Light Microscopic Observations, Ultrastructure, and Molecular Phylogeny of Hicanonectes teleskopos n. g., n. sp., a Deep-Branching Relative of Diplomonads

ABSTRACT. We describe Hicanonectes teleskopos n. g., n. sp., a heterotrophic flagellate isolated from low-oxygen marine sediment. Hicanonectes teleskopos has a ventral groove and two unequal flagella, and rapidly rotates during swimming. At the ultrastructural level H. teleskopos is a "typical excavate": it displays flagellar vanes, a split right microtubular root, "I,""B," and "C" fibres, a singlet microtubular root, and a possible composite fibre. Small subunit rRNA (SSU rRNA) gene phylogenies and an "arched" B fibre demonstrate that H. teleskopos belongs to Fornicata (i.e. diplomonads, retortamonads, and relatives). It forms a clade with the deep-branching fornicate Carpediemonas , with moderate-to-strong bootstrap support, although their SSU rRNA gene sequences are quite dissimilar. Hicanonectes differs from Carpediemonas in cell shape, swimming behaviour, number of basal bodies (i.e. 4 vs. 3), number of flagellar vanes (i.e. 2 vs. 3), anterior root organization, and by having a cytopharynx. Like Carpediemonas and Dysnectes, Hicanonectes has conspicuous mitochondrion-like organelles that lack cristae and superficially resemble the hydrogenosomes of parabasalids, rather than the mitosomes of their closer relatives the diplomonads (e.g. Giardia ).     

Cell morphology and formal description of Ergobibamus cyprinoides n. g., n. sp., another Carpediemonas-like relative of diplomonads

About 20 new isolates of Carpediemonas-like organisms (CLOs) have been reported since 2006. Small subunit rRNA gene phylogenies divide CLOs into six major clades: four contain described exemplars (i.e. Carpediemonas, Dysnectes, Hicanonectes, and Kipferlia), but two include only undescribed organisms. Here we describe a representative of one of these latter clades as Ergobibamus cyprinoides n. g., n. sp., and catalogue its ultrastructure. Ergobibamus cyprinoides is a bean-shaped biflagellated cell, 7-11.5 μm long, with a conspicuous groove. Instead of classical mitochondria there are cristae-lacking rounded organelles 300-400 nm in diameter. The posterior flagellum has a broad ventral vane and small dorsal vane. There are normally four basal bodies, two non-flagellated. There is one anterior root (AR), containing six microtubules. The posterior flagellar apparatus follows the "typical excavate" pattern of a splitting right root supported by fibres "I,"B," and "A," a "composite" fibre, a singlet root, and a left root (LR) with a "C" fibre. The B fibre originates against the LR--a synapomorphy of the taxon Fornicata--supporting the assignation of Ergobibamus to Fornicata, along with diplomonads, retortamonads, and other CLOs. Distinctive features of E. cyprinoides include the complexity of the AR, which is intermediate between Hicanonectes, and Carpediemonas and Dysnectes, and a dorsal extension of the C fibre.     

Molecular phylogenetic analysis places Percolomonas cosmopolitus within Heterolobosea: evolutionary implications

Percolomonas cosmopolitus is a common free-living flagellate of uncertain phylogenetic position that was placed within the Heterolobosea on the basis of ultrastructure studies. To test the relationship between Percolomonas and Heterolobosea, we analysed the primary structure of the actin and small-subunit ribosomal RNA (SSU rRNA) genes of P. cosmopolitus as well as the predicted secondary structure of the SSU rRNA. Percolomonas shares common secondary structure patterns of the SSU rRNA with heterolobosean taxa, which, together with the results of actin gene analysis, confirms that it is closely related to Heterolobosea. Phylogenetic reconstructions based on the sequences of the SSU rRNA gene suggest Percolomonas belongs to the family Vahlkampfiidae. The first Bayesian analysis of a large taxon sampling of heterolobosean SSU rRNA genes clarifies the phylogenetic relationships within this group.     

Culture and Phylogenetic Characterization of Trichomitus trypanoides Duboscq & Grassè 1924, n. comb.: a Trichomonad Flagellate Isolated from the Hindgut of the Termite Reticulitermes santonensis Feytaud

ABSTRACT. A trichomonad flagellate strain R1 was isolated from the hindgut contents of the termite Reticulitermes santonensis Feytaud. The flagellate was cultivated at 28° C in anaerobic medium containing yeast extract, minerals and vitamins. The isolate fed on living bacteria. It showed the typical morphological and ultrastructural features of the trichomonads. closely resembling Trichomitus trypanoides. In order to determine its phylogenetic position the small subunit ribosomal DNA (SSU rDNA) of the flagellate was amplified in vitro using the polymerase chain reaction (PCR), cloned in a plasmid vector and sequenced. Comparison of the obtained sequence with so far available SSU rRNA/rDNA sequences showed strongest similarity (89%) to the sequence of Tritrichomonas foetus. The phylogenetic analysis with parsimony and distance matrix methods placed Trichomitus trypanoides strain R1 near by the root of the phylogenetically so far analyzed eukaryotic organisms. This confirms that termites harbour hindgut symbionts, which originate from very early evolved eukaryotes.     

Esquamula lacrimiformis n. g., n. sp., a New Member of Thaumatomonads that Lacks Siliceous Scales

We report a new naked cercozoan flagellate, Esquamula lacrimiformis n. g., n. sp., collected from a sandy beach in Japan. Its cells were 4.5–11.3 μm in length and 3.9–8.8 μm in width and possess two unequal flagella. Cells move in a smooth gliding motion and have a trailing long posterior flagellum. Phylogenetic analyses with small and large subunit ribosomal RNA genes revealed that E. lacrimiformis forms a novel lineage within the Thaumatomonadida, the members of which are flagellates with siliceous scales. However, our light and electron microscopic observations indicated that E. lacrimiformis cells do not possess any siliceous structures. Furthermore, other morphological characteristics, such as the shape of the extrusomes and the structural arrangement of the microbody, were clearly different from those of previously described thaumatomonads. On the basis of a combination of these morphological observations and our phylogenetic analyses, we conclude that E. lacrimiformis should be treated as a new species of a new genus and placed into a new family, Esquamulidae n. fam., under Thaumatomonadida.     

Evolutionary history of "early-diverging" eukaryotes: the excavate taxon Carpediemonas is a close relative of Giardia

Diplomonads, such as Giardia, and their close relatives retortamonads have been proposed as early-branching eukaryotes that diverged before the acquisition-retention of mitochondria, and they have become key organisms in attempts to understand the evolution of eukaryotic cells. In this phylogenetic study we focus on a series of eukaryotes suggested to be relatives of diplomonads on morphological grounds, the "excavate taxa". Phylogenies of small subunit ribosomal RNA (SSU rRNA) genes, alpha-tubulin, beta-tubulin, and combined alpha- + beta-tubulin all scatter the various excavate taxa across the diversity of eukaryotes. But all phylogenies place the excavate taxon Carpediemonas as the closest relative of diplomonads (and, where data are available, retortamonads). This novel relationship is recovered across phylogenetic methods and across various taxon-deletion experiments. Statistical support is strongest under maximum-likelihood (ML) (when among-site rate variation is modeled) and when the most divergent diplomonad sequences are excluded, suggesting a true relationship rather than an artifact of long-branch attraction. When all diplomonads are excluded, our ML SSU rRNA tree actually places retortamonads and Carpediemonas away from the base of the eukaryotes. The branches separating excavate taxa are mostly not well supported (especially in analyses of SSU rRNA data). Statistical tests of the SSU rRNA data, including an "expected likelihood weights" approach, do not reject trees where excavate taxa are constrained to be a clade (with or without parabasalids and Euglenozoa). Although diplomonads and retortamonads lack any mitochondria-like organelle, Carpediemonas contains double membrane-bounded structures physically resembling hydrogenosomes. The phylogenetic position of Carpediemonas suggests that it will be valuable in interpreting the evolutionary significance of many molecular and cellular peculiarities of diplomonads.     

Cryptic diversity of free-living parabasalids, Pseudotrichomonas keilini and Lacusteria cypriaca n. g., n. sp., as inferred from small subunit rDNA sequences

Ultrastructural and molecular phylogenetic evidence indicate that the Parabasalia consists of seven main subgroups: the Trichomonadida, Honigbergiellida, Hypotrichomonadida, Tritrichomonadida, Cristamonadida, Spirotrichonymphida, and Trichonymphida. Only five species of free-living parabasalids are known: Monotrichomonas carabina, Ditrichomonas honigbergii, Honigbergiella sp., Tetratrichomonas undula, and Pseudotrichomonas keilini. Phylogenetic analyses show that free-living species do not form a clade and instead branch in several different positions within the context of their parasitic relatives. Because the diversity of free-living parabasalids is poorly understood, the systematics of these lineages is in a significant state of disarray. In order to better understand the phylogenetic distribution of free-living parabasalids, we sequenced the small subunit rDNA from three different strains reminiscent of P. keilini; the strains were isolated from different geographical locations: (1) mangrove sediments in Japan and (2) sediments in Cyprus. These data demonstrated that the free-living parabasalids P. keilini and Lacusteria cypriaca n. g., n. sp., form a paraphyletic assemblage near the origin of a clade consisting mostly of parasitic trichomonadids (e.g. Trichomonas vaginalis). This paraphyletic distribution of similar morphotypes indicates that free-living trichomonadids represent a compelling example of morphostasis that provides insight into the suite of features present in the most recent free-living ancestor of their parasitic relatives.     

Ultrastructure and Molecular Phylogeny of Iotanema spirale gen. nov. et sp. nov., a New Lineage of Endobiotic Fornicata with Strikingly Simplified Ultrastructure

Fornicata (Metamonada) is a group of Excavata living in low‐oxygen environments and lacking conventional mitochondria. It includes free‐living Carpediemonas‐like organisms from marine habitats and predominantly parasitic/commensal retortamonads and diplomonads. Current modest knowledge of biodiversity of Fornicata limits our ability to draw a complete picture of the evolutionary history in this group. Here, we report the discovery of a novel fornicate, Iotanema spirale gen. nov. et sp. nov., obtained from fresh feces of the gecko Phelsuma madagascariensis. Our phylogenetic analyses of the small subunit ribosomal RNA gene demonstrate that I. spirale is closely related to the free‐living, marine strain PCS and the Carpediemonas‐like organism Hicanonectes teleskopos within Fornicata. Iotanema spirale exhibits several features uncommon to fornicates, such as a single flagellum, a highly reduced cytoskeletal system, and the lack of the excavate ventral groove, but shares these characters with the poorly known genus Caviomonas. Therefore, I. spirale is accommodated within the family Caviomonadidae, which represents the third known endobiotic lineage of Fornicata. This study improves our understanding of character evolution within Fornicata when placed within the molecular phylogenetic context.     

Tsukubamonas globosa n. gen., n. sp., a novel excavate flagellate possibly holding a key for the early evolution in "Discoba"

We report the ultrastructure and phylogenetic position of a free-living heterotrophic flagellate, Tsukubamonas globosa n. gen., n. sp. This flagellate was isolated from a pond in the University of Tsukuba, Japan. Under light microscopy, the spherical vegetative cells were naked and highly vacuolated, and always swam with rotating motion. Electron microscopic observations revealed that T. globosa possessed a ventral feeding groove, which is one of the hallmark characteristics of the supergroup Excavata. The position of T. globosa was unresolved in the small subunit ribosomal RNA phylogeny. On the other hand, a multigene phylogeny using α-tubulin, β-tubulin, actin, heat shock protein 90, and translation elongation factor 2 robustly united T. globosa with members of the "Discoba" clade of Excavata, composed of jakobids, euglenozoans, and heteroloboseans, although the precise position of T. globosa in this clade remained unresolved. Our detailed morphological comparisons elucidated that T. globosa possessed a novel set of morphological features, and could not be classified into any taxa in the Discoba clade. Instead we classified T. globosa into Tsukubamonadidae n. fam. under Tsukubamonadida n. ord.     

Notothrix halsei gen. n., sp. n., representative of a new family of freshwater cladocerans (Branchiopoda, Anomopoda) from SW Australia, with a discussion of ancestral traits and a preliminary molecular phylogeny of the order

The parthenogenetic female of a new anomopod crustacean, Notothrix halsei gen. n. et sp. n., is described from Lake Angove and found in five other sites in SW Australia. Although macrotrichid-like at first glance, a detailed morphological study including thoracic appendages revealed a set of primitive characters and similarities with primitive families, in particular with the Eurycercidae and Acantholeberidae. Ancestral traits of Notothrix gen. n. comprise: (i) a single large head pore; (ii) second maxilla; (iii) incomplete dorsal merger of valves; (iv) second antenna with a three- and a four-segmented branch; (v) six trunk limbs; (vi) two setae on a sixth endite in the first limb, vs. complete row of posterior setae on the second limb; (vii) large number of setae on exopodites III–V; (viii) well-developed gnathobase V; and (ix) massive postabdomen with wide, telson-like terminus between end-claws that show complex spinulation but no basal spine. Analysis of the complete 18S (SSU) rRNA gene sequence including taxa from all but four anomopod families and using Ctenopoda as an outgroup, confirms our separation of the new taxon, the Nototrichidae fam. n. Although different alignments resulted in different trees, the analyses confirm an isolated position of Notothrix , which has the shortest SSU rRNA gene length known for anomopods. However, the phylogenies derived from a comparison of 18S rRNA gene sequences between families of the order Anomopoda, does not resolve the descent of the various family groups.     

Morphology and Phylogeny of Two Novel Ciliates,Arcanisutura chongmingensis n. gen., n. sp. and Naxella paralucida n. sp. from Shanghai,China

The morphologies of two novel ciliates, Arcanisutura chongmingensis n. gen., n. sp. and Naxella paralucida n. sp., collected from Shanghai, China, have been investigated using live observation and silver staining methods. Arcanisutura n. gen. can be easily distinguished from related genera by its inconspicuous, oblique anterior suture. Arcanisutura chongmingensis n. sp. is mainly recognized by its elongated body with a tail‐like posterior end, 25–33 somatic kineties, and 4–11 excretory pores. Naxella paralucida n. sp. can be distinguished from its congeners based on its two short nassulid organelles, fusiform trichocysts, 37–49 somatic kineties, and 16 nematodesmal rods. The small‐subunit (SSU) rRNA gene sequences of these two species are presented, revealing the phylogenetic positions of Arcanisutura and Naxella. Phylogenetic analyses show that Arcanisutura forms a sister clade to other synhymeniid genera, namely, Chilodontopsis, Orthodonella, and Zosterodasys; Naxella is most closely related to Nassula spp. and is located within the monophyletic clade of the family Nassulidae.     

Phylogenetic position of Sphaerospora testicularis and Latyspora scomberomori n. gen. n. sp. (Myxozoa) within the marine urinary clade

An amendment of the family Sinuolineidae (Myxosporea) is proposed in order to include a newly described genus Latyspora n. gen. The type species Latyspora scomberomori n. gen. n. sp. is a coelozoic parasite in the kidney tubules of Scomberomorus guttatus. In addition to the morphological and molecular characterization of L. scomberomori n. gen. n. sp., we also present novel SSU rDNA data on Sphaerospora testicularis, a serious parasite of Dicentrarchus labrax. Performed phylogenetic analyses revealed that both species cluster within the marine urinary clade encompassing the representatives with a shared insertion within their V4 SSU rRNA region and grouping according to the shape of their spores' sutural line and their similar tissue tropism in the host. Sphaerospora testicularis is the closest relative to Parvicapsula minibicornis within the Parvicapsula subclade and L. scomberomori n. gen. n. sp. is the basal species of the Zschokkella subclade. The phylogenetic position of S. testicularis, outwith the basal Sphaerospora sensu stricto clade, and its morphology suggest it being a non-typical Sphaerospora. The sequence data provided on S. testicularis can help in future revisions of the strongly polyphyletic genus Sphaerospora. We recommend re-sequencing of several sphaerosporids as an essential step before such taxonomic changes are accomplished.     

Mesostigmatophyceae, a new class of streptophyte green algae revealed by SSU rRNA sequence comparisons

Complete nuclear-encoded SSU rRNA sequences have been obtained from three taxa of streptophyte green algae (Klebsormidium nitens, Nitella capillaris, Chaetosphaeridium globosum) and two strains of the scaly green flagellate Mesostigma viride. Phylogenetic analyses of 70 taxa of Viridiplantae (Chlorophyta and Streptophyta) and 57 taxa of streptophyte green algae and embryophyte plants using distance, parsimony and likelihood methods revealed a novel monophyletic lineage among the Streptophyta comprising the genera Mesostigma and Chaetosphaeridium. This lineage is described here as the Mesostigmatophyceae classis nova. Our analyses demonstrate that (1) scaly green flagellates (prasinophytes) are polyphyletic, (2) a scaly green flagellate is a member of the Streptophyta and forms a clade with the oogamous, filamentous Chaetosphaeridium to the exclusion of all other known streptophyte green algae, (3) a previously published SSU rRNA sequence of Chaetosphaeridium (AF113506) is chimeric and contains part of a fungal SSU rRNA, and (4) the phylogenetic relationships between the Mesostigmatophyceae and other streptophyte green algae remain unresolved by SSU rRNA sequence comparisons.     

Morphology and Molecular Phylogeny of Two New Marine Euplotids,Pseudodiophrys nigricans n. g., n. sp., and Paradiophrys zhangi n. sp. (Ciliophora: Euplotida)

ABSTRACT. The morphology, infraciliature, and molecular phylogeny of Pseudodiophrys nigricans n. g., n. sp., and Paradiophrys zhangi n. sp., isolated from a sandy beach near Qingdao, China, were investigated. Pseudodiophrys is characterized by the Diophrys‐like ciliature pattern, but having only a single, reduced undulating membrane. Pseudodiophrys nigricans, the type species by monotypy, is described from live and silver‐impregnated specimens. Paradiophrys zhangi is similar to the type species Paradiophrys irmgard but can be recognized by its border body and the number (7 vs. 8–10) and arrangement (in rows vs. sparsely distributed) of the frontoventral cirri. Small subunit (SSU) rRNA gene sequence data support the validity of both species. Phylogenetic analyses based on the SSU rRNA gene sequence data currently available for uronychiids and other related taxa indicate that P. nigricans is most closely related to Diophrys scutum and Diophrys apoligothrix, while P. zhangi clusters most closely with Apodiophrys ovalis within a clade that also includes two other Paradiophrys species.     

Two New Diophrys‐Like Genera and Their Type Species,Apodiophrys ovalis n. g., n. sp. and Heterodiophrys zhui n. g., n. sp. (Ciliophora: Euplotida), with Notes on Their Molecular Phylogeny

ABSTRACT. Based on both morphological and molecular information, two new euplotid genera Apodiophrys n. g. and Heterodiophrys n. g. are described in the present paper. Apodiophrys n. g. is defined as sculptured Diophryinae with bipartite adoral zone; frontoventral cirri arranged in Diophrys‐pattern; marginal cirri located in two clearly separated groups. Heterodiophrys n. g. is recognizable by the combination of Diophrys‐like frontoventral cirri and the unique structure of several marginal cirri that are arranged in a long row. The type species for both new genera, Apodiophrys ovalis n. sp. and Heterodiophrys zhui n. sp., collected from southern China sea, are described. The small subunit rRNA (SSU rRNA) gene sequences for both new taxa are determined. Phylogenetic analyses based on these data indicate that Apodiophrys is most closely related to Paradiophrys, which then clusters with Uronychia species. Thus, Apodiophrys–Paradiophrys is separated from other typical Diophrys‐like genera in the SSU rRNA gene trees. The new genus Heterodiophrys is basal to the sister group of Diophrys–Diophryopsis, hence belongs to the “core”Diophrys‐complex.     

Molecular Phylogeny and Surface Morphology of Marine Archigregarines (Apicomplexa), Selenidium spp., Filipodium phascolosomae n. sp., and Platyproteum n. g. and comb. from North-Eastern Pacific Peanut Worms (Sipuncula)

ABSTRACT. The trophozoites of two novel archigregarines, Selenidium pisinnus n. sp. and Filipodium phascolosomae n. sp., were described from the sipunculid Phascolosoma agassizii . The trophozoites of S. pisinnus n. sp. were relatively small (64–100 μm long and 9–25 μm wide), had rounded ends, and had about 21 epicytic folds per side. The trophozoites of F. phascolosomae n. sp. were highly irregular in shape and possessed hair-like surface projections. The trophozoites of this species were 85–142 μm long and 40–72 μm wide and possessed a distinct longitudinal ridge that extended from the mucron to the posterior end of the cell. In addition to the small subunit (SSU) rDNA sequences of these two species, we also characterized the surface morphology and SSU rDNA sequence of Selenidium orientale , isolated from the sipunculid Themiste pyroides . Molecular phylogenetic analyses demonstrated that S. pisinnus n. sp. and S. orientale formed a strongly supported clade within other Selenidium and archigregarine-like environmental sequences. Filipodium phascolosomae n. sp. formed the nearest sister lineage to the dynamic, tape-like gregarine Selenidium vivax . Overall, these data enabled us to reassess the molecular systematics of archigregarines within sipunculid hosts and make the following revisions: (1) Filipodium was transferred from the Lecudinidae (eugregarines) to the Selenidiidae (archigregarines), and (2) Platyproteum n. g. was established for Platyproteum vivax n. comb. (ex. S. vivax ) in order to account for the highly divergent morphological features and better resolved phylogenetic position of this lineage.     

The Morphology,Ultrastructure and SSU rRNA Gene Sequence of a New Freshwater Flagellate,Neobodo borokensis n. sp. (Kinetoplastea,Excavata)

A small free‐living freshwater bacteriotrophic flagellate Neobodo borokensis n. sp. was investigated by electron microscopy and analysis of its SSU ribosomal RNA gene. This protist has paraxonemal rods of typical bodonid structure in the flagella, mastigonemes on the proximal part of the posterior flagellum, two nearly parallel basal bodies, a compact kinetoplast, and discoid mitochondrial cristae. The flagellar pocket is supported by three microtubular roots (R1, R2 and R3) originating from the kinetosome. The cytopharynx is supported by the root R2, a microtubular prism, cytopharynx associated additional microtubules (CMT) and cytostome associated microtubules (FAS) bands. Symbiotic bacteria and small glycosomes were found in the cytoplasm. Cysts have not been found. The flagellate prefers freshwater habitats, but tolerates salinity up to 3–4‰. The overall morphological and ultrastructural features confirm that N. borokensis represents a new species of the genus Neobodo. Phylogenetic analysis of SSU rRNA genes is congruent with the ultrastructure and strongly supports the close relationship of N. borokensis to Neobodo saliens, N. designis, Actuariola, and a misidentified sequence of “Bodo curvifilus” within the class Kinetoplastea.     

Mataza hastifera n. g., n. sp.: a possible new lineage in the Thecofilosea (Cercozoa)

A new cercozoan flagellate Mataza hastifera n. g., n. sp. is described from a surface seawater sample collected in Tokyo Bay. Cells are 3-5 μm in diameter and have two flagella. The cells alternate between swimming and stationary states in culture. Swimming cells have a nodding motion. Phylogenetic analyses using small subunit rDNA sequences demonstrate that M. hastifera belongs to the clade comprised of only environmental sequences closely related to thecofilosean cercozoans. Ultrastructural observations reveal that M. hastifera is quite similar to members of Cryomonadida, an order in Thecofilosea, and especially to Cryothecomonas spp. The cell of M. hastifera is covered with a thin double-layered theca and possesses a cylinder-shaped extrusome, as reported from cryomonads. On the other hand, the funnel that is characteristic of cryomonads was not found in the flagellar pit of M. hastifera. Combining both morphological and molecular analyses, we conclude that M. hastifera is a new lineage in Thecofilosea and suggest that Thecofilosea may be a larger group than previously thought.     

Moramonas marocensis gen. nov., sp. nov.: a jakobid flagellate isolated from desert soil with a bacteria-like,but bloated mitochondrial genome

A new jakobid genus has been isolated from Moroccan desert soil. The cyst-forming protist Moramonas marocensis gen. nov., sp. nov. has two anteriorly inserted flagella of which one points to the posterior cell pole accompanying the ventral feeding groove and is equipped with a dorsal vane—a feature typical for the Jakobida. It further shows a flagellar root system consisting of singlet microtubular root, left root (R1), right root (R2) and typical fibres associated with R1 and R2. The affiliation of M. marocensis to the Jakobida was confirmed by molecular phylogenetic analyses of the SSU rRNA gene, five nuclear genes and 66 mitochondrial protein-coding genes. The mitochondrial genome has the high number of genes typical for jakobids, and bacterial features, such as the four-subunit RNA polymerase and Shine–Dalgarno sequences upstream of the coding regions of several genes. The M. marocensis mitochondrial genome encodes a similar number of genes as other jakobids, but is unique in its very large genome size (greater than 264 kbp), which is three to four times higher than that of any other jakobid species investigated yet. This increase seems to be due to a massive expansion in non-coding DNA, creating a bloated genome like those of plant mitochondria.