Environmental, social, morphological, and behavioral constraints on opportunistic multiple paternity

Peer reviewedPostprin

Maternal fructose and/or salt intake and reproductive outcome in the rat: effects on growth, fertility, sex ratio, and birth order

Maternal diet can significantly skew the secondary sex ratio away from the expected value of 0.5 (proportion males), but the details of how diet may do this are unclear. Here, we altered dietary levels of salt (4% salt in the feed) and/or fructose (10% in the drinking water) of pregnant rats to model potential effects that consumption of a "Western diet" might have on maternofetal growth, development, and sex ratio. We demonstrate that excess fructose consumption before and during pregnancy lead to a marked skew in the secondary sex ratio (proportion of males, 0.60; P < 0.006). The effect was not mediated by selective developmental arrest of female embryos or influenced by fetal position in the uterine horn or sex-specific effects on sperm motility, suggesting a direct effect of glycolyzable monosaccharide on the maternal ovary and/or ovulated oocyte. Furthermore, combined excess maternal consumption of salt and fructose-sweetened beverage significantly reduced fertility, reflected as a 50% reduction in preimplantation and term litter size. In addition, we also noted birth order effects in the rat, with sequential implantation sites tending to be occupied by the same sex

Revisiting non-offspring nursing: Allonursing evolves when the costs are low

This is the accepted manuscript. The final published version is available from Royal Society Publishing at http://rsbl.royalsocietypublishing.org/content/10/6/20140378.abstract.Allonursing, the nursing of another female's offspring, is commonly assumed to have evolved through the benefits of kin selection or reciprocity. The evolution of allonursing may also be influenced by variation in the possible costs to allonurses. The relative influence of costs and benefits on the incidence of allonursing in mammals remains unexplored. We show, using comparative analyses, that where females group with kin, the presence or the absence of allonursing is not associated with further variation in relatedness. Allonursing is most common where females produce litters; here the relative investment per offspring is low, and the costs of nursing additional young are likely to be reduced. Our results suggest that variation in the potential benefits is not associated with the distribution of allonursing, but that allonursing can quickly evolve when the costs to allonurses of nursing additional offspring are low.D.L. received funding from ERC grant no. 294494-THCB2011

The male fetal biomarker INSL3 reveals substantial hormone exchange between fetuses in early pig gestation

The peptide hormone INSL3 is uniquely produced by the fetal testis to promote the transabdominal phase of testicular descent. Because it is fetal sex specific, and is present in only very low amounts in the maternal circulation, INSL3 acts as an ideal biomarker with which to monitor the movement of fetal hormones within the pregnant uterus of a polytocous species, the pig. INSL3 production by the fetal testis begins at around GD30. At GD45 of the ca.114 day gestation, a time at which testicular descent is promoted, INSL3 evidently moves from male to female allantoic compartments, presumably impacting also on the female fetal circulation. At later time-points (GD63, GD92) there is less inter-fetal transfer, although there still appears to be significant INSL3, presumably of male origin, in the plasma of female fetuses. This study thus provides evidence for substantial transfer of a peptide hormone between fetuses, and probably also across the placenta, emphasizing the vulnerability of the fetus to extrinsic hormonal influences within the uterus

Ingestion of Amniotic Fluid Enhances\ud Opiate Analgesia in Rats

Placenta ingestion has recently been shown to enhance opiate-mediated analgesia produced by morphine injection, footshock, or vaginal/cervical stimulation. The enhancement of the effect of endogenous opiates (especially analgesia) may be one of the principal benefits to mammalian mothers of placentophagia at delivery. During labor and delivery, however, mothers also ingest amniotic fluid (AF) which, unlike placenta, becomes available during, or even before expulsion of the infant. The present experiments were undertaken to determine (a) whether AF ingestion, too, enhances analgesia; if so, (b) whether the effect requires ingestion of, or merely exposure to, AF; (c) whether the effect can be produced by AF delivered directly to the stomach by tube; and (d) whether the enhancement, if it exists, can be blocked by administering an opiate antagonist. Nulliparous Long-Evans rats were tested for analgesia using tail-flick latency. We found that (a) rats that ingested AF after receiving a morphine injection showed significantly more analgesia than did rats that ingested a control substance;' (b) AF ingestion, alone, did not produce analgesia; (c) ingestion of AF, rather than just smelling and seeing it, was necessary to produce analgesia enhancement; (d) AF produced enhancement\ud when oropharyngeal factors were eliminated by delivering it through an orogastric tube; and (e) treatment of the rats with naltrexone blocked the enhancement of morphine-induced analgesia that results from AF ingestion

Socially mediated polyandry: a new benefit of communal nesting in mammals

In many species, females have evolved behavioral strategies to reduce the risk of infanticide. For instance, polyandry can create paternity confusion that inhibits males from killing offspring they could have sired. Here, the authors propose that females could socially obtain the same benefits by nesting communally. Singly sired litters could be perceived as a large multiply sired litter once pooled together in a single nest. Long-term data from a wild house mouse population showed that monandrous litters (singly sired) were more common in communal than in solitary nests and 85% of them were raised with litters sired by different males hence becoming effectively polyandrous (multiply sired). These socially polyandrous litters had significantly higher offspring survival than genetically or socially monandrous litters and reached a similar survival to that of multiply sired litters raised in solitary or communal nests. Furthermore, the number of sires within nests significantly improved offspring survival whereas the number of mothers did not. These results suggest that the survival benefits associated with communal nesting are driven by polyandry and not communal defense. This socially mediated polyandry was as efficient as multiple paternity in preventing infanticide, and may also occur in other infanticidal and polytocous species where the caring parent exhibits social behavio

Does intrauterine crowding affect the force generating capacity and muscle composition of the piglet front limb?

In the pig, intrauterine competition (IUC) greatly affects postnatal traits, such as birth weight, but also locomotor capacities. In a previous study, our group discovered a lower motor performance in piglets with a low birth weight and low vitality (L piglets), compared to piglets with a normal birth weight and normal vitality (N piglets). In order to explain the force deficit causing this reduced motor performance, in a subsequent study, we investigated whether this deficit in L piglets was caused by a lower force generating capacity (FGC) of the extensors of the hind limb and/or a lower number of type II (fast-twitch) fibers in m. vastus lateralis. L piglets had a lower absolute FGC, but surprisingly, a higher relative FGC (to birth weight) in the hind limb, compared to N piglets. In addition, we found no differences in fiber composition of m. vastus lateralis. In the present study, we assessed whether this higher relative FGC is a common feature for front and hind limb locomotor muscles of L piglets. To that end, the physiological cross-sectional area of the main extensor muscles of the front limb was calculated from their volume and fiber length, in order to calculate both the absolute and the relative FGC. By immunohistochemical staining of m. triceps brachii caput longum, the percentage of type II (fast-contracting) fibers could be determined. Similar to the results of the hind limb, we found a smaller absolute FGC, but a larger relative FGC in the front limb of L piglets, compared to N piglets. In addition, m. triceps brachii caput longum did not have a different muscle fiber composition in L and N piglets. As such, we can conclude that IUC affects the locomotor muscles in the front and hind limb in a similar way and that the observed force deficit in L piglets cannot be explained by a different force generating capacity or a lower percentage of type II muscle fibers

How does intrauterine crowding affect locomotor performance in newborn pigs? : a study of force generating capacity and muscle composition of the hind limb

Intrauterine crowding (IUC) considerably influences postnatal traits in a polytocous species such as the pig. Previously, our group described how IUC affects locomotion during the piglet's first days of life (until 96 h after birth). We noted a reduced motor performance in piglets with a low birth weight and low vitality (L piglets), compared to piglets with a normal birth weight and normal vitality (N piglets), indicating L piglets are unable to produce enough force. Our current study investigates whether this observed force deficit in L piglets is caused by a reduced force generating capacity in the muscles and/or a lower percentage of type II (fast-contracting) fibers. Volume and fiber length of the main extensor muscles of the hind limb were used to estimate the physiological cross-sectional area (PSCA) and hence calculate the maximal isometric force generating capacity (Fiso-max) of the hind limb. To check for developmental differences between the muscles of L and N piglets, Fiso-max was normalized to body weight (BW), thus yielding a dimensionless variable F'iso-max. To check for differences in muscle composition, m. vastus lateralis was stained immunohistochemically in order to determine the percentage of type II fibers through image analysis. Our results indicate that L piglets have a reduced absolute force generating capacity due to a lesser muscle mass, compared to N piglets. However, when normalized to BW L piglets actually show a larger force generating capacity, suggesting their muscles are more voluminous, given their body mass, than those of N piglets. However, no differences between L and N piglets were detected with regard to muscle composition of the m. vastus lateralis. Based on our data, we can say that neither normalized force generating capacity, nor muscle composition (of the m. vastus lateralis) can explain the observed force deficit in L piglets and as such the effect of IUC on locomotor performance

CONGENITAL CONJOINT TRIPLET KITTENS (TRIPLOPAGUS): A CASE REPORT

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