Order Ostracoda—”ostracon” means shell in Greek
•Abundant in freshwater and marine environments. > 8000 living species. Freshwater ostracods are usually
smaller than 1 mm.
> 10,000 or so fossil species from the Late Cambrian period (about 500 million years ago) to recent times.
•Their great abundance and widespread distribution have made them useful index fossils for dating marine
sediments, notably in oil exploration.
•the most complete fossil record of any crustacean group.
•littoral zone among the submerged plants, but also in the profundal benthos.
•swim smoothly with appendages extended from between the two halves of their carapace.
• When disturbed, they withdraw their limbs and clamp the halves of their tiny shells tightly together.
•Sexes are separate and females brood eggs in the chamber of the carapace.
•males must tranfer sperm to the female before the eggs are laid and a special long leg is used to do this.
•Some freshwater species are parthenogenetic, and males of these species are unknown.
Ostracods are little more than a head.
•the typical 5 pr of crustacean head
appendages,
•but only 1-3 pr of thoracic appendages
•and a caudal fork at the posterior end.
Ostracods have no growth rings on the
carapace because it is shed at each moult
http://www.snv.jussieu.fr/bmedia/PetitBuffon/crustaces/ostracodes/284BB.jpg
The famous white cliffs of Dover are composed mainly of Ostracod fossils
http://www.uky.edu/OtherOrgs/KPS/images/ostracodnelson.jpg
Cypris is shown in typical feeding mode, with its shell
opened to allow the mouth parts to graze epiphytes
from a filament of Oedogonium, propelled by two pairs
of legs bearing long claws and a caudal furca. The
prominent black spot of the single eye can be seen
near the hinge of the shell.
http://www.micrographia.com/specbiol/crustac/ostraco/ostr0100/cypris00.htm
Candona species are generally white all over and live in the profundal sediments of lakes
Candona candida—a species found in profundal lake sediments
http://biology.missouristate.edu/ostracods/Ostracod%20Website/Candona%20distincta%202a.jpg
Candona decora
Candona ohioensis
Candona caudata
Candona indigena
Cyclocypris ovum
Cyclocypris ampla
Order Amphipoda—”amphi means both”
Mostly marine benthic organisms,>7000 spp
•>100 fw species, adults 5-30 mm long
•elongate and more or less compressed
laterally. no carapace,
•head with chewing mouthparts, omnivores
(algae detritus, large specimens carnivorous)
•2 pr antennae, 1pr mandibles, 2 pr maxillae
• 7 thoracic appendages
•1pr maxillipeds, 2pr gnathopods, 5 pr
walking/swimming legs
.
•5 pr pleopods, abdominal appendages
•Eggs held within a brood pouch on the
ventral side of the females thorax—young
leave the pouch when the female moults
•Males have enlarged gnathopods for holding
the female during precopula
•Gammaridae—Gammarus
•Taltridae—Hyalella
•Pontoporeidae--Diporeia
Amphipod appendages
Mouthparts of an amphipod
http://www.faunaitalia.it/keys/images/gammar1.gif
In some species the enlarged 2nd gnathopod of the male is very conspicuous
Gammarus in precopula, the male will carry the female for about a
week or so until she moults, at which point he will insert the
spermatophore
http://www.shef.ac.uk/aps/mbiolsci/amy/gammarus.jpg
Gammarus fasciatus, the most common gammarid in eastern Canada
Gammarus lacustris—found throughout the northern hemisphere in glaciated
regions, the only gammarid in Alberta,
http://www.usask.ca/biology/skabugs/Candlelakebugs/CLcrustacea/gammarus.JPG
Hyalella azteca—found throughout North and South America
One of the two amphipod species found in Alberta
Diporeia, a profundal benthic amphipod in large lakes
This is what we call a glacial relict, because it only occurs in large lakes that
were once part of a proglacial lake.
Proglacial lakes
•Following the retreat of the last
glaciation most of the Canadian landscape
was covered by proglacial lakes
•Species tolerant of coldwater (salmonid
and coregonids) became very widespread.
•Opportunities for dispersal of
cool and warmwater species were much more limited
because these water bodies disappeared with the ice.
Waterton Lakes were at one time part of a proglacial lake system, and the
upper lake has both Diporeia and Mysis.
Amphipods can feed and grow during winter on under ice diatoms
http://www.oceanexplorer.noaa.gov/explorations/02arctic/logs/mis_sum_ice/media/amphipod_600.jpg
Lake Baikal—the largest and oldest lake in the world, > 1700 m deep
Has more than 270 species of amphipods over 95% of which occur nowhere else
Lake Baikal has a
rich endemic fauna of
molluscs and fish as
well, and even has its
own endemic seal
population
http://www.raphaelk.co.uk/web%20pics/Russia/first/Lake%20Baikal.jpg
Endemic amphipods of Lake Baikal
Pallasea cancellus
Acanthogammarus maximus
Paragarjajewia petersi
Odontogammarus calcaratus
Boeckaxelia potanini
http://www.naturalsciences.be/amphi/eulimnogam.htm