|
|
|||||||||||
|
|
|||||||||||
 |
 |
||||||||||
|
|||||||||||
A Diversity of Animals
Four classes of mollusk occur in the Chesapeake Bay. Gastropods, or snails, have a single shell, and include such animals as periwinkles, whelks, nudibranchs, land slugs and slipper shells. The class Cephalopoda includes species of squid and octopus, the most highly developed mollusks, with large heads and tentacles, and the chambered nautilus, which has a complex external shell. The bivalves, including oysters, clams and mussels, have two shells and a foot for burrowing into soft sediments. They feed either by filtering water through a set of gills, or by sucking organic material from the bottom through a siphon-like organ. Chitons, from the class Polyplacophora, are elliptical animals that use a sucker-like foot to graze slowly for food over rocky surfaces. The higher salinity regions of the mouth of the Bay contain one species from this class, the common eastern chiton. Echinoderms (from the Greek, which means "spiny-skinned") are ancient animals that are radially symmetrical, with no head or tail, and generally have appendages radiating from a central axis in a pattern or multiple of five. They move using hundreds of tiny tubular, suction-like "feet," and use these feet to open the shells of clams and oysters, which they then consume. The sea squirt, a sessile marine animal that looks like a shapeless, soft potato, has a thick "tunic" or skin covering its body, and an opening at either end. One end sucks in water while the other expels water filtered of its plankton and debris. They range in diameter from less than one inch to three inches. In larval phases, the sea squirt has a notochord, which in other animal species would develop into a spinal column, but which the sea squirt eventually loses. Sponges that live in the Bay are not the large soft sponges one uses in the bath; instead they are tightly formed organisms that encrust pilings and rocks, or which sometimes have long projections. Their porous fibers are the framework for living cells. Water enters the sponge’s tiny chambers, bringing food and oxygen to these cells. Anthozoans (the sea anemones and corals) belong to the phylum Cnidaria, which includes the jellyfish, but this class has no medusal phase in their development, unlike the sea nettles commonly found in the Bay. Sea anemones are soft-bodied polyps that either attach to a firm substrate or bury themselves in bottom sediments. Bay anemones are less flamboyantly colored than tropical species, and can appear formless and jellylike in areas where the tides have receded, but underwater they have graceful, flowerlike forms. Soft coral colonies, each with eight featherlike tentacles, are unusual in the Chesapeake Bay; however one species, the whip coral, can be found in subtidal waters near the mouth of the Bay. Arthropods have jointed external skeletons, or exoskeletons, and grow by molting or shedding their old shell and forming a new, larger one. There are two major groups of arthropods: the first includes horseshoe crabs, scorpions and terrestrial spiders (making the horseshoe crab a closer relative to the garden spider than to the blue crab). The second group includes crustaceans such as crabs, lobsters, shrimp, and barnacles and thousands of species of terrestrial and aquatic insects, many of which inhabit the Chesapeake Bay region. To bookmark this page, please use this URL: http://www.chesapeakebay.net/animals.htm For more information, contact the Chesapeake
Bay Program Office: Terms
of Use | Privacy Policy
| Contact Us |
|||||||||||
 |
 |
||||||||||
The
Chesapeake Bay contains an amazingly rich diversity of aquatic and terrestrial
species, some common, others rare, or at least rarely seen. For example,
the Bay is home to many animals belonging to the phylum Mollusca, which
includes species of squid, snails, whelks and octopus. Echinoderms,
including sea stars, sea urchins and sand dollars, are prevalent in
high-salinity Bay waters. Tunicates, including the familiar sea squirt,
from the phylum Urochordata, are also common in the Bay. Other animals
common to the Bay include sponges (phylum Porifera), some species of
coral and sea anemones (phylum Cnidaria) and the thousands of species
belonging to the phylum Arthropoda, which includes everything from insects
to all species of crabs and spiders. Eighty percent of all known species
in the world belong to this phylum.
