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Species
Basic Characteristics of a Bivalve
Species of the class Bivalvia have soft bodies (characteristic
of their phylum, Mollusca) and are enclosed in a hard shell.
Bivalve mollusks include many species of clams, oysters, mussels,
and scallops. All the bivalves have shells divided into two halves,
hence their name.
Filter Feeders
Most bivalves are filter-feeders that trap fine food particles
in mucus that coats the gills and then use hair-like cilia to
transport the particles to the mouth. Water flows into the gill
chamber through an incurrent siphon, passes over the gills, and
then exits the mantle cavity through an excurrent siphon. Being
filter-feeders, most bivalves lead rather sedentary lives.
Soft Bodies with Strong Parts
Bivalves, being mollusks, are soft-bodied animals (from the Latin
molluscus, "soft"). They are protected by two
hard shells made of calcium carbonate which are drawn together
by powerful muscles.
All bivalves have a similar body plan with three main parts: a
muscular foot usually used for movement, a body mass containing
most of the internal organs, and a mantle, a heavy fold of tissue
that drapes over the body mass and may secrete a shell. Mussels secrete strong threads that tether to rocks, docks, boats,
and the shells of other animals.
Basic Characteristics of an Arachnid
There are over 57,000 species of scorpions, spiders, ticks, and
mites in the world that belong to Class Arachnida. Arachnids
have one or two main parts while insects have three. Arachnids
have eight pairs of appendages rather than six (chelicerae, pedipalps,
four pairs of walking legs) and are primarily terrestrial.
Lips for Arms
Spiders use their fanglike chelicerae (from the Greek cheilos,
"lips," and cheir, "arm"), equipped
with poison glands, to attack prey. As the chelicerae and pedipalps
chew the prey, the spider spills digestive juices onto the torn
tissues. The food softens, and the spider sucks up the liquid
meal.
Endangered Species
Of the 25 000 species of invertebrates that are known in British
Columbia, many are threatened by loss or degradation of their
habitats and are at risk because their ecosystems are at risk.
In the South Okanagan, hardly anything is known about the six
species of sun scorpions that are known from the south Okanagan
and few specimens of the Western Ridge Mussel have been found.
The environmentally sensitive, Western Ridge Mussel (Gonidea
angulata), is a rare and endangered mollusc in the Thompson-Okanagan
belonging to Class Bivalvia, Order Unionoida.
The sun-shy, Sun Scorpion (Eremobates gladiolus),
is an example of an endangered arachnid of the Class Arachnida,
Order Solpugida that lives in dry southern interior of the Okanagan
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