measurement-survival-time-brachionus-rotifers-synchronization

Measurement of Survival Time in <em>Brachionus </em>Rotifers: Synchronization of Maternal Conditions

Rotifers are microscopic cosmopolitan zooplankton used as models in ecotoxicological and aging studies due to their several advantages such as short ...

A suite of morphological, histological, and molecular techniques was used to reveal for the first time division, sexuality, mandatory dormancy period of hypnozygotes, and identity of life-history stages of any Protoperidinium spp. In both Protoperidinium steidingerae and Protoperidinium depressum, asexual division occurred by eleutheroschisis within a temporary cyst, yielding two daughter cells. Daughter cells were initially round and one-half to two-thirds the size of parent cells then rapidly increased in size, forming horns before separating. Gamete production and fusion was constitutive in clonal and non-clonal cultures, indicating that both species may be homothallic. Gametes were isogamous, approximately half the size and lacking the pink pigmentation of the vegetative cells, and were never observed to feed. Gamete fusion resulted in a planozygote with two longitudinal flagella. Planozygotes of P. steidingerae formed hypnozygotes. The fate of planozygotes of P. depressum is unknown. Hypnozygotes of P. steidingerae had a mandatory dormancy period of ca. 70 days. Germination resulted in planomeiocytes with two longitudinal flagella. Nuclear cyclosis occurred in the planozygotes of P. depressum, but in the planomeiocytes of P. steidingerae. The plate tabulation and gross morphology of gametes of P. steidingerae and P. depressum differed markedly from those of vegetative cells. Thus, misidentification of morphologically distinct life-history stages and incomplete examination of thecal plate morphology in field specimens has likely led to taxonomic confusion of Protoperidinium spp. in previous studies.

Sexual and asexual processes in Protoperidinium steidingerae Balech (Dinophyceae), with observations on life-history stages of Protoperidinium depressum (Bailey) Balech (Dinophyceae).

Mate choice is of central importance to most animals, influencing population structure, speciation, and ultimately the survival of a species. Mating behavior of male brachionid rotifers is triggered by the product of a chemosensory gene, a glycoprotein on the body surface of females called the mate recognition pheromone. The mate recognition pheromone has been biochemically characterized, but little was known about the gene(s). We describe the isolation and characterization of the mate recognition pheromone gene through protein purification, N-terminal amino acid sequence determination, identification of the mate recognition pheromone gene from a cDNA library, sequencing, and RNAi knockdown to confirm the functional role of the mate recognition pheromone gene in rotifer mating.

Genetic determinants of mate recognition in Brachionus manjavacas (Rotifera).

Partnerwahl ist von zentraler Bedeutung f&uuml;r die meisten Tiere, Bev&ouml;lkerungsstruktur, Speziation und letztlich das &Uuml;berleben einer Art zu beeinflussen. Verhalten des m&auml;nnlichen Brachionid R&auml;dertierchen Paarung wird durch das Produkt eines chemosensory Gens, ein Glykoprotein auf der K&ouml;rperoberfl&auml;che Weibchen das incorporate Anerkennung Pheromon namens ausgel&ouml;st. Das Mate-Anerkennung-Pheromon biochemisch gepr&auml;gt, aber wenig &uuml;ber die geh&auml;uft bekannt war. Wir beschreiben die Isolierung und Charakterisierung des Gens Pheromon incorporate Anerkennung durch Proteinreinigung, N-terminalen Aminos&auml;ure-Sequenz Bestimmung, Identifizierung des Gens Pheromon incorporate Anerkennung von eine cDNA-Bibliothek, Sequenzierung und RNAi Niederschlag, die funktionale Rolle des Gens Pheromon incorporate Anerkennung in Rotifer Paarung zu best&auml;tigen.

Genetische Determinanten der Partnererkennung im Zooplankton Manjavacas (Rotifera).

Chemically mediated prezygotic barriers to reproduction likely play an important role in speciation. In facultatively sexual monogonont rotifers from the Brachionus plicatilis cryptic species complex, mate recognition of females by males is mediated by the Mate Recognition Protein (MRP), a globular glycoprotein on the surface of females, encoded by the mmr-b gene family. In this study, we sequenced mmr-b copies from 27 isolates representing 11 phylotypes of the B. plicatilis species complex, examined the mode of evolution and selection of mmr-b, and determined the relationship between mmr-b genetic distance and mate recognition among isolates.

The mate recognition protein gene mediates reproductive isolation and speciation in the Brachionus plicatilis cryptic species complex.

We measured life span and fecundity of three reproductive modes in a clone of the monogonont rotifer Brachionus manjavacas subjected to chronic caloric restriction (CCR) over a range of food concentrations or to intermittent fasting (IF). IF increased life span 50%-70% for all three modes, whereas CCR increased life span of asexual females derived from sexually or asexually produced eggs, but not that of sexual females. The main effect of CR on both asexual modes was to delay death at young ages, rather than to prevent death at middle ages or to greatly extend maximum life span; in contrast CR in sexual females greatly increased the life span of a few long-lived individuals. Lifetime fecundity did not decrease with CCR, suggesting a lack of resource allocation trade-off between somatic maintenance and reproduction. Multiple outcomes for a clonal lineage indicate that different responses are established through epigenetic programming, whereas differences in life-span allocations suggest that multiple genetic mechanisms mediate life-span extension.

Life-span extension by caloric restriction is determined by type and level of food reduction and by reproductive mode in Brachionus manjavacas (Rotifera).

Caloric restriction (CR) is cited as the most robust means of increasing lifespan across a range of taxa, yet there is a high degree of variability in the response to CR, both within and between species. To examine the intraspecific evolutionary conservation of lifespan extension by CR, we tested the effects of chronic caloric restriction (CCR) at multiple food levels and of intermittent fasting (IF) in twelve isolates from the Brachionus plicatilis species complex of monogonont rotifers. While CCR generally increased or did not change lifespan and total fecundity, IF caused increased, unchanged, or decreased lifespan, depending upon the isolate, and decreased total fecundity in all but one isolate. Lifespan under ad libitum (AL) feeding varied among isolates and predicted the lifespan response to CR: longer-lived isolates under AL were less likely to have a significant increase in lifespan under CCR and were more likely to have a significantly shortened lifespan under IF. Lifespan under AL conditions and the response to CR were not correlated with hydroperiodicity of native habitat or with time in culture. Lack of trade-off between lifespan and fecundity under CCR, and differences in lifespan and fecundity under CCR and IF, even when average food intake was similar, suggest that longevity changes are not always directly determined by energy intake and that CCR and IF regimens extend lifespan through diverse genetic mechanisms.

Patterns of intraspecific variability in the response to caloric restriction.

While many studies have focused on the detrimental effects of advanced maternal age and harmful prenatal environments on progeny, little is known about the role of beneficial non-Mendelian maternal inheritance on aging. Here, we report the effects of maternal age and maternal caloric restriction (CR) on the life span and health span of offspring for a clonal culture of the monogonont rotifer Brachionus manjavacas. Mothers on regimens of chronic CR (CCR) or intermittent fasting (IF) had increased life span compared with mothers fed ad libitum (AL). With increasing maternal age, life span and fecundity of female offspring of AL-fed mothers decreased significantly and life span of male offspring was unchanged, whereas body size of both male and female offspring increased. Maternal CR partially rescued these effects, increasing the mean life span of AL-fed female offspring but not male offspring and increasing the fecundity of AL-fed female offspring compared with offspring of mothers of the same age. Both maternal CR regimens decreased male offspring body size, but only maternal IF decreased body size of female offspring, whereas maternal CCR caused a slight increase. Understanding the genetic and biochemical basis of these different maternal effects on aging may guide effective interventions to improve health span and life span.

Maternal caloric restriction partially rescues the deleterious effects of advanced maternal age on offspring.

Comparative biogerontology has much to contribute to the study of aging. A broad range of aging rates has evolved to meet environmental challenges, and understanding these adaptations can produce valuable insights into aging. The supra Phylum Lophotrochozoa is particularly understudied and has several groups that have intriguing patterns of aging. Members of the lophotrochozoan phylum Rotifera are particularly useful for aging studies because cohort life tables can be conducted with them easily, and biochemical and genomic tools are available for examining aging mechanisms. This paper reviews a variety of caloric restriction regimens, small molecule inhibitors, and dietary supplements that extend rotifer lifespan, as well as important interactions between caloric restriction and genotype, antioxidant supplements, and TOR and JNK pathways, and the use of RNAi to identify key genes involved in modulating the aging response. Examples of how rapamycin and JNK inhibitor exposure keeps mortality rates low during the reproductive phase of the life cycle are presented, and the ease of conducting life table experiments to screen natural products from red algae for life extending effects is illustrated. Finally, experimental evolution to produce longer-lived rotifer individuals is demonstrated, and future directions to determine the genetic basis of aging are discussed.

Article	Year
Sexual and asexual processes in Protoperidinium steidingerae Balech (Dinophyceae), with observations on life-history stages of Protoperidinium depressum (Bailey) Balech (Dinophyceae). The Journal of eukaryotic microbiology\| PubMed ID: 19335779	2009
Genetic determinants of mate recognition in Brachionus manjavacas (Rotifera). BMC biology\| PubMed ID: 19740420	2009
The mate recognition protein gene mediates reproductive isolation and speciation in the Brachionus plicatilis cryptic species complex. BMC evolutionary biology\| PubMed ID: 22852831	2012
Life-span extension by caloric restriction is determined by type and level of food reduction and by reproductive mode in Brachionus manjavacas (Rotifera). The journals of gerontology. Series A, Biological sciences and medical sciences\| PubMed ID: 22904096	2013
Patterns of intraspecific variability in the response to caloric restriction. Experimental gerontology\| PubMed ID: 24384399	2014
Maternal caloric restriction partially rescues the deleterious effects of advanced maternal age on offspring. Aging cell\| PubMed ID: 24661622	2014
Rotifers as experimental tools for investigating aging. Invertebrate reproduction & development\| PubMed ID: 25642019	2015

Kristin E. Gribble

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