251 research outputs found
Unraveling lipopolysaccharide-induced behavioral and molecular effects in Lymnaea stagnalis, an emerging model organism for translational neuroscience
Get PDF: In this study, we employed a reductionist (yet not simplistic) approach utilizing the established invertebrate model system of the pond snail, Lymnaea stagnalis, to investigate the behavioral and molecular effects of systemic administration of lipopolysaccharide (LPS)-a bacterial endotoxin-on the snails' central ring ganglia. Snails received injections of either a low dose (2.5 μg) or a high dose (25 μg) of LPS, and their behavioral and molecular responses were assessed at 2, 6, and 24 h post-injection. With the high dose, snails exhibited a significant increase in homeostatic aerial respiration lasting for at least 24 h, consistent with a sickness-like state induced by the immune challenge. Additionally, we found that when administered 2, 6, or 24 h before operant conditioning training, the high dose of LPS, impaired memory formation. To further explore the underlying molecular mechanisms, we examined the transcriptional effects of the two doses of LPS in the snails' central ring ganglia. Our analysis showed a dose- and time-dependent upregulation of immune and stress-related genes, including key enzymes involved in the kynurenine pathway (KP), toll-like receptor 4 (TLR4), and heat shock protein 70 (HSP70). Metabolomic analysis suggested that the high LPS dose shifted KP metabolism toward the production of neurotoxic metabolites within the ganglia, indicating a LPS-induced neuroinflammatory state. Together, our findings provide valuable insight into the conserved mechanisms of neuroinflammation in this invertebrate model, offering a simplified yet effective tool to further explore the molecular interactions between the immune and central nervous systems
Sexual selection and sex allocation in a simultaneous hermaphrodite
Get PDFSince Darwin’s pioneering work, sexual selection theory has become a unifying framework in evolutionary biology successfully explaining the variation in sexual dimorphism, reproductive strategies and mating systems. Although, it has long been argued that sexual selection is an important evolutionary agent in all sexually reproducing organisms, the vast majority of empirical studies on sexual selection in animals focus on separate sexed organisms. However, given that hermaphroditism is a widespread reproductive strategy among animals, empirical work on sexual selection in this group of organisms is required to evaluate the general importance of sexual selection for animals of all types of gender expression. In my PhD project, I aimed to determine the characteristics of sexual selection that operates in the outcrossing simultaneously hermaphroditic flatworm Macrostomum lignano, with a particular focus on the conditions that have been proposed to affect the sex allocation (i.e., the resource allocation to the male versus the female sex function) in simultaneous hermaphrodites.
Sex allocation theory predicts that the average mating group size (i.e., the number of mating partners plus one) within a population is one of the main parameters that affect the sex allocation in simultaneous hermaphrodites. I studied the determinants of mating group size and sperm transfer success in M. lignano and found substantial between individual variation in both traits. My results suggest that mating group size is primarily affected by the number of available mating partners, but I also found that worms with relatively larger testes acquired more mates. Apart from this, I also explored the role of mate choice for its potential to restrict the number of mating partners in M. lignano. I found that sequentially mated worms copulated more frequently with well-fed worms compared to starved worms. This suggests that worms have a preference to mate more well-fed partners, presumably because well-fed partners have a higher female fecundity and therefore represent more attractive sperm recipients.
Simultaneous hermaphrodites are predicted to allocate more reproductive resources into the male sex function if the mating group size increases. Until now, empirical studies testing this prediction primarily focussed on phenotypic plasticity in testis size as an estimate of male allocation. However, sperm competition theory predicts that sperm competition does not only select for larger testes but also for the production of bigger sperm. I experimentally tested for a phenotypically plastic response in sperm length to different levels of sperm competition in M. lignano. Despite that fact that my experimental manipulation of the level of sperm competition induced a phenotypically plastic response in testis size and ovary size, I found no difference in the sperm length between individuals that either experienced no or intense sperm competition. Thus, there seems to be no phenotypic plasticity in sperm length in response to the level of sperm competition in M. lignano.
One crucial assumption of sexual selection theory for simultaneous hermaphrodites is that Bateman’s principle applies to this group of organisms. Consequently, the reproductive success of the female sex function is expected to be primarily limited by the resources available for egg production rather than the number of mating partners. In support of this prediction, I could demonstrate that the food availability but not the number of mating partners has an effect on the number of offspring produced by the female sex function in M. lignano.
Previous research on sex allocation in simultaneous hermaphrodites mainly focused the factors that influence the resource allocation towards the male versus the female sex function, but very few attempts have been made to understand the behavioural consequences of differences in the sex allocation among individuals. I hypothesised that sex allocation has an effect on the mating behaviour in simultaneously hermaphroditic animals and predicted that individuals adopt a mating strategy that is most beneficial to the sex function that is relatively more pronounced compared to the average sex allocation in a population. An experimental test of this hypothesis revealed that more male-biased individuals mate more frequently compared to more female-biased individuals, which has been predicted if Bateman’s principle applies to M. lignano.
In conclusion, my studies suggest a high potential for pre- and post-copulatory sexual selection in the simultaneously hermaphroditic flatworm M. lignano
Tales of the two snails: sexual selection and sexual conflict in Lymnaea stagnalis and Helix aspersa
No full textSynopsis Sexual selection and sexual conflict have been shown to play key roles in the evolution of species with separate sexes. Experimental evidence is accumulating that this is also true for simultaneous hermaphrodites. For example, many species of land snails forcefully stab their mating partners with love darts. In the brown garden snail (Helix aspersa, now called Cantareus asperses), this dart increases sperm storage and paternity, probably via the transfer of an allohormone that inhibits sperm digestion. A recent interspecies comparison of dart-possessing land snails revealed coevolution between darts and spermatophore-receiving organs that is consistent with counteradaptation against an allohormonal manipulation. The great pond snail (Lymnaea stagnalis) seems to use a seminal product to manipulate its partner and mates in the male role when enough seminal fluid is available in the prostate gland. Receipt of semen not only initiates egg laying in virgin animals, but also feminizes the mating partner later in life. These increases in the female function have been shown to go at the expense of growth and seminal fluid production of the sperm recipient. Although in Helix, and probably also Lymnaea, the sperm donor benefits from the induced changes through increased fertilization success, the sperm recipient may experience injury, imposed reallocation of resources, and altered sperm storage. These findings support the existence of sexual conflict in simultaneously hermaphroditic snails, and its importance for the evolution of mating behaviors and reproductive morphologies is discussed. Introduction By extending Darwin's theory of sexual selection, research has now firmly established that sexual encounters are usually accompanied by conflicts of interest between partners (for example, Most of these previous reports of sexual conflict focused on species with separate sexes. Up to now, hermaphrodites have received relatively little attention in this respect, even though the existence of sexual selection and sexual conflict in hermaphrodites is conceptually challenging. Moreover, because hermaphroditism is common and widespread in the plant and animal kingdom, it is of fundamental importance to understand the selective forces involved. The realization that sexual selection and sexual conflict occur should provide new insights into the radiation and speciation of hermaphrodites, the diversification of hermaphroditic mating behaviors and reproductive structures as well as the underlying genetical, neurophysiological, and developmental mechanisms. Interestingly, Darwin (1871) believed that sexual selection, which drives sexual conflict, could not act in hermaphroditic organisms, mainly because the sexes are joined within one individual (Darwin 1871). Admittedly, sexual conflict in simultaneous hermaphrodites may seem paradoxical. Nonetheless, it does seem to occur. Here, I want to review several examples of sexual selection and the resulting potential conflicts in simultaneous hermaphrodites. This review will include examples from research on several different hermaphrodites and will especially focus on 2 examples from my own research, the common garden snail H. aspersa and the great pond snail L. stagnalis. At the same time, these 2 examples nicely illustrate 2 different modes of allohormone transfer, respectively, 419 via hypodermic injection and via semen Ter Maat 2001, 2002; Sexual conflict in simultaneous hermaphrodites Sexual conflict arises when a trait that is beneficial to one mating partner is detrimental to the other. Sperm donors are usually interested in maximizing the number of offspring produced with their sperm, whereas sperm recipients optimize the fitness of their offspring (Chapman and others 2003). These two objectives rarely coincide but are often in conflict, especially when sperm recipients store sperm, mate with different partners, and have specialized sperm-digesting organs. Under such circumstances sexual selection favors sperm donors that manipulate these processes. In turn, such manipulations can evoke counteradaptations by the sperm recipient. In this way, sexual conflict can drive counteradaptive coevolution in hermaphrodites The above suggests that sexual selection and sexual conflict have the potential to drive the evolution of the bizarre mating systems and complex reproductive morphologies found in hermaphrodites Dart shooting in land snails, with a focus on H. aspersa A spectacular example of a bizarre mating behavior in land snails is the shooting of so-called love darts (for example, To give a better impression of what actually happens when a dart is shot, I will provide here a brief description of the complete courtship and mating sequence of H. aspersa (also referred to as C. aspersus). This behavior is mainly controlled by the right mesocerebrum, a brain region that has an evolutionarily conserved function in gastropod mollusks others 1999, 2000). During the initial stages of courtship the genital atrium is everted and becomes visible as a gradually increasing white bulge on the right side of the animal's head Following dart shooting, the penis is everted and each snail attempts to intromit its partner. Simultaneous intromission is required for successful copulation and is achieved when the penes of both snails are inserted into the partners' vaginal duct After transfer, sperm can leave the spermatophore by actively swimming out via the spermatophore's tail (formed by the flagellum). In this way they enter the vaginal duct and have a chance of reaching the sperm storage site, the spermathecae (Lind 1973). The spermatophore and the sperm that are left behind in the diverticulum get transported to the bursa copulatrix, the gametolytic part of the spermatophore-receiving organ, for digestion. As a result of this digestion process, only a very small proportion of the sperm makes it up to the spermathecal sacs, where they are stored prior to being used for the fertilization of eggs (Lind 1973; 0.025%: Rogers and Chase 2001). At this point, it is important to note that sperm can be stored for up to 4 years Numerous hypotheses have been proposed for the evolution of dart shooting. (reviewed by Kothbauer 1988; Landolfa 2002). One explanation derives from the fact that the dart is made of calcium, in the form of the calcium carbonate crystal aragonite (Tompa 1980). Because calcium is important for the development of snails Given that none of the above findings support the nuptial gift hypothesis, 2 other types of explanations remain. In the first type the dart is assumed to represent a sexual signal. For example, the dart might signal the readiness of the shooter to lay eggs, thus making it an attractive partner to donate sperm to. No experimental support was found for this idea (Koene and Chase 1998a). The dart could also have a signaling function that could be used in female choice Previous studies have also reported nonvirgin H. aspersa occasionally not shooting their darts (Giusti and Lepri 1980; Adamo and Chase 1990; Koene and Chase 1998a; virgins do not shoot: Chung 1986a). Some other species sometimes skip dart shooting (for example, Helix lucorum: Giusti and Lepri 1980; Arianta arbustorum: Baur and others 1998), and at least for A. arbustorum dart shooting may be an optional component of courtship (Baminger and others 2000). But for H. aspersa, Therefore, in search of a better explanation, the possibility of a physiological effect caused by the mucus that is present on the dart was further explored. Adamo and Chase (1990), again using H. aspersa, were able to demonstrate that the mucus that is present on the love dart is introduced into the blood of the partner. This finding indicated that the dart could indeed act as a hypodermic device to deliver a bioactive substance to the interior of the recipient. In a series of physiological experiments I was subsequently able to show that the mucus affects the recipient's female reproductive system (Koene and Chase 1998b). As it turns out, a bioactive component in the mucus causes a reconfiguration of the tract resulting in the closing of the entrance to the duct leading to the bursa copulatrix. This observation suggested that more sperm are enabled to reach the sperm storage organ. Indeed follow-up studies demonstrated that when a dart hits its target, the number of sperm reaching the sperm storage site is higher (Rogers and Chase 2001) and so is paternity (Landolfa and others 2001; These findings indicate that the dart influences the sperm storage process of the partner. The advantage for the shooter of increasing sperm storage in its partner is obvious, especially given that these snails mate several times during a mating season and can store sperm for 4 years. Hence, the dart may have evolved in the competition for the fertilization of eggs. But, while these effects are beneficial for the shooter, receiving a dart may negatively affect the recipient's reproductive fitness. Besides changing the sperm storage process, thus interfering with cryptic female choice, the skin is damaged (especially in species that stab each other repeatedly, see below) and infection rates may be increased. First copulation J. M. Koene Taking the above into account, the manipulative effect of the love dart potentially causes a sexual conflict between the shooter and the receiver. In turn, this sexual conflict could lead to countermeasures on the receiver side. Recently this idea was investigated in an interspecies comparison. That study, based on evidence for repeated as well as correlated evolution, revealed that morphological changes in the spermatophore-receiving organs occur in parallel with the evolution of more elaborate darts and dart glands (Koene and Schulenburg 2005). The counteradaptations primarily entail the appearance and subsequent lengthening of a diverticulum, thus increasing the distance sperm need to travel to the spermathecae and thereby offsetting the increased sperm survival caused by more efficient darts. These results support that sexual conflict can drive the coevolutionary arms race between love darts and spermatophore-receiving organs Besides morphological adaptations to increase the efficiency of the dart, behavioral adaptations can also occur. As I will illustrate below, there is clear evidence that the dart can be used in a range of different ways. At the same time, it will become apparent that there are still a lot of dart-possessing species that warrant close investigation. Within the Helicidae (to which H. aspersa also belongs) all investigated species shoot once during courtship, lose their dart in the process, and can make a new dart within a few days. These species all have a single dart with 2-4 perpendicular blades (for example, A. arbustorum, Cepaea nemoralis, and Helix pomatia; Fedoseeva 1994 Seminal fluid transfer in L. stagnalis The above illustrates an example of sexual conflict in hermaphrodites that mate simultaneously reciprocal. By looking at L. stagnalis, I now want to address the question of how such a conflict may work in simultaneous hermaphrodites that do not mate in both roles at the same time. At first sight, mating behavior in the simultaneously hermaphroditic pond snail L. stagnalis may seem much less spectacular than the biting, piercing, and stabbing examples described above. But there is more than meets the eye because large amounts of semen are transferred during mating. Besides sperm, the bulk of ejaculate seems to be seminal fluid, originating from the prostate gland. Again, to give a better impression of what actually happens during semen transfer, I will first briefly review the process of reproduction in L. stagnalis. Although L. stagnalis is a simultaneous hermaphrodite that can mate in the male and female role, within a copulation one sexual role is performed. Animals seem usually receptive as females and are relatively inactive when copulating in this role Tales of two snails 423 Pond snails are not always motivated to mate in the male role. Male sexual drive increases when individuals have not mated for several days (De Boer and others 1997). The male behavior consists of a fixed sequence of events that starts with shell mounting. The animal crawls to the tip of the shell in a counterclockwise fashion (circling). It then descends to the right side of the partner's shell where it positions itself on the edge. Circling and positioning can be repeated several times. When the right position is found, the partially everted preputium becomes visible. Once the preputium, which carries the penis, is completely everted it probes to find the female opening. After one to several attempts, the penis is intromitted and semen is transferred (De Visser and others 1994; De Boer and others 1997). The seminal fluid is produced by the prostate gland and the increase in size of this gland during sexual isolation motivates the animal to mate in the male role (De Boer and others 1997). This size increase is detected by the brain via a small branch of the penial nerve (De Boer and others 1997). The brain area that receives this information, the anterior lobe, controls male reproductive behavior and is the evolutionary equivalent of the mesocerebrum of H. aspersa The above indicates that pond snails normally only mate as a male after a period of sexual isolation, when enough seminal fluid is present The above implies that sex role alternation is entirely driven by the motivation to mate as a male, based on the state of the prostate gland. This makes sense, given that male reproductive investment equals the energetic costs for the hermaphrodite's female reproduction. This was elegantly demonstrated by De Visser and colleagues (1994) via experimental elimination of the male behavior, which resulted in doubled egg production. In the original publication of those results, 2 experimental control groups were lumped together in the statistical analysis. Some have interpreted this as a weakness in the analysis or data, and it has therefore not received the appreciation that this study deserves. As I show here in a reanalysis of the original data, the experimental group differs significantly from both control groups (oneway ANOVA: F 2,25 ¼ 9.22 P ¼ 0.001; Post-hoc Tukey: P < 0.005; Understanding these motivation issues also provides insight into the way that this simultaneous hermaphrodite attempts to optimize its male investment. Clearly, the above findings illustrate the importance of the transfer of seminal fluid alongside with the sperm. And it is the seminal fluid, originating from the prostate gland, that makes up the bulk of the ejaculate. This gland produces several bioactive substances that can potentially act as allohormones Conflict over sperm use occurs because digestion of the majority of received sperm is common practice in hermaphrodites. In L. stagnalis this sperm digestion takes place in a specialized, gametolytic gland called the bursa copulatrix. Although a large ejaculate is transferred (De Visser and others 1994) only a small proportion of the sperm reaches the sperm storage site (J. M. Koene, K. Montagne-Wajer, and A. Ter Maat, unpublished data), from which these sperm can be used for fertilization for up to 3 months Conflict over resource allocation occurs because simultaneous hermaphrodites can divide their resources in a phenotypically plastic way over growth, the male and female function (Hughes and others 2002; Schärer and others 2003). Although this allows for short-term adjustments in sex allocation in response to environmental factors affecting mating group size and composition, this flexibility can also be disadvantageous. The disadvantage arises because individuals may not agree about the allocation of resources in their mating partners. In turn, this can result in a sexual conflict over resource allocation, in which individuals attempt to manipulate their partner's allocation. Concluding remarks From the above review, I conclude that in simultaneous hermaphrodites-like in species with separate sexessexual conflict can severely impact the evolution of reproductive morphologies and mating behaviors. For dart shooting land snails, coevolution between love darts and spermatophore-receiving organs has been revealed. That this results in a coevolutionary arms race is supported by evidence for both correlated and repeated evolution. But besides morphological adaptations, evidence is accumulating that behavioral adaptations can also occur to optimize mucus transfer via the dart. E. subnimbosa seems to represent an extreme case where the partners stab each other a staggering number of times before donating sperm. Recent experiments with L. stagnalis indicate that sexual conflict also occurs in simultaneous hermaphrodites where the sexual roles are performed separately. Repeated mating results in a feminization of the partner and at the same time seems to decrease seminal fluid production. This finding illustrates the tradeoff between the female and male function in this simultaneous hermaphrodite. Moreover, it hints at a conflict over resource allocation between the sperm donor and the sperm recipient, which may be mediated by an allohormone. Evidently, the 2 species that this review focused on differ in many important aspects of their reproductive habits. For instance, H. aspersa donates a spermatophore and mates simultaneously reciprocal in a faceto-face position, whereas L. stagnalis donates sperm in seminal fluid and mates unilaterally in a shellmounting fashion. Whether these differences are responsible for the different manifestations of sexual selection and sexual conflict observed in these species clearly requires a more substantial comparative study (but see Davison and others 2005). The foregoing also illustrated that the mating partner can be influenced by an allohormone that can be transferred via hypodermic injection or semen. Finally, the resulting sexual conflict has the potential of playing a key role in the evolution of reproductive morphology and mating behavior of simultaneous hermaphrodites, and can result in a coevolutionary arms race
Coolidge effect in pond snails: male motivation in a simultaneous hermaphrodite
Get PDFBackground. The simultaneously hermaphroditic pond snail, Lymnaea stagnalis, can mate in the male and female role, but within one copulation only one sexual role is performed at a time. Previous work has shown that male motivation is determined by the availability of seminal fluid in the prostate gland, which is detected via a nervous connection by the brain area controlling male behaviour. Based on this knowledge, patterns of sexual role alternations within mating pairs can be explained. Results. The data presented here reveal that these snails can donate and receive sperm several times within 24 hours, and that they have increased mating rates in larger groups (i.e. more mating opportunities). For mating pairs we show, by introducing novel mating partners after copulation, that animals do inseminate new partners, while they are no longer motivated to inseminate their original partners. Conclusion. Our findings provide the first direct evidence for higher motivation in a hermaphrodite to copulate when a new partner is encountered. This Coolidge effect seems to be attenuated when mucus trails are excluded, which suggests that a chemical or textural cue may be responsible for mediating this response to sperm competition. © 2007 Koene and Ter Maat; licensee BioMed Central Ltd
Reproductive strategies, genetic diversity, and invasive ability in Lymnaeidae
No full textThe family Lymnaeidae is a worldwide-distributed group that originated and diversified 200 Myr ago, which now inhabits freshwater areas from all continents (except for Antarctica) ranging from tropical and to arctic regions and from sea level to very high altitudes. Researchers have studied genetic diversity, life-history traits and reproductive strategies to better understand their ecological and evolutionary history, and how they are related to the current distribution of the family. Yet, compared to other zoological groups (e.g., insects, vertebrates), relatively few studies have been conducted on this group and they have focused mainly on a handful of species. In this chapter, we review the life-history traits associated with lymnaeid survival and invasion by focusing on evolutionary and ecological studies performed in this family. We also call upon studies performed in other animal groups, and sometimes in plants, in an attempt to understand lymnaeid ecological and evolutionary success. We review the morphological, behavioral and physiological traits involved in lymnaeid reproduction. We also discuss the factors that can affect lymnaeid mating systems, and how lymnaeids have expanded their geographical range by natural, as well as human-mediated ways. Finally, we explain why we believe that lymnaeids are suitable model organisms for studying mechanisms and processes involved in the ecology and evolution of mating systems and biological invasions. In the whole chapter, we draw heavily on results obtained in the most studied species––that is, the great pond snail Lymnaea stagnalis and the Galba genus, putting emphasis on the mating system (selfing vs. outcrossing).Fil: Bonel, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Nakadera, Yumi. Vrije Universiteit Amsterdam; Países BajosFil: Piza, Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Vázquez, Antonio A.. Instituto de Medicina Tropical Pedro Kourí; Cuba. Université Montpellier II; FranciaFil: Koene, Joris M.. Vrije Universiteit Amsterdam; Países BajosFil: David, Patrice. Université Montpellier II; FranciaFil: Jarne, Philippe. Université Montpellier II; FranciaFil: Alda, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentin
Shooting darts: co-evolution and counter-adaptation in hermaphroditic snails.
Get PDFBackground: Evolutionary conflicts of interest between the sexes often lead to co-evolutionary arms races consisting of repeated arisal of traits advantageous for one sex but harmful to the other sex, and counter-adaptations by the latter. In hermaphrodites, these antagonistic interactions are at least an equally important driving force. Here, we investigate the evolution of one of the most striking examples of sexual conflict in hermaphrodites, the so-called shooting of love-darts in land snails. Stabbing this calcareous dart through the partner's skin ultimately increases paternity. This trait is obviously beneficial for the shooter, but it manipulates sperm storage in the receiver. Hence, an arms race between the love-dart and the spermatophore receiving organs may be expected. Results: We performed a detailed phylogenetic analysis of 28S ribosomal RNA gene sequences from dart-possessing land snail species. Both the Shimodaira-Hasegawa test and Bayesian posterior probabilities rejected a monophyletic origin of most reproductive structures, including the lovedart, indicating that most traits arose repeatedly. Based on the inferred phylogenetic trees, we calculated phylogenetically independent contrasts for the different reproductive traits. Subsequent principal component and correlation analyses demonstrated that these contrasts covary, meaning that correlated evolution of these traits occurred. Conclusion: Our study represents the first comprehensive comparative analysis of reproductive organ characteristics in simultaneous hermaphrodites. Moreover, it strongly suggests that coevolutionary arms races can result from sexual conflict in these organisms and play a key role in the evolution of hermaphroditic mating systems. © 2005 Koene and Schulenburg; licensee BioMed Central Ltd
FIGURE 2 in Ptomaphagus thebeatles n. sp., a previously unrecognized beetle from Europe, with remarks on urban taxonomy and recent range expansion (Coleoptera: Leiodidae)
No full textFIGURE 2 Neotype of P. sericatus from Kiev, Ukraine: a, habitus; b, aedeagus, dorsal view (angle of view somewhat more rostral than in fig. 4); c, aedeagus, lateral view; d, genital segment; e, labels.Published as part of Schilthuizen, Menno, van Oostenbrugge, Wesley, Visser, Stefan, van der Meer, Marrit, Delval, Richard, Dias, Claudia, Köster, Heko, Maarschall, Rudie, Peeters, Norbert, Venema, Peter, Zaremba, Ryan, Beltrami, Cristina, Rossato, Marzia, Latella, Leonardo, Nieuwenhuis, Florinda, de Rop, Nicole, Njunjić, Iva, Perreau, Michel & Koene, Joris M., 2021, Ptomaphagus thebeatles n. sp., a previously unrecognized beetle from Europe, with remarks on urban taxonomy and recent range expansion (Coleoptera: Leiodidae), pp. 1-20 in Contributions to Zoology 90 (1) on page 9, DOI: 10.1163/18759866-BJA10007, http://zenodo.org/record/834327
Temporal expression profile of an accessory-gland protein that is transferred via the seminal fluid of the simultaneous hermaphrodite Lymnaea stagnalis
Get PDFMale accessory-gland proteins are known to affect female physiology in multiple ways, maximizing a male’s reproductive success—often at a cost to the female. Due to this inherent sexual conflict, accessory gland proteins (ACPs) are generally studied in separate-sex organisms. While ACPs have also been identified in simultaneous hermaphrodites as an important part of post-copulatory sexual selection processes, their study has lagged behind that of ACPs in organisms with separate sexes. In the great pond snail, Lymnaea stagnalis, an ACP affecting egg laying, ovipostatin, is produced in the prostate gland. Based on the published partial Ovipostatin gene sequence, we now provide the complete mRNA and gene sequences, and confirm that gene expression is prostate gland-specific. More importantly we observed a significant increase in Ovipostatin expression in sperm donors after ejaculation. Ovipostatin gene expression did not differ between donors giving their ejaculate first (primary donors) and those donating an ejaculate after having been inseminated (secondary donors). These observations support a role for ovipostatin in reproduction and highlight the importance of standardizing the time point when measuring expression levels of ACPs
Sex determination and gender expression: Reproductive investment in snails
No full textSex determination is generally seen as an issue of importance for separate-sexed organisms; however, when considering other sexual systems, such as hermaphroditism, sex allocation is a less-binary form of sex determination. As illustrated here, with examples from molluscs, this different vantage point can offer important evolutionary insights. After all, males and females produce only one type of gamete, whereas hermaphrodites produce both. In addition, sperm and accessory gland products are donated bidirectionally. For reciprocal mating, this is obvious since sperm are exchanged within one mating interaction; but even unilaterally mating species end up mating in both sexual roles, albeit not simultaneously. With this in mind, I highlight two factors that play an important role in how reproductive investment is divided in snails: First, the individual's motivation to preferentially donate rather than receive sperm (or vice versa) leads to flexible behavioral performance, and thereby investment, of either sex. Second, due to the presence of both sexual roles within the same individual, partners are potentially able to influence investment in both sexual functions of their partner to their own benefit. The latter has already led to novel insights into how accessory gland products may evolve. Moreover, the current evidence points towards different ways in which allocation to reproduction can be changed in simultaneous hermaphrodites. These often differ from the separate-sexed situation, highlighting that comparison across different sexual systems may help identify commonalities and differences in physiological, and molecular mechanisms as well as evolutionary patterns. Mol. Reprod. Dev. 84: 132-143, 2017. © 2016 Wiley Periodicals, Inc
Neuro-endocrine control of reproduction in hermaphroditic freshwater snails: mechanisms and evolution.
Get PDFInvertebrates are used extensively as model species to investigate neuro-endocrine processes regulating behaviours, and many of these processes may be extrapolated to vertebrates. However, when it comes to reproductive processes, many of these model species differ notably in their mode of reproduction. A point in case are simultaneously hermaphroditic molluscs. In this review I aim to achieve two things. On the one hand, I provide a comprehensive overview of the neuro-endocrine control of male and female reproductive processes in freshwater snails. Even though the focus will necessarily be on Lymnaea stagnalis, since this is the best-studied species in this respect, extensions to other species are made wherever possible. On the other hand, I will place these findings in the actual context of the whole animal, after all these are simultaneous hermaphrodites. By considering the hermaphroditic situation, I uncover a numbers of possible links between the regulation of the two reproductive systems that are present within this animal, and suggest a few possible mechanisms via which this animal can effectively switch between the two sexual roles in the flexible way that it does. Evidently, this opens up a number of new research questions and areas that explicitly integrate knowledge about behavioural decisions (e.g., mating, insemination, egg laying) and sexual selection processes (e.g., mate choice, sperm allocation) with the actual underlying neuronal and endocrine mechanisms required for these processes to act and function effectively
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