Natural variation in reproductive timing and X-chromosome nondisjunction in Caenorhabditis elegans

Caenorhabditis elegans hermaphrodites first produce a limited number of sperm cells, before their germline switches to oogenesis. Production of progeny then ensues until sperm is depleted. Male production in the self-progeny of hermaphrodites occurs following X-chromosome nondisjunction during gametogenesis, and in the reference strain increases with age of the hermaphrodite parent. To enhance our understanding of the reproductive timecourse in C. elegans, we measured and compared progeny production and male proportion during the early and late reproductive periods of hermaphrodites for 96 wild C. elegans strains. We found that the two traits exhibited natural phenotypic variation with few outliers and a similar reproductive timing pattern as previous reports. Progeny number and male proportion were not correlated in the wild strains, implying that wild strains with a large brood size did not produce males at a higher rate. We also identified loci and candidate genetic variants significantly associated with male-production rate in the late and total reproductive periods. Our results provide an insight into life-history traits in wild C. elegans strains.

Isabelle

Isabelle is the sister of Delbert and the daughter of Sharmaine. She is also the mother of 10 children of her own: six biological children fathered by four different men in addition to the four children of her deceased younger sister. Having survived a succession of abusive relationships with various men, this mother hen has been the sole provider for her large brood for most of the time that the author has known her. In many respects, Isabelle can be called the “white sheep” of the Benally family. While the rest of her siblings have battled alcoholism and chronic unemployment for most of their adult lives, she has never imbibed alcohol and has been gainfully employed for the past 40 years. She is not unlike a Native American version of Horatio Alger: a girl from the rez who, through diligence and determination, vowed to raise herself up from her bootstraps and overcome any obstacles placed in front of her. This chapter introduces Isabelle.

Caenorhabditis elegans as a Model Host to Monitor the Candida Infection Processes

C. elegans has several advantages as an experimental host for the study of infectious diseases. Worms are easily maintained and propagated on bacterial lawns. The worms can be frozen for long term storage and still maintain viability years later. Their short generation time and large brood size of thousands of worms grown on a single petri dish, makes it relatively easy to maintain at a low cost. The typical wild type adult worm grows to approximately 1.5 mm in length and are transparent, allowing for the identification of several internal organs using an affordable dissecting microscope. A large collection of loss of function mutant strains are readily available from the C. elegans genetic stock center, making targeted genetic studies in the nematode possible. Here we describe ways in which this facile model host has been used to study Candida albicans, an opportunistic fungal pathogen that poses a serious public health threat.

HYBRID NARRATIVES: THE MAKING OF CHARACTER AND NARRATIVE AUTHORITY IN RUDYARD KIPLING'S “HIS CHANCE IN LIFE”

When Rudyard Kipling offeredhis wry observations on officialdom in Imperial India to his cousin, Margaret Bourne-Jones, in 1885, he might have been toying with the kernel of one of his more perplexing stories on race and hybridity, written for his 1888 anthology,Plain Tales from the Hills. When Kipling actually came to address this theme fictionally, in his short story entitled “His Chance in Life,” he made one crucial change: he substituted a dark-skinned telegraphist of mixed race for an Englishman, thereby engaging with the illogics of character that hybridity posed for narratives on race and Empire. In Kipling's story, his hybrid hero, stationed in the mofussil town of Tibasu, experiences a sudden surge of Britishness in the mixed blood flowing in his veins at the moment when crisis strikes, and leads a group of terrified policemen in quelling a communal riot between Hindus and Muslims. He is found guilty of exercising unconstitutional authority by a Hindu sub-judge, but the verdict is set aside by the British Assistant Collector. As a reward, he is promoted to an up-country Central Telegraph Office, where he proceeds to marry his ugly sweetheart, also of mixed race parentage, and live happily with a large brood of children in quarters on the office premises, a loyal government servant, “at home” with officialdom and Empire.

Long-term effects of manipulated natal brood size on metabolic rate in zebra finches

Long-term effects of developmental conditions on health, longevity and other fitness components in humans are drawing increasing attention. In evolutionary ecology, such effects are of similar importance because of their role in the trade-off between quantity and quality of offspring. The central role of energy consumption is well documented for some long-term health effects in humans (e.g. obesity), but little is known of the long-term effects of rearing conditions on energy requirements later in life. We manipulated the rearing conditions in zebra finches ( Taeniopygia guttata ) using brood size manipulation and cross-fostering. It has previously been shown in this species that being reared in a large brood has negative fitness consequences, and that such effects are stronger in daughters than in sons. We show that, independent of mass, standard metabolic rate of 1-year-old birds was higher when they had been reared in a large brood, and this is to our knowledge the first demonstration of such an effect. Furthermore, the brood size effect was stronger in daughters than in sons. This suggests that metabolic efficiency may play a role in mediating the long-term fitness consequences of rearing conditions.

Adoption as a gosling strategy to obtain better parental care? Experimental evidence for gosling choice and age-dependency of adoption in greylag geese

Adoptions of unrelated young by successful breeders are a form of alloparental care which has been observed in many species of geese. Depending on costs and benefits to the parents, adoptions might represent an inter-generational conflict or a mutually beneficial strategy. Although most studies of wild populations suggest benefits of large brood sizes, incidental observations mostly report aggressive behaviour of parents towards lone goslings. No studies have investigated mechanisms and behaviour during adoptions in order to test whether adoptions are driven by parents or goslings. To test whether goslings might use adoption as a strategy to obtain better parental care, we carried out an experiment where lone greylag goose (Anser anser) goslings could choose between a dominant and a subordinate foster family. In a second experiment we also tested whether adoption was age-dependent. Except for one case, all lone goslings (N = 16) chose the dominant family. Parents showed very little aggression towards lone goslings at three days after hatch, but aggression increased until 9 days and remained high thereafter. At the same time as aggression increased, the chance of successful adoption decreased. In the first five weeks of life, goslings which had been adopted were no further away from parents than original goslings during grazing. These results show that goslings might choose foster families according to dominance. The fact that with increasing gosling age parents are less willing to adopt could be due to improved individual recognition and reflect decreasing benefits of gaining an additional family member. More detailed studies on state-dependent costs and benefits of adoptions are required to determine whether adoptions in geese represent conflict or mutualism, and why this changes with gosling age.