Seminar # 1:
Marine Invertebrate Classification
Standard Classification
Developed by Carolus Linnaeus in the
18th century
Organizes organisms into groups and
subgroups based on evolutionary
relationships
Often revised when new relationships
are discovered (DNA evidence)
Example: Pseudocalanus spp.
Classification levels:
Kingdom (broad)
Phylum
Class
Order
Family
Genus
Species (specific)
Marine Invertebrates
Kingdom: Animal
Marine Invertebrates are those animals that
do not have a backbone and include:
Phylum
Phylum
Phylum
Phylum
Phylum
Phylum
Phylum
Phylum
Porifera
Cnidaria
Ctenophora
Mollusca
Annelida
Arthropoda
Bryzoa
Echinodermata
Phylum Porifera (Sponges)
Animals that form encrusting colonies that
attach themselves to underwater objects
They have a porous structure (Spongebob
Squarepants is an example)
Seawater is pumped through its body by
flagella (microscopic filaments)
Body is supported by a skeletal framework
composed of tiny needlelike structures called
spicules
Examples of Phylum Porifera:
Phylum Cnidaria (stinging
jellies)
Either attached to an underwater object
or free swimming/floating
Gelatinous body that is usually umbrella
shaped or bell shaped
The tentacles of this phylum all have
stinging cells
Examples of Phylum Cnidaria:
Phylum Ctenophora (nonstinging jellies)
Free swimming or floating
Clear gelatinous bodies with rows of
comb-like plates made of cilia (small
hairs) that help to move the jelly
around
No stinging cells
Also called comb jellies
Examples of Phylum Ctenophora:
Phylum Mollusca
Focus on Classes Gastropoda and
Bivalvia
Gastropods have a single shell (coiled
or uncoiled)
Bivalves have two shells (valves) joined
by a hinge
Examples of Gastropods:
Examples of Bivalves:
Phylum Annelida
Focus on Class Polychaeta (Under the
microscope these look like worms with
a walrus beard)
Sometimes hard to identify (some
require a microscope to distinguish)
Worms that are segmented (divided
into ring-like sections) and have bristles
(setae) on each segment
Examples of Phylum Annelida:
Phylum Arthropoda
Focus on Classes Merostomata and Crustacea
“Joint-legged” with an external skeleton
Class Merostomata = horseshoe crabs!
Crustaceans are gill breathing
Primarily aquatic
2 pairs of antennae and 4 or more pairs of
legs and/or claws
Includes zooplankton!!!
Examples of Merostomata:
Examples of Crustacea:
Phylum Bryzoa
Highly branched
Can be calcified or soft
Forms crusts that cover a surface
Tend to be a common fouling organism
(meaning it grows on boat hulls,
mooring lines, pilings, lobster pots, and
other hard objects)
Examples of Phylum Bryzoa:
Phylum Echinodermata
Spiny-skinned
Usually rounded with bodies separated
into 5 parts
Have been known to scrub the sea floor
of all organisms (some are extremely
predatory)
Includes sea urchins, sand dollars, sea
stars, and sea cucumbers
Examples of Phylum
Echinodermata:
Phylum Chordata (not
invertebrates!)
Bag-like creatures often mistaken for
invertebrates
Their larvae (young) start out like
tadpoles with gills, a backbone, and a
nerve cord…like us
Often mistaken for sea anemones
Includes tunicates and sea squirts
Examples of Phylum Chordata: