Direct Comparisons of 2D and 3D Dental Microwear Proxies in Extant Herbivorous and Carnivorous Mammals

The analysis of dental microwear is commonly used by paleontologists and anthropologists to clarify the diets of extinct species, including herbivorous and carnivorous mammals. Currently, there are numerous methods employed to quantify dental microwear, varying in the types of microscopes used, magnifications, and the characterization of wear in both two dimensions and three dimensions. Results from dental microwear studies utilizing different methods are not directly comparable and human quantification of wear features (e.g., pits and scratches) introduces interobserver error, with higher error being produced by less experienced individuals. Dental microwear texture analysis (DMTA), which analyzes microwear features in three dimensions, alleviates some of the problems surrounding two-dimensional microwear methods by reducing observer bias. Here, we assess the accuracy and comparability within and between 2D and 3D dental microwear analyses in herbivorous and carnivorous mammals at the same magnification. Specifically, we compare observer-generated 2D microwear data from photosimulations of the identical scanned areas of DMTA in extant African bovids and carnivorans using a scanning white light confocal microscope at 100x magnification. Using this magnification, dental microwear features quantified in 2D were able to separate grazing and frugivorous bovids using scratch frequency; however, DMTA variables were better able to discriminate between disparate dietary niches in both carnivorous and herbivorous mammals. Further, results demonstrate significant interobserver differences in 2D microwear data, with the microwear index remaining the least variable between experienced observers, consistent with prior research. Overall, our results highlight the importance of reducing observer error and analyzing dental microwear in three dimensions in order to consistently interpret diets accurately.     

Caecal size and function in the rock elephant shrew Elephantulus myurus (Insectivora, Macroscelididae) and the Namaqua rock mouse Aethomys namaquensis (Rodentia, Muridae)

1. The relative size of the digestive organs and the function of the caeca of an insectivorous elephant shrew Elephantulus myurus (Macroscelididae) and of a herbivorous rodent Aethomys namaquensis (Muridae) were compared. 2. Both species had similar body mass but A. namaquensis had a significantly heavier total digestive tract, full stomach, and caecum and a longer large intestine and caecum than E. myurus. 3. Both species had similar total volatile fatty acid (VFA) concentration and VFA % composition although A. namaquensis had a significantly higher % of n-butyric acid. Both had a similar caecal NH3-N concentration. 4. The presence of a functional caecum in E. myurus supports the view that Macroscelididae have evolved from ancestral herbivores and not from insectivores.     

Neuronal organization of the ascidian (Urochordata) branchial basket revealed by cholinesterase activity

Summary Innervation of the ascidian branchial basket and other structures is demonstrated by staining for cholinesterase. Cholinesterase activity is not restricted to synaptic sites but is present throughout the neurons. Primary and secondary axonal bundles form a bilaterally symmetric innervation pattern around the large dorsal visceral nerve. These bundles continue to split into progressively smaller bundles as they course throughout the basket. Axons are suspended in a fibrous matrix and run within the blood sinuses on the atrial side of the basket. Stigmatal ciliated cells of the branchial basket are innervated by highly branched distal portions of neurons, whose cell bodies are located in the ganglion. Synaptic boutons, containing electron-lucent vesicles, are found at nearly all stigmatal ciliated cells. NiCl₂backfills of the visceral nerve reveal a distinct population of central neurons, some of which presumably control ciliary arrest.     

Isolation and characterization of the cDNA for pulmonary surfactant-associated protein-B (SP-B) in the rabbit

Pulmonary surfactant contains phospholipids including dipalmitoyl-phosphatidylcholine and three surfactant-associated proteins designated SP-A, SP-B and SP-C. A cDNA for rabbit SP-B has been isolated from a fetal (30 days gestation) rabbit lung cDNA library constructed in lambda gt11. The cDNA and deduced amino acid sequences show strong homology with the cDNAs and predicted 40 kDa proproteins for human and canine SP-B. Strong homology is also observed with the amino acid sequences directly determined for the mature 8 kDa bovine and porcine SP-B isolated from lung lavage. SP-B is remarkable for its high cysteine and proline content and for the hydrophobic nature of the organic solvent-soluble, mature protein. In vitro translation of sense but not antisense RNA transcribed from the cDNA led to the production of 40 kDa and 32 kDa proteins. These proteins were immunoprecipitated by an antibody raised against bovine SP-B. Northern blot analysis revealed the mRNA for rabbit SP-B appears in fetal rabbit lung late in gestation and falls slightly in the neonate.     

Microbiological evaluation of the intraruminal in sacculus digestion technique.

The influence of nature of the feed sample, feeding frequency and pore size on the influx of bacteria and protozoa into synthetic fiber bags suspended in the rumens of sheep fed different diets was studied. Counts of total culturable bacteria in bags with a pore size of 10 microns were less than 30% of the ruminal counts for animals that were fed the lucerne hay and high-roughage diets. The maximum count (62 and 82% of the ruminal count) for these specific diets was obtained by using bags with a pore size of 53 microns. Protozoal counts in bags with pore sizes of 30 and 53 microns were equal to or higher than the ruminal counts for the lucerne hay and high-roughage diets but less than half of the ruminal count for the low-roughage diet. An interaction between incubation time, feeding frequency of the host animals, and the microbial populations developing inside the bags was also demonstrated. The results clearly show that the microbial population inside the bag differed from that of the surrounding ruminal ingesta and that caution must be taken in interpreting results on feed evaluation and especially on rates of degradation when using the in sacculus technique. Factors influencing the influx of bacteria and protozoa into bags with different pore sizes and containing a variety of substrates are discussed together with suggestions for the use of this technique.     

Midwater macroplankton of British Columbia studied by submersible PISCES IV

Data are reported from 30 dives during winter and spring 1980–83at sites in the Strait of Georgia and inlets running off it,and in inlets on the west coast of Vancouver Island. Observationswere made from the surface to the bottom (maximum 733 m) butmost attention was given to the midwater plankton community.The vertical distribution and abundance of hydromedusae, siphonophores,ctenophores, euphausiids, pelagic worms and molluscs were recordedsystematically, along with data for one copepod species (Neocalanusplumchrus). The midwater environment was found to be stablein terms of species composition and depth ranges, which permittedthe data for several years and many locations to be pooled.Four categories of plankton are recognized: (a) epipelagic (concentratedin the top 50 m); (b) mesopelagic (50–175 m); (c) bathypelagic(below 175 m); and (d) meso-bathypelagic (forms living in bothmeso- and bathypelagic zones). Species in this last categorybehave like mesopelagic forms at the upper end of their ranges,migrating to the surface at night. Deeper-lying members of thesame species do not migrate. For six such species, the cut-offpoint between migratory and non-migratory components was foundto lie at a mean depth of 175 m. This depth is therefore takenas the demarcation point between the meso- and bathypelagiczones. Taking account of published data on light penetration,it is estimated that, for the whole region, daytime light intensityat 175 m, and hence the effective limit for phototaxis of thespecies in question, lies in the range 10^–8–10^–9µW cm^–2.     

Mapping of the lipoprotein signal peptidase gene (lsp)

A pBR322 plasmid which contains a fragment of Escherichia coli DNA encoding the lipoprotein signal peptidase gene was used to transform Hfr polA1 strains. Ampr transformants were used as donors in conjugation experiments, and the location of the plasmid amp gene adjacent to the chromosomal lsp gene was determined to be near the thr ara loci of the E. coli chromosome. P1 transduction experiments established that the location of the lsp gene is closely linked to that of dapB , at 0.5 to 0.6 min on the E. coli genetic map. The position of the lsp gene was further determined to be between ileS and dapB by complementation analysis of an E. coli mutant showing temperature-sensitive prolipoprotein signal peptidase activity.     

Effects of changes in discharge level on temperature and oxygen regimes in a new reservoir and downstream

Temperature and oxygen regimes were monitored weekly in a four-year old reservoir and downstream for ten weeks during the summer (May 15 to July 30, 1979), and monthly in the fall and winter. During the summer discharge levels were changed from top to bottom in the eighth week, back to top in the ninth, all at 0.71 m³/s (= 25 cfs), and returned to the bottom in the tenth, but at 1.14 m³/s (= 40 cfs). Changing the discharge level had little or no impact on the thermal regime within the lake or downstream at 1.14 m³/s and only a moderate impact on water in the lake near the dam at 0.71 m³/s bottom discharge by generating double thermoclines. Oxygen depletion rates were greatest near the surface of the lake, mainly due to temperature effects, but increased greatly at the 3 m depth, the level of the top discharge port, when discharge was changed from bottom to top. Discharge of anoxic waters through the bottom of the dam caused a drop in oxygen content immediately downstream but oxygen content returned to inflow values within 1 km downstream of the dam.