leaf litter as a major and stemflow water as a minor source of mosquito nutrition, but did not consider the role of the benthic detritus or how the aggregate or relative contribution of these sources of mosquito nutrition changed during the year. We use the leaf litter, benthic detritus, and stemflow water from tree holes in western Oregon (USA) to determine how these substrates affect mass at metamorphosis, biomass yield, and fitness (cohort replacement rate; R 0) of the mosquito, Aedes sierrensis, through both natural and simulated winters, the normal growing season for larvae in tree holes. We found that fresh leaf litter constitutes the major determinant of mosquito fitness by a factor of >15:1 over any other substrate taken directly from tree holes in nature. The other substrates, including the benthic detritus, individually make only a meager contribution to mosquito fitness but, when added to the leaf litter, can sustain yield and improve fitness at high, limiting larval densities. Nutritional quality of tree-hole substrates declines by >90% from early (fall) to late (spring) in the larval growing season. At both times of year, the coarse or fine detritus provide minor resources, and stemflow water provides no detectable contribution to mosquito nutrition. The resources in the litter are not transported during the year to the benthic detritus; rather, these resources are either exploited by mosquitoes when they first become available, or they deteriorate and become progressively more unavailable to them. Growth and development of A. sierrensis feeding on dried and reconstituted tree-hole contents during a 6-month simulated winter in the laboratory showed: (1) the same relative contributions of leaf litter, benthic detritus, and stemflow water to mosquito nutrition, (2) that the winter deterioration of substrate quality is a direct consequence of microbial decomposition, and (3) that pre-emptive competition from pre-existing A. sierrensis greatly increases substrate deterioration. We conclude that the progressive winter deterioration of larval resources in combination with the dry summers of western North America are the most likely environmental factors that limit species diversity in tree holes and that have selected for early recruitment (autumnal hatching) of A. sierrensis and for its univoltine life cycle from Mexico to Canada.

Testing a Nitrogen-Cycling Model of a Forest Stream by Using a Nitrogen-15 Tracer Addition

Cycling of nitrogen (N) is commonly studied in aquatic ecosystems; however, most studies examine only parts of the N cycle, such as budgets, N uptake lengths, or oxidative transformations. To integrate conceptually and experimentally several aspects of the N cycle in a stream, we combined a N-cycling model and a tracer addition of nitrogen-15 (15N) to Hugh White Creek, a second-order forested mountain stream in North Carolina (USA). We calibrated a steady-state box model for N cycling in 5-m stream segments that included dissolved, detrital, and biotic compartments. This model was parameterized based on prior studies and used to predict the expected distribution of tracer 15N in all compartments through both time and distance downstream of the addition site. We tested the model results with a 23-day continuous addition of 15N-NH4 + to the stream. Deviations of field data from model predictions suggested areas in which we lacked understanding of the N cycle. Downstream distribution of 15N in epilithon and moss matched model predictions, indicating that our prior estimations of N uptake rates were correct. Leaves and fine detritus contained less label than predicted by the model, yet their consumers had both higher δ15N than predicted and higher δ15N than the detritus itself, suggesting selective assimilation of microbial N from ingested detritus. Splitting fine benthic organic N (FBON) into a microbial and recalcitrant pool gave better predictions of FBON and seston δ15N values relative to field data, yet overestimated invertebrate consumer δ15N possibly because our estimates of the fraction of invertebrate N derived from microbes were too high. We predicted that much of the labeled N would move downstream via FBON suspension and transport. We found that most of the 15N remained near the addition site 33 days after the addition was stopped, suggesting that the stream is highly retentive of particulate N.

Environmental perturbation and the structure and functioning of a tropical aquatic ecosystem

In Tissawewa, a shallow, eutrophic reservoir in southeastern Sri Lanka, the effect of a major drought on the ecosystem was studied by monitoring the size-structured fish community and its resource base. Primary production was determined as well as the production and diets of ten taxa belonging to four trophic guilds (i.e. herbivorous/detritivorous, benthivorous, zooplanktivorous/insectivorous, piscivorous) that made up more than 98% of the total fish biomass. Two extreme states of the ecosystem were distinguished. Before the drought most primary production was generated by phytoplankton, suspended fine particulate detritus was an important food source and total fish density was high. After the drought the ecosystem was characterised by high macrophyte density, low concentration of suspended detritus and low total fish density. The availability and origin of detritus appeared to be the major factor influencing fish production in Tissawewa. The small pelagic herbivore/detritivore A. melettinus contributed the most biomass and production to the fish community before the drought. After the drought, however, biomass and production dropped considerably. In contrast, the production of the most important species in terms of fisheries yield, the exotic herbivorous/detritivorous tilapias, was hardly affected. Although the compo In Sri Lankan reservoirs a subsidiary fishery for pelagic minor cyprinids was suggested to increase the current yield which is based almost entirely on the exotic tilapia species. The perturbation observed in this study, however, showed that the production of pelagic species was affected particularly by the environmental changes. Exploitation of these species can, therefore, only be considered in combination with hydrological and other management measures that control the environmental condition [KEYWORDS: drought, pelagic minor cyprinids, foodweb, fisheries management, production, reservoir, yield]

A method for the experimental determination of light absorption by aquatic heterotrophic bacteria

A method has been set up for the experimental determination of the volume coefficient for light absorption in vivo by aquatic heterotrophic bacteria. The application described here is the absorption measurement of the bacterial fraction that passes through the commonly used GF/F filter and remains unaccounted for. The experimental samples were prepared by successive water nitra- tions through GF/F and 0.22 urn Millipore membranes. Light-transmission and light-reflection measurements of the filter-retained samples were performed using a dual-beam spectrophotometer equipped with an integrating sphere attachment. Sample absorption was derived from the data by a procedure that corrects for the contamination of the results due to the high degree of light scattering by the bacteria. The bacterial absorption was discriminated from fine detritus absorption by bleaching the bacterial respiratory pigments using a K^Og solution. The absorption amplification caused by multiple scattering in the filter was corrected for by an expression that was obtained experimentally. A test of the method, including error analysis, was performed on samples collected in both marine and inland waters. The relative contributions to light absorption by heterotrophic bacteria and various types of paniculate matter were also measured for a typical situation. Combining the measured volume absorption coefficients with backscattering coefficients computed by Mie theory yields a set of input data to multicomponen t optical models that is needed to assess the contribution of these heterotrophic bacteria to the radiative transfer process.

Resistivity and georadar mapping of lacustrine and glaciofluvial sediments in the late-glacial to postglacial Store Amose basin, Denmark

Resistivity profiling, resistivity sounding, georadar profiling and analyses of borings are used in a sedimentological and geomorphological study of shallow subsurface deposits in the proximal (southeastern) part of the Store Amose lacustrine basin in eastern Denmark. Areas of low, intermediate and high resistivities are located by resistivity profiling. Low-resistivity areas (type I) correspond to a thick unit of water-saturated lake sediments (fine detritus gyttja and siltlclay) which were deposited in a large lake system from the late Weichselian to the late Holocene. In intermediate-resistivity areas (type II), a relatively thick top layer of fresh-water peat and drifted gyttja or dry gyttja occurs. Fine-grained lake sediments, drifted gyttja and peat are equivaIent to transparent facies and low penetration (max. c. 2 m) in georadar profiles. Resistivity soundings indicate a shallower high-resistive substratum of meltwater sand and gravel in type II areas than in type I areas. The lake and fen sediments fil1 a highly irregular lake bottom relief, interpreted to have been formed in glaciofluvial channel systems and as dead-ice holes during the final Weichselian deglaciation. Sandy and gravelly domes and ridges, interpreted as proximal glaciofluvial deposits, are exposed at the ground surface in high-resistivity areas (type III). Convex surfaces of glaciofluvial bars and sides of meltwater channels are distinct georadar reflectors. Shallow, glaciofluvial bars were islands in the Holocene lake system and surrounding intermediate-resistivity areas represent shore zones of these islands (possible settlement areas).

Trophic relationships and food webs of the benthic invertebrate fauna of two aseasonal tropical streams on Bougainville Island, Papua New Guinea

ABSTRACTThe trophic ecology of Konaino Creek, a small mountain headwater stream draining rainforest in the aseasonal tropics on Bougainville Island, Papua New Guinea, was examined and a food web was constructed. The major source of energy in Konaiano Creek was allochthonous detritus, most of which had been terrestrially degraded to fine particulate organic matter rather than entering the stream as leaf litter. This fine detritus was collected by the filter-feeders (mostly Simuliidae and also Hydropsychidae) which formed the dominant functional feeding group (64.4% of the fauna). Thus filterers processed most of the allochthonous detritus and made the energy available to other trophic levels, rather than shredders (1.7% of the fauna) which perform this role in temperate headwater streams. Collector-gatherers made up 22.7% of the fauna, carnivorses, mostly Odonata, Decapoda (crabs) and Hydrobiosidae, comprised 2.8% of the fauna and grazer-scrapers made up 7.4%. The latter were inhibited by low instream production owing to heavy shading and the instability and abrasion of the substrate due to frequent spates. In comparison, the trophic ecology of the nearby, coastal, Bovo River (with a catchment mainly in rainforest but mostly cleared with introduced species at the study site) was quite different and it was dominated by collector-gatherers (74%) and grazer-scrapers (15%).

Heavy metals in water, periphytonic algae, detritus, and insects from two streams in Shillong, Notheastern India

Cadmium, copper, manganese, lead and zinc concentrations were determined in water, periphytonic algae, detritus, and larvae of three aquatic insects, viz. Baetis sp. (Ephemeroptera: Baetidae), Hydropsyche sp. (Trichoptera: Hydropsychiidae), and Chironomus ramosus Choudhury and Das (Diptera: Chironomidae), during two surveys from an unpolluted and a polluted stream in Shillong, Meghalaya State, Northeastern India. Metal concentrations were higher in all the samples from the polluted stream, possibly reflecting the contributions from various non-point sources of metal contamination present in its catchment. Among the three insects, Baetis sp. was found to accumulate cadmium, copper, and zinc, and Hydropsyche sp. manganese, to concentrations significantly higher than those found in the other taxa. The concentrations of all the metals were higher in fine detritus than in C. ramosus, although Cd and Zn concentrations were elevated in Baetis as compared to those in periphytonic algae and fine detritus, indicating possible bioconcentration of these metals by this animal.

Chironomid microdistribution in gravel of an English chalk river

SUMMARY1. The study aimed to determine the relative importance of certain environmental variables to the distribution of instars of chironomid species in mid‐stream gravels of the River Pang.2. Core samples of gravel substrata were collected over 1 year. Water depth, current, particle size distribution, substratum porosity and detritus were recorded for each sample. The four principal components from a linear ordination of the environmental variables were used to constrain the ordination of chironomid data using the program CANOCO.3. Microdistribution was principally related to a temporal gradient of water depth, current and substratum heterogeneity. There was significant spatial separation of instars along a gradient of fine detritus, silt and substratum porosity. The distributions of early instars of three taxa were also significantly related to particle size. There was a significant relationship between the size distribution of larvae and the spatial distribution of fine sediments and detritus. This relationship was strengthened when restricted to larvae classified as scrapers.

Kurnell Fen: an eastern Australian coastal wetland, its Holocene vegetation, relevant to sea-level change and aboriginal land use

Pollen analysis of a 3.4 m core from residual fenland at the eastern end of Kurnell Peninsula shows that woodland cover of Eucalyptus spp., Angophora costata, Banksia integrifolia/B. serrata and Casuarina spp. suffered losses about 5000 BP when a nearby coastal protobarrier was destabilised by rising sea level, while rapidly-formed fen peat replaced slowly formed O 2-depleted, algal and FeS-rich fine detritus gyttja. Fire frequency was low up to this time. Woodland partly recovered over a 2000 yr period despite heavier or more frequent firing coincident with the entry of hunter-gathering aboriginal (Pre-Bondaian) people. The peatland, formerly sedge/ Triglochin, became dominated by marsh ferns between 4000 and 2000 BP; these were largely replaced during a major change to a more acid peat, with an expansion of Sphagnum bog elements, associated with acidiphilous diatoms. Minor destabilisation of local duneland ca. 1700 BP brought fine sand into the fen basin. Dryland plant cover increased after 1700 BP but mainly dominated locally by a more seral Monotoca/Leptospermum scrub. Bog has reverted to Baumea rubiginosa-Triglochin procera fen with few diatoms, possibly due to recent salt-spray access. This and the more seral vegetation may be linked to higher population density or greater continuity of tenure of later (Bondaian) aboriginal peoples, post-2000 BP.

Cyclic Architecture of a Carbonate Sequence, Early Aptian Shuaiba Formation, Al Huwaisah Field, Oman

Sequence stratigraphy of carbonates is a topic of ongoing controversy. In particular, small-scale shallowing-upward cycles can provide some key information needed for interpretation of carbonate sequences and/or third-order sea level changes. The early Aptian Shuaiba Formation in the Al Huwaisah field consists of about 90 m of shallow-water limestones. Throughout the formation, an overall decreasing influx of fine detritus is notable toward the top. The sequence can be subdivided into a basal unit and an overlying unit. Both units are composed of meter-scale shallowing-upward cycles of different composition, which can be recognized in core and well logs. Fourier analysis of the first principle component of a set of well logs (GR, FDC, CNL, Sonic) revealed an abrupt change in spectral behavior between the two units. Toward the top, the spectra are [open quotes]cleaning upward[close quotes] with an increasing pronunciation of a peak grouping of 1: 2: 5, suggesting a better preservation of orbital variations in the upper unit. Preservation of orbital forcing in shallowing-upward cycles requires rapid rates of sedimentation. In addition, increased shallow-water carbonate production on the platform is indicated by the appearance of reefal organisms. Hence, a higher rate of sedimentation and therefore a faster aggradation of themore » platform is inferred for the upper unit, which could have resulted from an increased rate of relative sea level rise. The sudden facies differentiation on the broad Arabian shelf in the upper part of the early Aptian reflects the development of an intrashelf basin. Changes in rate of relative sea level rise on the Arabian shelf might explain the repeated alternation from an easily correlatable ramp-type sedimentation, with slightly higher input of fine terrigenous sediment (e.g., lower unit of Shuaiba Formation) and a differentiation into platform and intrashelf basin facies due to faster aggradation (e.g., upper unit of Shuaiba Formation).« less

A tectonically controlled alluvial fan which developed into a marine fan-delta at a complex triple junction: Miocene Gildirli Formation of the Adana Basin, Turkey

The sediments of the Gildirli Formation in the Karaisali embayment of the Adana Basin, southern Turkey, records the evolution, under tectonic control at a complex triple junction, of an alluvial fan into a fan-delta during a rapid Early Miocene transgression. The alluvial fan is represented by the lower part of the formation (Çakmak Member) and is characterized by an internal architecture, recording an overall progradation of the coarse proximal fan conglomerates over distal fine-grained sediments. The conglomerates contain mostly Upper Cretaceous limestone clasts of various sizes derived from the faulted mountain front of the Taurus range where this limestone is widely exposed. This active mountain front delimited the Karaisah embayment to the north and provided, during the fault activity, abundant coarse clasts to this area throughout the deposition of both the alluvial fan and the overlying fan-delta sediments. The production of fine detritus during the faulting was very limited and therefore this source contributed little fine grain detritus to the sediments. Provenance studies indicate that the fine clastics in the Gildirli Formation were carried by streams during periods of active faulting and also during periods of tectonic quiescence from a far-distant source in the hinterlands of the Taurus Mountains. The recurrent activity along the northern boundary-fault resulted in the intercalation of these fine clastics with the predominant coarse sediments in this formation. When the study area was flooded from the south by a rapidly deepening Early Miocene sea, the accumulation of all these sediments took place in a fan-delta environment. The fan-delta sediments constitute the upper parts of the Gildirli Formation (Kabalaktepe Member) and display an inverse facies pattern in which foreset beds overlie topsets and hence an upward-fining and deepening sequence. This deviation from a genetic upward-coarsening sequence of a typical marine delta was perhaps the result of a rapid relative rise in sea-level, due to tectonically induced subsidence of the area possibly coupled with a short-term global sea-level rise in the Burdigalian.

Colonization by Lotic Macroinvertebrates: A Review of Processes and Patterns

Ways in which invertebrates colonize lotic habitats are reviewed, tracing patterns in behaviour, trophic ecology, and life history that could lead to predictions concerning resilience of stream communities after disturbance. Patterns are described for small-scale experimental studies using introduced or natural substrates, for large-scale observations of new or rewatered channels, for rivers recovering from pollution, and for unstable rivers with fluctuating discharge. Colonization depends on invertebrate mobility (drift, swimming, crawling, and flight), substrate texture and associated food supplies, competition, and predation. Epilithon-browsers and filter feeders can use the resources of smooth stones; gatherers colonize as fine detritus accumulates; grazers increase as periphyton becomes established; shredders and predators tend to be late arrivals. Propagules for colonization are made more available by asynchronous and aseasonal life cycles, long oviposition periods, and refuges in the streambed or neighbouring waterbodies. Species in frequently disturbed streams benefit from these characteristics. Although disturbance may be due to stochastic factors, recovery is not due to chance. Recurring ecological patterns among early colonizers suggest that knowledge of the hydrologic regime, food resources, and dominant taxa can be used to predict the overall resilience of a stream community.

Feeding patterns of four macroinvertebrate taxa in the headwaters of the Buffalo River, eastern Cape

Gut content analysis, field and laboratory observations, and food choice experiments were used to assign four abundant macroinvertebrate taxa in the headwaters of the Buffalo River, eastern Cape, to functional feeding groups. The mayfly Adenophlebia auriculata (Leptophlebiidae) was classified as a collector: brusher; while the caddisflies, Dyschimus ensifer (Pisuliidae) and Goerodes caffrariae (Lepidostomatidae), and stoneflies Afronemoura spp. (Notonemouridae) were classified as shredders. The effects of organism size, season and biotope on dietary composition were tested, with size accounting for most of the dietary variability within each taxon. Larger individuals consumed more material, larger items, and, in the case of A. auriculata, a wider variety of food-types. There was little variation in the feeding of the taxa in different seasons or biotopes. Shredders ingested mainly leaf fragments, and this, rather than the size of particles in the gut, is a more useful basis for the shredder designation. A. auriculata was the most opportunistic feeder, and items in its diet additional to fine detritus varied seasonally and in the various biotopes. Of the shredders, Afronemoura spp. and D. ensifer were more varied in their diet, augmenting the staple intake of leaf material with other items. G. caffrariae was the most specialised feeder, being exclusively a shredder, regardless of biotope or season. Despite criticisms of the applicability of the FFG concept in the literature, we conclude that these taxa can reasonably be accommodated in functional feeding classes, and that the results are useful in describing the functions performed by the organisms in the river. The relationship between feeding function and river process is emphasised: we suggest that collectors contribute primarily to organic particle retention, while shredders facilitate organic particle size reduction and mobilisation, and the enhancement of substrates for microbial colonisation. An emphasis on river function is a useful context within which to view the FFG concept.

Tube-building behavior in Grandidierella, and two species of Cerapus

Individuals of Grandidierella bonnieroides and Cerapus sp. R commence tube formation by enrolling themselves in a blanket of detritus and gluing together clumps of the material with strands of silk in a few minutes. The initial tubes are very ragged. G. bonnieroides then expands the initial tube by simply dragging in more detritus. In contrast, Cerapus sp. R. commences building an architectured tube outward from the ragged initial tube using very fine detritus collected either by grasping nearby benthic material or by filter feeding particles from the water column. The diameter of the nearly circular architectured tube is tailored very exactly to the height of the body for which we propose a formula. The more advanced Cerapus sp. K skips the initial phase of blanket-tube formation and only makes short architectured tubes as long as the body, carries these about in a fashion analogous to hermit crabs, and attaches them temporarily to epfloral-faunal substrates well above the sediment surface; therefore, no detritus masses are available to Cerapus sp. K. Tube-building in amphipods is roughly classified into 12 kinds having many subdivisions. Advancement of, or specialization in tube building, lacks apparent correlation with morphological advancement or systematic and evolutionary deployment.

Habitat partitioning among the mayfly species (Ephemeroptera) of Yuccabine Creek, a tropical Australian stream.

This study examines the distributions among microhabitats of 12 detritivorous species of mayfly in Yuccabine Creek, an upland tropical rainforest stream. Analysis of data from regular benthic sampling and from in situ experiments using implanted substrata showed that although all species occurred in all the microhabitats examined, different species had significantly different peaks of abundance in different microhabitats, leading to distinct partitioning of the available habitat. The observed patterns of distribution were closely associated with the distribution of fine detritus deposits (FPOM). In the absence of FPOM in fast-flowing regions of the stream, leaf litter was the prime determinant of species distribution. Current velocity and substratum particle size influenced the distribution of the detritus and leaf litter. Abundance of mayflies was greatest in the pool habitat for all except two of the species.