Category America North – Atlantic Coast – sub-polar ecoregion

Asteroidea, but not A. vulgaris or A. forbsii

Sea stars (group name Stelleroidea) are sometimes called starfish, though lacking both vertebrae and fins, they are not real fish. There are two sub-types of sea stars: Asteroideas are the true sea stars and sun stars, whereas Ophiuroideas are brittle stars and basket stars.

Ophiuroid means ‘snake-like’, referring to the form and motion of the arms. The arms of brittle stars are easily broken off, but will regenerate in a few days to weeks. Sea stars can also regenerate arms that are broken off, but for most species, the central region of the body must remain intact Class Asteroidea, the true sea stars, contains about 1700 living species of these echinoderms...

Didemnum sp.

Tunicates are a group of marine animals that spend most of their short lives attached to docks, rocks or the undersides of boats. To most people they look like small, coloured plantlike growth. It often comes as a surprise to learn that they are actually more closely related to vertebrates like ourselves, than to most other invertebrate animals.

Nothing can be seen of a vertebrate relationship in the adult animals, but the tadpole-like larva has a notochord, (a stiff rod) in its tail. After hatching, this little creature, rarely more than 5mm long, swims for a few hours to find a spot somewhere on a solid surface...

Codium fragile subspecies Tomentosoides

Green sea fingers (Codium fragile) is a pale to dark green algal plant with very bush-like appearance. The branches are 5 – 10 mm in diameter, and rise from a disk shaped pad, known as a holdfast. The holdfast is responsible for keeping the plant securely fastened to rocks on the seabed. As the plant grows, the branches sub-divide into two new branches. It is an annual plant and reproduces during the summer.

Believed to be native to Japan, the sub-species tomentosoides is known locally as dead man’s fingers and is one of the most invasive seaweeds in the world. It is principally sub-tidal in the waters of the region to depths of 15m, but can be found in the inter-tidal zone...

Homarus americanus

Because they belong to the invertebrate phylum Arthropoda (see our Help pages for an explanation of taxonomic classification), lobsters are actually closely related to insects.

This relationship arises because of two main characteristics that they share: they all have an exoskeleton (outer skeleton) and they all have joint appendages. Lobsters are farther categorized into the class Crustacea, along with other marine organisms like crabs and shrimp. These crustaceans are distinguishable from other Arthropods with hard exoskeletons, like mussels and clams, because their shell is softer and more flexible. As lobsters have ten legs they also belong to the order Decapoda (derived from the Latin word, ten feet).

The American lobster (Homarus americanus), also known ...