The Effects of Birth Weight and Maternal Care on Survival of Juvenile Steller Sea Lions (Eumetopias jubatus)

Steller sea lions were listed as endangered following a collapse of the western distinct population beginning in the late 1970s. Low juvenile survival has been implicated as a factor in the decline. I conducted a multistate mark-recapture analysis to estimate juvenile survival in an area of the western population where sea lions are showing signs of recovery. Survival for males and females was 80% between 3 weeks and 1 year of age. Approximately 20% of juveniles continued to be nursed by their mothers between ages 1 and 2 and 10% between ages 2 and 3. Survival for juveniles that suckled beyond 1 year was 88.2% and 89.9% to ages 2 and 3, respectively. In contrast, survival for individuals weaned by age 1 was 40.6% for males and 64.2% for females between ages 1 and 2. Birth mass positively influenced survival for juveniles weaned at age 1 but had little effect on individuals continuing to suckle. Cumulative survival to age 4 was double that estimated during the population decline in this region. Evidence suggests that western Steller sea lions utilize a somewhat different maternal strategy than those in the eastern distinct population. Western adult females generally invest more in their pups during the first year but wean offspring by age 1 more often. This results in better survival to age 1, but greater mortality between ages 1 and 3 compared to the eastern population. Different maternal strategies may reflect density dependent pressures of populations at opposite levels of abundance.     

The Gastrointestinal Mucosa in Young Milk-Fed Calves

Gastrointestinal segments from 4 healthy, 17-, 21-, 22- and 23-day-old calves fed on whole cow’s milk were examined. Scanning electron microscopy showed that the anterior duodenum had short villi varying in shape from leaf-shaped to nodular; the middle duodenum had broad, tongue-shaped villi and the anterior, middle, and parts of the posterior jejunum had slender, finger-shaped or leaf-shaped villi. The villi of the mucosa covering Peyer’s patches in the posterior jejunum were short and either conical or tongue-shaped; there were also small “pseudovilli” caused by bulges in the lymphoid tissue. Morphometry showed that the villi were longer in the anterior jejunum than in the duodenum and the posterior parts of the jejunum (P < 0.005). Morphologically fat absorption was most heavy in the anterior third of the small intestine. Moderate amounts of fat were also found in the epithelium of the posterior jejunum and of the abomasum. Large fat droplets were seen in apical duodenal enterocytes, in contrast to the small epithelial droplets in other areas with fat absorption. Nile blue staining indicated that the fat in the large droplets was esterified.     

Genetic divergence in South African Wildebeest: comparative cytogenetics and analysis of mitochondrial DNA.

The blue and the black wildebeest, Connochaetes taurinus and C. gnou, are currently classified as congeneric, but previous reports have placed C. taurinus in its own genus, Gorgon. To further clarify the evolutionary relationship between these two species, we examined and compared their mitotic chromosomes and mitochondrial DNA (mtDNA). No species-specific G-banded or C-banded chromosomal markers were found, and we conclude that the karyotypes are invariant at the level of resolution obtained. An evolutionary divergence time of approximately 1 million years was calculated from mtDNA restriction fragment data, indicating a close phylogenetic relationship for the two wildebeest species. The low nucleotide diversity detected within the black wildebeest (0.09%) is thought to reflect the recent population bottleneck to which the species has been subjected. In contrast, the limited heterogeneity (0.02%) within the South African blue wildebeest herds sampled in this study was surprising, and we argue that for many populations, especially those on smaller reserves, this may reflect common descent from a small number of animals through management-controlled translocations.     

The Bacterial Flora of the Rumen of Healthy and Bloating Calves

Rumen samples from five healthy milk-fed calves and one healthy calf given a milk-replacer diet containing yeast protein had pH values of 6.5–8.0, total counts of ca. 10¹⁰/ml and viable counts of 10⁸-10¹⁰/ml. The facultatively and strictly anaerobic, and obligately aerobic, components of the floras were enumerated and identified. Similar tests performed on samples from two calves bloating on the yeast diet had pH values of 4.8 and 5.3, and although total and viable counts were of the same order as those from healthy calves, obligately aerobic bacteria were not detected and counts of lactobacilli were elevated. Infusion of the rumen of a calf with yeast diet caused a reduction in pH from 7.3–5.1 and an increase of at least 100-fold in the numbers of organisms capable of forming copious gas from yeast diet. Results suggest that milk or milk-replacer diet normally does not enter the rumen to any extent but when it does, due perhaps to poor palatability, bloat may ensue.     

The Function of Mounting Behaviour in Farmed Red Deer Calves

The function of mounting behaviour was studied in farmed red deer (Cervus elaphus) calves. On the basis of previous work, we tested two alternative hypotheses about the function of this behaviour. The first hypothesis deals with the proximate function of the behaviour. Three predictions were tested: (1a) mounting behaviour attracts the attention of the mother and/or consolidates the mother–calf bond; (1b) mounting is intended to obtain more milk; (1c) mounting is intended to prevent other calves from sucking from the mother. The second hypothesis deals with an ultimate function in practising for future life with two predictions tested: (2a) mounting behaviour is part of calves' play behaviour promoting development of the calf's locomotor and social skills; (2b) calves gain sexual experience through mounting behaviour. For the study, 50 hind‐calf pairs were observed. The maternity of individual hinds was confirmed by a genetical analysis. The hinds were classified as ‘maternal’ and ‘non‐maternal’ and the calves as ‘filial’ and ‘non‐filial’. We recorded 40 cases of mounting behaviour involving 25 hinds and 21 calves. Our results suggest that the mounting behaviour of red deer calves serves several different functions depending on the circumstances. In association with suckling, calves of both sexes mounted maternal hinds mainly to attract their attention and to achieve another suckling. In situations not associated with suckling, mounting by male calves might be considered part of their sexual training. On the other hand, mounting by female calves probably reflects the attempt to maintain contact with their mother in tense situations.     

The Birth of the Centromere

The centromere is the region of the eukaryotic chromosome that determines kinetochore formation and sister chromatid cohesion. Centromeres interact with spindle microtubules to ensure chromatid segregation during mitosis and homologous chromosome segregation during meiosis I. In recent years, the overall organization of centromeres in several eukaryotic species has been described, yet the mechanisms of centromere definition remain elusive. Understanding the evolutionary origin of the centromere may well elucidate aspects of its function. With such intention, we hypothesize that centromeres were derived from telomeres during the evolution of the eukaryotic chromosome. We propose that the proto-eukaryotic cell could not have evolved a nucleus without concurrently evolving a new tubulin-based cytoskeleton, the microtubules, and a specific chromosomal region that enabled the chromosome-microtubule interaction, the centromere. The repetitive nature of the subtelomeric regions that gave rise to the centromeres forced the concerted evolution of the centromeres. Although this implies the absence of a conserved primary sequence, a conserved centromere-specific structural motif could still exist and determine where in the chromosome the centromere is to be formed.To support the “centromeres-from-telomeres” hypothesis, we discuss several situations, in meiosis and mitosis, where telomeric regions took over centromeric roles. The recently discovered phenomenon of centromere repositioning is also discussed because it has revealed new insights into how neocentromeres evolve.     

The Birth of Redox Regulation

When we obtained evidence for redox regulation in 1967, I would never have imagined that those experiments would lay the foundation for a field that was destined to embrace all types of living cells. The possibility that the early experiments with chloroplast ferredoxin （Fdx） would prompt the publication of a Special Issue on ＇Redox and Photosynthesis＇ was equally far-fetched. In view of these unforeseen developments, I think it is timely to introduce this Special Issue by briefly describing how the field of thiol-based redox regulation started. In the interest of space, my recounting of events leading to the discovery of the mechanism is brief. Most noticeably, the names of collaborators, who were so critical in this research, have been left out. Their names and other details are given in the earlier, more complete accounts listed in the References.     

The Effects of Birth Order and Birth Interval on the Phenotypic Expression of Autism Spectrum Disorder

A rise in the prevalence of diagnosed cases of autism spectrum disorder (ASD) has been reported in several studies in recent years. While this rise in ASD prevalence is at least partially related to increased awareness and broadened diagnostic criteria, the role of environmental factors cannot be ruled out, especially considering that the cause of most cases of ASD remains unknown. The study of families with multiple affected children can provide clues about ASD etiology. While the majority of research on ASD multiplex families has focused on identifying genetic anomalies that may underlie the disorder, the study of symptom severity across ASD birth order may provide evidence for environmental factors in ASD. We compared social and cognitive measures of behavior between over 300 first and second affected siblings within multiplex autism families obtained from the Autism Genetic Resource Exchange dataset. Measures included nonverbal IQ assessed with the Ravens Colored Progressive Matrices, verbal IQ assessed with the Peabody Picture Vocabulary Test, and autism severity assessed with the Social Responsiveness Scale (SRS), an instrument established as a quantitative measure of autism. The results indicated that females were more severely impacted by ASD than males, especially first affected siblings. When first and second affected siblings were compared, significant declines in nonverbal and verbal IQ scores were observed. In addition, SRS results demonstrated a significant increase in autism severity between first and second affected siblings consistent with an overall decline in function as indicated by the IQ data. These results remained significant after controlling for the age and sex of the siblings. Surprisingly, the SRS scores were found to only be significant when the age difference between siblings was less than 2 years. These results suggest that some cases of ASD are influenced by a dosage effect involving unknown epigenetic, environmental, and/or immunological factors.     

发刊词

随着我国改革开放、对外贸易和市场经济的迅速发展,社会经济和生态环境中的生物安全问题日益突出。全球气候变暖加剧了自然物种行为变异,频繁的国际贸易加剧了自然物种迁移,人类的生产活动和生境恶化改变了物种生存策略,外来入侵生物对生态环境、生物多样性、农林业生产、对外贸易及人类健康造成了巨大的影响,而且这些灾害极易因环境条件、人类社会活动等的变化而发生灾变,危害极大,     

发刊词

随着我国改革开放、对外贸易和市场经济的迅速发展,社会经济和生态环境中的生物安全问题日益突出。全球气候变暖加剧了自然物种行为变异,频繁的国际贸易加剧了自然物种迁移,人类的生产活动和生境恶化改变了物种生存策略,外来入侵生物对生态     

The Influence of Feeding and Oral Rehydration on the Bioavailability of Oxytetracycline in Calves

The influence of feeding on the bioavailability of oxytetracycline was studied in preruminant calves. Oxytetracycline was given in water as a drench to fasting calves or was mixed in the milk replacer. Compared to water the bioavailability was significantly reduced (53.5%) when oxytetracycline was mixed in the milk re-placer. A further reduction, 83.3 %, occurred when the calves were treated one hour post milk feeding. Also concentrate was found to reduce the bioavailability. Very high serum levels were recorded when the drug was given in an oral rehydration solution, pH 4.9, containing glycine. The values obtained when an alkaline (pH 8.3) solution without glycine was used did not differ from the levels recorded when oxytetracycline was given in water. It was suggested that the use of oxytetra-cyclines in feeds may be questioned because of their well-known complex forming ability.