Identification of uncultured bacteria tightly associated with the intestine of the earthworm Lumbricus rubellus (Lumbricidae; Oligochaeta)

The bacteria associated with the intestine and casts of the earthworm Lumbricus rubellus Hoffmeister, 1843, were examined by direct counts, culturability studies, 16S rRNA gene clone libraries, and fluorescent in situ hybridization (FISH). A significant fraction, 24-47%, of the total numbers of prokaryotes remaining in the intestine after casting were tightly associated with the intestinal wall. Bacterial 16S rRNA gene clone libraries constructed from washed earthworm intestinal tissue suggested that the bacterial community was dominated by a few phylotypes that were either absent from, or in low abundance, in the casts. The specific phylotypes present depended on the date of sampling and included representatives of the Acidobacteria, Firmicutes, β-Proteobacteria, and one phylogenetically deep, unclassified group. Juvenile earthworms subsequently collected contained three of the four phylotypes observed in the intestine clone libraries. The Firmicutes phylotype was examined by FISH and was found to be a short rod that represented only a small fraction of the total population of the juvenile samples. These results suggested that the microbial community tightly associated with the intestine was dominated by a small number of phylotypes and that this association was opportunistic rather than obligate.     

Decomposition,nutrient loss and microarthropod densities in herbicide-treated grass litter in a Georgia piedmont agroecosystem

A litterbag experiment was made to investigate the influence of the herbicides atrazine, paraquat and glyphosate on several aspects of the decomposition of grass litter in a fallow field. Litter-bags containing dried Johnson grass (Sorghum halepense) leaves were dipped in herbicide solutions at recommended and 10 × recommended field application rates, placed in the field, and randomly collected every 3 weeks from July to November 1982. At the highest treatment levels of paraquat and glyphosate, the leaves showed slower weight loss, faster losses of P, Ca and Mg, and higher densities of microfloral-grazing microarthropods than untreated controls. Using a conceptual model of the decomposition subsystem, it is hypothesized that herbicide treatment altered the system by (1) promoting microbial utilization of the herbicide or additive as a carbon source; (2) increasing the importance of microarthropod grazing relative to comminution; (3) eliminating or reducing the importance of the predatory microarthropods; and (4) increasing the rate of nutrient loss from the litter via microbial and microarthropod activity. The system thus became simplified with fewer recycling loops, accelerated soluble nutrient loss, and slower decay of carbon from the leaf tissue.     

Rapid incorporation of carbon from fresh residues into newly formed stable microaggregates within earthworm casts

Earthworms play an important role in protecting carbon in the soil, but the exact influence of their activity on the distribution and protection of C is still poorly understood. We investigated the effect of earthworms on the formation of stable microaggregates inside newly formed macroaggregates and the distribution of C in them. We crushed (< 250 µm) soil, and subjected it to three treatments: (i) soil + ¹³C‐labelled residue + earthworms (these added after 8 days' incubation), (ii) soil + ¹³C‐labelled residue, and (iii) control (no additions), and then incubated it for 20 days. At the end, we measured the aggregate size distribution, total C and ¹³C, and we isolated microaggregates (53–250 µm) from macroaggregates (> 250 µm) formed. The ¹³C in fine particulate organic matter between and within the microaggregates was determined. Earthworms helped to form large macroaggregates (> 2000 µm). These large macroaggregates contained four times more stable microaggregates than those from samples without earthworms. There was more particulate organic matter within and between microaggregates in macroaggregates in the presence of earthworms. The larger amounts of organic matter inside stable microaggregates in casts than in bulk soil after 12 days of incubation (140 mg ¹³C kg^?1 soil compared with 20 mg ¹³C kg^?1 soil) indicates that these microaggregates are formed rapidly around freshly incorporated residues within casts. In conclusion, earthworms have a direct impact on the formation of stable microaggregates and the incorporation of organic matter inside these microaggregates, and it seems likely that their activity is of great significance for the long‐term stabilization of organic matter in soils.     

Influence of earthworm activity on aggregate-associated carbon and nitrogen dynamics differs with agroecosystem management

Earthworms are known to be important regulators of soil structure and soil organic matter (SOM) dynamics, however, quantifying their influence on carbon (C) and nitrogen (N) stabilization in agroecosystems remains a pertinent task. We manipulated population densities of the earthworm Aporrectodea rosea in three maize-tomato cropping systems [conventional (i.e., mineral fertilizer), organic (i.e., composted manure and legume cover crop), and an intermediate low-input system (i.e., alternating years of legume cover crop and mineral fertilizer)] to examine their influence on C and N incorporation into soil aggregates. Two treatments, no-earthworm versus the addition of five A. rosea adults, were established in paired microcosms using electro-shocking. A ¹³C and ¹⁵N labeled cover crop was incorporated into the soil of the organic and low-input systems, while ¹⁵N mineral fertilizer was applied in the conventional system. Soil samples were collected during the growing season and wet-sieved to obtain three aggregate size classes: macroaggregates (>250 μm), microaggregates (53-250 μm) and silt and clay fraction (<53 μm). Macroaggregates were further separated into coarse particulate organic matter (cPOM), microaggregates and the silt and clay fraction. Total C, ¹³C, total N and ¹⁵N were measured for all fractions and the bulk soil. Significant earthworm influences were restricted to the low-input and conventional systems on the final sampling date. In the low-input system, earthworms increased the incorporation of new C into microaggregates within macroaggregates by 35% (2.8 g m⁻² increase; P=0.03), compared to the no-earthworm treatment. Within this same cropping system, earthworms increased new N in the cPOM and the silt and clay fractions within macroaggregates, by 49% (0.21 g m⁻²; P<0.01) and 38% (0.19 g m⁻²; P=0.02), respectively. In the conventional system, earthworms appeared to decrease the incorporation of new N into free microaggregates and macroaggregates by 49% (1.38 g m⁻²; P=0.04) and 41% (0.51 g m⁻²; P=0.057), respectively. These results indicate that earthworms can play an important role in C and N dynamics and that agroecosystem management greatly influences the magnitude and direction of their effect.     

Carbon exchange rates, chlorophyll content, and carbohydrate status of two forest tree species exposed to carbon dioxide enrichment

Seedlings of yellow-poplar (Liriodendron tulipifera L.) and white oak (Quercus alba L.) were exposed continuously to one of three CO(2) concentrations in open-top chambers under field conditions and evaluated after 24 weeks with respect to carbon exchange rates (CER), chlorophyll (Chl) content, and diurnal carbohydrate status. Increasing the CO(2) concentration from ambient to +150 or +300 microl l(-1) stimulated CER of yellow-poplar and white oak seedlings by 60 and over 35%, respectively, compared to ambient-grown seedlings. The increases in CER were not associated with a significant change in stomatal conductance and occurred despite a reduction in the amounts of Chl and accessory pigments in the leaves of plants grown in CO(2)-enriched air. Total Chl contents of yellow-poplar and white oak seedlings grown at +300 microl l(-1) were reduced by 27 and over 55%, respectively, compared with ambient-grown seedlings. Yellow-poplar and white oak seedlings grown at +300 microl l(-1) contained 72 and 67% more morning starch, respectively, than did ambient-grown plants. In contrast, yellow-poplar and white oak seedlings grown at +300 microl l(-1) contained 17 and 27% less evening sucrose, respectively, than did plants grown at ambient CO(2) concentration. Diurnal starch accumulation and the subsequent depletion of sucrose contributed to a pronounced increase in the starch/sucrose ratio of plants grown in CO(2)-enriched air. All seedlings exhibited a substantial reduction in dark respiration as CO(2) concentration increased, but the significance of this increase to the carbohydrate status and carbon economy of plants grown in CO(2)-enriched air remains unclear.     

Staphyloma in a cat

A unilateral scleral staphyloma in an 18-month-old, female spayed Domestic Short-haired cat was treated with excision, primary closure and fascial graft. Other ocular abnormalities noted on examination included iris coloboma, anterior cortical cataract, focal lens equator flattening and retinal dysplasia. The staphyloma was presumed to be congenital in origin.     

Effects of oral administration of methazolamide on intraocular pressure and aqueous humor flow rate in clinically normal dogs

OBJECTIVE: To determine magnitude and duration of the effect of oral administration of methazolamide at 2 dosages on intraocular pressure (IOP) in dogs in single-dose and multiple-dose trials and to determine aqueous humor flow rate (AHFR) by use of anterior segment fluorophotometry before and during treatment. ANIMALS: 25 healthy adult Beagles. PROCEDURE: Baseline IOPs and AHFRs were determined on days 0 and 1, respectively. On day 2, the single-dose trial was initiated with oral administration of 25 or 50 mg of methazolamide at 7 AM to 2 groups of 10 dogs each. Five dogs served as controls. In the multiple-dose trial, the same dogs received 25 or 50 mg of methazolamide at 7 AM and at 3 and 11 PM on days 3 through 9. RESULTS: Intraocular pressures varied diurnally with highest IOPs in the morning. In the single-dose trial, IOP decreased significantly at 3 to 6 hours after treatment and then increased significantly at later time points, compared with baseline values. In the multiple-dose trial, dogs in both treatment groups had significantly lower IOPs during the treatment period at 10 AM and 1 PM but not at 6 and 9 PM, compared with baseline values. In both treatment groups morning IOPs had returned to baseline values by the first day after treatment. Evening IOPs were significantly increased by 2 to 3 days after treatment, compared with baseline values. The AHFRs in both treatment groups were significantly lower than pretreatment AHFRs. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of methazolamide decreases IOPs and AHFRs in clinically normal dogs, with effectiveness diminishing in the evening.     

The effects of heated and room-temperature abdominal lavage solutions on core body temperature in dogs undergoing celiotomy

To document the magnitude of temperature elevation obtained with heated lavage solutions during abdominal lavage, 18 dogs were lavaged with sterile isotonic saline intraoperatively (i.e., during a celiotomy). In nine dogs, room-temperature saline was used. In the remaining nine dogs, saline heated to 43+/-2 degrees C (110+/-4 degrees F) was used. Esophageal, rectal, and tympanic temperatures were recorded every 60 seconds for 15 minutes after initiation of the lavage. Temperature levels decreased in dogs lavaged with room-temperature saline. Temperature levels increased significantly in dogs lavaged with heated saline after 2 to 6 minutes of lavage, and temperatures continued to increase throughout the 15-minute lavage period.     

Fluorophotometric determination of aqueous humor flow rate in clinically normal dogs

OBJECTIVE: To determine aqueous humor flow rate in clinically normal dogs, using fluorophotometry. ANIMALS: 20 clinically normal Beagles. PROCEDURE: A study was performed on 5 dogs to establish an optimal protocol for fluorophotometric determination of aqueous humor flow rate. This protocol then was used to measure aqueous humor flow rate in 15 dogs. Corneas were loaded with fluorescein by topical application, and corneal and aqueous humor fluorescein concentrations were measured 5, 6.5, and 8 hours after application. Concentration-versus-time plots were generated, and slopes and ratios of the fluorescein concentration in the cornea and aqueous humor from these graphs were used to calculate flow rates. Calculations were performed by use of automated software provided with the fluorophotometer and by manual computation, and the 2 calculation methods were compared. RESULTS: The protocol established for the 5 dogs resulted in semilogarithmic and parallel decay of corneal and aqueous humor concentrations. Manually calculated mean +/- SD aqueous humor flow rates for left, right, and both eyes were 5.58 +/- 2.42, 4.86 +/- 2.49, and 5.22 +/- 1.87 microl/min, respectively, whereas corresponding flow rates calculated by use of the automated software were 4.54 +/- 3.08, 4.54 +/- 3.10, and 4.54 +/- 2.57 microl/min, respectively. Values for the left eye were significantly different between the 2 computation methods. CONCLUSIONS AND CLINICAL RELEVANCE: Aqueous humor flow rates can be determined in dogs, using fluorophotometry. This technique can be used to assess pathologic states and medical and surgical treatments that alter aqueous humor dynamics.