Chironomidae (Diptera) of the Colorado River, Grand Canyon, Arizona, USA, I: systematics and ecology

We describe the chironomid midge fauna of the Colorado River between Glen Canyon Dam and Lake Mead, Arizona. This depauperate fauna, consisting of 38 species, is dominated by euryecious Nearctic or Holarctic orthocladine taxa. In addition, a small Neotropical faunal component is represented by Polypedilum obelos Sublette & Sasa and Rheotanytarsus hamatus Sublette & Sasa. The following new synonyms are given: Protenthes riparius Malloch 1915 with Tanypus bellus Loew 1866 [= Procladius (Psilotanypus) bellus (Loew)]; Cricotopus olivetus Boesel 1983 with Cricotopus (Circotopus) annulator (Goetghebuer) 1927; Cricotopus edurus Sublette & Sublette 1971 with Orthocladius infuscatus Malloch 1915 [= Cricotopus (Cricotopus) infuscatus (Malloch)]. The following new species are described: Cricotopus (Cricotopus) blinni Sublette, Cricotopus (Cricotopus) hermanni Sublette, Metriocnemus stevensi Sublette, and Cladotanytarsus marki Sublette. We discuss the distribution and ecology of each chironomid species in this large, regulated, aridlands river.     

Benthos recovery after an episodic sediment release into a Colorado Rocky Mountain river

During late September 1996, approximately 7000 m 3 of clay- to gravel-sized sediment was flushed from Halligan Reservoir, Larimer County, Colorado, into the North Fork Cache la Poudre River during dam inspections. Approximately 9.6 km of this river was partially or completely affected by this episodic sediment release. Pools up to 3.2 km downstream from the dam lost 50% of their volume. Hess samples taken from October 1996 to September 1997, 100 m downstream from the dam (site 1) and 3.2 km downstream (site 2), revealed effects of sediment on recovery patterns of benthic communities. A 2-way ANOVA was used to determine significant interactions using site and date as main factors. Pairwise differences were then compared using least squares means to determine significant dates within and between sites. Ten days after the sediment release, both density and taxa richness at site 1 (55 organisms per m 2 , 5 taxa) were significantly lower ( P 2 , 25 taxa). These differences remained until June when species richness and densities increased. Plecoptera and Trichoptera colonized from June to September after being eliminated at site 1 and reduced at site 2. No permanently flowing tributaries exist within the study area; therefore, passive downstream drift from such inputs apparently did not influence recovery. Increased densities of taxa such as Baetidae, Hydroptilidae, Hydropsychidae, Chironomidae, Simuliidae, and Oligochaeta occurred plausibly by rapid reproduction. Based on pre-event data, community function completely changed at site 2 from a scraper community to one dominated by collector-gatherers.     

Macrobenthic communities in water bodies and streams of Svalbard,Norway

Diversity of macrobenthic communities was studied from water bodies and streams of Spitsbergen, Svalbard archipelago, Norway. In total 162 quantitative samples from different regions of Spitsbergen were analysed in relation to environmental variables. Macrobenthic communities were found on all kinds of substrates (except for the periglacial zone), representing a wide range of biological communities: solid-bottom, soft-bottom, macrophytes and small brook associated. However, taxonomical structure is very simplified, with particular dominance of the Chironomidae family. Chironomid larvae dominated highly in diversity, abundance and biomass. Overall macrobenthic communities were characteristic, with remarkable dominance of one species and general omnipresent taxonomical scarcity (average 2.8 species per sample). In total we found 30 taxa. We distinguished 16 types of macrobenthis communities, with characteristic dominance of different taxa: chironomids (11 types), oligochaete Enchytraeidae family (3), caddisfly Apatania zonella (1) and gammarid amphipod Gammarus setosus (1). Regarding environmental variables, temperature and pH had the most significant influence on the abundance of macrobenthic organisms. It is hypothesized that the structural convergence of different types of communities is their common response to extreme high Arctic living conditions. On the other hand, different chironomids may dominate in the same habitats and water bodies. This gives the effect of lower average similarity of communities and high β-diversity.     

Ecological studies of a regulated stream: Huntington River, Emery County, Utah

A 36.9x10 6 m 3 reservoir constructed on Huntington River, Emery County, Utah, resulted in changes in physical habitat, water quality, temperature, and flow regime. The greatest changes in physical habitat resulted from: (1) sediment additions from dam and road construction plus erosion of reservoir basin during filling; and (2) changing stream flow from a spring high runoff regime to a moderated flow regime. Elimination of spring nutrient concentration peaks and overall reduction of total dissolved nutrient availability in the river plus moderate reductions in pH were the most apparent water quality changes below the reservoir. Water temperature changes were an increased diurnal and seasonal constancy, summer depression, and winter elevation, generally limited to a 10–12 km reach below the dam. Physical and chemical changes altered macroinvertebrate community structure, with changes greatest near the dam and progressively less as distance downstream increased. Below the dam: (1) more environmentally tolerant taxa increased their dominance; (2) relative numbers of smaller sized individuals increased in relation to larger individuals; and (3) filter feeding, collector/gatherers, and scrapers gained an advantage over shredders. Insect taxa such as Rhithrogena robusta, Pteronarcella badia, and Ephemerella doddsi were eliminated from stream reaches near the dam, and other taxa such as Arctopsyche grandis, Chironomidae, and Simuliidae increased in numbers. Late spring to early summer egg hatch proved to be a disadvantage to Brachycentrus occidentalis, and B. americanus, with a fall hatch, was less impacted by altered river flow patterns. Macroinvertebrate taxa with small instar larvae present from late summer to early fall were negatively impacted by the unnaturally high July and August flows. The reservoir became a physical barrier to downstream larval drift and upcanyon and downcanyon immigration of adults, resulting in reduced numbers of several species above and below the reservoir.         

Chironomidae (Diptera) species distribution related to environmental characteristics of the metal-polluted Arkasas River, Colorado

Mining in the Upper Arkansas catchment has polluted the river with heavy metals for 140 yr. Pupal and adult chironomid species distribution and sedimentary metal concentrations are provided for 22 stations along 259 km of main river during 1984-85. Complete species identification was achieved only recently. This has produced an unprecedented record of chironomid species distribution for a comparable length of river in the USA. Chemically or physically perturbed sites had poor species richness compared with the next site downstream, suggesting that larvae may drift through unfavorable habitats to benign ones. Using canonical correspondence analysis, we found species composition to be most strongly related to variables expressing the longitudinal axis of the river (distance/altitude, temperature, latitude), while toxicity to zinc was a significant secondary correlate. These river-related environmental variables accounted for a greater proportion of pupal species variation than for adults. This was considered to result from a proportion of adults emerging from habitats beyond the main river. Multivariate analysis identified metal-tolerant and -intolerant species. Generic data revealed the same major trends but indicator taxa were lost. The study provides a disturbed-state reference for monitoring effects of remedial actions begun in 1991, and for comparisons with other Colorado rivers.     

Feeding ecology of Gila boraxobius (Osteichthyes: Cyprinidae) endemic to a thermal lake in southeastern Oregon

Gila boraxobius is a dwarf species of cyprinid endemic to a thermal lake in southeastern Oregon. Despite a relatively depauperate fauna and flora in the lake, 24 food items were found in intestines of G. boraxobius. Ten of the 24 foods, including six insects, were of terrestrial origin. The relative importance of food items fluctuated seasonally. Diatoms, chironomid larvae, microcrustaceans, and dipteran adults were the primary foods during spring. In summer, diatoms decreased and terrestrial insects increased in importance. During autumn important foods were terrestrial insects, chironomid larvae, and diatoms. Diatoms and microcrustaceans increased in importance during winter. Chironomid larvae were of importance in winter, when the importance of terrestrial food items decreased substantially. Similar food habits were observed between juveniles and adults, except that adults consumed more gastropods and diatoms and juveniles consumed more copepods and terrestrial insects. Gila boraxobius feeds opportunistically with individuals commonly containing mostly one food item. Fish typically feed by picking foods from soft bottom sediments or from rocks. However, fish will feed throughout the water column or on the surface if food is abundant there. Gila boraxobius feeds throughout the day, with a peak in feeding activity just after sunset. A daily ration of 11.1 percent body weight was calculated for the species during June. A comparison of food habits among G. boraxobius and populations of G. alvordensis during the summer shows that all are opportunistic in feeding, but that G. boraxobius relies more heavily on terrestrial foods.     

An austral anuran assemblage in the Neotropics: seasonal occurrence correlated with photoperiod

The study describes habitat use and temporal occurrence of calling males for an austral anuran assemblage in the Neotropics, southern Brazil. Three study sites (S1 – a permanent river and a stream, S2 – a dam and backwater, S3 – two permanent ponds periodically connected) were sampled between August 2005 and July 2006. The site S3 presented the richest and most diverse assemblage and habitat use within studied sites, and was partitioned by species groups. Richness and abundance of calling males for overall assemblage were seasonal, concentrated in spring and summer and correlated with photoperiod. Temperature, rainfall and air humidity were not correlated with the richness and abundance of calling males. Photoperiod also explained the calling seasons when species were analyzed individually. Habitat use and temporal occurrence were complementary in the partitioning of breeding resources, explaining species coexistence.     

Home-range fidelity and use of historic habitat by adult Colorado pikeminnow ( Ptychocheilus lucius ) in the White River, Colorado and Utah

Twelve wild adult Colorado pikeminnow ( Ptychocheilus lucius ), captured in the tailwaters of Taylor Draw Dam on the White River, Colorado, were implanted with radio transmitters and their movement patterns monitored from 1992 to 1994. The spawning migration of these fish was extensive. In 1993, the only full year of the study, the fish migrated an average of 658 km from the White River to spawning sites in the Yampa or Green rivers and back to the White River. Eight of these fish were translocated in the river upstream of the dam in April 1993. These fish and the 4 others below the dam remained in the river until May 1993. All 12 had migrated down the White River to spawning sites in the Green and Yampa rivers by July 1993. The fish that were located above the dam successfully passed over the dam during their downstream migration. Seven fish migrated upstream toward the Yampa River Canyon spawning site and 5 migrated downstream toward the Green River Desolation/Gray Canyon spawning site. Five of 7 Yampa River fish were found at the spawning site. The other 2 were found 5-8 km downstream of the site. One of 5 Green River fish was found at the spawning site, the other 4 between 16 and 62 km upstream of the site. All fish migrated back to the White River by August 1993 and were found near the dam by October 1993. Two fish were recaptured and translocated above the dam in September 1993. Five fish were located below the dam and 2 above the dam in April 1994. By July 1994 seven of the same fish that had migrated toward the Yampa River in 1993 were found at the Yampa Canyon spawning site. At the same time, 3 of 5 fish that migrated toward the Green River in 1993 were found at the Desolation/Gray Canyon spawning site. This included 2 fish that had been found upstream of the site in 1993. The 12 fish traveled an average of 6 km d -1 (range: 4-10 km d -1 ) during the migration period from May through October 1993. Generally, fish moved faster to the spawning site than back from the site to the White River. These fish moved very little within their home ranges in the White River. Six fish tagged in 1992 moved only 0.1-2.3 km in the tailwater reach below Taylor Draw Dam from September 1992 through April 1993. All fish, after their spawning runs, had moved up to or near the dam by October 1993. These fish were not tracked again until April 1994. Their movement patterns in April 1994 were similar to those observed in April 1993. The greatest amount of fish movement in the White River was displayed by the 8 fish placed above Taylor Draw Dam in April 1993 and the 2 placed in Kenney Reservoir in September 1993. They moved 1.1-40.6 km in the river before and after their spawning migration in spring and autumn 1993. These spawning migrations suggest that adult Colorado pikeminnow in the White River were recruited from both Green and Yampa river spawning populations and were presumably imprinted to these respective spawning sites. Those fish placed above Taylor Draw Dam established home ranges in habitats previously occupied by Colorado pikeminnow before the dam was completed. They remained there until they migrated downstream during the spawning period. Although we did not study fish passage, our study demonstrates that adult Colorado pikeminnow will use habitat if access is provided. Translocation of wild adult fish into historic but unoccupied habitats may be a valuable recovery option.     

Leafhopper assemblages on native and reseeded grasslands in southwestern Montana

Using sweep samples, we surveyed leafhoppers (Homoptera: Cicadellidae) on grassland sites in the Gallatin Valley of Montana during 1988 and 1991. We sampled 12 sites representing 2 habitat types defined by their dominant plant species in an undisturbed state ( Stipa comata / Bouteloua gracilis and Festuca idahoensis / Agropyron spicatum ). At half of the sites the native plant communities were present, whereas the remainder had been reseeded with either Agropyron spicatum (to replace the S. comata / B. gracilis assemblage ) or Bromus inermis (to replace the F. idahoensis / A. spicatum assemblage). We found at least 66 species of leafhoppers among 44,428 adults collected. Seven taxa comprised 83% of all individuals collected: Doratura stylata (26%), Ceratagallia spp. (18%), Endria inimica (17%), Orocastus perpusillus (7%), Sorhoanus spp. (6%), Athysanella spp. (5%), and Psammotettix lividellus (4%). Sites with similar vegetation had broadly similar leafhopper assemblages, and assemblages differed most between the relatively xeric Stipa comata / Bouteloua gracilis sites and the more mesic sites dominated by Bromus inermis . The composition of a leafhopper assemblage at a site tended to be more similar to those on noncontiguous sites with the same overall vegetation than to those on contiguous sites with different vegetation. These patterns are likely related to the fact that many Cicadellidae are host specialists. In fact, variation in abundance of some of the most common leafhopper taxa on our sites was correlated with the percent cover of their known host plants. Our analyses of the leafhopper assemblages generally support the contention that terrestrial plant associations are among the more useful indicators of insect community composition.     

Coincidence of agonistic larval behaviour,uniform dispersion,and unusual pupal morphology in a genus of marine midges (Diptera: Chironomidae)

Field observations, corroborated by laboratory study, show that older larvae of the marine chironomid, Paraclunio spp., aggressively defend the silken tubes in which they eventually pupate. Depending on the nature of the substrate, the spatial dispersion of these tubes is occasionally uniform. These patterns of behaviour and dispersion coincide with the presence of terminal sclerotized structures in the pupa. Speculation of the causal relationships among these features is presented.     

First specimen records for Ruffed Grouse in Colorado

We report the first specimen records for Ruffed Grouse ( Bonasa umbellus ) collected in Colorado, provide the location, describe the habitat, and briefly discuss the rarity of this species within the state. Three Ruffed Grouse were collected, an adult male in September 1988 and a juvenile male and adult female in September 1990, on Hoy Mountain, Moffat County, Colorado, within 0.6 km of Utah. The habitat is primarily open Douglas-fir ( Pseudotsuga menziesii ) forest with scattered clumps of quaking aspen ( Populus tremuloides ) and Utah serviceberry ( Amelanchier utahensis ). Habitats to the north, east, and south are primarily dominated by sagebrush ( Artemisia spp.) steppe and pionjuniper ( Pinus spp.-- Juniperus spp.) woodland. We hypothesize that natural expansion of Ruffed Grouse further east, north, and south is prohibited by unsuitable habitat exacerbated by the limited flight range capability of the species.     

Plecoptera and Trichoptera species distribution related to environmental characteristics of the metal-polluted Arkansas River, Colorado

The Upper Arkansas catchment has been polluted with heavy metals from mining for almost 140 yr. Adult Plecoptera and Trichoptera species distributions were recorded from 22 stations along 259 km of main river during 1984-85 so that these could be related to metal deposition and other environmental characteristics. Chemically or physically perturbed sites had poor species richness compared with adjacent sites. There was no sequential downstream increase in species numbers. Filter-feeders proportionally increased downstream as predators declined; these proportions were reset at a high-energy site before the trend resumed. Using canonical correspondence analysis, we found that species composition was most strongly related to changes in distance/altitude and to temperature, particularly after regulatory flows entered the river. The proportion of biological variation explained by river measurements indicated that collected adults were largely derived from the main Arkansas River. Species tolerant of high sedimentary metal concentrations were identified while some other species appeared to be sensitive. The study provides a disturbed-state reference for monitoring effects of remedial actions begun in 1991, and for comparisons with other Colorado rivers.     

Morphological and host-symbiont studies of Trichodina tenuiformis and Apiosoma campanulatum infesting mottled cculpin ( Cottus baird i) from Provo River, Utah

Trichodina tenuiformis Stein, 1979 and Apiosoma campanulactum Timofeev, 1962 were found on gills of mottled sculpin ( Cottus bairdi ) from two locations in the Provo River, UT. They were studied by light and electron optics. Dimensions and morphology of the adhesive disc and denticles of T. tenuiformis were differentiated from other Trichodina species. A. campanulatum was characterized by its spindle-shaped cell body. Fine features examined by scanning electron microscopy included body shape, pellicle, elements of the adhesive disc, aboral ciliary complex, and aboral ciliary spiral. Histopathological studies suggested that the organisms are ectocommensals. Ecological aspects of organism infestation between two areas were also investigated. This report establishes a new host and distribution record for these two species in mottled sculpin from the Provo River, UT.     

Exclusion experiments with backwater invertebrate communities of the Green River, Utah

The role of biotic interactions in structuring freshwater invertebrate communities has been extensively studied but with mixed results. For example, fish effects on invertebrates are most pronounced in pelagic and soft-sediment benthic habitats that lack structural complexity, yet appear insignificant in benthic rubble habitats. Backwaters of the Green River, Utah, are shallow, structurally simple, quiet-water embayments adjacent to the river. These habitats form in middle to late summer and are colonized by benthic and epibenthic invertebrates that produce standing crops significantly higher than the river. Backwaters are also utilized by a large number of fish species. We used cages to determine if selective exclusion of backwater organisms could significantly change invertebrate community structure. Results showed that backwater invertebrate community components changed significantly in response to exclusion treatments. Two taxa (both predators), the chironomid genus Tanypus (Diptera: Chironomidae) and the corixid genus Trichocorixa (Hemiptera: Corixidae), increased in density in exclusion cages while cladocerans, immature copepods, the cyclopoid copepod Eucyclops speratus , and the chironomid genus Procladius all decreased in density. Diversity of adult copepods was reduced by exclusion treatments, though density of only a single species changed significantly.     

New records of bats (Chiroptera: Mammalia) from Malawi,east-central Africa,with an assessment of their status and conservation

This paper reports 97 new species-locality records of bats from Malawi. Of particular interest are four species of bats (Rhinolophus swinnyi, Triaenops persicus, Eptesicus flavescens, Tadarida nigeriae) which have not been recorded previously from Malawi. The relative status of bats in Malawi was estimated and the species were placed in five categories ranging from ‘rarely-recorded’ to ‘very commonly-recorded’. Of the 59 species of bats known to occur in Malawi, 28 are rarely-recorded in Malawi. The relative status and species-locality records of bats were analysed to assess which species, and which localities, need special conservation effort. Seventeen species which are rare throughout their ranges in Africa as well as being rarely-recorded or seldom-recorded in Malawi, are considered to require special effort. Checklists of bats are given for 11 localities, including Liwonde NP in the Upper Shire Valley (29 spp.), two localities on the Shire Highlands (28, 22 spp.), Thyolo on the boundary between the Shire Highlands and Phalombe Plain (22 spp.), and Chiromo in the Lower Shire valley (30 spp.), which have particularly rich bat faunas. Localities in need of urgent conservation effort include Ntchisi FR in the Central Region, and Chiromo. Ninety-two percent of the species of bats known to occur in Malawi have been recorded from the Southern Region. Most of these species will probably continue to survive in southern Malawi provided that the National Parks (especially Liwonde NP) are maintained and well-managed, and there is no further destruction of the indigenous vegetation at Chiromo and Thyolo, and on the Shire Highlands.     

Effects of turbidity on feeding rates of Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) and Lahontan redside shiner ( Richardsonius egregius )

The spawning of Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) in Summit Lake, Nevada, has reportedly declined since the early 1970s, coincident with the appearance of Lahontan redside shiner ( Richardsonius egregius ) in the lake. We investigated the relative predatory abilities of the 2 fish species foraging on live Daphnia magna in turbidity conditions commonly observed in Summit Lake. Experiments were performed under controlled light and temperature condition. In separate trials we fed trout and shiner 1 of 3 size classes of D. magna (1.7 mm, 2.2 mm, and 3.0 mm) at 6 levels of turbidity ranging from 3.5 to 25 NTU. Feeding rates for both species varied inversely with turbidity for all prey sizes. Feeding rates of shiner were greater than trout at all turbidity levels. In low turbidity (5 TNU), shiner consumed approximately 3% more prey during 2-h feeding trials. However, at high turbidity levels, the difference in feeding rates between species was proportionally higher (10%). At high turbidity levels (≥ 20 NTU) trout predation rates were relative insensitive to prey size. However, shiner continued to consume more, larger prey at the highest turbidity levels. These results indicate that Lahontan redside shiner may be superior to Lahontan cutthroat trout as zooplankton predators at high turbidity levels, and may explain the recent success of shiner in Summit Lake.     

Quaternary paleontology and paleocology of Crystal Ball Cave, Millard County, Utah: with emphasis on mammals and description of a new species of fossil skunk

Crystal Ball Cave is located in a small outlier of the Snake Range in Snake Valley 1.7 km (1 mile) west of Lake Bonneville at its highest level. Original vertebrate skeletal material (mostly mammalian) has been found in shallow dry dust 61 m (200 feet) inside the cave. Radiocarbon dates show that fossils have been accumulating since at least 23,000 Y.B.P. It appears that wood rats and possibly small carnivores transported the fossils into the cave because only the smallest elements of large mammals are represented. The fossil assemblage represents a much more boreal community than the present local fauna. Fish, Ondatra zibethicus , and Mustela cf. vison , which require perennial water, were recovered, as were Ochotona princeps , Lepus cf. Americana , Microtus cf. pennsylvanicus , Vulpes vulpes , and Martes americana , which have also been extirpated from the Snake Range. Marmota flaviventris , Neotoma cinerea , cf. Cervus elaphus , and Ovis Canadensis were recovered but now occur only at higher elevations in the range. Extinct taxa recovered are Smilodon cf. fatalis , Equus species, Camelops cf. hesternus , Hemiauchenia cf. macrocephala , cf. Symbos cavifrons , and a new species of Brachyprotoma , herein named B. brevimala . This is the first recovery of Brachyprotoma from the western United States.      

Review of the Fridericia species (Oligochaeta: Enchytraeidae) possessing two spermathecal diverticula and description of a new species

A new Fridericia species (Fridericia lacii sp. nov.) is described. Including this new species the number of valid Fridericia species with two diverticula per spermatheca is 50. The present study provides an opportunity for the comparison and separation of Fridericia species on the basis of spermatheca and diverticulum characteristics. Nine tables summarize the two larger groups and five subgroups of species possessing bidiverticulate spermathecae. The new species is distinguished from all known valid congeners in this assemblage by the following combination of traits: (1) 4–7 mm long, 200–290 µm wide (in vivo) with 30–36 segments; (2) maximum four chaetae per bundle; (3) all pairs of pharyngeal glands with ventral lobes, the third is the largest with posterior projections; (4) only three pairs of preclitellar nephridia; (5) oesophageal appendages type a; (6) mucocytes type a, lenticytes small; (7) chylus cells in preclitellar segments; (8) clitellum girdle‐shaped, glands in transverse rows, between the bursal slits only granulocytes; bursal slit is longitudinal; (9) seminal vesicle small or absent; (10) sperm funnel one‐half as long as the body diameter, collar narrower than the funnel body; (11) subneural glands absent; (12) the ampulla of the spermatheca with two sessile (or with short stalks), spherical, thin‐walled diverticula, communication with the oesophagus separate, ectal duct about as long as body diameter, one floppy ectal gland at the orifice.     

Distribution, movements, and habitat use of razorback sucker ( Xyrauchen texanus ) in a lower Colorado River reservoir, Arizona-Nevada

Distribution, movements, and habitat use of 10 wild adult razorback suckers ( Xyrauchen texanus ) were examined in Lake Mohave, Arizona-Nevada, from November 1994 through July 1997. Movement rates (0.00-17.35 km d -1 ) and ranges ( x = 39 km) were similar to those for riverine populations. All study fish returned to spawning sites used in previous years, but they also visited other spawning areas. Spawning females were significantly ( P = 0.031) more active than males (480 vs. 87 m d -1 ) and moved substantial distances between spawning sites during peak reproduction (1-28 February). Fish became most active (m d -1 , km month -1 ) after spawning and moved to areas known to support higher algal production. Fish were typically within 50 m ( P 30.0 m). Adults were detected throughout the available thermal gradient (12°-30°C), but during summer typically had body temperatures between 18° and 22°C. Vertical movements within the water column showed no correlation with depth or time of day, but seasonal shifts suggest fish may regulate body temperature by seeking specific temperatures during reservoir stratification.     

Diversity and distribution of marine Gastrotricha along the northern beaches of the state of São Paulo (Brazil), with description of a new species of Macrodasys (Macrodasyida,Macrodasyidae)

Forty-three putative species were found in this first-ever survey of the marine gastrotrich fauna of Brazil. Samples from 23 locations and 37 sites along the northern coasts of the state of São Paulo yielded 21 species of Macrodasyida (12 genera and five families) and 22 species of Chaetonotida (seven genera and two families). Based on morphology, 26 species appear to be taxa not previously described and thus far endemic to Brazil, 13 are known species, while one in each of the genera Diplodasys, Paradasys and Tetranchyroderma remains undetermined. The overall high diversity contrasts with the generally low number of species from single locations, averaging 4.3 (SD 3.5) spp. per location; very few species were found in sites characterized by very fine sand sediment loaded with detritus and by high water turbidity (e.g. 1 sp. in praia da Fazenda), whereas a well-diversified gastrotrich community was found in localities characterized by medium or fine sand with little detritus and clear water (e.g. 14 spp. in praia de Castelhanos). The macrodasyidans, Paraturbanella sp. 1, Pseudostomella sp. 1 and Tetranchyroderma sp. 1, and the chaetonotidan Heteroxenotrichula sp. 1 were the most common species, often sympatric and particularly frequent and abundant along the continental shoreline (recorded in 50–65% of these localities); on the other hand, Macrodasys fornerise n. sp., Ptychostomella sp. 1, Tetranchyroderma sp. 3 and Thaumastoderma sp. 2, while occurring sometimes in very high numbers, exhibited a much narrower range, being encountered only once or twice during the survey. The main morphometric traits are described of the 13 species considered to be cosmopolitan or with at least an amphi-Atlantic distribution, including Chaetonotus apechochaetus and Halichaetonotus marivagus, reported here for the first time from the Americas; of the 26 species thus far endemic to Brazil, Macrodasys fornerise n. sp., which is characterized by a noticeable 145?µm-long frontal organ, is also described and figured.