Approximately two decades after the first pioneering analyses, the study of shape asymmetry with the methods of geometric morphometrics has matured and is a burgeoning field. New technology for data collection and new methods and software for analysis are widely available and have led to numerous applications in plants and animals, including humans. This review summarizes the concepts and morphometric methods for studying asymmetry of shape and size. After a summary of mathematical and biological concepts of symmetry and asymmetry, a section follows that explains the methods of geometric morphometrics and how they can be used to analyze asymmetry of biological structures. Geometric morphometric analyses not only tell how much asymmetry there is, but also provide information about the patterns of covariation in the structure under study. Such patterns of covariation in fluctuating asymmetry can provide valuable insight about the developmental basis of morphological integration, and have become important tools for evolutionary developmental biology. The genetic basis of fluctuating asymmetry has been studied from empirical and theoretical viewpoints, but serious challenges remain in this area. There are many promising areas for further research that are only little explored at present.

Analyzing Fluctuating Asymmetry with Geometric Morphometrics: Concepts, Methods, and Applications

Biomphalaria snails are instrumental in transmission of the human blood fluke Schistosoma mansoni With the World Health Organization's goal to eliminate schistosomiasis as a global health problem by 2025, there is now renewed emphasis on snail control Here, we characterize the genome of Biomphalaria glabrata, a lophotrochozoan protostome, and provide timely and important information on snail biology We describe aspects of phero-perception, stress responses, immune function and regulation of gene expression that support the persistence of B glabrata in the field and may define this species as a suitable snail host for S mansoni We identify several potential targets for developing novel control measures aimed at reducing snail-mediated transmission of schistosomiasis

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Whole genome analysis of a schistosomiasis-transmitting freshwater snail.

Developments of microfluidic paper-based analytical devices (μPADs) for water analysis: A review.

The Evolution of Primary Sexual Characters in Animals, Janet L. Leonard, Alex Cordoba-Aguilar (Eds.). Oxford University Press, Oxford (2010), Pp. ix+537. Price £50 hardback

Hermaphrodites combine the male and female sex functions into a single individual, either sequentially or simultaneously. This simple fact means that they exhibit both similarities and differences in the way in which they experience, and respond to, sexual conflict compared to separate-sexed organisms. Here, we focus on clarifying how sexual conflict concepts can be adapted to apply to all anisogamous sexual systems and review unique (or especially important) aspects of sexual conflict in hermaphroditic animals. These include conflicts over the timing of sex change in sequential hermaphrodites, and in simultaneous hermaphrodites, over both sex roles and the postmating manipulation of the sperm recipient by the sperm donor. Extending and applying sexual conflict thinking to hermaphrodites can identify general evolutionary principles and help explain some of the unique reproductive diversity found among animals exhibiting this widespread but to date understudied sexual system.

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Sexual Conflict in Hermaphrodites

http://joriskoene.com/publications/Nakadera_et_al_2014b.pdf

Receipt of Seminal Fluid Proteins Causes Reduction of Male Investment in a Simultaneous Hermaphrodite

An individual optimizes its reproductive success by adopting a particular reproductive strategy. Studying the details of a reproductive strategy leads to an understanding of how sexual selection acts, as the former is the process via which the individual reproduces successfully. Hermaphroditic gastropods display a bewildering diversity of reproductive strategies, which may be due to their mode of gender expression, when compared with well-studied separate-sexed species. Extensive theoretical, observational, and experimental research has been conducted on this topic. However, despite our knowledge about the repro- ductive system of hermaphroditic gastropods, we still need to fill the gap between pre- and post-copulatory processes and reproductive success. Here, we review and propose conceptual and empirical approaches aimed at understanding reproductive strategies of hermaphroditic gastropods. In sum, our suggestions are (i) to focus on sex-biased traits, (ii) to take biologically reliable measurements at both the pre- and post-copulatory level that relate to reproductive success, and (iii) to examine the fitness consequences of biased sex allocation. Resume : Les individus optimisent leur succes de reproduction en adoptant des strategies reproductives qui leur sont propres. L'etude des details d'une strategie de reproduction permet une meilleure comprehension des mecanismes de selection sexuelle, puisqu'il s'agit du processus par lequel l'individu se reproduit avec succes. Comparativement ades especes bien etudiees dont les sexes sont distincts, les gasteropodes hermaphrodites presentent une extreme diversite de strategies de reproduction qui pourrait etre le fait du mode d'expression du sexe. De nombreux travaux theoriques, experimentaux et d'observation sur ce theme ont deja ` ete realises. Cependant, malgre les connaissances acquises sur le systeme reproducteur de gasteropodes her- maphrodites, le lien entre les processus pre- et post-copulatoires et le succes de reproduction n'est pas encore bien etabli. Nous passons en revue et proposons des approches conceptuelles et empiriques visant amieux comprendre les strategies de repro- duction des gasteropodes hermaphrodites. Nous suggerons (i) de mettre l'accent sur les caracteres dont la distribution depend du sexe, (ii) de prendre des mesures fiables sur le plan biologique aux stades pre- et post-copulatoires, qui sont reliees au succes de reproduction et (iii) d'examiner les consequences d'une determination asymetrique des sexes sur l'aptitude. (Traduit par la Redaction)

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Reproductive strategies in hermaphroditic gastropods: conceptual and empirical approaches1

Reproductive success is a crucial variable to understand the action of sexual selection, but its quantification is not straightforward because several factors cause nonrandom fertilization success. One of these factors is female sperm storage, which leads to prolonged paternity gain ( paternity longevity). In particular, knowledge about paternity longevity is crucial in simultaneous hermaphrodites, since their ability to self-fertilize adds a further layer of complexity to the quantification of male reproductive success. Here, we investigated the pattern of outcrossing over time after a single mating in a freshwater snail, Lymnaea stagnalis, using a microsatellite marker. We found that offspring are produced from stored sperm for a little over 2 months on average. Furthermore, the pattern of paternity indicates an active role for the female reproductive system in the transport of received sperm to the sperm storage organ. To quantify paternity longevity in a sperm-storing mating system, we propose to use the time when half the offspring are sired by a focal donor (Paternity Longevity 50; PL50), in addition to total storage duration. Intriguingly, we reveal that overall body size is positively correlated with paternity longevity. Although the exact mechanism of sperm storage and its contribution to male reproductive success remain to be revealed, this study provides useful information and new perspectives on sperm storage and sexual selection in this simultaneous hermaphrodite.

https://www.jkoene.dds.nl/publications/Nakadera_et_al_2014a.pdf

Duration of sperm storage in the simultaneous hermaphrodite lymnaea stagnalis

Contrasting with separate-sexed animals, simultaneous hermaphrodites display unique reproductive strategies as they are male and female at the same time. Simultaneous hermaphrodites that copulate unilaterally, for instance, make a decision to mate as a male or female. Previous studies have demonstrated that sex role preference in hermaphrodites is flexible and is controlled by several, often confounding, factors. We examined the relationship between sex role decisions and 3 life-history traits (age, size, and mating history) in the great pond snail, Lymnaea stagnalis. Based on our field observations, which indicate that adult individuals show overlapping generations and large variation in body size during the breeding season, we performed a sex role choice experiment in the laboratory. We found that young and small snails mate as males first. Both age and size significantly affected sex role decision, with age having a stronger effect. Furthermore, we tested whether L. stagnalis becomes reluctant to inseminate a mate after being inseminated because it is known that after insemination, male investment substantially reduces. Contrary to expectations, our results indicate that the receipt of seminal fluid does not seem to reduce male motivation. In sum, sex role decisions in L. stagnalis are largely determined by age and size but not by having received seminal fluid. This mating pattern, however, does not fully support the size-advantage model because large or old individuals did not perform better as females in our experiment. These results imply a conflicting mating interest, rather than harmonious agreement, between age- and size-different hermaphrodites.

Effects of age, size, and mating history on sex role decision of a simultaneous hermaphrodite

In internally fertilizing animals, seminal fluid is usually added to the spermatozoa, together forming the semen or ejaculate. Besides nourishing and activating sperm, the components in the seminal fluid can also influence female physiology to augment fertilization success of the sperm donor. While many studies have reported such effects in species with separate sexes, few studies have addressed this in simultaneously hermaphroditic animals. This video protocol presents a method to study effects of seminal fluid in gastropods, using a simultaneously hermaphroditic freshwater snail, the great pond snail Lymnaea stagnalis, as model organism. While the procedure is shown using complete prostate gland extracts, individual components (i.e., proteins, peptides, and other compounds) of the seminal fluid can be tested in the same way. Effects of the receipt of ejaculate components on egg laying can be quantified in terms of frequency of egg laying and more subtle estimates of female reproductive performance such as egg numbers within each egg masses. Results show that seminal fluid proteins affect female reproductive output in this simultaneous hermaphrodite, highlighting their importance for sexual selection.

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Yumi Nakadera

Papers

Receipt of Seminal Fluid Proteins Causes Reduction of Male Investment in a Simultaneous Hermaphrodite

Reproductive strategies in hermaphroditic gastropods: conceptual and empirical approaches1

Duration of sperm storage in the simultaneous hermaphrodite lymnaea stagnalis

Effects of age, size, and mating history on sex role decision of a simultaneous hermaphrodite

Effect of male accessory gland products on egg laying in gastropod molluscs.