In the UK it is now compulsory to wear eyewear at CPSA registered shoots and almost all shooting schools/grounds. Even most clubs strongly advise that eyewear is worn. Eyewear lenses for shooting should be made from polycarbonate or Trivex as both materials provide a very high level of impact protection whether from a stray or falling pellet but more likely a shard of broken clay. A piece of broken clay hitting an unprotected eye will likely cause permanent eye damage. Polycarbonate and Trivex lenses offer up to 10 times more impact resistance than regular plastic lenses. All Evolution shooting models have polycarbonate lenses with a minimum thickness of 2mm sufficient to withstand the impact test requirement of EN166F.

Another important and often overlooked factor is that good quality UKCA/CE marked eyewear will be UV400 rated providing maximum protection from harmful solar ultraviolet radiation (UVR). Long term exposure to UVR can damage eyesight, potentially causing serious eye health issues such as cataracts, cancer of the eyelids and macular degeneration.

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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.

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 love-dart, 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.

Our study represents the first comprehensive comparative analysis of reproductive organ characteristics in simultaneous hermaphrodites. Moreover, it strongly suggests that co-evolutionary arms races can result from sexual conflict in these organisms and play a key role in the evolution of hermaphroditic mating systems.

Evolutionary conflicts of interest between the sexes have been convincingly demonstrated in species with separate sexes [1]. These sexual conflicts often give rise to traits that are advantageous for one sex but harmful to the other. If these detrimental effects are counteracted, a co-evolutionary arms race may ensue in which harmful traits and corresponding counter-adaptations arise repeatedly [2]. Such antagonistic interactions can bring about major changes in the mating behaviour, genital morphology, gametes and seminal products, potentially leading to speciation [2]. Similar arms races seem to occur in hermaphrodites, contrary to Darwin's conviction [3] that sexual selection cannot act in hermaphroditic organisms. In fact, theoretical modeling indicates that these processes can become even more extreme in hermaphroditic species (N.K. Michiels and J.M. Koene, unpublished data), mainly because within one mating simultaneous hermaphrodites gain paternity (male fitness) which can outweigh the loss in female fitness. Here we investigate the evolution of a most peculiar reproductive behaviour that occurs in simultaneously hermaphroditic land snails (Stylommatophora), the "shooting" of a so-called love-dart into the mating partner.

Several explanations have been offered for the evolution of the enigmatic dart shooting behaviour. The dart is made of calcium carbonate and has therefore been proposed to serve as a nuptial gift of calcium for the production of eggs [4, 5]. However, in Cantareus aspersus (previously Helix aspersa) the dart does not contain enough calcium to significantly contribute to egg production and darts are only rarely incorporated by the recipient [6]. Likewise, in other investigated species darts are even retained by shooters to be reused on the next mate [[7, 8], J.M. Koene and S. Chiba, unpublished data). Therefore two other hypotheses have been put forward. In the female choice hypothesis the dart represents a sexual signal and recipients select on dart shooting effectiveness [5, 9]. The important prediction of this hypothesis is that this can only be beneficial for the recipient if the dart is shot consistently by individuals (assuming that shooting ability is heritable). Tests in C. aspersus do not support this, because dart shooting of individually-identified animals in consecutive matings is unpredictable (G-test: N = 29 snails, df = 1, G = 6.745, P < 0.01; J.M. Koene, unpublished data). Besides, in Arianta arbustorum dart shooting seems to be an optional component of courtship [10].

Schematic morphological drawing of the reproductive morphology of a land snail with one dart and a diverticulum. The love-dart (D) is produced and stored in the stylophore (S, often called dart sac) and shot by a forceful eversion of this organ. The mucus glands (MG) produce the mucus that is deposited on the dart before shooting. The penis (P) is intromitted to transfer the spermatophore. The sperm container is formed in the epiphallus (EP), while the spermatophore's tail is formed by the flagellum (FL). When a bursa tract diverticulum (BTD) is present, the spermatophore is received in this organ. Together with the bursa tract (BT) and bursa copulatrix (BC) these form the spermatophore-receiving organ (SRO, indicated in grey), which digest sperm and spermatophores. Sperm swim out via the tail of the spermatophore to enter the female tract and reach the sperm storage organ (SP, spermathecae) within the fertilization pouch (FP)-spermathecal complex. Other abbreviations: AG, albumen gland; G, genital pore; HD, hermaphroditic duct; OT, ovotestis; PRM, penis retractor muscle; SO, spermoviduct; V, vaginal duct; VD, vas deferens.

Interestingly, love-darts display an astonishing diversity between species, both in number and shape, ranging from several simple cone-shapes to one elaborately bladed structures [21, 22]. The most elaborate darts show surface enlargement with blades that is likely to enhance the transfer of gland product. We therefore predict that dart elaboration should covary with allohormone production, which should be mirrored in the gland morphology as surface enlargement. Moreover, the dart specializations that enhance gland product transfer are potentially more successful at manipulating fertilization. If so, adaptations to counteract this effect are expected, which could give rise to a co-evolutionary arms race. These predictions are tested here using a comparative analysis of dart-possessing land snail species. Note that we are only focussing on the Helicoidea superfamily; we do not include species with non-homologous dart-like structures (see also [22]). Because the phylogeny of land snails is heavily based on reproductive morphology [23, 24], we first reconstructed an independent phylogeny based on part of the 28S ribosomal RNA (rRNA) gene [25]. Our findings represent the first comprehensive comparative analysis of reproductive organ characteristics in simultaneously hermaphroditic animals and are consistent with co-evolution and counter-adaptation predicted by sexual conflict theory.

Within the land snails that possess love-darts, there is a large diversity in reproductive structures and the darts themselves provide an impressive range of shapes. There are species with one dart, while others have several or none. Darts of some species have a simple cone-shape, whereas others show surface enlargement with blades. Additionally, darts vary from straight to curved and contorted. This variety in dart shapes is illustrated in the electron microscopic photographs in Figure 2 and the line drawings in Figure 3. We found similar levels of variation between species in the other reproductive organs. These differences include the number, relative size and placement of both functional and vestigial stylophores; the number, relative size, type of branching, and placement of the glands; the presence, relative length and placement of the diverticulum in the SRO; and the presence and relative length of the flagellum.

Diversity of love-darts. The different shapes of love-darts are illustrated with electron microscopic photographs of side views and cross sections of darts from different species. Scale bars indicate 500 m for side views and 50 m for cross-sections.

Phylogeny of land snails and their love-darts. Cross-section and side views of the darts are shown. For comparability, the line drawings are all at the same size. When two cross-sections are shown, that species possesses two functional darts. The shown phylogeny was obtained by Bayesian inference (BI). Branch lengths correspond to the number of substitutions per site (see scale bar). Maximum likelihood (ML) produced an almost identical tree (see Results). Clade support is given next to the nodes such that values before slashes refer to BI posterior probabilities above 0.5 and values behind slashes to ML bootstrapping results above 50.

Both ML and BI yielded a single optimal phylogenetic tree (see Figure 3 for the BI tree). These two trees had almost identical topologies. The only differences consisted of the exact position of Fruticicola fruticum within the Bradybaenidae, of Leptaxis erubescens within the Hygromiidae, the relationship of the four major lineages of the Helicidae, and the position of Cernuella cisalpina, C. hydruntina, C. virgata, and Xerosecta cespitum in relation to each other. Moreover, although BI produced high support values for a much larger number of clades than ML bootstrapping, the clades with high ML bootstrap scores also always had high BI posterior probabilities (Figure 3). Furthermore, the four main families were all correctly identified (Figure 3). The only exception being that Polymita picta was not grouped with the other species of the Helminthoglyptidae. However, this taxon is found at the end of a comparatively long branch. Hence, its position at the base of the superfamily Helicoidea could be due to long branch attraction to the outgroup and may therefore be unreliable. 152ee80cbc

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