Gregarine apicomplexans are unicellular parasites commonly found in the intestines and coeloms of invertebrate hosts. Traits associated with the conspicuous feeding stage of gregarines, known as the ...trophozoite, have been used in combination with molecular phylogenetic data for species delimitation and the reconstruction of evolutionary history. Trophozoite morphology alone is often inadequate for inferring phylogenetic relationships and delimiting species due to frequent cases of high intraspecific variation combined with relatively low interspecific variation. The current study combined morphological data with small subunit (SSU) rDNA sequences to describe and establish two novel marine gregarine species isolated from the intestine of a polychaete host Lumbrineris inflata collected in British Columbia (Canada): Paralecudina anankea n. sp. and Lecudina caspera n. sp. The sister species to the host is Lumbrineris japonica, which can be found on the opposite side of the Pacific Ocean (Japan) and contains two different species of gregarine parasites: Paralecudina polymorpha and Lecudina longissima. Molecular phylogenetic analyses placed P. anankea n. sp. as the sister species to P. polymorpha and L. caspera n. sp. as the sister species to L. longissima. This phylogenetic pattern demonstrates a co-evolutionary history whereby speciation of the host (Lumbrineris) corresponds with simultaneous speciation of the two different lineages of intestinal gregarines (Paralecudina and Lecudina).
Platyproteum is an enigmatic, monotypic genus formerly assigned to the Apicomplexa, until a recent phylogenomic study demonstrated that it diverged from the base of the chromerid/colpodellid ...(chrompodellid) taxa and apicomplexan clade. In the present study, a new species, P. noduliferae n. sp., is described using a combination of morphological and molecular data. Moreover, a reconstruction of the flagellar apparatus is presented to characterize the presence of flagella which was, until this study, an unknown trait for this genus. Phylogenetic analyses using rDNA sequences suggested that P. noduliferae n. sp. is a sister species of P. vivax, diverging from the base of chrompodellids and apicomplexans. This study provides new morphological data that corroborates the position of Platyproteum amongst other biflagellate species, contributing to an improved understanding of Platyproteum and the evolutionary changes undergone by some marine alveolates as they transitioned into obligate parasitic life styles.
The 2021 summer heat waves experienced in the Pacific Northwest led to considerable fruit damage in many apple production zones. Sunburn browning (SB) was a particularly evident symptom. To ...understand the mechanism underlying the damage and to facilitate the early assessment of compromised fruit quality, we conducted a study on external characteristics and internal quality attributes of SB 'Ambrosia' apple (
var. Ambrosia) and evaluated the fruit loss on five rootstocks. The cell integrity of the epidermal and hypodermal layers of fruit skins in the SB patch was compromised. Specifically, the number of chloroplasts and anthocyanin decreased in damaged cells, while autofluorescent stress-related compounds accumulated in dead cells. Consequently, the affected sun-exposed skin demonstrated a significant increase in differential absorbance between 670 nm and 720 nm, measured using a handheld apple DA meter, highlighting the potential of using this method as a non-destructive early indicator for sunburn damage. Sunburn browning eventually led to lower fruit weight, an increase in average dry matter content, soluble solids content, acidity, deteriorated weight retention, quicker loss of firmness, and accelerated ethylene emission during ripening. Significant inconsistency was found between the sun-exposed and shaded sides in SB apples regarding dry matter content, firmness, and tissue water potential, which implied preharvest water deficit in damaged tissues and the risk of quicker decline of postharvest quality. Geneva 935 (G.935), a large-dwarfing rootstock with more vigor and higher water transport capacity, led to a lower ratio of heat-damaged fruits and a higher yield of disorder-free fruits, suggesting rootstock selection as a long-term horticultural measure to mitigate summer heat stress.
Uncovering factors that shape variation in brain morphology remains a major challenge in evolutionary biology. Recently, it has been shown that brain size is positively associated with level of ...parental care behavior in various taxa. One explanation for this pattern is that the cognitive demands of performing complex parental care may require increased brain size. This idea is known as the parental brain hypothesis (PBH). We set out to test the predictions of this hypothesis in wild populations of threespine stickleback (Gasterosteus aculeatus). These fish are commonly known to exhibit (1) uniparental male care and (2) sexual dimorphism in brain size (males>females). To test the PBH, we took advantage of the existence of closely related populations of stickleback that display variation in parental care behavior: common marine threespine sticklebacks (uniparental male care) and white threespine sticklebacks (no care). To begin, we quantified genetic differentiation among two common populations and three white populations from Nova Scotia. We found overall low differentiation among populations, although FST was increased in between‐type comparisons. We then measured the brain weights of males and females from all five populations along with two additional common populations from British Columbia. We found that sexual dimorphism in brain size is reversed in white stickleback populations: males have smaller brains than females. Thus, while several alternatives need to be ruled out, the PBH appears to be a reasonable explanation for sexual dimorphism in brain size in threespine sticklebacks.
The parental brain hypothesis predicts that the sex performing parental care should have a larger brain than the non‐caring sex. We test this idea by examining brains of a unique white form of threespined stickleback that, unlike the common stickleback it co‐occurs with, does not perform paternal care. We found that male white sticklebacks have smaller relative brain weights than females – the opposite of the pattern in common sticklebacks.
High temperature deteriorates apple tree performance and fruit growth. In the summer of 2021, heat waves affected the apple production zones in the Pacific Northwest of North America. In a 'Buckeye ...Gala' experimental trial in Summerland, British Columbia, Canada, heat caused fruit skin sunburn browning (SB), and affected fruit mass, dry matter content, soluble solid content, titratable acidity, firmness and flesh water potential. We studied fruit skin δAbsorbance at 670–720 nm (δA670–720), cuticle characteristics, and key stress response compounds in peel and flesh, to elucidate the SB mechanism. SB was associated with thickened cuticle, chloroplast degradation, decreased anthocyanin content and increased firmness on the affected sunlit side of the fruit. As sunburn damage intensified, anthocyanin content in peel decreased, while the concentration of tartaric ester and total phenolics in flesh increased. The δA670–720, measured using Delta Absorbance (DA) meter, was positively correlated with the total amount of phenolics and tartaric esters in peel and flesh. This suggested that the accumulation of the phenolics and tartaric ester triggered by heat stress contributed to the high δA670–720 despite the degradation/absence of chloroplasts. The study improved our understanding of the impacts of sunburn severities on fruit quality and of the heat stress responses in 'Buckeye Gala' apple, and demonstrated the potential use of DA meter as a rapid, non-destructive tool in facilitating heat stress ecophysiology study and predicting SB severity in red apple varieties.
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•New gregarine parasites (Apicomplexa) were discovered from sea squirts.•Species were described using morphology and SSU rDNA.•Data revealed a history of host switching.•Two major ...genera were found to be taxonomically problematic.
Apicomplexa (sensu stricto) are a diverse group of obligate parasites to a variety of animal species. Gregarines have been the subject of particular interest due to their diversity, phylogenetically basal position, and more recently, their symbiotic relationships with their hosts. In the present study, four new species of marine eugregarines infecting ascidian hosts (Lankesteria kaiteriteriensis sp. nov., L. dolabra sp. nov., L. savignyii sp. nov., and L. pollywoga sp. nov.) were described using a combination of morphological and molecular data. Phylogenetic analysis using small subunit rDNA sequences suggested that gregarines that parasitize ascidians and polychaetes share a common origin as traditionally hypothesized by predecessors in the discipline. However, Lankesteria and Lecudina species did not form clades as expected, but were instead intermixed amongst each other and their respective type species in the phylogeny. These two major genera are therefore taxonomically problematic. We hypothesize that the continued addition of new species from polychaete and tunicate hosts as well as the construction of multigene phylogenies that include type-material will further dissolve the currently accepted distinction between Lankesteria and Lecudina. The species discovered and described in the current study add new phylogenetic and taxonomic data to the knowledge of marine gregarine parasitism in ascidian hosts.
Apicomplexans are diverse single-celled eukaryotes that parasitize animals. The most notorious members include those of particular human interest such as the causative agents of malaria, ...toxoplasmosis, and cryptosporidiosis. While a subset of apicomplexans has been intensively studied from a medical or veterinary perspective, the diversity of remaining groups is underrepresented in existing literature. This lack of data has left the deep relationships among apicomplexan taxa enigmatic and in turn has hindered the revelation of some major evolutionary processes that sparked the apicomplexan radiation. The dearth of understanding surrounding apicomplexan systematics can be addressed in part through the discovery of novel species and the identification of how morphological and molecular characters are distributed across the apicomplexan phylogeny. Some lineages of marine gregarines have retained plesiomorphic characters that offer unique insight into the earliest stages of apicomplexan evolution. The current thesis describes and establishes two novel marine gregarine species isolated from a polychaete hosts (Lumbrineris inflata). Species delimitation and description was based on morphological data acquired using light and electron microscopy and a molecular phylogenetic analysis of 18S small subunit (SSU) rDNA sequences. Paralecudina anankea n. sp. possessed an elongated body, an oval nucleus, and gliding motility. The sister relationship of P. anankea n. sp. with P. polymorpha was robustly supported by molecular phylogenetic analysis (100 MLB, 1.00 BPP) and the SSU rDNA sequences between the two were 12% divergent. In contrast, L. caspera n. sp. was morphologically dissimilar to its closest relative L. longissima and possessed an acorn-shaped body, a distinct mucron, and gliding motility. Molecular phylogenetic analysis recovered L. caspera n. sp. as a sister species to L. longissima with strong support (100 MLB, 1.00 BPP) and their SSU rDNA sequences which were 8% divergent. The generation of additional morphological and molecular traits in gregarines will improve the phylogenetic resolution of the apicomplexan backbone and improve inferences about the evolutionary transition from photosynthetic ancestors to obligate parasites.
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