Quantitative genetics of costly neonatal sexual size dimorphism in squirrel monkeys (Saimiri boliviensis)

Maternal effects on reproduction in the precocial European hare (Lepus europaeus)

In female mammals, reproduction, and in particular lactation, is the energetically most exigent life-history phase. Reproduction is strongly controlled by body reserves and food availability, so females with better body condition or food supply are believed to have higher reproductive output. Additionally, the growth and mortality of young mammals depends on their postnatal development. Therefore, the degree of precociality affects energetic demands for both mothers and young. To study the reproductive performance of the precocial European hare (Lepus europaeus), we analysed relationships between six predictor variables describing maternal and environmental effects and nine response variables relating to reproduction from 217 captive females. We compared the data with those of precocial and altricial mammal species from an extensive literature search. For hares, we found: (1) Heavier females had heavier litters at birth. (2) In summer and spring, total litter mass was larger than in winter. (3) At the end of lactation, the litters of multiparous females were heavier than those of primiparous females. (4) Both older females and females giving birth for the first time had relatively high leveret mortality during lactation. Comparing our results with the literature for other mammals revealed that the body condition (i.e., body mass) of females before birth is predictive of reproductive parameters in both precocial and altricial species. In the precocial hare, female body condition is no longer predictive of reproductive parameters at the end of lactation, whereas in altricial species, female body condition remains predictive of reproduction (litter mass at the end of lactation, offspring mortality) until the end of lactation. We conclude that these effects are caused by precocial offspring feeding on solid food soon after birth and, thus, being less dependent on the mother's body condition during lactation than altricial offspring. In line with this, precociality might have evolved as a way of buffering offspring against maternal effects.

Small for gestational age: the familial perspective

BACKGROUND

There are multiple etiologies for being born small for gestational age (SGA). However, extended familial data in idiopathic cases have been scarcely reported.

OBJECTIVE

Our aim was to explore the familial history of SGA newborns and describe the proportion and distribution of SGA in their parents and parental siblings.

METHODS

This was a retrospective study performed at an obstetrics clinic holding a detailed reliable electronic database. Between 2008 and 2017, data of 14,003 patients and 20,617 pregnancies were recorded. Parents of SGA infants were identified and extended familial history was obtained by questionnaires, including birth weights (BWs) and gestational age at birth of the parents and parents' siblings. SGA was defined as a BW below the 10th percentile. Proportions of maternal, paternal, and parental siblings' SGA were calculated. Chi-square test was performed to assess the relationship between SGA family member's gender and SGA infants' gender, and between the relative's gender and their family relationship to the infant.

RESULTS

About 2100 women had a history of a previous infant born SGA, however, after exclusion the final cohort comprised 926 women with a previous SGA infant. In 473 cases there was at least one other family member of the infant born SGA: father, mother, aunt, or uncle of the infant, representing a prevalence of 51% (473/926) of familial SGA. Out of familial SGA cases, maternal SGA was found in 55% (260/473), and paternal SGA was found in 28.1% (133/473). 27.6% had more than one SGA relative. Eighteen infants had both an SGA father and an SGA mother (3.8%). A history of an SGA aunt or uncle was found in 44% (209/473) of familial SGA cases, which was 22.5% (209/926) of the entire cohort. Parental sibling SGA occurred almost twice in mother's siblings as compared to father's siblings. Chi-square test revealed no association between the SGA relative's gender and their family relationship to the infant. There was no association between the SGA infant's gender and the SGA relative's gender.

CONCLUSIONS

A family history of SGA is common in SGA infants, and occurs most often in mothers. This study found 22% SGA in parental siblings, in maternal siblings more than paternal siblings, supporting the possibility of a genetic component in SGA trait transmission. In clinical practice, when counseling parents with a growth-restricted fetus from an unknown etiology, extended familial birthweight history should be obtained and taken into account, which may be helpful in reducing parental anxiety.

Transthoracic echocardiography and cardiac biomarkers in healthy captive male and female squirrel monkeys (Saimiri spp.)

Background

Echocardiography is the most frequently used non -invasive diagnostic tool to evaluate cardiac anatomy and function in domestic species but increasingly also in non -domestic species, especially since cardiac disease is being recognized as an important cause of death in captive primates. The purpose of this cross -sectional study was to investigate the feasibility of transthoracic echocardiography in healthy squirrel monkeys as well as to provide species specific normal values for standard echocardiographic measurements. A secondary aim was to determine plasma and serum levels of the cardiac biomarkers, N -terminal pro -brain natriuretic peptide (NT -proBNP) and cardiac troponin T (cTnT). Furthermore, a commercial, non -invasive, smartphone -based ECG (AliveCor Vet TM) monitoring device was used to evaluate the heart rate and rhythm and to diagnose possible arrhythmias.

Results

In this study, transthoracic echocardiography of 14 squirrel monkeys was performed in right and left lateral recumbency. Similar standard right parasternal and left apical images were obtained as in dogs and cats and normal values for routine two -dimensional, time motion mode and Doppler mode measurements were generated. Thirteen animals were considered healthy and one squirrel monkey was identified with significant aortic dilation and regurgitation and consequently values obtained from this animal were not used when species specific normal values were calculated. NT -ProBNP and cTnT concentrations were available for 7 of the 13 healthy monkeys with NT -proBNP concentrations below detection limit in all animals and a mean cTnT concentration of 0.049 ng/mL. Electrocardiography was performed in all squirrel monkeys. The mean heart rate was 172 bpm. Frequent supraventricular premature beats were diagnosed in the squirrel monkey suffering from significant aortic dilation and regurgitation.

Conclusion

This study presents echocardiographic normal values and additional cardiovascular data in anaesthetised Saimiri monkeys, fundamental from both the perspective of zoo animal health care as well as scientific research, since the squirrel monkey is often used as an animal model for human disease.

Thoracic radiography of healthy captive male and female Squirrel monkey (Saimiri spp.)

The purpose of this prospective study was to describe the normal anatomy and provide reference ranges for measurements of thoracic radiography on Squirrel monkeys (n = 13). Thoracic radiography is a common non-invasive diagnostic tool for both cardiac and non-cardiac thoracic structures. Furthermore cardiac disease is a common condition in captive primates. In this study, left-right lateral, right-left lateral and dorsoventral projections of 13 healthy Squirrel monkeys were reviewed during their annual health examinations. The mean Vertebral Heart Score on the left-right and right-left lateral projections were 8,98 ± 0,25 and 8,85 ± 0,35 respectively. The cardio-thoracic ratio on the dorsoventral projection was 0,68 ± 0,03. The trachea to inlet ratio was 0,33 ± 0,04. Other measurements are provided for the skeletal, cardiac and respiratory systems. Knowledge of the normal radiographic thoracic anatomy is fundamental in clinical as well as research settings for accurate diagnosis of diseases.

Function-related Drivers of Skull Morphometric Variation and Sexual Size Dimorphism in a Subterranean Rodent, Plateau Zokor (Eospalax baileyi)

Sexual dimorphism is prevalent in most living organisms. The difference in size between sexes of a given species is generally known as sexual size dimorphism (SSD). The magnitude of the SSD is determined by Rensch's rule where size dimorphism increases with increasing body size when the male is the larger sex and decreases with increasing average body size when the female is the larger sex. The unique underground environment that zokors (Eospalax baileyi) live under in the severe habitat of the Qinghai‐Tibetan Plateau (QTP) could create SSD selection pressures that may or may not be supported by Rensch's rule, making this scientific question worthy of investigation. In this study, we investigated the individual variation between sexes in body size and SSD of plateau zokors using measurements of 19 morphological traits. We also investigated the evolutionary mechanisms underlying SSD in plateau zokors. Moreover, we applied Rensch's rule to all extant zokor species. Our results showed male‐biased SSD in plateau zokors: The body‐ and head‐related measurements were greater in males than in females. Linear regression analysis between body length, body weight, and carcass weight showed significant relationships with some traits such as skull length, lower incisor length, and tympanic bulla width, which might support our prediction that males have faster growth rates than females. Further, the SSD pattern corroborated the assumption of Rensch's rule in plateau zokors but not in the other zokor species. Our findings suggest that the natural underground habitat and behavioral differences between sexes can generate selection pressures on male traits and contribute to the evolution of SSD in plateau zokors.

Selection on parental performance opposes selection for larger body mass in a wild population of blue tits

There is abundant evidence in many taxa for positive directional selection on body size, and yet little evidence for microevolutionary change. In many species, variation in body size is partly determined by the actions of parents, so a proposed explanation for stasis is the presence of a negative genetic correlation between direct and parental effects. Consequently, selecting genes for increased body size would result in a correlated decline in parental effects, reducing body size in the following generation. We show that these arguments implicitly assume that parental care is cost free, and that including a cost alters the predicted genetic architectures needed to explain stasis. Using a large cross-fostered population of blue tits, we estimate direct selection on parental effects for body mass, and show it is negative. Negative selection is consistent with a cost to parental care, mainly acting through a reduction in current fecundity rather than survival. Under these conditions, evolutionary stasis is possible for moderately negative genetic correlations between direct and parental effects. This is in contrast to the implausibly extreme correlations needed when care is assumed to be cost-free. Thus, we highlight the importance of accounting correctly for complete selection acting on traits across generations.