Total Parental Investment Research Articles

How do biparental species optimally provision young when begging is honest?

Offspring transmit signals to parents to communicate their resource demands. Parents interpret these signals and should adjust provisioning efforts to meet offspring demands but only to the point at which the benefits of enhanced offspring quality stops exceeding the increased costs to future reproduction. We investigated both proximate behavioral mechanisms in these interactions and ultimate-level decisions for total parental investment in streaked shearwaters Calonectris leucomelas by recording begging calls, monitoring parental attendance, and altering states of chicks by supplementing food. In our study, chicks seemed to honestly communicate satiety and body condition via begging. The parents, however, did not downwardly adjust feeding rates, meal sizes delivered to chicks, and total investment in nests in which chicks were regularly supplementary-fed partial meals. But on nights when both parents visited the nest, the second-arriving parents recognized that chicks had already received a full meal because they reduced the food they gave to chicks and also lengthened their subsequent foraging trip. Our findings therefore suggest that although chick begging appeared to reflect need, parents only responded to variation in begging that indicated that chicks had already received a full meal. In a simulation, we show that this strategy prevents parents from exceeding the optimal amount of parental investment. Their insensitivity to slightly reduced begging after partial meals caused them to exceed optimal investment in supplementary-fed nests, suggesting that parental investment is largely regulated by responses to feeding rate of the other parent rather than being fine-tuned to cues about body condition of chicks.

Effects of competition and egg predation on shelter use by Octopus tehuelchus females

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 482:141-151 (2013) - DOI: https://doi.org/10.3354/meps10237 Effects of competition and egg predation on shelter use by Octopus tehuelchus females Maite Narvarte1,2,*, Raúl Alberto González1,2, Lorena Storero1,2, Miriam Fernández3 1Consejo Nacional de Investigaciones Científicas y Técnica (CONICET), Av. Rivadavia 1917, C1033AAJ, Ciudad Autónoma de Buenos Aires, Argentina 2Instituto de Biología Marina y Pesquera Almirante Storni, Escuela Superior de Ciencias Marinas, Universidad Nacional del Comahue, Av. Güemes 1030, San Antonio Oeste 8520, Argentina 3Estación Costera de Investigaciones Marinas de Las Cruces, and Center for Advanced Studies in Ecology and Biodiversity, Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile *Email: mnarvarte@gmail.com ABSTRACT: Parental care in the ocean ranges from provision to eggs and embryos to protection from predators. In particular, nest attendance has several benefits associated with relatively higher survival rates, lower vulnerability to predation and parasitism, and faster development rates. The quality of shelters matters, and adults of many species have to compete for suitable shelters. Here, we studied whether shelter type for brooding and egg protection from predation could be a determinant of competition among adults in the cephalopod Octopus tehuelchus. To this end, we (1) assessed the abundance of different types of shelters and preference under field and laboratory conditions, (2) tested the effect of intraspecific competition for shelters, (3) estimated density of potential sources of embryo mortality, and (4) determined the role of female protection in egg survival against predators. We found that in areas where shelters for development are scarce, females compete with males for the most suitable shelters. Fecundity depends on the female size, and shelters with higher volume are preferably selected by females. Excluding the brooding female from shelters resulted in increased egg mortality due to predation by octopus males and removal by chitons. We suggest that, in this species, shelter availability poses a constraint to brooding and affects total parental investment in reproduction and predation risk on eggs. This constraint may also take place in other marine invertebrates with similar life history traits, especially in areas where shelter is limited. KEY WORDS: Shelter use · Competition · Predation on eggs · Octopus tehuelchus Full text in pdf format PreviousNextCite this article as: Narvarte M, González RA, Storero L, Fernández M (2013) Effects of competition and egg predation on shelter use by Octopus tehuelchus females. Mar Ecol Prog Ser 482:141-151. https://doi.org/10.3354/meps10237 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 482. Online publication date: May 22, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Paternal deprivation induces dendritic and synaptic changes and hemispheric asymmetry of pyramidal neurons in the somatosensory cortex

Similar to maternal care, paternal care is a source of neonatal sensory stimulation, which in primates and rodents has been shown to be essential for developing structure and function of sensory cortices. The aim of our study in the biparental rodent Octodon degus was to assess the impact of paternal deprivation on dendritic and synaptic development in the somatosensory cortex. We (i) quantified the amount of paternal care in relation to total parental investment and (ii) compared dendritic and synaptic development of pyramidal neurons in the somatosensory cortex of animals raised by a single mother or by both parents. On the behavioral level we show that paternal care comprises 37% of total parent-offspring interactions, and that the somatosensory stimulation provided by the fathers primarily consists of huddling, licking/grooming, and playing. On the morphological level we found that, compared with offspring raised by both parents (mother and father), the father-deprived animals displayed significantly reduced spine numbers on the basal dendrites of pyramidal neurons. Furthermore, paternal deprivation induces hemispheric asymmetry of the dendritic morphology of somatosensory pyramidal neurons. Father-deprived animals show shorter and less complex basal dendrites in the left somatosensory cortex compared with the right hemisphere. These findings indicate that paternal deprivation results in delayed or retarded dendritic and synaptic development of somatosensory circuits.

Does Late Reproduction Extend the Life Span? Findings from European Royalty

Statistical associations between late reproduction and female longevity led to speculations that a late birth increases a mother's life span. The database used here includes all descendants of King George I of England (1660–1727) and his wife, Sophie Dorothea (1666–1726), born in the royal dynasties in Europe up to 1939 (n=1,672). In the era of British world supremacy, these descendants formed the uppermost layer of the European aristocracy, occupying all royal thrones from 1850 onward. Novel in this study is the use of pedigree information. In pairs of ever‐married full sisters (brothers), both surviving to 45 (50) years, both having at least one child, the study examines whether the sibling with the first—or last—child born later in life also lived a longer life. This design controls for genetics, socioeconomic status, parity, social support, child mortality, birth cohort, and various environmental factors. In the 157 pairs of sisters and 191 pairs of brothers, later reproduction did not extend the life span.

Egg Components and Utilization of Yolk Lipids during Development of the Flatback Turtle Natator depressus

Abstract The materials and energy invested in each egg by most oviparous reptiles represent the majority of total parental investment in offspring. For Natator depressus from eastern Queensland, Australia, the shell contributed approximately 5%, the albumin 45%, and the yolk 50% to the total egg mass (74 g). Water averaged 79% of the total egg mass. Lipids averaged 29% of the total dry mass of the egg and 35% of the yolk dry mass. Eggs of N. depressus contained a high proportion of yolk lipids and water, with greater “parental investment” than those of nonmarine turtles. Approximately 26–27% of lipids in the egg was used for embryogenesis, whereas 73–74% was transferred to the entire hatchling. Initial yolk lipid in the residual yolk was approximately 30–37% but varied with incubation environment. Residual yolk lipids are likely to be used as the immediate energy source for the hatchlings.

Egg Components and Utilization of Yolk Lipids during Development of the Flatback Turtle Natator depressus

The materials and energy invested in each egg by most oviparous reptiles represent the majority of total parental investment in offspring. For Natator depressus from eastern Queensland, Australia, the shell contributed approximately 5%, the albumin 45%, and the yolk 50% to the total egg mass (74 g). Water averaged 79% of the total egg mass. Lipids averaged 29% of the total dry mass of the egg and 35% of the yolk dry mass. Eggs of N. depressus contained a high proportion of yolk lipids and water, with greater “parental investment” than those of nonmarine turtles. Approximately 26–27% of lipids in the egg was used for embryogenesis, whereas 73–74% was transferred to the entire hatchling. Initial yolk lipid in the residual yolk was approximately 30–37% but varied with incubation environment. Residual yolk lipids are likely to be used as the immediate energy source for the hatchlings.

Comparison of parental behavior in male and female prairie voles (Microtus ochrogaster)

A comparison of male and female parental investment patterns is needed before predictions can be generated from parental investment theory. One aspect of parental investment is parental care, therefore behavioral observations were conducted to compare the parental behavior of male and female prairie voles. Females brooded pups more frequently than did males during the first week of pup life and, in the absence of their mates in the nest, brooded pups more frequently throughout the preseparation period (between birth and separation from parents on day 20). Females also licked pups more frequently than did males during the entire preseparation period. Conversely, males spent more time outside the nest throughout the preseparation period. There were no differences between the sexes in the proportion of time spent in indirect parental behaviors such as nest building, food caching, or runway maintenance. These differences in direct parental care combined with a female's energetic investment in gestation and lactation result in greater total parental investment for female than for male prairie voles.

Optimal Allocation of Parental Investment

Optimal investment decisions are evaluated for parents which allocate resources equally among offspring. Optimal investment predicts that: 1) Brood size should be positively correlated with total parental investment. 2) Brood size should decline with increases in maximum juvenile survival. 3) Brood size should increase as the minimum investment in offspring declines. 4) Brood size should increase with increases in the rate of change of juvenile survival with parental investment. Total parental investment and juvenile survival should vary with environmental conditions. Optimum brood size should often be higher in good than in poor periods, but may be just the opposite in good and poor habitats. Optimal investment may frequently be achieved by differential allocation of resources among offspring. Sexual investment theory is a subset of optimal investment theory. 5) The degree of preferential partitioning of investment should depend upon the phenotypic variability of offspring and the length of parental care. 6) Investment-induced changes in phenotypic proportions (e.g., sex ratio) depend upon brood size. Optimal investment differs from other life history models in its assumption that brood size is one of a series of mechanisms operating to optimize parental investment. 7) Reproductive costs should not generally increase with increased brood size.

Sex ratios of an aphid subject to local mate competition with variable maternal condition

Fisher1 was the first to argue that natural selection would adjust the sex ratio so as to equalize parental investment (PI) in the two sexes, where mating is at random. Hamilton2 then showed that female-biased sex ratios would be favoured where male siblings compete for matings, a situation referred to as ’local mate competition‘ (LMC). In Hamilton's original model and in most subsequent LMC models, the females founding a local breeding population have equal amounts of PI to be allocated between sons and daughters. But in nature, females may differ in total PI and, as a consequence, in fecundity. Here I describe a model for the sex ratios of n co-foundresses, all of which differ in total PI. The model shows that each female with more than a specified minimum amount of PI is selected to make the same absolute investment in sons. All previously published cases of dramatic sex-ratio control occur in haplodiploid species. Here I test my theoretical model against sex-ratio data for an aphid, Prociphilus oriens, which has a normal diploid genetic system.

Models of parent-offspring conflict. V. Effects of the behaviour of the two parents

In the absence of any parent-offspring conflict, the total parental investment per offspring should be less when two parents collaborate in caring for the offspring than when only one parent invests. This does not necessarily mean that offspring fare less well when both parents invest. The ‘ideal’ amount of parental investment for an offspring to take is always greater than is ‘ideal’ for the parent to allocate (Trivers 1974). The offspring's optimum is higher if the offspring's action affects the reproductive success of only one parent and lower if both parents are affected (e.g. two-parent investment, or lifelong monogamy). The difference between the parental optimum and the offspring optimum depends on the mating system and on the form of conflict (between successive broods, or within broods), and prescribes a ‘conflict range’. The extent of conflict cannot be deduced solely from a knowledge of the average relatedness between siblings. The conflict is likely to be resolved by an ESS in which intermediate (compromise) levels of investment are paid out to offspring, which nevertheless continue to make costly demands for yet more investment. The degree of conflict can be measured by the extent to which offspring subject their parents to aggressive demands for extra investment, and is likely to be greater when two parents collaborate equally over investment than when only one parent invests. When only one parent invests, conflict is higher if sibling-competition is between siblings in the same broods (intra-brood) than when it is between progeny in successive broods (inter-brood). However, the reverse will tend to be the case when both parents invest equally.

THE IMPLICATIONS OF OVUM SIZE VARIABILITY FOR OFFSPRING FITNESS AND CLUTCH SIZE WITHIN SEVERAL POPULATIONS OF SALAMANDERS (AMBYSTOMA).

A prevalent attitude concerning parentoffspring relationships maintains that either preor post-fertilization care by parents toward offspring results in increased offspring survival at the expense of additional present or future reproductive success. This has led to models that have as an assumption monotonically increasing functions which relate parental investment per offspring to offspring fitness (Smith and Fretwell, 1974; Brockelman, 1975; Wilbur, 1977). A second assumption of such models, that offspring number is sacrificed for increased offspring care, has recently been found valid in some real situations in salamanders (Kaplan and Salthe, 1979). A third assumption is that there is intrapopulational variability in the energy invested in offspring which allows for the possibility of change in the system. Reproductive patterns of populations can evolve (or be maintained) only if there is sufficient intrapopulational variability in at least some of their components. The present study will establish the amount of intrapopulational variability in ovum size (pre-fertilization parental care) in several salamander populations. Focusing on the first assumption, the physiological ramifications of intrapopulational ovum size variability that may be related to fitness will be assessed. Whether such ramifications are monotonically associated with ovum size variability over the range of variability found will be determined. This approach will allow for an evaluation of how parameters that may be related to offspring fitness are affected by variation in pre-ovipositional parental investment. For example, if the timing of a developmental event (e.g., hatching) is of critical importance in some environments and changes in ovum size affect such timing, then in those environments variability in ovum size will potentially affect offspring fitness. However, in an environment where the timing of such an event is unimportant, variance in investment per offspring will not affect the offspring's fitness through this route. This study also relates to the problem of the determination of clutch size, that is, how and why parental investment during any breeding period is partitioned differentially among offspring within a population. Factors that determine the degree of total parental investment during a single breeding period have been dealt with elsewhere (Kaplan and Salthe, 1979), and for the purposes intended here can be assumed to be constant among individuals.