Someone here wanted Ebriids and Ellobiopsids. Since I'm still in a bit of Rhizarian mood, let's do Ebriids first. Just as you thought we couldn't get any more obscure than Phaeodaria...
Ebriids are biflagellate Cercozoans (see the Pawlowski & Burki 2009 Rhizaria tree in the Coelodiceras post for their phylogenetic neighbourhood) with a characteristic silica endoskeleton, permanently condensed nuclear chromatin and lack of cell wall or scales. They are rare and still unculturable, so very little is known about them. The taxon name derives from ebrius ('drunken' lat.) as they apparently swim in a strange fashion. (Hoppenrath & Leander 2006 Protist)
They feed on diatoms and dinos, likely using pseudopodia in their feeding (an interesting feature of Cercozoans is their affinity for pseudopodia despite being flagellate...) Interestingly, they too, like some dinos, can devour diatom chains in a process that seems similar to palium feeding. Due to their silicoflagelate nature, they have been caught up in the taxonomic chaos and have been considered to be dinos or radiolarians; they were thrown around between the two for decades, until the eerie Enlightenment through molecular biology placed them in Cercozoa. (all from Hoppenrath & Leander 2006)
(Hoppenrath & Leander 2006; arrow in A points to nucleus; scalebar: 10μm)
The silica endoskeleton leaves behind a nice fossil record stretching back to the Cretaceous, although very few modern species have been found (Hargraves 2002 Plankton Biol).
(Korhola & Grönlund 1999 J Paleolimnol. Silica Ebriid skeletons from Baltic sediment)
I wonder if their genomes too conceal some quirky stuff. Permanently condensed chromosomes tend to do that (see dinos; Euglenids have them too but nothing seems to be known about their genomes yet).
A bit tired and sleepy... apologies for low energy post today.
As for "just why is everything about dinoflagellates just so *%&$ing weird?"* - Simple. On the 7th day of creation, the intelligent designer took a break, got really high off some awesome shit he'd just finished creating, and made the protists. Dinos were created near the climax of his hallucinations, while ciliates were definitely made right AT the climax. Thus, ciliates are the Higher Eukaryotes, with dinos and the rest of Protista close behind. Now for a reading from the Book of Tom... oh, has anyone tried that while 'under influence'? Does it help?
*In case some are as clueless about dinos as I was less than a year ago, the following is some of the oddities:
- permanently condensed chromatin
- massive genomes (>10x that of humans)
- chromosome structure on crack
- mandatory trans-splicing of 5'-cap-bearing splice leaders onto mRNA transcripts. Ie each mRNA transcript must have another specific mRNA sequence attached to its beginning, otherwise it gets degraded. Interestingly, Trypanosomes and some genome in C.elegans do that too, and have polycistronic genes, which is highly unusual for eukaryotes. Ie. several genes following one promotor... more on that later sometime!
- tiny genomes
- rRNA assembled from fragments, some of which are imported from the nucleus
- some species: single gene linear chromosomes; some have long scrambled repeating permutations of three conserved mitochondrial genes (COX1,3; COB)
- post-transcriptional RNA editing; ie a transcript is made, and then some bases are modified prior to translation
- trans-splicing (of exons located on different loci) (usually splicing happens in cis, by remvoing a region between two exons; trans-splicing involves taking two exons from different regions and gluing them together.
- single-gene minicircles - genome consists of tiny circles usually containing a single gene and a replication origin sequence.
- closed mitosis (Nu envelope doesn't break apart; although not that unusual)
- prone to tertiary endosymbiosis (eg. Karlodinium, Karenia, Kryptoperidinium, Lepidodinium, Dinophysis)
- diversity of lifestyles, from endo- and ectoparasitism and endosymbiosis to myzocytosis (sucking prey through a 'straw') to palium-feeding; all while roughly half of them are photosynthetic
- Warnowiid dinos with... camera eyes!
Since it's kinda late and I'm sleepy and don't have time to reference all that... let's just pretend this footnote never happened, k? ^_~ I should blog about this properly later...
Hoppenrath, M., & Leander, B. (2006). Ebriid Phylogeny and the Expansion of the Cercozoa Protist, 157 (3), 279-290 DOI: 10.1016/j.protis.2006.03.002
Hargraves, P.E. (2002). The ebridian flagellates Ebria and Hermesinum Plankton Biology and Ecology, 49 (1), 9-16
Korhola, A., & Grönlund, T. (1999). Observations of Ebria tripartita (Schumann) Lemmermann in Baltic sediments Journal of Paleolimnology, 21 (1), 1-8 DOI: 10.1023/A:1008019504122
Information and Structure in Complex Systems
1 day ago in PLEKTIX