F1 Cohorts Research Articles

Long-term survival, growth, and reproduction of Acropora palmata sexual recruits outplanted onto Mexican Caribbean reefs.

Acropora palmata is a foundational yet endangered Caribbean reef-building coral species. The lack of recovery after a disease outbreak and low recruitment has led to widespread use of fragmentation to restore populations. Another option is the production of sexual recruits (settlers) via assisted reproduction to improve the genetic diversity of depleted populations; however, the viability of this approach has not been tested over the long term. In 2011 and 2012, A. palmata larvae were cultured, settled, and the sexual recruits raised in an ex-situ nursery. Survival and growth were monitored over time. In 2014, these two F1 cohorts were moved to an in-situ nursery and after one year, a subset (29 colonies) was outplanted onto Cuevones Reef in the Mexican Caribbean. Growth and survival of these colonies were monitored periodically and compared to colonies that remained in the in-situ nursery. In 2019, samples were collected and analyzed for fertility and fecundity. 53% of the colonies were gravid and fecundity was 5.61 ± 1.91 oocytes and 3.04 ± 0.26 spermaries per polyp. A further 14 colonies from these two cohorts were outplanted in 2020 onto Picudas Reef and monitored during the subsequent spawning seasons. Two years after outplanting onto Picudas Reef, all colonies were alive and spawning of three of these colonies was recorded in 2022 in synchrony with the wild population. Gametes were collected from two colonies and crossed, with 15% fertilization success. Spermatozoa from wild colonies were then added and fertilization success increased to 95%. The resultant larvae followed normal development and symbiont uptake was visible within two weeks. The F2 generation was settled, maintained in an ex-situ nursery, and monitored for survival and growth. Both F1 and F2 generations followed a Type III survival curve with high initial mortality while in the ex-situ nursery and low later-stage mortality. The growth rates of these colonies increased three-fold after outplanting when compared to their growth rates in the ex-situ and in-situ nurseries. All colonies survived while in the in-situ nursery and for an additional nine years after outplanting onto Cuevones Reef. Overall, our results show that colonies produced by assisted breeding, once outplanted, may contribute to the genetic diversity and establishment of self-sustaining sexually-reproducing populations, which is an overarching goal of coral restoration programs.

Reproductive incompatibility between Amblyomma maculatum (Acari: Ixodidae) group ticks from two disjunct geographical regions within the USA.

The Amblyomma maculatum Koch group of ixodid ticks consists of three species: A. maculatum, A. triste, and A. tigrinum. However, since Koch described this group in 1844, the systematics of its members has been the subject of ongoing debate. This is especially true of A. maculatum and A. triste; recent molecular analyses reveal insufficient genetic divergence to separate these as distinct species. Further confounding this issue is the discovery in 2014 of A. maculatum group ticks in southern Arizona (AZ), USA, that share morphological characteristics with both A. triste and A. maculatum. To biologically evaluate the identity of A. maculatum group ticks from southern Arizona, we analyzed the reproductive compatibility between specimens of A. maculatum group ticks collected from Georgia (GA), USA, and southern Arizona. Female ticks from both Arizona and Georgia were mated with males from both the Georgia and Arizona Amblyomma populations, creating two homologous and two heterologous F1 cohorts of ticks: GA ♀/GA ♂, AZ ♀/AZ ♂, GA ♀/AZ ♂, and AZ ♀/GA ♂. Each cohort was maintained separately into the F2 generation with F1 females mating only with F1 males from their same cohort. Survival and fecundity parameters were measured for all developmental stages. The observed survival parameters for heterologous cohorts were comparable to those of the homologous cohorts through the F1 generation. However, the F1 heterologous females produced F2 egg clutches that did not hatch, thus indicating that the Arizona and Georgia populations of A. maculatum group ticks tested here represent different biological species.

Soy-deficient diet induces renal lesions in juvenile rats

Certified LabDiet® 5K96 Advanced Protocol™ Verified Casein Diet 10 IF (5K96) is a commercial diet low in soy isoflavones developed for use in developmental and reproductive toxicity (DART) studies, especially those designed to detect endocrine disruptors. The objective of this study was to determine the incidences and severities of 5K96-associated renal lesions in control F0 and F1 cohorts of rats fed the 5K96 diet. Kidneys from control animals of four DART studies involving Sprague-Dawley rats fed the 5K96 diet, were evaluated microscopically. Mineralization and basophilic tubules were present in high incidence/severity in males and females compared to historical controls fed conventional diets. F1 cohorts were affected to a far greater degree than F0 cohorts, and females were affected more than males. Consideration of target tissue and mode of action should be given before automatically incorporating the 5K96 diet into DART study designs, and caution should be exercised when identifying and interpreting renal toxicity in the F1 cohorts of such studies.

Long-term experimental hybrid swarms between moderately incompatible Tigriopus californicus populations: hybrid inferiority in early generations yields to hybrid superiority in later generations

The deleterious effects of hybridization are a serious concern for the conservation and management of species, particularly when populations mix as a result of human activity. Outbreeding depression is the typical result observed in early-generation interpopulation hybrids of Tigriopus californicus. We examined both controlled crosses and long-term, freely-mating, experimental hybrid populations composed of southern California populations Royal Palms (RP) and San Diego (SD). Controlled crosses included parentals plus all reciprocal F1, F2, F3 and backcross cohorts, and only F2 cohorts showed significant declines in fitness compared to midparent values, indicating recovery in the F3. For long-term studies, four treatment groups were initiated: 100% RP, 100% SD, 50% RP: 50% SD, and 80% RP: 20% SD. Replicates were surveyed at 3-month intervals for morphometric, census and fitness measures. Fitness of hybrid treatments showed declines relative to midparent values followed by rapid recovery, with two hybrid replicates ultimately showing higher fitness than parentals at the final 15-month time-point (up to 20 generations). In contrast, both males and females in hybrid treatments were larger than the midparent for several morphometric characters at the first time-point, and smaller than the midparent at the final time-point, indicating a possible tradeoff between fitness and body size. Microsatellites for a subset of samples revealed extensive introgression in hybrid treatments. This adds to previous evidence that hybrid breakdown in early generations may be a temporary phenomenon followed by the persistence of highly fit recombinant genotypes.

Genetic and gender influences on sensitivity to focal cerebral ischemia in the stroke-prone spontaneously hypertensive rat.

We have investigated genetic transmission of increased sensitivity to focal cerebral ischemia and the influence of gender in the stroke-prone spontaneously hypertensive rat (SHRSP). Halothane-anesthetized, 3- to 5-month-old male and female Wistar-Kyoto rats (WKY), SHRSP, and the first filial generation rats (F1 crosses 1 and 2) underwent distal (2 mm) permanent middle cerebral artery occlusion (MCAO) by electrocoagulation. Infarct volume was measured by using hematoxylin-eosin-stained sections and image analysis 24 hours after ischemia and expressed as a percentage of the volume of the ipsilateral hemisphere. Infarct volume in males and females grouped together were significantly larger in SHRSP, F1 cross 1 (SHRSP father), and F1 cross 2 (WKY father), at 36.6+/-2.3% (mean+/-SEM, P<0.001, n=15), 25.4+/-2.4% (P<0.01, n=14), and 33. 9+/-1.6% (P<0.001, n=18), respectively, compared with WKY (14+/-2%, n=17). Male F1 cross 1 (18.9+/-2.4%, n=6) developed significantly smaller infarcts than male F1 cross 2 (32.8+/-2%, n=8, P<0.005). Females, which underwent ischemia during metestrus, developed larger infarcts than respective males. A group of females in which the cycle was not controlled for developed significantly smaller infarcts than females in metestrus. Thus, the increased sensitivity to MCAO in SHRSP is retained in both F1 cross 1 and cross 2 hybrids, suggesting a dominant or codominant trait; response to cerebral ischemia appears to be affected by gender and stage in the estrous cycle. In addition, the male progenitor of the cross (ie, SHRSP versus WKY) influences stroke sensitivity in male F1 cohorts.

Die invloed van blootstelling aan mirasidiums &lt;i&gt;Schistosoma mansoni&lt;i/&gt; op mortaliteitskoerse van kohorte van vier geografiese stamme van &lt;i&gt;Biomphalaria pfeifferi&lt;i/&gt;

First generation cohorts of 25 specimens each of parental populations of Biomphalaria pfeifferi from four different localities, were each exposed to three Schistosoma mansoni miracidia per snail at an age of four weeks. The effect on survival was evaluated by calculating the weekly per capita mortality rates and the mean life-expectancy of the exposed snails. No significant differences could be demonstrated between the per capita mortality rates of F₁ cohorts of the two parental strains originating from localities in endemic bilharzia areas. Likewise there were no significant differences in this respect as far as F₁ cohorts of the two strains originating from localities in non-endemic bilharzia areas were concerned.

Analysis of the New Zealand Black contribution to lupus-like renal disease. Multiple genes that operate in a threshold manner.

F1 progeny of New Zealand Black (NZB) and New Zealand White (NZW) mice spontaneously develop an autoimmune process remarkably similar to human systemic lupus erythematosus. Previous studies have implicated major genetic contributions from the NZW MHC and from a dominant NZB gene on chromosome 4. To identify additional NZB contributions to lupus-like disease, (NZB x SM/J)F1 x NZW backcross mice were followed for the development of severe renal disease and were comprehensively genotyped. Despite a 50% incidence of disease, significant associations between the presence of the NZB genotype and disease were noted on chromosomes 1, 4, 7, 10, 13, and 19. The data indicated that multiple NZB genes, in different combinations, contribute to severe renal disease, and that no single gene is required. To further investigate this NZB contribution, NZB x SM/J (NXSM) recombinant inbred (RI) strains were crossed with NZW mice, and F1 progeny were analyzed for the presence of lupus-like renal disease. Interestingly, nearly all of the (RI x NZW)F1 cohorts studied expressed some level of disease. Five RI strains generated a high incidence of disease, similar to (NZB x NZW)F1 mice, and nearly one-half of the cohorts developed disease at intermediate levels. Only two cohorts demonstrated very little disease, supporting the conclusion that multiple genes are capable of disease induction. Experiments correlating the genotypes of these RI strains with their ability to generate disease revealed that none of the disease-associated loci defined by the backcross analysis were present in all five RI strains that generated disease at high levels. Overall, both the backcross data and RI analysis provide additional support for the genetic complexity of lupus nephritis and uphold the conclusion that heterogeneous combinations of contributing NZB genes seem to operate in a threshold manner to generate the disease phenotype.

The effect of pH onBrachionus calyciflorus Pallas (Rotifera)

Cohorts of the rotiferBrachionus calyciflorus were grown in media with pH of between 2.5 and 11.5 in increments of 1 unit. pH was shown to exert a major influence on the growth rate and reproductive capacity of theB. calyciflorus. At pH 2.5 theB. calyciflorus showed a negative capacity for population increase (r c). Ther c values of the cohorts reared at pH 3.5 and 4.5 were positive and these cohorts showed high net reproductive rates (R0). Ther c's of cohorts reared at pH of 5.5 and 6.5 were negative, while those of cohorts reared at pH 7.5 to 10.5 were positive with a peak in theR 0 and cohort generation time (T c) at pH 8.5 and 9.5. Total mortality occurred in less that 24 h at pH 11.5. Successive generations of the progeny from the cohort held at pH 3.5 were reared under the same conditions. Although ther c of the F1 and F2 cohorts increased, the organism was unable to maintain the increased population growth rate, and the F4 generation showed anr c of almost 0.