Genital Spines Research Articles

Sex wars: a female genital spine forces male damselflies to shorten copulation duration.

In some species, males use weapons to harm females, increasing their short-term fitness. Here we show that females can use genital adaptations against males. Females of the damselfly Enallagma cyathigerum have a conspicuous vulvar spine on the eighth abdominal segment, which contacts with the male during copulation. We tested 3 hypotheses for its function: it (a) inflicts damage to the male during copulation; (b) facilitates endophytic oviposition; and (c) stimulates males during copulation to increase their investment. We found that males mated on average for 54 min with control females, but increased copulation to 99 min with females without spine. There was no evidence of physical harm of the spine on the male's seminal vesicle, which shows 8- to 18-folds, exactly where the spine contacts during copulation. Females with and without spine exhibited the same egg-laying rates and showed similar fecundity and fertility. Longevity was also similar in males mated to control and spineless females. In contrast to many species where females resist male harassment by behavioral responses, the morphological adaptation observed in E. cyathigerum appears to act as a sexual weapon, allowing females to control copulation duration. We suggest that the spine has evolved because of sexual conflict over mating duration.

Monogeneans from Catfishes in Lake Tanganyika. II: New Infection Site, New Record, and Additional Details on the Morphology of the Male Copulatory Organ of Gyrodactylus transvaalensis Prudhoe and Hussey, 1977.

The ichthyofauna of Lake Tanganyika consists of 12 families of fish of which five belong to Siluriformes (catfishes). Studies on Siluriformes and their parasites in this lake are very fragmentary. The present study was carried out to help fill the knowledge gap on the monogeneans infesting the siluriform fishes of Lake Tanganyika in general and, more particularly, Clarias gariepinus. Samples of gills of Clarias gariepinus (Clariidae) were examined for ectoparasites. We identified the monogenean Gyrodactylus transvaalensis (Gyrodactylidae). This is the first time this parasite was found infecting gills. We are the first to observe a large spine in the male copulatory organ of this species and to provide measurements of its genital spines; this completes the description of the male copulatory organ, which is important in standard monogenean identification. This is the first monogenean species reported in C. gariepinus at Lake Tanganyika and the third known species on a representative of Siluriformes of this lake. It brings the total number of species of Gyrodactylus recorded in Lake Tanganyika to four. Knowing that other locations where this species has been reported are geographically remote from Lake Tanganyika, we propose a "failure to diverge" phenomenon for G. transvaalensis.

New perspectives on morphological and genetic variability of Corynosoma bullosum [Linstow, 1892] parasitizing southern elephant seals from the Antarctic Peninsula.

Previous descriptions of Corynosoma bullosum (Linstow, 1892) show that specimens vary greatly in the proportions of different body structures, measurements of females and males, number of rows of hooks, and egg measurements, among other features. We redescribe this species from specimens found in southern elephant seal faeces from King George Island. We also provide a molecular characterization, in addition to 5.8S and internal transcribed spacer (ITS) existing sequences. We examined 41 elephant seals, and 30 adult acanthocephalans were found in 15 of them. The specimens were identified as belonging to the genus Corynosoma due to each having a tubular body with an inflated anterior part forming a thorny disk and the posterior part bearing somatic spines on the ventral surface, and genital spines surrounding the genital pore. Individual morphology corresponded to C. bullosum: large size, marked sexual dimorphism, and proboscis with 16-18 rows of spines with 11-15 spines per row. The molecular profile of three specimens of C. bullosum was analysed using 18S rDNA. We inferred phylogenetic relationships of the family Polymorphidae using maximum likelihood and Bayesian inference. We provide an updated morphological redescription for C. bullosum including electron microscopy photographs and molecular data. The 18S gene sequences showed low genetic variation and supported that C. bullosum is a sister to Corynosoma australe.

New species of Polystomoides (Monogenoidea: Polystomatidae) parasitizing the urinary bladder of a freshwater turtle in Brazil.

Trachemys dorbigni is the most abundant freshwater turtle species in Rio Grande do Sul, southern Brazil. Chelonians are known to host a wide variety of pathogens, including viruses, bacteria, hemoparasites and helminths. Among these, nine genera of polystomatid flatworms (Monogenoidea; Polystomatidae) infect freshwater turtles: Apaloneotrema, Aussietrema, Fornixtrema, Manotrema, Pleurodirotrema, Polystomoidella, Polystomoides, Uropolystomoides and Uteropolystomoides. However, little is known about the biology of these parasites in the Neotropical Realm. Through investigative cystoscopy, specimens of Polystomatidae were located inside the urinary bladder of the host T. dorbigni. Retrieved specimens were fixed and stained whole mounts prepared for taxonomic identification. In the present paper, a new species of Polystomoides (Monogenoidea: Polystomatidae) parasitizing the urinary bladder of a freshwater turtle of the species T. dorbigni in Brazil is described. Polystomoides santamariensis n. sp. differs from the congeneric species on the length of the genital spines, which are longer. Given the enormous diversity of freshwater turtles around the world, it is likely that a large number of chelonian polystomatids are still unknown.

First morphological and molecular characterization of cystacanths of Corynosoma evae Zdzitowiecki, 1984 (Acanthocephala: Polymorphidae) from Antarctic teleost fishes.

Cystacanths of the polymorphid acanthocephalan Corynosoma evae Zdzitowiecki, 1984 were examined and redescribed based on newly collected material from teleost fishes from coastal waters of the Galindez Island (Argentine Islands, West Antarctica). Detailed morphological data, measurements and photomicrographs, including scanning electron microscopy images, are presented. Our morphological and morphometrical analyses confirmed the validity of C. evae; however, three key characteristics of taxonomic importance (i.e., the number of rows of hooks on the proboscis, and the number and arrangement of genital spines in males) showed significant morphological variability. In addition, a genital spine in the posterior body end of a female is reported for the first time. This study provides the first sequences of the small and large subunits nuclear ribosomal RNA genes (SSU and LSU) and the mitochondrial cytochrome c oxidase subunit 1 (cox1) for C. evae. Maximum likelihood and Bayesian inference analyses of the SSU+LSU+cox1 and the cox1 datasets placed C. evae as a sister lineage to a clade formed by C. validum Van Cleave, 1953 and C. villosum Van Cleave, 1953, although with low support. In contrast, the position of C. evae in the phylogenetic analysis of the SSU+LSU dataset remained unresolved. Finally, C. arctocephali Zdzitowiecki, 1984 from pinnipeds from the subantarctic and Antarctic regions is considered as a valid species.

Male wasp genitalia as an anti-predator defense

Predators can cause selection that drives the evolution of various anti-predator defenses in prey1,2,3. Some prey species have evolved specific defensive devices, while others simply use body parts that evolved for reasons other than defense to repel predators1. For example, many animal species have strong canine teeth or mandibles to kill prey and to counterattack their enemies1,2,3. Bees and wasps (Insecta: Hymenoptera) use their ovipositors as stings to repel attackers, including humans4. Stinging by injecting venom can cause intense pain and allergic reactions in humans4. Therefore, stinging hymenopterans that are recognized as dangerous have evolved warning signals, such as conspicuous body coloration4. Hymenopteran males, which lack ovipositors, are believed to be harmless, and the males avoid predators by mimicking the females' coloration and behavior4. Here, we report that males of the mason wasp Anterhynchium gibbifrons (Hymenoptera: Vespidae: Eumeninae) use sharp genital spines to counterattack predators. A potential predator, the tree frog Dryophytes japonica (= Hyla japonica) (Anura: Hylidae) or the pond frog Pelophylax nigromaculatus (Anura: Ranidae), was housed with male A. gibbifrons under laboratory conditions. All tree and pond frogs attacked the male wasps. Although all of the pond frogs ate the male wasps, 35.3% of the tree frogs ultimately rejected them. Male wasps were frequently observed to pierce the mouth or other parts of frogs with their genitalia while being attacked. The tree frogs were also housed with male wasps from which the genitalia were removed. All these frogs ate the genitalia-less males. Therefore, male wasps used their genitalia to prevent tree frogs from swallowing them. This study highlights the importance of male genitalia as an anti-predator defense and provides a new perspective for understanding the ecological roles of male genitalia in animals.

Morphology and molecular characterization of Polystoma goeldii n. sp. (Monogenea, Polystomatidae) parasite from the urinary bladder of Physalaemus ephippifer (Steindachner) (Anura, Leptodactylidae)

Polystomatid flatworms of amphibians are represented in the Neotropical realm by species of Mesopolystoma, Nanopolystoma, Parapseudopolystoma, Polystoma, Riojatrema and Wetapolystoma but only species of Polystoma are known from Brazil, namely Polystoma cuvieri, P. knoffi, P. lopezromani and P. travassosi. During a survey of monogeneans infecting amphibians in the north-eastern region of Pará State, the Cayenne Caecilian Typhlonectes compressicauda was found to be infected with Nanopolystoma tinsleyi and the Veined Tree Frog Trachycephalus typhonius was found to harbor Polystoma lopezromani. A yet unknown species of Polystoma was also encountered in the urinary bladder of the Steindachner's Dwarf Frog, Physalaemus ephippifer. This new species, which is the second species reported from Physalaemus spp., is described herein as Polystoma goeldii n. sp. and its life cycle is also illustrated. The new species can be distinguished from Polystoma spp. from other neotropical realm by a combination of characteristics, including hamuli morphology, outer/inner hamuli length ratio, haptor/total body length ratio, genital bulb/total body length ratio, genital spine number and COI molecular characters.

Classification of pleurodire polystomes (Platyhelminthes, Monogenea, Polystomatidae) revisited with the description of two new genera from the Australian and Neotropical Realms.

Polystomatids are platyhelminth parasites that infect mostly amphibian and chelonian hosts. Polystomatid of testudines were, for more than seven decades, classified in the three genera – Neopolystoma Price, 1939, Polystomoides Ward, 1917 and Polystomoidella Price, 1939. The genus delimitation was primarily based on the absence of hamuli in Neopolystoma, the presence of one pair of hamuli in Polystomoidella, and two pairs in Polystomoides. From 2016 to 2020, five new genera were erected - namely Uropolystomoides Tinsley and Tinsley, 2016, Uteropolystomoides Tinsley, 2017, Apaloneotrema Du Preez and Verneau, 2020, Aussietrema Du Preez and Verneau, 2020 and Fornixtrema Du Preez and Verneau, 2020. The generic diagnosis was based not only on the size and shape of morphological characters such as hamulus 1, uterus and eggs, but also on the site of infestation (i.e. urinary bladder, oral cavity or conjunctival sacs). Despite large advancements in polystome classification over the last decade, Neopolystoma was still polyphyletic with some species nested within Polystomoides and others being closely related to the Australian Aussietrema. Regarding the distribution of freshwater turtles of the two suborders Pleurodira (Southern continents) and Cryptodira (distributed worldwide except in Australia), one may wonder whether Australian chelonian polystomes of the genus Neopolystoma may have diverged from species infecting other pleurodires of South America. In the present study based on the analysis of several species selected among all genera, we reveal striking morphological differences within polystomes infecting pleurodiran turtles, which herein led to the proposal of two new chelonian polystome genera, Pleurodirotrema n. g. and Manotrema n. g. Pleurodirotrema n. g. is characterized by the absence of hamuli, presence of latero-ventral vaginae and includes species that infect either the oral region or the urinary bladder of Australian hosts of the Pleurodira. Manotrema n. g. is characterized by the presence of small hamuli, latero-ventral vaginae, deep incisions between suckers, a low genital spine number (<10) and includes species that infect the oral region of South American Pleurodira.

Pseudocorynosoma enrietti (Molfi & Freitas Fernandes, 1953) (Acanthocephala: Polymorphidae) from Patagonia (Argentina): life cycle, localities, and new host records.

All Pseudocorynosoma species inhabit freshwater environments of the American continent, but little is known about their life cycles. We report Pseudocorynosoma enrietti (Molfi & Freitas Fernandes, 1953) from natural and experimental specimens in Patagonia and identify the intermediate and definitive hosts of its life cycle for the first time in South America. Adult worms were recovered from Anas platyrhynchos (Linnaeus) and from a new definitive host, Coscoroba coscoroba Molina. Naturally infected amphipods, Hyalella patagonica Ortmann, were collected to obtain cystacanths that were fed to Gallus gallus domesticus (Linnaeus) and Anas platyrhynchos. Specimens of P. enrietti are described in detail using light and scanning electron microscopy. A key to species of the genus Pseudocorynosoma is included. Worms are characterized in both sexes by fore-trunk spines, and genital spines in an isolated field. The proboscis has 19-20 hook rows; males have 9-11 (10) hooks per row and females 7-9 (8). Males with four cement glands similar in size. Eggs elongated, with filaments. Experimental male and female worms were recovered from A. platyrhynchos at seven and 14 days, post-infection.

Direct and indirect effects of male genital elaboration in female seed beetles.

Our understanding of coevolution between male genitalia and female traits remains incomplete. This is perhaps especially true for genital traits that cause internal injuries in females, such as the spiny genitalia of seed beetles where males with relatively long spines enjoy a high relative fertilization success. We report on a new set of experiments, based on extant selection lines, aimed at assessing the effects of long male spines on females in Callosobruchus maculatus. We first draw on an earlier study using microscale laser surgery, and demonstrate that genital spines have a direct negative (sexually antagonistic) effect on female fecundity. We then ask whether artificial selection for long versus short spines resulted in direct or indirect effects on female lifetime offspring production. Reference females mating with males from long-spine lines had higher offspring production, presumably due to an elevated allocation in males to those ejaculate components that are beneficial to females. Remarkably, selection for long male genital spines also resulted in an evolutionary increase in female offspring production as a correlated response. Our findings thus suggest that female traits that affect their response to male spines are both under direct selection to minimize harm but are also under indirect selection (a good genes effect), consistent with the evolution of mating and fertilization biases being affected by several simultaneous processes.

Quantifying variation in female internal genitalia: no evidence for plasticity in response to sexual conflict risk in a seed beetle.

Sexually antagonistic coevolution can drive the evolution of male traits that harm females, and female resistance to those traits. While males have been found to vary their harmfulness to females in response to social cues, plasticity in female resistance traits remains to be examined. Here, we ask whether female seed beetles Callosobruchus maculatus are capable of adjusting their resistance to male harm in response to the social environment. Among seed beetles, male genital spines harm females during copulation and females might resist male harm via thickening of the reproductive tract walls. We develop a novel micro computed tomography imaging technique to quantify female reproductive tract thickness in three-dimensional space, and compared the reproductive tracts of females from populations that had evolved under high and low levels of sexual conflict, and for females reared under a social environment that predicted either high or low levels of sexual conflict. We find little evidence to suggest that females can adjust the thickness of their reproductive tracts in response to the social environment. Neither did evolutionary history affect reproductive tract thickness. Nevertheless, our novel methodology was capable of quantifying fine-scale differences in the internal reproductive tracts of individual females, and will allow future investigations into the internal organs of insects and other animals.

First record of Metapolystoma (Monogenea: Polystomatidae) from Boophis tree frogs in Madagascar, with the description of five new species.

Although Madagascar has more than 350 frog species of which all but two are endemic to the island, the known polystome (Monogenea: Polystomatidae) diversity parasitizing Malagasy frogs is low, encompassing five species of Madapolystoma, one species of Kankana and one Metapolystoma. Investigating the parasite diversity of frog parasites at selected Malagasy localities led to the discovery of undescribed polystomes. Five treefrogs, Boophis albilabris, Boophis doulioti, Boophis luteus, Boophis madagascariensis and Boophis occidentalis were found to be infected and are reported here as hosts for new Metapolystoma species. Morphological investigation, combining examination of body length, haptor length, genital bulb width, genital crown diameter, genital spine number, genital spine length, ovary length, egg length, hamulus length, hamulus guard length and hamulus hook length, revealed five distinct morphotypes. Phylogenetic analysis and genetic divergences obtained for three of the five morphotypes, support the distinction of new species. Metapolystoma ansuanum n. sp. is described from B. luteus, Metapolystoma falcatum n. sp. from B. doulioti, Metapolystoma multiova n. sp. from B. occidentalis, Metapolystoma theroni n. sp. from B. madagascareniensis and Metapolystoma vencesi n. sp. from B. albilabris. Finally, although the validity of Metapolystoma as taxon is not fully resolved yet, the phylogenetic position of the described species and their morphology provide clear evidence for new metapolystome taxa.

Tỷ lệ giới tính ốc bươu đồng (Pila polita Deshayes, 1830) ở đồng bằng sông Cửu Long

The black apple snail (Pila polita) is one of the snails (Ampullariidae) distributing in Mekong Delta, especially in the interior with high economic value. Study on the sex ratio of black apple snail distributed in some types of water bodies was conducted from November 2016 to October 2017 in some provinces of the Mekong Delta, Vietnam. A total of 3967 individuals in garden ditches, 1208 individuals in canals and 612 individuals in rice fields were collected for analysis. Gender identification was based on the external morphology and surgery through genital spenis, ovary and penis. Black apple snail specimen were distinguished, then separated into male and female. Male reproductive organs have vas deferens, penis, pouches containing sperm and sexual spines, genital spines. The female genitalia has genital holes, pallial oviduct, gonads and egg pouch and albumin glands. The sex ratio of the black apple snail in the garden ditches (1:1.24) was higher in irrigation canals (1:0.64) and the rice field (1:0.66). Percentage of male snails in the garden ditches was always lower than female snails and vice versa when distributed in irrigation canals and rice fields. The proportion of female snails increased with increasing size.

Individual and synergistic effects of male external genital traits in sexual selection.

Male genital traits exhibit extraordinary interspecific phenotypic variation. This remarkable and general evolutionary trend is widely considered to be the result of sexual selection. However, we still do not have a good understanding of whether or how individual genital traits function in different competitive arenas (episodes of sexual selection), or how different genital traits may interact to influence competitive outcomes. Here, we use an experimental approach based on high-precision laser phenotypic engineering to address these outstanding questions, focusing on three distinct sets of micron-scale external (nonintromittent) genital spines in male Drosophila kikkawai Burla (Diptera: Drosophilidae). Elimination of the large pair of spines on the male secondary claspers sharply reduced male ability to copulate, yet elimination of the other sets of spines on the primary and secondary claspers had no significant effects on copulation probability. Intriguingly, both the large spines on the secondary claspers and the cluster of spines on the primary claspers were found to independently promote male competitive fertilization success. Moreover, when large and small secondary clasper spines were simultaneously shortened in individual males, these males suffered greater reductions in fertilization success relative to males whose traits were altered individually, providing evidence for synergistic effects of external genital traits on fertilization success. Overall, the results are significant in demonstrating that a given genital trait (the large spines on the secondary claspers) can function in different episodes of sexual selection, and distinct genital traits may interact in sexual selection. The results offer an important contribution to evolutionary biology by demonstrating an understudied selective mechanism, operating via subtle trait interactions in a post-insemination context, by which genital traits may be co-evolving.

Morphological observations on three Baltic species of Corynosoma Lühe, 1905 (Acanthocephala, Polymorphidae)

Necropsies of Baltic grey (Halichoerus grypus) and ringed seals (Pusa hispida) presented a rare opportunity to study their acanthocephalan fauna. Both species hosted adults of three species of the genus Corynosoma Lühe, 1904, namely C. magdaleni Montreuil, 1958, C. semerme (Forsell, 1904) Lühe 1911 and C. strumosum (Rudolphi, 1802) Lühe 1904. A comparative morphological analysis of these three species of Corynosoma, combining both light and scanning electron microscopy, was performed for the first time. Sexual dimorphism in the size and shape of the trunk was observed in both C. magdaleni and C. semerme, but there was insufficient material to investigate this phenomenon in C. strumosum. Genital spines were not observed in any of the female acanthocephalans. Three possible explanations for the presence of genital spines in some females, but not others are (i) cryptic speciation, (ii) phenotypic variation and (iii) loss by extraction or shearing when the copulatory cap is released. Copulatory caps were observed on female C. semerme. The size and morphology showed considerable variability and all caps were strongly autofluoresecent.

Males of the tortricid moth Amorbia cuneana (Walsingham, 1879) shed their genital spines inside the female during copulation

The genitalia of most insect species are composed of several structures whose functions are poorly understood in many cases. The deciduous genital spines (deciduous cornuti, DC) found on the endophallus of many species of Lepidoptera are a clear example of this problem. We performed two experimental studies with the western avocado leafroller Amorbia cuneana (Tortricidae), aimed at answering some basic questions about the biology of DC. We found that the number of DC shows positive allometry with male forewing length, indicating that larger males have disproportionally more DC than smaller males. Males, with very few exceptions, shed virtually all their DC in their first copulation. The position of DC within the female varies depending on time elapsed after copulation. We observed that mated males without DC are able to remate and transfer an ejaculate. Finally, we found that resource restriction during the last larval instar of males results in a reduction in the number of DC. We suggest that DC reduce the chances of recopulation of mated females, that the production of DC is physiologically costly, and that first copulations are more important for male fitness.

First record of viviparity in polystomatid flatworms (Monogenea: Polystomatidae) with the description of two new species of Madapolystoma from the Madagascan anuran hosts Blommersia domerguei and Mantella expectata.

Two frog species, Blommersia domerguei and Mantella expectata, are reported as hosts for new species of Madapolystoma. Phylogenetic analyses and genetic divergences observed in the genus supported the distinction of two morphotypes infesting selectively each host species and morphological investigation combining marginal hooklet morphometrics, genital spine number and measurements further showed that polystomes from the two host species differed from each other and from all other known polystomes. Madapolystoma magnahami n. sp. and Madapolystoma isaloensis n. sp. are therefore described as two new species. Advanced in utero development was illustrated in both polystome species following the observation of well developed hamuli and two pairs of haptoral suckers in developing embryos. Inside some of these in utero embryos a F2 generation embryo was also observed. This is the first report of true viviparity among polystomatid flatworms.

Mating has No Effect on Male Longevity in the MothAmorbia cuneana(Tortricidae)

In some insects, males invest heavily in each mating thus reducing the typical sexual imbalance in potential reproductive rates which, in turn, influences the mode and intensity of sexual selection. In Lepidoptera, males invest in mate searching, courtship, ejaculate production and, in some species, in genital spines shed inside the female. Despite this substantial investment, evidence regarding its effect on male survival is contradictory. The effect of successful mating (i.e. copulations resulting in transfer of an ejaculate and deciduous genital spines) on male longevity was experimentally estimated in the moth Amorbia cuneana (Tortricidae), a pest of avocado. Our results do not support the prediction that mating costs result in a reduction in male longevity: virgin (n = 16) and mated (n = 26) males lived a similar number of days. It is hypothesized that reduced mating opportunities have selected for virgin males that are always ready to transfer large ejaculates and thus against the diversion of resources from reproductive tissues to somatic maintenance in unmated males.

Sexual Conflict: Mechanisms and Emerging Themes in Resistance Biology.

Sexual conflict is acknowledged as pervasive, with the potential to generate and maintain genetic variation. Mechanistic studies of conflict have been important in providing direct evidence for the existence of sexual conflict. They have also led to the growing realization that there is a striking phenotypic diversity of adaptations whose evolution can be shaped by sexually antagonistic selection. The mechanisms involved range from the use of genital spines, claspers, songs, and smells to ejaculate molecules. In one well-studied example, sexual conflict can occur over the sexually antagonistic effects of seminal fluid proteins in Drosophila melanogaster. However, an important puzzle remains, namely, why seminal fluid proteins are so numerous and complex, hence whether all or some are involved in mediating sexual conflict. I hypothesize that this rich diversity and the complexity of traits subject to sexually antagonistic selection in general may arise, at least in part, due to the deployment of sexually antagonistic adaptations in males in a way that lessens the probability of broadscale, strong resistance evolution in females. In elaborating this hypothesis, I explore how research into the evolution of resistance to insecticides, antimicrobials, and vaccines might be used to provide insights into the evolution of female resistance to the effects of sexually antagonistic manipulative traits of males. In this manner, the manipulative traits of males can be resistance-proofed.

Males harm females less when competing with familiar relatives.

Sexual conflict occurs when reproductive partners have different fitness optima, and can lead to the evolution of traits in one sex that inflict fitness costs on the opposite sex. Recently, it has been proposed that antagonism by males towards females should be reduced when they compete with relatives, because reducing the future productivity of a female would result in an indirect fitness cost for a harmful male. We tested this prediction in the seed beetle Callosobruchus maculatus, the males of which harm females with genital spines and pre-copulatory harassment. We compared lifespan, lifetime egg production and lifetime offspring production among females housed with groups of males that varied in their familiarity and relatedness. Females produced significantly more eggs and offspring when grouped with males who were both related and familiar to each other. There was no effect of male relatedness or familiarity on female lifespan. Our results suggest that males plastically adjust their harmfulness towards females in response to changes in inclusive fitness payoffs, and that in this species both genetic relatedness and social familiarity mediate this effect.