Marine Invertebrate Gallery
These pictures were taken of marine invertebrates sampled in Pleasant Bay in the summer of 2014. The species pictured are a selection of the over 80 species found. Photographs were made using a microscope at the Cape Cod National Seashore North Atlantic Coastal Lab
Crustaceans Polychaete Worms Bivalves Other Invertebrates
These alien-looking amphipods attach to algae and eelgrass with their rear legs and can be extremely abundant. People most often encounter them when pulling up their anchor.
These amphipods build muddy tubes in mixed algae, often in estuaries and have distinctly larger second antennae.
This tube-building amphipod is often found in muddy and silty sediment, and has an unusually large first claw.
These amphipods burrow in sand and mud, and have a “hood” coming to a point over their upper antennae, with large dark eyes.
These amphipods burrow in shelly-sandy mud and have distinctly short, stubby antennae.
As their name suggests, Haustoriidae burrow in sandy sediment and have highly reduced sensory features with no apparent eyes.
These tube-building amphipods bury in mud and sandy environments and are extremely common in our samples.
This amphipod species tends to be larger than other amphipods, with a larger first claw and thicker, shorter second antennae.
This isopod clings to eelgrass and seaweed, and has a distinct telson (tail) shaped like curly brackets.
This common isopod is found on muddy shores, pilings, and decaying eelgrass. It looks similar to a trilobite fossil as its name suggests. (mm scale)
This unusual-looking cumacean with a short, oval-shaped body and a long narrow tail is found in shallow water in soft sediment.
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Opal worms live in mud and sand and beneath stones. They often have a shimmering, glossy appearance that gives them their name.
These worms burrow in mud and gravel and under rocks. The long, stringy filaments on the body segments towards the head are gills.
Thread worms are found in sandy mud, and are often one of the first species to colonize an area that has been affected by pollutants.
These worms are often quite tiny and can be found under stones, shells, seaweeds, and other benthic organisms. They are distinguished by their fused or partially fused palps (fleshy protrusions from the head) and three antennae.
Mudworms build soft, mud-covered vertical tubes attached to shells and hard objects in shallow water. They can be identified by their two long tentacles and two banded gills protruding from their head segment.
These worms can be found burrowing in mud, and can be easily identified by the single tentacle protruding from their head.
Orbiniidae live in mud and sand near low tide level. Their parapodia (fleshy, feet-like protrusions) migrate from the sides to the ventral surface of the worm at the midsection, making the rear of the worm look “furry.”
These worms burrow headfirst into shallow sand, and have a characteristic groove that runs the length of the body. These specimens tend to be more intact than many other worm species.
Clam worms are common in mudflats and sandflats where bivalves are also found, and often have a frilly-looking appearance with two pairs of eyes. Some species can live inside the tubes of bamboo worms.
Bamboo worms live in tubes constructed out of sand grains cemented together. Aptly named, these worms have long, bamboolike body segments and a hoodlike head.
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These tiny clams are very common in sand and silty sand in shallow water. The individuals pictured are mature adults measuring 2-3 millimeters across. (mm scale)
This bivalve has a row of teeth on each side of the umbo (the “point” of the shell) which can be clearly seen in this picture.
These bivalves are common in fine sand and mud and have a distinct, asymmetrical oval shape.
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This is a juvenile horseshoe crab, which needs to molt 16 to 17 times to reach adult size – up to two feet long from head to tail! Horseshoe crabs are considered “living fossils” since they first appeared on this earth 450 million years ago.
Like their seastar cousins, brittle stars use their arms to crawl across the seafloor. They are also known as “serpent stars” for their long, sinuous arms.
This female sea spider is carrying a clutch of eggs that will soon hatch out even tinier sea spiders. Because these spiders have such a high surface-to-volume ratio, they do not need lungs or gills to breathe – they can rely on direct diffusion for respiration.
Nudibranchs are soft-bodied gastropods that can come in a wide range of colors and shapes. This tiny nudibranch has soft, yellow spines that give it a bumpy appearance and is a barnacle predator.
Green Sea Urchin
Green sea urchins can occur most commonly in rocky subtidal areas and the intertidal zone. The urchin grazes on predominantly seaweed, and is eaten in turn by many marine animals (despite the spines!) including sea stars, crabs, and fish.
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