The opercular brood chambers of Spirorbidae

Brood chambers of Januinae are cuticular and have to be shed to liberate the larvae, whereas those of Pileolaria are bounded by two epithelia and are used repeatedly. Links for interpreting these differences are to be found amongst some of the smaller genera of Pileolariinae. In Amplicaria and Vinearia the embryos are held between a pair of opercular plates, which form distal and proximal cups with the concavities facing each other. They are successive units in a series of sheddings and renewals, found generally in Spirorbidae even on non-brooding opercula. A Janua brood chamber corresponds with the distal component of such a pair, the proximal component being represented by the basal plate. In most Pileolariinae the brood chamber is formed entirely by the proximal component. Amongst Nidificaria species, some hold the embryos in a simple cup with no distal protection, but others have the aboral side of the cup extended and growing over distally, like the dorsal lip of a blastopore. The aperture that remains may be almost closed but can open again to liberate the larvae. Brood chambers of Pileolaria are exactly like that, except that they lack any calcification proximally. Those of Jugaria and Bushiella are similar, but with additional protection through retention of distal plates. Protoleodora species are subarctic and very close to Jugaria and Bushiella in distribution and morphology, but they have less calcification, readily lose their distal plates, and develop soft-walled brood pouch extensions which can accommodate very large broods. There seem to be tenuous links between the Pileolariinae and the Romanchellinae, southern hemisphere spirorbids which incubate in their tubes. Fertilization and spawning need further study.     

Inter‐regional comparison of land‐use effects on stream metabolism

1. Rates of whole‐system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first‐order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. 2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban‐influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. 3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. 4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike’s information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land‐use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land‐use categories in the catchment as regulators of ER. 5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land‐use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER. 6. Overall, consideration of the data separated by land‐use categories showed reduced inter‐regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.     

The Scientific Basis for Shipibo Soil Classification and Land Use: Changes in Soil-Plant Associations with Cash Cropping

Since the Shipibo began cash cropping rice, their land use patterns have changed with proportionately less utilization of soft sandy soils, which are best for staple Musa production, and greater use of harder clayey soils, which are more suitable for rice and root crops. Statistical analysis of soil samples reveals the physical-chemical basis for Shipibo soil categories and indicates the effect ofswidden agriculture on levels of important soil characteristics. While cultural principles for planting have summarized these important ecological relationships in the past, they are often violated with increasing rice production. Examination of time allocation and food consumption data shows that changes in Shipibo land use patterns are associated with higher labor costs during brief periods of the agricultural cycle and greater dependence on domesticated animal foods.     

The sedimentation of amyloplasts in living statocytes of the dandelion flower stalk

Abstract The sedimentation of amyloplasts in inverted statocytes of the flower stalk of dandelion (Taraxacum officinale Weber) was followed using light microscopy. Much variety in sedimentation pattern was evident with complete sedimentation occurring in as little as 3–4 min to as much as a few h and individual amyloplasts showing barely perceptible sedimentation or sedimenting at speeds of up to 40 μm min^?1. It was also apparent that amyloplasts were subjected to considerable movement after they had sedimented. Large vacuoles and cytoplasmic streaming in statocytes were confirmed and are considered to greatly influence amy-loplast sedimentation pattern. The implications of these observations for the starch-statolith hypothesis of geotropism are discussed.     

Linnaeus' Neptunea (Mollusca: Gastropoda)

Three species of the arcto-boreal, large gastropod Neptunea , described by Linnaeus in 1758 and 1771, occur in large numbers over wide areas of the inshore North Atlantic and adjacent Arctic seas and are conspicuous among Pliocene and Pleistocene molluscs in the Icelandic, North Sea, and western Mediterranean basins. Selections of lectotypes for these species from shells in the collection of the Linnean Society of London, and designations of their type localities, establish the identity of Linnaeus' neptunes and more accurately determine their geographic and geologic distribution. The geographic range of Neptunea (Neptunea) antiqua (L.), the type species, now extends from southern Norway to the northern Biscay coast of France and from the westernmost Baltic Sea to southwestern Ireland; this species also occurs in Pliocene-Holocene marine deposits in West and East Germany, Sweden, the Netherlands, England and France. Its type locality is determined to be the North Sea. N. (Neptunea) despecta (L.) lives in the eastern Canadian Arctic, off southern Greenland, the Barents Sea, and North Atlantic as far south as Massachusetts and Portugal; it also occurs in Pliocene-Holocene strata of eastern Canada, east-central Greenland, Norway (including Svalbard), the Soviet Union, Sweden and England. Its type locality is determined to be the postglacial deposits at Uddevalla in southwestern Sweden. N. (Sulcosipho) contraria (L.) now extends from the southern Biscay coast of France to Cape Spartel, Morocco; this species also occurs in Pleistocene and lower Holocene sequences of the western Mediterranean. Its type locality is determined to be Vigo Bay, Spain. A closely related fossil species, N. (S.) angulata (S. V. Wood), occurs in Pliocene and Pleistocene deposits of the North Sea basin.     

Experiments with MBC derivatives for the control of Dutch elm disease

Preparations of methyl benzimidazol-2-ylcarbamate (MBC) hydrochloride stabilized with HC1, MBC nitrate stabilized with lactic acid and MBC bisul-phate stabilized with KHS0₄ were made from technical MBC. As it was the least phytotoxic to elm shoots, the hydrochloride was selected for field experiments on the control of Dutch elm disease using 6 m elms. In protectant experiments using 1.51 of 0.25 or 0.5 % MBC per tree, only five of eighteen injected trees became infected while all the control trees were severely diseased. In curative experiments, injection with 0.25 % MBC 2 and 4 wk after inoculation with Ceratocystis ulmi kept symptoms to < 1 and 5% respectively, compared with 76% in untreated inoculated trees. MBC at 0.5 % Save similar results.     

A Sightability Model for Mountain Goats

ABSTRACT Unbiased estimates of mountain goat (Oreamnos americanus) populations are key to meeting diverse harvest management and conservation objectives. We developed logistic regression models of factors influencing sightability of mountain goat groups during helicopter surveys throughout the Cascades and Olympic Ranges in western Washington during summers, 2004–2007. We conducted 205 trials of the ability of aerial survey crews to detect groups of mountain goats whose presence was known based on simultaneous direct observation from the ground (n = 84), Global Positioning System (GPS) telemetry (n = 115), or both (n = 6). Aerial survey crews detected 77% and 79% of all groups known to be present based on ground observers and GPS collars, respectively. The best models indicated that sightability of mountain goat groups was a function of the number of mountain goats in a group, presence of terrain obstruction, and extent of overstory vegetation. Aerial counts of mountain goats within groups did not differ greatly from known group sizes, indicating that under-counting bias within detected groups of mountain goats was small. We applied Horvitz-Thompson-like sightability adjustments to 1,139 groups of mountain goats observed in the Cascade and Olympic ranges, Washington, USA, from 2004 to 2007. Estimated mean sightability of individual animals was 85% but ranged 0.75–0.91 in areas with low and high sightability, respectively. Simulations of mountain goat surveys indicated that precision of population estimates adjusted for sightability biases increased with population size and number of replicate surveys, providing general guidance for the design of future surveys. Because survey conditions, group sizes, and habitat occupied by goats vary among surveys, we recommend using sightability correction methods to decrease bias in population estimates from aerial surveys of mountain goats.     

Factors influencing egg parasitism in sub‐social insects: insights from the treehopper Alchisme grossa (Hemiptera,Auchenorrhyncha, Membracidae)

相似文献