Solute and particle retention in a small grazing antelope, the blackbuck (Antilope cervicapra).

Digesta retention patterns have been suggested to play a major role in ruminant diversification. Two major digestion types have been proposed, termed 'cattle-type' and 'moose-type', that broadly correspond to the feeding categories of grazers and intermediate feeders on the one, and browsers on the other hand. We measured and calculated the mean retention time (MRT) of a solute and a particle (<2 mm) marker in the gastrointestinal tract (GIT) and the reticulorumen (RR) of a small grazer, the Indian blackbuck (Antilope cervicapra, n=5, body mass of 26±4 kg) and an intermediate feeder, the nilgai (Boselaphus tragocamelus, n=5, body mass of 168±21 kg). MRT(solute) and MRT(particle) were 29±4.1 h and 60±6.6 h in blackbuck and 28±2.5 h and 54±8.9 h in the nilgai for the GIT, and 14±1.7 h, 45±5.0 h, 19±2.0 h and 45±8.4 h for the RR, respectively. With a selectivity factor (SF, the ratio of MRT(particle) to MRT(solute)) in the RR of 3.2±0.28 for blackbuck and 2.3±0.36 for nilgai, both species are clearly in the category of 'cattle-type' ruminants. In particular, the high SFRR of blackbuck, in spite of its small body size, is remarkable, and leads to specific predictions on the RR anatomy of this species (such as a particularly large omasum), which can be tested in further studies. The adaptive value of a high SFRR is mainly considered as an increase in microbial productivity in the RR.

Pattern and timing of diversification of Cetartiodactyla (Mammalia, Laurasiatheria), as revealed by a comprehensive analysis of mitochondrial genomes.

The order Cetartiodactyla includes cetaceans (whales, dolphins and porpoises) that are found in all oceans and seas, as well as in some rivers, and artiodactyls (ruminants, pigs, peccaries, hippos, camels and llamas) that are present on all continents, except Antarctica and until recent invasions, Australia. There are currently 332 recognized cetartiodactyl species, which are classified into 132 genera and 22 families. Most phylogenetic studies have focused on deep relationships, and no comprehensive time-calibrated tree for the group has been published yet. In this study, 128 new complete mitochondrial genomes of Cetartiodactyla were sequenced and aligned with those extracted from nucleotide databases. Our alignment includes 14,902 unambiguously aligned nucleotide characters for 210 taxa, representing 183 species, 107 genera, and all cetartiodactyl families. Our mtDNA data produced a statistically robust tree, which is largely consistent with previous classifications. However, a few taxa were found to be para- or polyphyletic, including the family Balaenopteridae, as well as several genera and species. Accordingly, we propose several taxonomic changes in order to render the classification compatible with our molecular phylogeny. In some cases, the results can be interpreted as possible taxonomic misidentification or evidence for mtDNA introgression. The existence of three new cryptic species of Ruminantia should therefore be confirmed by further analyses using nuclear data. We estimate divergence times using Bayesian relaxed molecular clock models. The deepest nodes appeared very sensitive to prior assumptions leading to unreliable estimates, primarily because of the misleading effects of rate heterogeneity, saturation and divergent outgroups. In addition, we detected that Whippomorpha contains slow-evolving taxa, such as large whales and hippos, as well as fast-evolving taxa, such as river dolphins. Our results nevertheless indicate that the evolutionary history of cetartiodactyls was punctuated by four main phases of rapid radiation during the Cenozoic era: the sudden occurrence of the three extant lineages within Cetartiodactyla (Cetruminantia, Suina and Tylopoda); the basal diversification of Cetacea during the Early Oligocene; and two radiations that involve Cetacea and Pecora, one at the Oligocene/Miocene boundary and the other in the Middle Miocene. In addition, we show that the high species diversity now observed in the families Bovidae and Cervidae accumulated mainly during the Late Miocene and Plio-Pleistocene.

Solute and particle retention in the digestive tract of the Phillip's dikdik (Madoqua saltiana phillipsi), a very small browsing ruminant: biological and methodological implications.

Morphological characteristics of the forestomach, as well as reports of a natural diet that mostly excludes monocots, suggest that dikdiks (Madoqua spp.), among smallest extant ruminants, should have a 'moose-type' forestomach physiology characterised by a low degree of selective particle retention. We tested this assumption in a series of feeding experiments with 12 adult Phillip's dikdiks (Madoqua saltiana phillipsi) on three different intake levels per animal, using cobalt-EDTA as a solute marker and a 'conventional' chromium-mordanted fibre (<2 mm; mean particle size 0.63 mm) marker for the particle phase. Body mass had no influence on retention measurements, whereas food intake level clearly had. Drinking water intake was not related to the retention of the solute marker. In contrast to our expectations, the particle marker was retained distinctively longer than the solute marker. Comparisons with results in larger ruminants and with faecal particle sizes measured in dikdiks suggested that in these small animals, the chosen particle marker was above the critical size threshold, above which particle delay in the forestomach is not only due to selective particle retention (as compared to fluids), but additionally due to the ruminal particle sorting mechanism that retains particles above this threshold longer than particles below this threshold. A second study with a similar marker of a lower mean particle size (0.17 mm, which is below the faecal particle size reported for dikdiks) resulted in particle and fluid retention patterns similar to those documented in other 'moose-type' ruminants. Nevertheless, even this smaller particle marker yielded retention times that were longer than those predicted by allometric equations based on quarter-power scaling, providing further support for observations that small ruminants generally achieve longer retention times and higher digestive efficiencies than expected based on their body size.

Body size development of captive and free-ranging Leopard tortoises (Geochelone pardalis).

The growth and weight development of Leopard tortoise hatchings (Geochelone pardalis) kept at the Al Wabra Wildlife Preservation (AWWP), Qatar, was observed for more than four years, and compared to data in literature for free-ranging animals on body weight or carapace measurements. The results document a distinctively faster growth in the captive animals. Indications for the same phenomenon in other tortoise species (Galapagos giant tortoises, G. nigra; Spur-thighed tortoises, Testudo graeca; Desert tortoises, Gopherus agassizi) were found in the literature. The cause of the high growth rate most likely is the constant provision with highly digestible food of low fiber content. Increased growth rates are suspected to have negative consequences such as obesity, high mortality, gastrointestinal illnesses, renal diseases, "pyramiding," fibrous osteodystrophy or metabolic bone disease. The apparently widespread occurrence of high growth rates in intensively managed tortoises underlines how easily ectothermic animals can be oversupplemented with nutrients.

Fluid and particle retention in the digestive tract of the addax antelope (Addax nasomaculatus)--adaptations of a grazing desert ruminant.

Retention time of food in the digestive tract is a major aspect describing the digestive physiology of herbivores. Differences in feed retention times have been described for different ruminant feeding types. In this study, a dominantly grazing desert ruminant, the addax (Addax nasomaculatus), was investigated in this respect. Eight animals with a body weight (BW) of 87+/-5.3 kg on an ad libitum grass hay (Chloris gayana) diet were available. Co-EDTA and Cr-mordanted fibers (<2 mm) were used as pulse-dose markers. Mean retention time (MRT) in the digestive tract was calculated from faecal marker excretion. Average daily intake of the addax was found to be 1.7 kg dry matter (DM) or 60+/-8.3 g DM/kg BW(0.75). The MRT of fluid and particles in the reticulo-rumen (MRT(fluid)RR and MRT(particle)RR) were quantified to be 20+/-5.8 and 42+/-7.0 h respectively. When compared to literature data, MRT(fluid)RR was significantly longer than in cattle species, and MRT(particle)RR was significantly longer than in 11 taxa of all feeding types. The ratio of MRT(particle)RR/MRT(fluid)RR (2.3+/-0.5) was found to be within the range described for grazing ruminants. The long retention times found in the addax can be interpreted as an adaptation to a diet including a high proportion of slow fermenting grasses, while the long retention time of the fluid phase can be interpreted as a consequence of water saving mechanisms of the desert-adapted addax with a potentially low water turnover and capacious water storing rumen.