pregnant rotifer

Images made through a microscope. All subject types.

Moderators: Pau, rjlittlefield, ChrisR, Chris S.

bernhardinho
Posts: 563
Joined: Sun Aug 13, 2006 6:28 am
Location: Germany
Contact:

pregnant rotifer

Post by bernhardinho »

Hi again,

I've often encountered bdelloid rotifers featuring a second mastax in the middle of the body. I've often wondered, how that can be! Yesterday I found an explanation: it's the unborn offspring that we see. Some rotifers don't show the complicated mechanism of generation changes. The bdelloids multiply by parthenogenesis and their offspring hatch from the egg inside the mothers body. This can be cleary seen here:

400x

Image

Image


1000x

Image


Bernhard

ralfwagner
Posts: 438
Joined: Sat Aug 05, 2006 8:34 am
Location: Germany, Duesseldorf
Contact:

Post by ralfwagner »

Hello Bernhard,

very impressive shots and explanation of the second mastax. I assume you did these shots with your flash unity?

A few weeks ago I could see the mastax working even in an egg of a rotifer. ( http://www.photomacrography.net/forum/v ... hlight=egg ) .

bernhardinho
Posts: 563
Joined: Sun Aug 13, 2006 6:28 am
Location: Germany
Contact:

Post by bernhardinho »

Hi Ralf,

as a matter of fact, the critter was sort of trapped in a piece of plant detritus and didn't move very much, so I took the pics without the flash, with long exposure times (1/60 and 1/30).


All the best for 2007

Bernhard

Bruce Williams
Posts: 1120
Joined: Mon Oct 30, 2006 1:41 pm
Location: Northamptonshire, England
Contact:

Post by Bruce Williams »

Some very impressive photos Bernhard - informative too. The detail in the last pic is amazing!

Bruce

rjlittlefield
Site Admin
Posts: 21258
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Post by rjlittlefield »

I have read that the bdelloid rotifers are unique, in having a long evolutionary history with apparently no sexual reproduction at all. ("No sex for over 40 million years", says the title of one web page.)

A 2004 article in Proceedings of the National Academy of Sciences begins with this paragraph (emphasis added):
Sexual reproduction is nearly universal among multicellular organisms, and although asexual populations continually arise, they almost invariably suffer early extinction. The relatively brief evolutionary persistence of most asexual groups is seen in their failure to achieve high taxonomic rank and in the low degree of DNA sequence divergence between them and their nearest sexual relatives (1). Among higher-ranking animal taxa that have been considered candidates for ancient asexuality, many have proven on closer study to be sexual or of recent origin (1, 2). Thus, the abandonment of sexual reproduction is generally thought to be an evolutionary dead end. Against this generalization, however, rotifers of the class Bdelloidea stand out as an apparent exception. With some 370 described species (3, 4), they constitute the highest-ranking metazoan taxon in which males, hermaphrodites, and meiosis are unknown, eggs being formed from primary oocytes by mitosis (5, 6). The inference that bdelloids evolved asexually is further supported by the presence of chromosomes without morphological homologues and by the apparent lack of deleterious retrotransposons (5, 7, 8 ).
Much further information can be obtained by Googling on search strings like bdelloid rotifers dead-end (which is how I turned up the one quoted above). Copies of the above article can be downloaded as PDF from the PNAS web site at http://www.pnas.org/content/vol101/issue6/ .

Bdelloids are interesting critters, indeed!

--Rik

Bruce Williams
Posts: 1120
Joined: Mon Oct 30, 2006 1:41 pm
Location: Northamptonshire, England
Contact:

Post by Bruce Williams »

Thanks for that link Rik - very interesting.

...but why the "almost silent" B in Bdelloid? It even ties my brain in knots let alone my tongue :lol:

From Wikipedia:
Bdelloids (pronounced with a mouthed and almost silent B rather like "deltoids" with a silent 't')
Apparently from the Greek βδελλα or bdella, meaning leech (also from Wikipedia).

Bruce

Ken Ramos
Posts: 7208
Joined: Thu Jul 27, 2006 2:12 pm
Location: lat=35.4005&lon=-81.9841

Post by Ken Ramos »

All three images are good there Bernhard, I have to agree though, I do like the second one much better. Lots of detail, the mastix and the eyespots are well defined, nice work. :D

Charles Krebs
Posts: 5865
Joined: Tue Aug 01, 2006 8:02 pm
Location: Issaquah, WA USA
Contact:

Post by Charles Krebs »

Love that last shot... it's all curled up, staring out, and ready to go!

Post Reply Previous topicNext topic