Evolutionary conflict: sperm wars, phantom inseminations. (1/17)

A new experimental study has provided the first definitive evidence for conditional punishment of 'cheats' in a sperm-trading simultaneous hermaphrodite: the sea slug Chelidonura hirundinina. This also provides a rare unequivocal example of conditional reciprocity averting a 'tragedy of the commons' in biology.  (+info)

Self- and cross-fertilization in the solitary ascidian Ciona savignyi. (2/17)

Solitary ascidians are hermaphrodites that release sperm and eggs simultaneously. However, many species are self-sterile, owing to a self/non-self recognition system operating at the outer surface of the chorion during sperm-egg interaction. In Ciona intestinalis, self-incompatibility is thought to have a genetic basis. Here, we report a survey of the self-fertilization potential of a Santa Barbara, California, population of Ciona savignyi, a close relative of C. intestinalis. We found that, in contrast to reports on C. intestinalis, C. savignyi is highly self-fertile. However, using two nonlethal recessive mutant strains, aimless (aim) and immaculate (imc), and a stable transgenic strain that expresses green fluorescent protein (GFP) in the notochord to follow offspring genotype, we demonstrate that non-self sperm outcompete self-sperm in fertilization competition assays. When the chorion was removed, both self- and non-self sperm performed equally well in the competition assay. Thus the non-self/self gamete recognition in C. savignyi is not absolute but relative, and is mediated by one or more components in the chorion. We discuss the significance of this finding in the context of natural populations in the wild, where individuals of C. savignyi are typically found growing in large groups that spawn in unison and where self-fertilization would be expected to be very rare.  (+info)

Mouse chimaeras developed from electrofused blastocysts: new evidence for developmental plasticity of the inner cell mass. (3/17)

Blastocysts obtained from mice differing in pigmentation (albino versus pigmented) and the isoforms of glucose phosphate isomerase (GPI 1A versus 1B) were electrofused and those containing a single chimaeric inner cell mass (ICM) were transferred to the uterus of pseudopregnant recipients. The pups were recovered on the 20(th) day by Caesarian section and fostered by females that had littered on the previous night or 24 h earlier. Altogether nine adult animals and two pups, which died soon after delivery, were available for GPI analysis. Between 9 and 13 organs/tissues were examined and the relative contribution of the GPI 1A and 1B isoforms was estimated using an electrophoretic GPI assay. Eight adult animals were overtly chimaeric and one was chimaeric in some internal tissues only. Eight mice were males: seven were fertile, one was infertile. The ninth adult mouse was a hermaphrodite. The fertile animals produced sperm of one genotype only, i.e. derived either from the albino or from the pigmented component. This is the first report showing that adult chimaeras can be produced from two combined blastocysts, provided that fusion of the adhering trophectoderm cells is first induced and the orientation of blastocysts enables the two ICMs to integrate into a single ICM. Our results suggest that in the preimplantation blastocyst, the organisation of the ICM remains labile thus making it possible for the fused blastocysts to establish new embryonic organisation and to develop into a single organism.  (+info)

Extensive outcrossing and androdioecy in a vertebrate species that otherwise reproduces as a self-fertilizing hermaphrodite. (4/17)

The mangrove killifish (Kryptolebias marmoratus) is the only vertebrate known to be capable of self-fertilization. Its gonad is typically an ovotestis that simultaneously produces eggs and sperm, and fertilization is internal. Although most populations of this species consist primarily or exclusively of hermaphroditic individuals, gonochoristic males occur at approximately 20% frequency in a natural population at Twin Cays, Belize. Here we use a battery of 36 microsatellite loci to document a striking genetic pattern (high intraspecimen heterozygosities and low within-population linkage disequilibria) that differs qualitatively from the highly homozygous (or "clonal") genetic architecture characteristic of killifish populations previously studied in Florida, where males are much rarer. These findings document that outcrossing (probably between gonochoristic males and hermaphrodites) is common at the Belize site, and, more importantly, they demonstrate the dramatic impact that functional androdioecy can have on the population genetic architecture of this reproductively unique vertebrate species.  (+info)

Cloning and differential expression of estrogen receptor and aromatase genes in the self-fertilizing hermaphrodite and male mangrove rivulus, Kryptolebias marmoratus. (5/17)

The mechanisms underlying sex determination and differentiation in fishes are labile in response to environmental parameters. Sex-specific phenotypes are largely regulated by sex steroids, and the inhibition or the stimulation of aromatase can reverse sex as well as alter secondary sexual characteristics in fishes. Among vertebrates, the mangrove rivulus is the only known self-fertilizing hermaphrodite. Throughout most of its range, rivulus appear to exist as clonally reproducing hermaphrodites. However, outcrossing has been documented in Belize, where up to 25% of rivulus collected are males. The direct development of (primary) males occurs when embryos are incubated at 18 degrees C and hermaphrodites develop into secondary males when held at 28 degrees C. Given the importance of sex steroids, their receptors, and aromatase in sex determination and differentiation of fishes, we cloned, sequenced, and quantified the expression of estrogen receptors (ERalpha, ERbeta) and ovarian (AroA) and brain (AroB) aromatase genes. Hermaphrodites had increased ERalpha, ERbeta, AroA, and AroB gene expression in the liver, gonad, gonad, and brain respectively, compared to males. These data are consistent with the gene expression data reported for other species and are reflective of the presence of ovarian tissue in the hermaphrodites. Interestingly, we show the elevated expression of brain aromatase in the hermaphrodite brain. The role of the dimorphic expression of brain aromatase in the regulation of sex-specific characteristics is intriguing and requires further research. Because of the uniqueness of its reproductive biology, rivulus is an excellent model for elucidating the mechanisms regulating vertebrate sex determination and sexual differentiation.  (+info)

Hermaphroditism in 3 chimeric mice. (6/17)

Hermaphroditism was diagnosed in three, 6-month-old, male, chimeric mice generated by microinjection of 129/Ola XY recombinant embryonic stem cells into unsexed C57BL/6 blastocysts. Grossly, mice Nos. 1 and 2 had perigenital masses and hydrometra. All mice had unilateral ovaries and cystic endometrial hyperplasia. Mice Nos. 1 and 3 also had contralateral testes and epididymides. Histologically, mice Nos. 1 and 3 were true hermaphrodites with unilateral ovotestes, while mouse No. 2 was a pseudohermaphrodite with ovarian tissue only. The presence of a uterus with cystic endometrial hyperplasia in these mice resembles XY pseudohermaphroditism in miniature schnauzers. The mice were determined to be 95 to 100% chimeric via haircoat color; however, the presence of both male and female sex organs in these phenotypically male mice suggests otherwise. Published reports note incidences for sex chimeras and hermaphroditism in genetically engineered mice of 50% and 20%, respectively. Hermaphroditism is expected to increase as the numbers of chimeric mice rise with technical advances in genetic engineering.  (+info)

True hermaphroditism presenting as an inguinal hernia. (7/17)

A 21-year-old patient with cryptorchidism was found to have a left inguinal mass on physical examination. The patient was operated with a diagnosis of bilateral cryptorchidism and left inguinal hernia. Besides bilateral inguinal undescended testicles, female genital organs like fallopian tubes, uterus and ovary were found on the exploration.  (+info)

Hermaphroditism in a Sprague-Dawley rat. (8/17)

A spontaneous case of unilateral true hermaphroditism was observed during the routine necropsy of a 9-week-old presumed female Sprague-Dawley rat on a repeat-dose toxicity study. There were no drug-related effects observed. True hermaphroditism is rare in rats, and despite the large numbers of rats examined annually, few cases are reported in the literature.  (+info)