Oogenesis in Habrotrocha Tridens (Milne)

Hsu, W. Siang

doi:10.2307/1539143

Cited by 56 publications

(22 citation statements)

References 2 publications

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“…Each probe detected only one copy of the gene on one chromosome; because each chromosome contains only one DNA molecule (15,16), all copies of the hsp82 gene were detected, and two of them must be the alleles. Also, the karyotypes found in this article confirm earlier studies (17)(18)(19)(20) showing that bdelloid chromosomes are heteromorphic, another hallmark of asexuality.…”

Section: Are Bdelloids Really Asexual?supporting

confidence: 90%

Bdelloid rotifers revisited

Birky

2004

Proc. Natl. Acad. Sci. U.S.A.

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Section: Are Bdelloids Really Asexual?supporting

confidence: 90%

Bdelloid rotifers revisited

Birky

2004

Proc. Natl. Acad. Sci. U.S.A.

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“…Also, the paucity of vertically transmitted transposons in bdelloid genomes (Arkhipova and Meselson 2000), predicted by theory for asexuals, may alternatively be explained as the result of selection against aneuploidies produced by ectopic repair of DNA double-strand breaks or by enhanced silencing mechanisms (Flot et al 2013). Another finding that has been seen as suggestive of asexuality is the presence of odd chromosome numbers in the bdelloids P. roseola (Hsu 1956a;Mark Welch and Meselson 1998) and Habrotrocha tridens (Hsu 1956b). Probes that hybridize to the single long chromosome of P. roseola do so at two sites and to no other chromosomes, suggesting that it may be an isochromosome (Mark Welch 2001;Mark Welch et al 2009).…”

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confidence: 99%

Allele Sharing and Evidence for Sexuality in a Mitochondrial Clade of Bdelloid Rotifers

et al. 2015

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Rotifers of Class Bdelloidea are common freshwater invertebrates of ancient origin whose apparent asexuality has posed a challenge to the view that sexual reproduction is essential for long-term evolutionary success in eukaryotes and to hypotheses for the advantage of sex. The possibility nevertheless exists that bdelloids reproduce sexually under unknown or inadequately investigated conditions. Although certain methods of population genetics offer definitive means for detecting infrequent or atypical sex, they have not previously been applied to bdelloid rotifers. We conducted such a test with bdelloids belonging to a mitochondrial clade of Macrotrachela quadricornifera. This revealed a striking pattern of allele sharing consistent with sexual reproduction and with meiosis of an atypical sort, in which segregation occurs without requiring homologous chromosome pairs.KEYWORDS clonal erosion; cyclic parthenogenesis; meiosis; monogonont; Oenothera B DELLOID rotifers are minute freshwater invertebrates commonly found in lakes, streams, and ponds and in ephemerally aquatic environments such as rock pools and the water films on moss and lichens where they are able to survive because of their unusual ability to withstand desiccation. Although typically only several tenths of a millimeter in size, bdelloids have ganglia; muscles; reproductive, digestive, excretory, and secretory systems; photosensitive and tactile sensory organs; and structures for crawling, feeding, and swimming. Characterized by their ciliated head and bilateral ovaries and classified in four families and hundreds of morphospecies, their ancient origin is indicated by the considerable synonymous sequence divergence between families and by the finding of bdelloid remains in 35-to 40-million year old amber (Mark Welch et al. 2009).Despite much observation of field and laboratory populations and except for one heavily qualified account of having twice seen a male among many females in a sample from a lake (Wesenberg-Lund 1930), neither males, hermaphrodites, mating, nor meiosis have ever been reported within the class (Birky 2010). The only known mode of bdelloid reproduction is via eggs produced by two mitotic divisions from primary oocytes (Hsu 1956a,b). Most recently, further evidence suggestive of asexuality has come from genomic sequencing of the bdelloid Adineta vaga, showing it to be devoid of homologous chromosome pairs and therefore excluding the possibility of standard meiosis (Flot et al. 2013). Nevertheless, the possibility remains that bdelloids reproduce sexually under unknown or inadequately investigated conditions, employing a form of meiosis known in certain plants in which segregation occurs without homologous chromosome pairs-a possibility that can be tested by methods of population genetics.For any two individuals in a population descended from a common ancestor without sexual reproduction or any other sort of genetic transfer between individuals, the phylogenetic distance between a sequence in one individual and its Librar...

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“…Egg production, however, involves two maturation divisions starting from primary oocytes present in the hatched animal (24,25) yet is also essentially unaffected even at the highest doses tested, suggesting either that egg production can proceed without maturation divisions or that the sterilizing effect of IR is manisfested only later in development.…”

Section: Discussionmentioning

confidence: 98%

Extreme resistance of bdelloid rotifers to ionizing radiation

Gladyshev

Meselson

2008

Proc. Natl. Acad. Sci. U.S.A.

239

193

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Rotifers of class Bdelloidea are common invertebrate animals with highly unusual characteristics, including apparently obligate asexuality, the ability to resume reproduction after desiccation at any life stage, and a paucity of transposable genetic elements of types not prone to horizontal transmission. We find that bdelloids are also extraordinarily resistant to ionizing radiation (IR). Reproduction of the bdelloids Adineta vaga and Philodina roseola is much more resistant to IR than that of Euchlanis dilatata, a rotifer belonging to the desiccation-intolerant and facultatively sexual class Monogononta, and all other animals for which we have found relevant data. By analogy with the desiccation-and radiationresistant bacterium Deinococcus radiodurans, we suggest that the extraordinary radiation resistance of bdelloid rotifers is a consequence of their evolutionary adaptation to survive episodes of desiccation encountered in their characteristic habitats and that the damage incurred in such episodes includes DNA breakage that is repaired upon rehydration. Such breakage and repair may have maintained bdelloid chromosomes as colinear pairs and kept the load of transposable genetic elements low and may also have contributed to the success of bdelloid rotifers in avoiding the early extinction suffered by most asexuals.desiccation ͉ DNA repair ͉ asexual reproduction ͉ anhydrobiosis

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Oogenesis in Habrotrocha Tridens (Milne)

Cited by 56 publications

References 2 publications

Bdelloid rotifers revisited

Bdelloid rotifers revisited

Allele Sharing and Evidence for Sexuality in a Mitochondrial Clade of Bdelloid Rotifers

Extreme resistance of bdelloid rotifers to ionizing radiation

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