Pneumocystis carinii and Pneumocystis wakefieldiae in Wild Rattus norvegicus Trapped in Thailand

ABSTRACT. This work reports for the first time the presence of two Pneumocystis species in wild Rattus norvegicus specimens from Thailand. Pneumocystis DNA was detected in 57.7% (15/26) wild rats without apparent association with typical pneumocystosis. Pneumocystis carinii was found alone in five rats (19.2%), Pneumocystis wakefieldiae was detected alone in six rats (23.1%), and two rats were infected by both species (7.7%). In addition, a new P. wakefieldiae variant sequence has been identified in three wild R. norvegicus specimens caught in the same geographical area. The high frequency of Pneumocystis in wild rats documented in this study and the apparent scarcity of severe pneumocystosis were consistent with an efficient circulation of rat Pneumocystis species in ecosystems.     

Testate Amoebae from a Cretaceous Forest Floor Microbiocoenosis of France

ABSTRACT. Amber‐preserved shells of testate amoebae often provide as many diagnostic features as the tests of modern taxa. Most of these well‐preserved microfossils are morphologically assignable to modern species indicating either evolutionary stasis or convergent evolution. Here we describe two Lower Cretaceous testate amoebae that are clearly distinguishable from modern species. Centropyxis perforata n. sp. and Leptochlamys galippei n. sp. possessed perforate shells that were previously unknown in these genera. They are preserved in highly fossiliferous amber pieces from the Upper Albian (ca. 100 million years old) of Archingeay/Les Nouillers (Charente‐Maritime, southwestern France). Syninclusions of soil and litter dwelling arthropods and microorganisms indicate a limnetic‐terrestrial microhabitat at the floor of a coastal conifer forest.     

Long-term seasonal variation in the biological traits of benthic-macroinvertebrates in two Mediterranean-climate streams in California, U.S.A.

1. We investigated the seasonal variation of biological traits and the influence of interannual rainfall variability on this pattern. Using long‐term survey data (6–19 years) from an intermittent and a perennial stream in the Mediterranean‐climate region of northern California, we examined 16 fuzzy‐coded biological traits (e.g. maximum size, life cycle duration, and mode of respiration). 2. Seasonal habitat variability is higher in the intermittent stream than in the perennial stream. During the winter and spring wet‐season both streams flood; however, during the summer dry‐season, the intermittent stream forms isolated pools in (occasionally drying completely). 3. Seasonal habitat variability influenced both taxonomic and biological trait composition. Distinct taxonomic communities were present in each season, particularly in the intermittent stream. The intermittent stream also exhibited more seasonal variation in biological traits than the perennial stream. 4. Despite statistically significant seasonal variation, trait composition was relatively stable among seasons in comparison with taxonomic composition and abundance. Taxonomic composition varied considerably between seasons, because of high seasonal and interannual replacement of taxa resulting from seasonal habitat changes. 5. The seasonality of taxonomic composition and abundance was sensitive to interannual rainfall variability. In dry years, the taxonomic composition of communities was more similar between seasons than in wet years, while trait composition was relatively insensitive to rainfall variability. 6. Despite high seasonal variation in abundance and taxonomic composition, biological traits of aquatic macroinvertebrates varied less and exhibited seasonal stability, which may be a result of the unpredictability and harshness of stream environments.     

Permeability to Sugars and Fatty Acids in Polytoma obtusum

SYNOPSIS. Whole cells of Polytoma obtusum do not utilize glucose or other hexoses, but cell-free extracts show glucokinase activity having a pH optimum at 8.5 and a Q₁₀ of 2.4 between 0–20°C. Lack of glucom utilization by whole cells reflects a permeability barrier to all sugars.
To determine whether inability of acetate-grown cells to utilize butyrate also denoted a permeability barrier, permeability to acetate and butyrate was studied in acetate- and butyrate-grown cells However, acetate-grown cells accumulated C-14 labeled butyrate against a concentration gradient. Therefore inability of acetate-grown cells to utilize butyrate does not denote a permeability barrier.
Acetate-kinase activity was consktently demonstrated in cell-free extracts of both acetate- and butyrate-grown cells. Butyrate kinase was consistently found only in butyrate-grown cells. However, the absence of buttymte kinase in acetate-grown cells cannot be claimed since occasionally butyrate kinase activity was demonstrated in extracts of acetate-grown cells.     

FORMS OF CALL OVERLAP AND THEIR IMPACT ON ADVERTISEMENT CALL ATTRACTIVENESS TO FEMALES OF THE GRAY TREEFROG,HYLA VERSICOLOR

ABSTRACT

Male gray Lreefrogs, Hyla versicolor, advertise for females in choruses in which calls often overlap. Previous research has demonstrated that such acoustic interference among conspecifics can impair the ability of a male to attract a mate. However, the stimulus set used in those studies was quite limited. Here we performed single-speaker and two-speaker tests of phonotaxis with female Hyla versicolor to explore the impact of different degrees and forms of call overlap on the relative attractiveness of male signals. We found that: (1) overlapped calls are recognized as acceptable signals by females, although they are less attractive than calls that are not overlapped; (2) the relative phase of the overlapping calls matters. When calls were time-shifted by 50% of their pulse-period (180 degree offset), attractiveness of overlapped calls was reduced relative to non-overlapped calls as much as it would be by a reduction in intensity of about 12 dB SPL or a drop in call duration of between one third to one half. A 90 degree phase offset was equivalent to a 3 dB drop in SPL; (3) partial call overlap may not impair call attractiveness if one third or less of the call is overlapped; (4) if the ending portion of a call is overlapped it may impair attractiveness less than if previous segments of a call are obscured; (5) if most (three fourths or more) of a male's calls are free of interference, overlap of his remaining calls does not significantly impair his attractiveness.