Larger Testes Research Articles

Sperm competition intensity shapes divergence in both sperm morphology and reproductive genes across murine rodents.

It remains unclear how variation in the intensity of sperm competition shapes phenotypic and molecular evolution across clades. Mice and rats in the subfamily Murinae are a rapid radiation exhibiting incredible diversity in sperm morphology and production. We combined phenotypic and genomic data to perform phylogenetic comparisons of male reproductive traits and genes across 78 murine species. We identified several shifts towards smaller relative testes mass, presumably reflecting reduced sperm competition. Several sperm traits were associated with relative testes mass, suggesting that mating system evolution selects for convergent suites of traits related to sperm competitive ability. We predicted that sperm competition would also drive more rapid molecular divergence in species with large testes. Contrary to this, we found that many spermatogenesis genes evolved more rapidly in species with smaller relative testes mass due to relaxed purifying selection. While some reproductive genes evolved rapidly under recurrent positive selection, relaxed selection played a greater role in underlying rapid evolution in small testes species. Our work demonstrates that postcopulatory sexual selection can impose strong purifying selection shaping the evolution of male reproduction, and that broad patterns of molecular evolution may help identify genes that contribute to male fertility.

Sperm competition intensity shapes divergence in both sperm morphology and reproductive genes across murine rodents.

It remains unclear how variation in the intensity of sperm competition shapes phenotypic and molecular evolution across clades. Mice and rats in the subfamily Murinae are a rapid radiation exhibiting incredible diversity in sperm morphology and production. We combined phenotypic and genomic data to perform phylogenetic comparisons of male reproductive traits and genes across 78 murine species. We identified several shifts towards smaller relative testes mass, presumably reflecting reduced sperm competition. Several sperm traits were associated with relative testes mass, suggesting that mating system evolution selects for convergent suites of traits related to sperm competitive ability. We predicted that sperm competition would also drive more rapid molecular divergence in species with large testes. Contrary to this, we found that many spermatogenesis genes evolved more rapidly in species with smaller relative testes mass due to relaxed purifying selection. While some reproductive genes evolved rapidly under recurrent positive selection, relaxed selection played a greater role in underlying rapid evolution in small testes species. Our work demonstrates that postcopulatory sexual selection can impose strong purifying selection shaping the evolution of male reproduction, and that broad patterns of molecular evolution may help identify genes that contribute to male fertility.

Photoperiodism, testosterone and adult neurogenesis in canaries (Serinus canaria).

Domestic strains of canaries (Serinus canaria) variably respond to photoperiod changes and apparently stay in breeding state for extended periods. Fife Fancy canaries are supposed to be similar to the native species living at 27-39° north where photoperiod significantly changes across the year. Our birds showed reproductive cycles when exposed to light regimes mimicking the annual cycle of photoperiod. However after 6 months in short days (SD: 8L:16D), males developed large testes, as observed by X-ray tomography, and intense singing. Switching to long days (LD: 16L:8D) did not further increase song rate nor testes size but increased song duration, number of syllables per song, and trill occurrence frequency. No sign of regression was observed after 12 weeks in LD but return to SD produced a rapid decrease in testes size and singing activity below values in birds maintained throughout in SD. Fife Fancy thus does not seem to develop absolute but only relative refractoriness. The relatively high singing activity expressed by SD-photosensitive males does not seem to depend on high testosterone (T) concentrations. Singing did not correlate with plasma testosterone (T). Treatment with ATD + Flutamide only marginally decreased song rate and did not affect song quality nor song control nuclei volume. These birds are either supersensitive to low T levels or their reproductive physiology is activated by other mechanisms. Neurogenesis is increased by T and by LD but the function of new neurons incorporated in HVC is poorly understood. We developed a procedure based on X-ray focal irradiation to deplete neural progenitors adjacent to HVC and study the functional consequences. The decrease in neurogenesis increased the variability of T-induced songs in females and decreased their bandwidth. Neurogenesis in HVC thus plays a role in song production and X-ray focal irradiation represents an excellent tool to analyze adult neurogenesis.

Extraosseous Plasmacytomas: A Radiologist's Perspective-A Narrative Review of the Literature.

Extraosseous plasmacytomas (EPs) are rare neoplasms originating from plasma cells, often associated with multiple myeloma. EPs are classified into three subtypes: extramedullary myeloma, solitary extramedullary plasmacytoma (SEP), and multiple solitary plasmacytomas. They can manifest in various anatomical sites, including the lung, mediastinum, breast, liver, pancreas, stomach, mesentery, kidney, small and large bowel, testis, and soft tissue. Despite their rarity, EPs present a diagnostic challenge due to their non-specific imaging appearances, which can mimic other neoplastic and inflammatory conditions. This review aims to describe the radiographic features of EPs in the chest, abdomen, and pelvis based on a thorough analysis of the existing literature. While imaging plays a crucial role in the detection and characterization of EPs, histological confirmation is necessary to differentiate them from other neoplastic entities. The review underscores the importance of considering EPs in the differential diagnosis, particularly in patients with a history of multiple myeloma. Understanding the imaging characteristics of EPs is essential for accurate diagnosis and appropriate management. Early imaging is crucial in these patients to exclude the possibility of EP, as timely diagnosis can significantly impact patient outcomes.

Parameters affecting the success rate of microscopic testicular sperm extraction in male patients with a solitary testis and non-obstructive azoospermia.

We aimed to compare the success rate of spermatozoa retrieval through microscopic testicular sperm extraction (mTESE) in non-obstructive azoospermic (NOA) men with a solitary testis with that of mTESE in NOA men with bilateral testes and the parameters affecting these rates. A retrospective cross-sectional study of factors contributing to infertility in NOA patients with a solitary testis and men with bilateral testes was carried out. In this multicenter study, 74 patients with NOA with a solitary testis were matched with 74 patients with bilateral testes in terms of age, duration of infertility, and volume of the solitary testis from 2770 patients with NOA with bilateral testes. Hormonal parameters, presence of varicocele, history of varicocelectomy, history of undescended testis and karyotype analysis results were compared. Spermatozoa were obtained from 40 (54.1%) patients with a solitary testis and 42 (56.76%) patients with bilateral testes. No differences were found regarding age, duration of infertility, or mean testicular volume between patients with a solitary testis and patients with bilateral testes. When serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were compared regardless of sperm retrieval status, it was observed that both levels were greater in the group of patients with a solitary testis (p < 0.01). Patients with solitary and bilateral testes from whom spermatozoa were obtained had larger testes than those from whom spermatozoa could not be obtained (p < 0.05). Similarly, the serum levels of FSH and LH were significantly greater in patients with a solitary testis than in those with bilateral testes (p < 0.05). To the best of our knowledge, this is the first study in the literature to evaluate the parameters that influence mTESE outcome in NOA patients with a solitary testis and NOA patients with bilateral testes. Greater testicular volume was found to positively affect spermatozoa retrieval for patients with a solitary testis. The higher levels of FSH and LH in patients with a solitary testis than in patients with bilateral testes of similar testicular volume may be due to a compensatory mechanism developed by the hypothalamic-pituitary-gonadal axis. The fact that these hormones are higher in patients with a solitary testis does not mean that the number of spermatozoa obtained through mTESE will be decreased.

Small-bodied males invest in larger testes when highly ornamented.

Sperm competition and male mating rate are two non-mutually exclusive key evolutionary pressures selecting for larger testes within and across animal taxa. A few studies have tried to test the role of mating rate in the absence of sperm competition. Under the mating rate hypothesis, particular phenotypes of a given population that are expected to gain more mates (e.g., more ornamented males) are expected to make higher investments in testes size (a proxy for sperm production). We test this prediction in Polistes simillimus, a neotropical paper wasp in which females are single mated (no sperm competition) and males can mate with multiple partners. Testes size was predicted by body size (positive association), sexual ornamentation (negative association), and their interaction (among small males, testes size was positively related to ornamentation, but the opposite pattern was observed among large males). We propose that small-bodied well-ornamented males may face the highest risk of sperm depletion. Small-bodied males make relatively higher investment in testes size when highly ornamented. This strategy might be less profitable to large males, as they have overall larger testes. Our results provide strong evidence for the mating rate hypothesis.

Variation in reproductive parameters of Rhinella arenarum (Hensel, 1867) (Anura: Bufonidae) between the reproductive and post-reproductive periods

We compared reproductive parameters of Rhinella arenarum in a wetland of the Monte in Argentina during reproductive and post-reproductive seasons. Individuals were collected at random, monthly from November 2001 to October 2002. August through November was considered the reproductive period, and December through April was considered the post-reproductive period. Of the 116 adults, 75 were males and 41 were females. The reproductive parameters measured included body mass, fat body mass, number of mature ova, ova size, and testicular volume. There were significant differences between the reproductive and post-reproductive periods in females for body mass, fat body mass, and number of mature ova. Likewise, males also had significant differences between these periods for body mass and fat body mass. Apparently, R. arenarum has an opportunistic and continuous reproductive strategy. Entering dormancy with large fat bodies and testes in apparent spermatogenesis allows males to reproduce immediately after emerging in the spring. However, females have mature but fewer ova during this period, which is a reproductive feature shared by most temperate amphibians. Our data, and the primarily tropical distribution of R. arenarum, suggest that this species recently invaded the temperate region wherein males retained acyclic reproductive activity and females, owing to their higher reproductive costs, have evolved cyclic reproduction.

Evolutionary trade-offs between testes size and parenting in Neotropical glassfrogs.

In males, large testes size signifies high sperm production and is commonly linked to heightened sperm competition levels. It may also evolve as a response to an elevated risk of sperm depletion due to multiple mating or large clutch sizes. Conversely, weapons, mate or clutch guarding may allow individuals to monopolize mating events and preclude sperm competition, thereby reducing the selection of large testes. Herein, we examined how paternal care, sexual size dimorphism (SSD), weaponry and female fecundity are linked to testes size in glassfrogs. We found that paternal care was associated with a reduction in relative testes size, suggesting an evolutionary trade-off between testes size and parenting. Although females were slightly larger than males and species with paternal care tended to have larger clutches, there was no significant relationship between SSD, clutch size and relative testes size. These findings suggest that the evolution of testes size in glassfrogs is influenced by sperm competition risk, rather than sperm depletion risk. We infer that clutch guarding precludes the risk of fertilization by other males and consequently diminishes selective pressure for larger testes. Our study highlights the prominent role of paternal care in the evolution of testes size in species with external fertilization.

Identification and Analysis of Genes Related to Testicular Size in 14-Day-Old Piglets.

The RNA-Seq technology was used to screen the key genes that affect the early development of the testes of Duroc × Landrace × Yorkshire piglets, to determine the regulatory pathway and provide reference for subsequent reproductive performance research, breeding, and other production practices. This study selected 14-day-old Duroc × Landrace × Yorkshire piglets as the trial animals. Testes from piglets with similar weights and no pathological changes were divided into small testis (ST) and large testis (LT) groups, and the RNA-Seq screening of differentially expressed genes (DEGs) was performed to find candidate genes and regulatory pathways related to early testicular development. The results show that 570 DEGs were found in the ST and LT groups, with 281 upregulated and 289 downregulated. The DEGs were mainly enriched on 47 gene ontology (GO) functional items. The Kyoto encyclopedia of genes and genotypes (KEGG) enrichment analysis found that there were 44 significantly enriched KEGG signal pathways, and the regulation of testicular development mainly focused on the arachidonic acid metabolism, Wnt signaling pathway and GnRH secretion pathways. The PTGES, SFRP1, SPP1, PLA2G4E, KCNJ5, PTGS2, and HCN1 genes were found to be as closely related to the testicular development of these Duroc × Landrace × Yorkshire piglets, and the differential gene expression was consistent with the real-time quantitative reverse transcription PCR (real-time qRT-PCR) validation results. This study was validated by high-throughput sequencing analysis and real-time qRT-PCR, and showed that the PTGES, SFRP1, SPP1, PLA2G4E, KCNJ5, PTGS2, and HCN1 genes may be involved in the regulation of germ cell development, spermatogenesis and semen traits. These should be further studied as candidate genes for early testicular development and reproductive trait regulation in boars.

Global Practice Patterns in the Evaluation of Non-Obstructive Azoospermia: Results of a World-Wide Survey and Expert Recommendations.

Non-obstructive azoospermia (NOA) represents the persistent absence of sperm in ejaculate without obstruction, stemming from diverse disease processes. This survey explores global practices in NOA diagnosis, comparing them with guidelines and offering expert recommendations. A 56-item questionnaire survey on NOA diagnosis and management was conducted globally from July to September 2022. This paper focuses on part 1, evaluating NOA diagnosis. Data from 367 participants across 49 countries were analyzed descriptively, with a Delphi process used for expert recommendations. Of 336 eligible responses, most participants were experienced attending physicians (70.93%). To diagnose azoospermia definitively, 81.7% requested two semen samples. Commonly ordered hormone tests included serum follicle-stimulating hormone (FSH) (97.0%), total testosterone (92.9%), and luteinizing hormone (86.9%). Genetic testing was requested by 66.6%, with karyotype analysis (86.2%) and Y chromosome microdeletions (88.3%) prevalent. Diagnostic testicular biopsy, distinguishing obstructive azoospermia (OA) from NOA, was not performed by 45.1%, while 34.6% did it selectively. Differentiation relied on physical examination (76.1%), serum hormone profiles (69.6%), and semen tests (68.1%). Expectations of finding sperm surgically were higher in men with normal FSH, larger testes, and a history of sperm in ejaculate. This expert survey, encompassing 367 participants from 49 countries, unveils congruence with recommended guidelines in NOA diagnosis. However, noteworthy disparities in practices suggest a need for evidence-based, international consensus guidelines to standardize NOA evaluation, addressing existing gaps in professional recommendations.

Molecular characterization of SPATA6 and association of its SNPs with testicular size in sheep

The testis is an important organ for maintaining fertility in males, and testis size is positively correlated with ejaculate volume, sperm motility, thus fertility. Spermatogenesis-associated 6 (SPATA6) is an evolutionarily conserved testis-specific gene reported in many species. However, the effect of SPATA6 expression levels on testicular development and the effect of single nucleotide polymorphisms (SNPs) on testis and epididymis phenotype in sheep have not been studied. The purpose of the research was to investigate the expression profile of SPATA6 and its effect on testicular development and to confirm the effect of SNPs on the testis and epididymis phenotype. In this study, we detected a 1245bp coding sequence (CDS) of SPATA6 and encoded 414 amino acids. The expression levels of SPATA6 were significantly higher in the testis than in other tissues and gradually increased with testis development. Moreover, the expression level in the large testis was significantly higher than that in the small testis at six months. A total of 11 SNPs were detected in the coding region of SPATA6 by cDNA-pooling sequencing and improved multiplex ligation detection reaction (iMLDR) methods. Correlation analysis showed that SNP2 (c. 3631C > G) significantly affected left epididymis weight (LEW) and right epididymis weight (REW), and SNP10 (c. 937 A > G) significantly affected REW. And the combined genotype of SNP1 (c. 4245 G > A) and SNP2 significantly affected REW. The current study concluded that SPATA6 plays an important role in testicular development and the SNPs significantly associated with the epididymis phenotype can provide molecular markers for the early selection of high-fertility Hu sheep.

IDENTIFICATION OF AQPS IN CHINESE HAMSTERS AND THEIR EXPRESSION PATTERNS IN TESTES OF DIFFERENT WEIGHTS

Aquaporins (AQPs) are a class of proteins encoded by MIP gene family, which play a critical role in maintaining cell morphology and small molecule transmembrane transport. In recent years, the role of AQPs in reproduction has gradually been revealed. They have been proved to be widely expressed in many species. The testicles of Chinese hamsters have the characteristics of large size and long spermatogenic cycle. This seems contradictory in evolution and has not been fully studied. At present, the whole genome analysis of AQPs in Chinese hamsters and the expression patterns in testes have not been reported. In this study, 13 AQPs were identified and characterized in the genome of Chinese hamster for the first time. Protein sequence analysis of AQPs showed that its structure and function were unified. The concentrations of testosterone are higher in larger testes. The expression patterns of AQPs in testes were different. AQP5, AQP7 and AQP11 were positively correlated with testicular weight. Sperm count showed that larger testes could produce more sperm and store it in epididymis. It is speculated that under the regulation of testosterone, AQPs affect the excretion of excess substances at the end of spermatogenesis, and adapt to the reproductive competition of Chinese hamsters by regulating the rate of spermatogenesis. The results provide basic resources for further studying the role of AQPs in spermatogenesis of Chinese hamster. Keywords: Chinese hamster; Testis; Reproduction competition; AQPs

Do male reproductive traits evolve at the intraspecific level in response to the amount of placentotrophy in a genus of viviparous fishes?

Placentotrophy is a particular type of maternal provisioning to developing embryos, in which mothers actively provide nutrients via complex placental structures. Placentotrophy implies less pre-fertilization investment, resulting in a shift from pre- to post-copulatory sexual selection. This change can potentially result in a conflict between females and males. This phenomenon has been demonstrated at the interspecific level in viviparous fishes of the family Poeciliidae, in which males of species that lack placentotrophy have evolved traits related to pre-copulatory sexual selection such as coloration, ornaments, and courtship behavior. Placentotrophic species, on the other hand, have evolved traits associated with post-copulatory sexual selection such as long intromittent organs (gonopodium) and increased sexual coercion behavior. Here we test, for the first time at the intraspecific level, whether there is a similar relationship between a higher degree of female placentotrophy and the evolution of male reproductive traits (larger testes and longer gonopodia) in three species of the genus Poeciliopsis (P. gracilis, P. infans, and P. prolifica). We observed a tendency towards longer gonopodia in males of P. gracilis as well as the largest testes of P. prolifica males in the populations with the highest degrees of placentotrophy. However, the statistical support for these findings was relatively weak. Therefore, we failed to support the hypothesis of a selective effect of female placentotrophy on male gonads and genitalia. We discuss other evolutionary forces that may have driven the observed intraspecific variation in male reproductive traits of Poeciliopsis fishes.

REVISION OF SANGUINICOLA PLEHN, 1905 WITH REDESCRIPTION OF SANGUINICOLA VOLGENSIS (RAŠÍN, 1929) MCINTOSH, 1934, DESCRIPTION OF A NEW SPECIES, PROPOSAL OF A NEW GENUS, AND PHYLOGENETIC ANALYSIS.

Sanguinicola Plehn, 1905 comprises 26 species that collectively infect fishes from 8 orders (Cypriniformes, Characiformes, Siluriformes, Esociformes, Salmoniformes, Labriformes, Centrarchiformes, and Perciformes). Its revision is warranted because several species assigned to the genus could represent new genera, nucleotide sequences are wanting, many species have incomplete descriptions, and types for most species are missing or of poor quality. Herein, we emend Sanguinicola based on morphology and the first nucleotide-based phylogenetic analysis that includes multiple sequences from morphologically identified adult specimens. We describe Sanguinicola plehnae Warren and Bullard n. sp. from the heart of northern pike, Esox lucius Linnaeus, 1758 from Russia; provide supplemental observations of Sanguinicola volgensis (Rašín, 1929) McIntosh, 1934 from the heart of sabrefish (type species), Pelecus cultratus (Linnaeus, 1758) Berg, 1949 from Russia; describe Sanguinicola cf. volgensis from the heart of ide, Leuciscus idus (Linnaeus, 1758) Berg, 1949 from Russia; and describe Pseudosanguinicola occidentalis (Van Cleave and Mueller, 1932) Warren and Bullard n. gen., n. comb. from the heart of walleye, Sander vitreus (Mitchill, 1818) Bailey, Latta, and Smith, 2004 from eastern North America. Sanguinicola plehnae differs from its congeners by having lateral tegumental spines that total 118-122, are small (3% of body width), and protrude 2-3 µm from the tegument (lacking associated conical protrusion) as well as by having a large testis (>40% of body length). Sanguinicola volgensis differs from its congeners by having posteriorly directed lateral tegumental spines encased in a tegumental conical protrusion as well as by having an ovoid egg. Specimens of S. cf. volgensis differ from those of S. volgensis by having a body that is 5-6× longer than wide (vs. 2-3× in S. volgensis) and <90 lateral tegumental spines (vs. >95). Pseudosanguinicola Warren and Bullard n. gen. differs from Sanguinicola by having densely transverse rows of lateral tegumental spines (vs. a single column of large spines). The phylogenetic analysis utilizing the large subunit ribosomal DNA (28S) failed to reject monophyly of Sanguinicola.

Sex chromosome aneuploidies and fertility: 47,XXY, 47,XYY, 47,XXX, and 45,X/47,XXX.

The overall incidence of sex chromosome aneuploidies is approximately 1 per 500 live-born infants, but far more common at conception. I shall review the fertility aspects of the sex chromosome trisomies, XXY, XYY, XXX, with special reference to the karyotype 45,X/47,XXX. Each has a "specific" (but variable) phenotype, but may be modified by mosaicism. Although the alterations in the hypothalamic-pituitary-gonadal axis are important (and discussed), the emphasis is on potential fertility. The reproductive axis is often affected in females with the 47,XXX karyotype with diminished ovarian reserve and accelerated loss of ovarian function. Fewer than 5 % of females with the Turner syndrome have the 45,X/47,XXX karyotype. They have taller stature and less severe fertility issues compared to females with the 45,X or other forms of Turner syndrome mosaicism. For the 47,XXY karyotype non-obstructive azoospermia is almost universal with sperm retrieval by micro-testicular sperm extraction possible in slightly fewer than half of the men. Men with the 47,XYY karyotype have normal to large testes and much less testicular dysfunction than those with the 47,XXY karyotype. They do have a slight increase in infertility compared to the reference population, but not nearly so severe as those with 47,XXY karyotype. Assisted reproductive technology, especially micro-TESE has an important role, especially for those with 47,XXY; however, more recent data show promising techniques for the in vitro maturation of spermatogonial stem cells and 3-D organoids in culture. Assisted reproductive technology is more complex for the female, but vitrification of oocytes has shown promising advances.

Laparoscopic cryptorchidectomy using a resorbable self-locking loop device in dorsally recumbent horses.

To report the use and feasibility of a self-locking resorbable loop device for cryptorchidectomy. Clinical prospective study. Twenty horses. Horses suspected to have an abdominal testicle/s after admission work-up were enrolled. Horses were anesthetized in dorsal recumbency and a standard laparoscopic technique was performed. The looped device was inserted into the abdomen, glided around the testis/cord and tightened. Then, the spermatic cord was transected prior testis removal. Surgical procedure details and remarks, perioperative complications and total surgical time were recorded. Short- (>3 weeks) and long-term (>6 months) follow-ups were obtained by telephone questionnaire. Median total surgical time was 67 min (range: 43-189 min) and significantly shortened after the first four horses. The loop device was easily glided around 13/20 abdominal testes and required more time and technical skills around larger testes (≥3 years). Excellent intraoperative hemostasis was achieved in 17 horses. Three horses demonstrated mild intraoperative bleeding that required retightening, device replacement or adding a second device, respectively. Three horses developed mild postoperative hemoabdomen identified ultrasonographically and were successfully managed medically. Follow-up revealed no significant complications related to the procedure. One horse was euthanized for colic 4 months after surgery and one died of hemolytic shock 17 months postoperatively. This device represents another method to perform equine cryptorchidectomy that requires minimal training and laparoscopic expertise but demands knowledge of the device and application to prevent complications. Laparoscopic cryptorchidectomy using this device is an alternative technique for horses <3 years.

Do female bluethroats without extra-pair offspring have more MHC-compatible social mates?

Genes of the major histocompatibility complex (MHC) are crucial for adaptive immunity in jawed vertebrates, and theory predicts that there should be mate choice for optimizing MHC constitution in the offspring. In a previous study, we demonstrated a non-random female choice of extra-pair males in the bluethroat (Luscinia svecica), yielding offspring that was closer to an intermediate MHC class II (MHCII) allele count than their within-pair halfsiblings. The present study tests whether social pairs with only within-pair young (WPY) in their brood, in the same study population, had a combined MHC-constitution closer to a presumed intermediate optimum, than social pairs with extra-pair young (EPY), with a corresponding pattern in their offspring. As expected, we found that WPY from pure WPY-broods were more MHC-optimal than WPY from mixed broods, but only in broods of young (second year) males. Correspondingly, there was a tendency for social pairs with only WPY in their brood to be more MHC-compatible than social pairs with EPY in their brood, when the male was young. Older bluethroat males have considerably larger testes than young males, and their higher sperm competitiveness could help them secure paternity in their own brood, also when they are not MHC-compatible. In other words, in the sexual conflict over paternity, females may be more likely to realise their preference for a MHC-compatible mate when paired to a young male. As a possible fitness indicator, immune responsiveness to an injected antigen (PHA) was elevated for offspring closer to “the golden mean” in MHCII allele count.Significance statementThis study contributes to our understanding of MHC-based mate choice in extra-pair mating systems, by showing that female bluethroats (Luscinia svecica) with an MHCII-compatible social mate tend to have no extra-pair young in their brood, but only when the social male is young. This elucidates a possible sexual conflict, in which older social males are able to override female preferences and prevent other males from gaining paternity in their brood through higher sperm production. Studying systems in which extra-pair paternity occurs offers an insight into the genetic benefits of mate choice, as extra-pair males, in contrast to social males, generally contribute only sperm. Further, the strict and thorough genotyping scheme applied in this study enabled us to demonstrate a preference for “the golden mean” in MHC-diversity in a species with one of the highest MHC class II-diversity known to date.

Xenos vesparum(Strepsiptera: Xenidae)—A New Insect Model and Its Endoparasitic Secondary Larva

AbstractXenos vesparum of the highly specialized Strepsiptera is a new insect model in the context of host-parasite relationships. The endoparasitic female and male secondary larvae were studied using µCT, 3D-reconstructions, histology, and photomicrography. The infectious primary larva is followed by a trophic and endoparasitic secondary larval stage. In contrast to immature stages of other holometabolous groups, the second instar increases dramatically in size. Compound eyes and external wing anlagen are present in male larvae before the pupal stage. In contrast to the females, the brain of males bears well-developed optic neuropils and retinula cells are present. The cephalothorax is comparatively simple in the female larvae, yet distinctly more complex than in the adult, where most muscles are reduced. Large testes are present in male larvae and numerous oocytes in the females, but they are still immature. The larval features are discussed in the context of holome­tabolous development and heterochronic processes. Unique features of Strepsiptera are the early differentiation of the sexes and the occurrence of compound eyes and external wing anlagen in male secondary larvae. The phylogenetic position of Strepsiptera suggests that this is a secondary feature and thus an autapomorphy. To address mature females of Stylopidia as neotenic adults is an oversimplification. They display a mosaic pattern of paedomorphic characters such as features of the nervous system and the presence of stemmata, but also non-paedomorphic structures, such as the spiracles.

Testis Size Variation and Its Environmental Correlates in Andrew's Toad (Bufo andrewsi).

Reproductive investments influenced by environmental conditions vary extensively among geographically distinct populations. However, investigations of patterns of intraspecific variation in male reproductive investments and the mechanisms shaping this variation in anurans remain scarce. Here, we focused on the variation in testis size in 14 populations of the Andrew's toad Bufo andrewsi, a species with weak dispersal ability but wide distribution in southwestern China, to establish whether male reproductive investment varies on an environmental gradient. Our analysis revealed a significant variation in relative testis size across populations, and a positive correlation between testis size and body condition. We, however, found no geographic trends explaining the variability in the testis size. The relative testis size did not increase with increasing latitude or altitude. We also found no relationship between relative testis size and rainfall, but a negative correlation with the coefficient of variation of temperature, with larger testes under stable environments. These findings suggest that the decreased male reproductive investment of this species may be a consequence of harsher or fluctuating environmental conditions.

OR05-1 Testicular Magnetic Resonance Imaging (MRI) Findings and Predictive Factors of Gonadal Neoplasia in Complete Androgen Insensitivity Syndrome

Abstract Introduction Complete Androgen Insensitivity Syndrome (CAIS) is characterized by a complete external genitalia appearance and testicular development in 46,XY individuals carrying inactivating mutations in the AR gene. Prophylactic gonadectomy versus saving gonads has been debatable in CAIS management, mainly due to the absence of an accurate biomarker for testicular germ cell tumors (GCT). Objective to cross the preoperative pelvic MRI data with the histological gonadal findings from CAIS patients who underwent prophylactic gonadectomy to identify predictive factors of GCT development. Methods We evaluated 30 gonads from 15 CAIS patients with proven AR mutation. All performed pelvic MRI before gonadectomy through the same MRI machine and were included in the MRI data analysis. Three blinded radiologists specialized in urology performed image analysis. The immunohistochemical markers PLAP, c-KIT, OCT3/4, SALL4, ER, alpha-inhibin, CD99, and calretinin were performed. Results Nine (60%) performed gonadectomy after puberty (&amp;gt;16 years old). We identified one case of classical seminoma and one case of Sertoli cell neoplasia (at 18 and 19 years of age, respectively). Overall, the prevalence of neoplasia was 13.3%. No case of premalignant intratubular germ cell neoplasia was detected.Histological data revealed a high prevalence of benign lesions (n=12; 80%). Leydig Cell Hyperplasia (67%), stromal fibrosis (53%), Sertoli Cell nodules (47%), hamartomatoums nodules (40%) and paratesticular cysts (67%) which are more frequent after puberty (p&amp;lt;.01). MRI detected heterogeneity in all cases harboring hamartomatoums nodules, Sertoli cell nodules, and testicular neoplasia. Benign lesions were bilateral in all cases. Regarding the MRI data, the presence of testicular cystic mass (by tumoral necrosis) on MRI and tumor size (higher among malignancies) correlated with malignancy (p=.008 and p=.03, respectively), whereas gonadal location (inguinal/abdominal), presence of solid nodules, T2WI and postcontrast features, nodule diffusion restriction, and presence of perigonadal cysts did not. Chronological age &amp;gt;16 years was associated with malignancy with a 4.3 OR (1.6–11.69). Conclusion Pelvic MRI is sensitive to detect gonadal nodules in CAIS patients, regardless of the gonad position, but most nodules are benign. Testicular malignancy should be suspicious in the presence of testicular cystic mass and large testis size in CAIS patients &amp;gt;16 years old. Presentation: Saturday, June 11, 2022 11:30 a.m. - 11:45 a.m.