Buoyancy Changes as Related to Respiratory Behavior in an Amphibious Snail, Pomacea Urceus (Müller), from Venezuela

The ampullariid Pomacea urceus uses its ctenidium and lung in respiration. The snails reach the surface with their siphon and ventilate their lung by withdrawing their head-foot in a pumping action. The lung gas also serves to change the buoyancy of the snails. After a ventilation a snail does not necessarily return to the same buoyancy level. They may achieve overall specific gravities of \u3c1 to \u3e 1 after a ventilation. They may remain submerged (s.g. \u3e 1) or float (s.g

Comparison of Carbon and Nitrogen Content of Infected and Uninfected Snails, Succinea ovalis, and the Trematode Leucochloridium variae

In June, 6.7% of adult Succinea ovalis collected near Urbana, Ohio, were infected with the trematode, Leucochloridium variae. The effects of parasitism were assessed as total organic carbon (equivalent to calorific values) and as total nitrogen. The parasite represents 23.8% of total (parasite + snail tissue) dry tissue weight, 21.4% of total carbon and 19.8% of total nitrogen of infected snails. The higher C:N ratio for parasite tissue indicates a higher proportion of nonproteinaceous compounds (e.g., fats and/or carbohydrates) as compared to host tissue. There is less snail tissue in parasitized S. ovalis. The C:N ratios for parasitized and nonparasitized snail tissue suggest identical percentage compositions of proteins, fats, and carbohydrates

Brief Note: Growth of Pisidium Casertanum (Poli) in West Central Ohio

Author Institution: Department of Biology, University of Dayto

Growth of Pisidium casertanum (Poli) in West Central Ohio

Clarke (1973) states that Pisidium casertanum (Poli) is perhaps the most common species of Pisidium and is truly cosmopolitan, occurring throughout Eurasia, Africa, Australia, and South, Central and North America. Populations of these clams are reported in habitats ranging from ephemeral ponds to benthic zones of deep lakes. Our study describes Manuscript received 29 May 1979 and in revised form 25 July 1980 (#79-34). 2 Present address: Department of Biology, University of Virginia, Charlottesville, VA 22901. 3 Present address: Department of Zoology, Miami University, Oxford, OH 45056. 41 aspects of the life-cycle of P. casertanum in a spring-fed stream with a relatively small annual temperature range. Clams were collected monthly during the winter and bimonthly or weekly during the summer of 1974 and less regularly during 1975 from the west branch of Cedar Run at Cedar Bog, near Urbana, Ohio (USGS) map quadrangle Urbana West, Champaign County, Ohio: 40° 03.42\u27N 83°47.98\u27W). At certain times (see fig. 1) physical and chemical characteristics of the stream were recorded, including temperature and oxygen concentration (YSI Model 54 oxygen meter), conductivity (YSI Model 33 conductivity meter) and hardness (EDTA method, American Public Health Association 1976)

Hawaiian Freshwater Polychaeta: A Potentially Substantial Trophic Component of Stream Depositional Habitats

In this paper we report the widespread occurrence of large annelids (Polychaeta: Nereididae) in Hawaiian stream depositional habitats, drawing attention to the lack of knowledge of Hawaiian stream energetics. Specimens of Namalycastis sp. were collected from five Hawaiian Islands from May–July 1995 and from the island of Maui from July–December 1999 and April–July 2000. Most specimens collected were N. hawaiiensis, while two specimens of N. abiuma were collected from a single site on the island of Molokai. Specimens were collected from elevations ranging from 3–240 m; several collections were from sites above at least one major (\u3e 15 m high) waterfall. Habitats were characterized by slow-moving or stagnant water, water temperatures ranging from \u3c 18–29 C, mixed gravel and sand substrates with organic detritus. Specimens were found among roots of vegetation along stream edges, in small lava pockets, buried in loose gravel, and in depressions between, under, and inside porous rocks. Body lengths of preserved specimens ranged from ~ 9 to 150 mm among islands and streams between years and seasons. Polychaetes were usually abundant in these habitats indicating a nearly ubiquitous distribution of Namalycastis, and suggesting ecological importance for stream benthic trophic dynamics throughout the Hawaiian archipelago

Effect of Water Removal On Introduced Caddisflies from a Tropical Mountain Stream

Tropical island streams worldwide are being threatened by existing or proposed dams and diversions. Numerous streams of the Hawaiian Islands have diversions that remove freshwater for human use; however, little research has addressed diversion effects on aquatic insect communities in tropical streams. We studied the effect of water removal by a stream diversion on density and biomass of two introduced Trichoptera, Cheumatopsyche analis (Banks) (Hydropsychidae) and Hydroptila potosina (Buenoa- Soria) (Hydroptilidae), in Iao Stream, Maui, Hawaii, from April-August 2000. Both species seem to have multivoltine life cycles. Pooled Trichoptera (both species) biomass was significantly greater above the diversion (178.3 mg.m-2 and 112.9 mg.m-2 for upstream and downstream, respectively). For each individual species the mean total instar biomass was significantly reduced below the diversion (38 % and 54 % reduction for C. analis and H. potosina, respectively). Both species had greater densities above the diversion; however, individual larval mass of H. potosina instars, but not C. analis instars, was significantly lower below the diversion. Our results suggest that reduced habitat quality, due to lowered stream flow, limits density of both species below the diversion, whereas lowered food quantity and quality may differentially affect H. potosina biomass through reduced body sizes. These data suggest that water removal not only reduces habitat quality, but significantly lowers the community biomass of these introduced Trichoptera species, affecting the trophic energetics of stream reaches downstream of a diversion in Hawaii. Similar changes to macroinvertebrate communities would be expected below dams and diversions of streams in other tropical regions

Interpopulation Variation in Calcareous and Proteinaceous Shell Components in the Stream Limpet, Ferrissia rivularis

Natural populations of the North American stream limpet, F. rivularis, were studied in upstate New York [USA], in a set of localities whose waters have a 15-fold range of dissolved Ca (4.6-67.6 mg/liter) and also range from oligotrophy to eutrophy. Shell component analyses (CaCO3, total organic C and total N) are reported as component mass-fractions (mg/g or .mu.g/g dry weight) and as values for a standard limpet shell of 35 mm aperture length (AL). More than 2-fold differences occur between populations in all 3 components, with relatively little variation occurring within each population. Expressed per standard limpet, CaCO3 values for different populations range from 0.8-1.97 mg with no direct relationship to environmental dissolved Ca. Nominal concentration ratios of body Ca to environmental Ca range from 1953:1-29,130:1. Values for total organic C (9.13-21.0 .mu.g) and total N (2.7-6.69 .mu.g) in the shells parallel each other, all C:N ratios being relatively uniform (3.0:1-3.4:1), and indicating that the non-calcareous components are largely proteinaceous. Although alternative hypotheses predict an inverse or a direct relationship between the organic and the calcareous components, neither is shown by these populations. Genetic controls of shell secretion for the 2-major components apparently are independent, and chance dispersal has resulted in some rather inappropriate shells in certain habitats. This irregular variation in Ferrissia is 1st discussed in relation to other patterns of shell component relationships known for other freshwater mollusk, including direct relationship of the mass of shell CaCO3 to the dissolved Ca available as in Lymnaea peregra and Laevapex fuscus and the apparent regulation producing standard shell weights in L. palustris and Physa gyrina. The results are then discussed in relation to assessment of radionuclide pollution using molluscan shells from fresh waters and in their more general relationship to modes and rates of evolutionary change in freshwater faunas

Seasonal Metabolism of the Sphaeriid Clam, Musculium partumeium (Say), from a Permanent and a Temporary Pond

Seasonal metabolic rates were examined for the sphaeriid clam, Musculium partumeium (Say) from a permanent and a temporary pond. For the fall-born generation from the permanent pond and for the single generation from the temporary pond, metabolic rates peak during periods of greatest growth and reproduction. Metabolic rates were consistently higher for the permanent pond population. These rates for Musculium partumeium extend the available information on the family Sphaeriidae to the genus Musculium

Life Cycle of a Torrenticolous Hawaiian Chironomid (Telmatogeton Torrenticola): Stream Flow and Microhabitat Effects

In this study we documented the instar densities and life cycle of Telmatogeton torrenticola Terry (Chironomidae : Telmatogetoninae) from Kinihapai Stream, Maui, Hawaii. Greatest larval densities of this midge are found on substrates of high velocity, shallow flows of cascades, and splash zones of waterfalls, with lower densities in riffles. In the summer of 1994 we compared the effects of two microhabitats (termed optimal and suboptimal) on inter-instar density and relative abundance. In a second year (1995), we evaluated the effect of long-term reduced stream flow on these variables only in optimal microhabitats. A significant reduction in stream flow from 1994 to 1995 was correlated with a similar reduction in larval densities that precluded larval colonization of suboptimal habitats in 1995, thereby preventing sampling in this microhabitat during that summer. Depth of optimal habitats of 1995 were significantly shallower than both habitats of 1994, with suboptimal habitats of 1994 the deepest. Total larval density was significantly higher in 1994 optimal habitats, while 1994 suboptimal and 1995 optimal habitats were statistically similar. Individual instar densities showed variable differences among habitats and years, with the first three instars always highest in 1994 optimal habitats. All instars and pupae were collected on most sampling dates in both years ; however, pupae were only collected on a two dates in suboptimal habitats of 1994. Based on larval size frequency histograms, T. torrenticola has a multivoltine, asynchronous life cycle, with continuous reproduction, which is variable among microhabitats characterized by different flow velocity and depth, and between years of differing stream discharge. Reduced stream flow during the summer of 1995 had effects of reducing densities and changing life cycle features similar to those found in 1994 (a year of higher stream flow) suboptimal habitats

Morphological Characteristics and Species Separation of Hawaiian Postlarval Amphidromous Fishes

There are five Hawaiian amphidromous fishes (Gobiidae: Lentipes concolor, Awaous guamensis, Sicyopterus stimpsoni, Stenogobius hawaiiensis; Eleotridae: Eleotris sandwicensis). Amphidromous adults deposit eggs on the stream bottom. After hatching, larvae drift to the ocean for growth followed by postlarval migration back into the streams. Postlarvae were collected to construct a dichotomous identification key based on 12 morphological measures and ray counts from four fins. Overall, the presense of fused pelvic fins, standard length (SL), and fin ray numbers were the most useful in species separation. Gobies were separated from the eleotrid by the former having fused pelvic fins. Within the gobies, S. stimpsoni had the largest SL [mean (SD) = 20.5 (1.0) mm] with A. guamensis [15.8 (0.6)mm] smaller and L. concolor [13.7 (1.3) mm] and S. hawaiiensis [13.3 (1.0) mm] the smallest. Although SL alone could not separate L. concolor and S. hawaiiensis, the former had 5 first dorsal fin rays compared to 6 in all other gobies. Nineteen pectoral fin rays separated S. stimpsoni from A. guamensis, and SL along with anal and second dorsal fin ray number, separated A. guamensis from S. hawaiiensis. Canonical discriminate function analysis was used as an exploratory approach to confirm the dichotomous key. With all morphological features entered into the analysis, three significant discriminate functions were generated with the most highly correlated morphological variables within each function the same as those used in the dichotomous key. Additionally, regression models were generated for predicting SL from total length (TL) of three postlarval species. Measures of TL do not require excessive handling or killing specimens; however, SL is usually the preferred measure for body size. The ability to identify migrating postlarvae under a variety of conditions aids in data acquisition under circumstances where preservation may or may not be necessary for the research objectives