A Meiofauna How-To:
Minute, Sand-Dwelling Animals of Eagle Cove


How to get meiofaunal animals off the sand for observation

a. Place a sample of wet sediment in a small plastic vessel with a cap.
b. Put as much isotonic magnesium chloride as sediment into the cup. Isotonic MgCl2 is made up as a 7.5% solution (using MgCl2.6H20).
c. Cap and give 3-4 hard shakes.
d. Let the sand settle, and decant the liquid without any sand.
e. Search through the decanted liquid with a dissecting microscope, and transfer animals to slides with a glass pipette. Use a small nick of clay at each corner of a coverslip to prevent damage to the organisms.


What you might see

The possibilities are numerous, and not limited to the following:

a. Protists: a large, diverse group of single-cell organisms (see possibilities below)
b. Polychaetes: similar in body form to larger marine worms, they may be recognizable by clear body segmentation and chaete along the edges of the body, sometimes extended from parapodia
c. Nematodes: ubiquitous, thread-like, undulating
d. Gastrotrichs: "hairy-stomachs," these animals have a ciliated ventral side, cuticular spines along the body, and often two "toes" at the posterior end
e. Rotifers: the head end is crowned by a corona of beating cilia, sometimes with two posterior "toes"
f. Crustaceans: copepods, cladocerans and other microcrustacea, recognizable by segmentation and jointed appendages (including legs and antennae)
g. Tardigrades: "water bears," typically with 4-6 pairs of appendages and extensible claws or hooks
h. Miscellaneous random larval forms


More detail about likely protists you will see

a. Ph. Ciliophora (ciliates): use many cilia for locomotion, fast swimmer
b. Ph. Dinoflagellata (dinoflagellates): biflagellate with one traverse and one longitudinal flagellum. The cell has a longitundinal and an equatorial groove
c. Ph. Stramenopila (diatoms): photosynthetic, so typically brownish or greenish in color.  Often pillbox shaped from the plankton, elongate in sediment.  Supported by a test made of silica, carbonate, or protein
d. Ph. Rhizopoda (amoebas): locomotion involves extension of cytoplasm to make psuedopodia.
e. Ph. Euglenida (euglenids): most are biflagellate, the two flagella different lengths, many photosynthetic. Maintain their shape with an outer pellicle
f. Ph. Granuloreticulosa (foraminiferans): locomotion involves long, filamentous extensions of cytoplasm to make reticulopodia (these look like what you get if you throw a rock through a window).  Foraminiferan tests are made of coiled chambers of increasing size.