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Phylogenetic analysis of algal symbionts associated with four North American amphibian egg masses.

Kim E, Lin Y, Kerney R, Blumenberg L, Bishop C - PLoS ONE (2014)

Bottom Line: We designate this group as the 'Oophila' clade, within which the symbiotic algae are further divided into four distinct subclades.Phylogenies of the host amphibians and their algal symbionts are only partially congruent, suggesting that host-switching and co-speciation both play roles in their associations.We also established conditions for isolating and rearing algal symbionts from amphibian egg capsules, which should facilitate further study of these egg mass specialist algae.

View Article: PubMed Central - PubMed

Affiliation: Division of Invertebrate Zoology and Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York, United States of America.

ABSTRACT
Egg masses of the yellow-spotted salamander Ambystoma maculatum form an association with the green alga "Oophila amblystomatis" (Lambert ex Wille), which, in addition to growing within individual egg capsules, has recently been reported to invade embryonic tissues and cells. The binomial O. amblystomatis refers to the algae that occur in A. maculatum egg capsules, but it is unknown whether this population of symbionts constitutes one or several different algal taxa. Moreover, it is unknown whether egg masses across the geographic range of A. maculatum, or other amphibians, associate with one or multiple algal taxa. To address these questions, we conducted a phylogeographic study of algae sampled from egg capsules of A. maculatum, its allopatric congener A. gracile, and two frogs: Lithobates sylvatica and L. aurora. All of these North American amphibians form associations with algae in their egg capsules. We sampled algae from egg capsules of these four amphibians from localities across North America, established representative algal cultures, and amplified and sequenced a region of 18S rDNA for phylogenetic analysis. Our combined analysis shows that symbiotic algae found in egg masses of four North American amphibians are closely related to each other, and form a well-supported clade that also contains three strains of free-living chlamydomonads. We designate this group as the 'Oophila' clade, within which the symbiotic algae are further divided into four distinct subclades. Phylogenies of the host amphibians and their algal symbionts are only partially congruent, suggesting that host-switching and co-speciation both play roles in their associations. We also established conditions for isolating and rearing algal symbionts from amphibian egg capsules, which should facilitate further study of these egg mass specialist algae.

No MeSH data available.


Related in: MedlinePlus

Light microscopic images of cultured strains of A. maculatum algae.The Oophila strains Hb_cul-rk (A−C) and BB_cul-B (D−F) belong to subclades I and III, respectively. Monotypic cultures displayed at least three different cell types, which include 1) free-swimming biflagellates (A, D), which correspond to zoospores or gametes, 2) cells enclosed within a mother cell wall (B, E), likely representing asexually dividing zoospores, and 3) larger non-motile zygotes (C, F). Scale bars: 10 µm (A−F).
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pone-0108915-g003: Light microscopic images of cultured strains of A. maculatum algae.The Oophila strains Hb_cul-rk (A−C) and BB_cul-B (D−F) belong to subclades I and III, respectively. Monotypic cultures displayed at least three different cell types, which include 1) free-swimming biflagellates (A, D), which correspond to zoospores or gametes, 2) cells enclosed within a mother cell wall (B, E), likely representing asexually dividing zoospores, and 3) larger non-motile zygotes (C, F). Scale bars: 10 µm (A−F).

Mentions: Our cultured strains of A. maculatum algal symbionts fall into two distinct subclades, I and III (Figure 2). Algae from both subclades appear to display the canonical chlamydomonad life cycle [33], consisting of vegetative cells (zoospores or gametes, and zygotes (Figure 3). Older cultures tend to have more putative zygotes, the formation of which may be a result of nutrient depletion, as in C. reinhardtii[34]. A major difference between strains of distinct phylogenetic groups, which were established and maintained using the same culturing method, is the shape of the zoospores (or gametes). Flagellated cells of the strain belonging to the subclade I are spherical and 9−11 µm in diameter (n = 10), whereas those of the clade II are oblong in shape and measure 10−11 µm in length and 6−7 µm in width (n = 10). Both types of strain are characterized by zoospores having two flagella, which are each nearly twice the length of the cell (Figure 3). Vegetative cell growth of these algae occurs within a parental cell wall, each containing up to eight daughter cells, which are released freely into the media.


Phylogenetic analysis of algal symbionts associated with four North American amphibian egg masses.

Kim E, Lin Y, Kerney R, Blumenberg L, Bishop C - PLoS ONE (2014)

Light microscopic images of cultured strains of A. maculatum algae.The Oophila strains Hb_cul-rk (A−C) and BB_cul-B (D−F) belong to subclades I and III, respectively. Monotypic cultures displayed at least three different cell types, which include 1) free-swimming biflagellates (A, D), which correspond to zoospores or gametes, 2) cells enclosed within a mother cell wall (B, E), likely representing asexually dividing zoospores, and 3) larger non-motile zygotes (C, F). Scale bars: 10 µm (A−F).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230919&req=5

pone-0108915-g003: Light microscopic images of cultured strains of A. maculatum algae.The Oophila strains Hb_cul-rk (A−C) and BB_cul-B (D−F) belong to subclades I and III, respectively. Monotypic cultures displayed at least three different cell types, which include 1) free-swimming biflagellates (A, D), which correspond to zoospores or gametes, 2) cells enclosed within a mother cell wall (B, E), likely representing asexually dividing zoospores, and 3) larger non-motile zygotes (C, F). Scale bars: 10 µm (A−F).
Mentions: Our cultured strains of A. maculatum algal symbionts fall into two distinct subclades, I and III (Figure 2). Algae from both subclades appear to display the canonical chlamydomonad life cycle [33], consisting of vegetative cells (zoospores or gametes, and zygotes (Figure 3). Older cultures tend to have more putative zygotes, the formation of which may be a result of nutrient depletion, as in C. reinhardtii[34]. A major difference between strains of distinct phylogenetic groups, which were established and maintained using the same culturing method, is the shape of the zoospores (or gametes). Flagellated cells of the strain belonging to the subclade I are spherical and 9−11 µm in diameter (n = 10), whereas those of the clade II are oblong in shape and measure 10−11 µm in length and 6−7 µm in width (n = 10). Both types of strain are characterized by zoospores having two flagella, which are each nearly twice the length of the cell (Figure 3). Vegetative cell growth of these algae occurs within a parental cell wall, each containing up to eight daughter cells, which are released freely into the media.

Bottom Line: We designate this group as the 'Oophila' clade, within which the symbiotic algae are further divided into four distinct subclades.Phylogenies of the host amphibians and their algal symbionts are only partially congruent, suggesting that host-switching and co-speciation both play roles in their associations.We also established conditions for isolating and rearing algal symbionts from amphibian egg capsules, which should facilitate further study of these egg mass specialist algae.

View Article: PubMed Central - PubMed

Affiliation: Division of Invertebrate Zoology and Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York, United States of America.

ABSTRACT
Egg masses of the yellow-spotted salamander Ambystoma maculatum form an association with the green alga "Oophila amblystomatis" (Lambert ex Wille), which, in addition to growing within individual egg capsules, has recently been reported to invade embryonic tissues and cells. The binomial O. amblystomatis refers to the algae that occur in A. maculatum egg capsules, but it is unknown whether this population of symbionts constitutes one or several different algal taxa. Moreover, it is unknown whether egg masses across the geographic range of A. maculatum, or other amphibians, associate with one or multiple algal taxa. To address these questions, we conducted a phylogeographic study of algae sampled from egg capsules of A. maculatum, its allopatric congener A. gracile, and two frogs: Lithobates sylvatica and L. aurora. All of these North American amphibians form associations with algae in their egg capsules. We sampled algae from egg capsules of these four amphibians from localities across North America, established representative algal cultures, and amplified and sequenced a region of 18S rDNA for phylogenetic analysis. Our combined analysis shows that symbiotic algae found in egg masses of four North American amphibians are closely related to each other, and form a well-supported clade that also contains three strains of free-living chlamydomonads. We designate this group as the 'Oophila' clade, within which the symbiotic algae are further divided into four distinct subclades. Phylogenies of the host amphibians and their algal symbionts are only partially congruent, suggesting that host-switching and co-speciation both play roles in their associations. We also established conditions for isolating and rearing algal symbionts from amphibian egg capsules, which should facilitate further study of these egg mass specialist algae.

No MeSH data available.


Related in: MedlinePlus