Snails, Limpets and Octopus

Snails, limpets and octopus are in a group called mollusks that have a couple of characteristics in common.  They possess a mantle (a fold of soft flesh which encloses several glands), and a radula (a toothed or rasping appendage, like a tongue, used for feeding).  Snails and limpets belong to a diverse group of invertebrates called gastropods (meaning "stomach foot") that primarily have the feature of a muscular 'foot' that runs along the underside of the body and is used for locomotion.  The group of mollusks of which octopus and squid belong have several remarkable characteristics in common.  A total of eight or more arms are positioned around the mouth.  Two gills, two kidneys and three hearts are also present.  A dark fluid produced by some species can be released to aid in defense against predators.

 

     
 Moon Snail (Polinices lewisii)  


 Moon Snail

Description: Large white to tan shell, with enormous translucent pink to brown foot. The snail pumps water into its mantle and foot, increasing its mass to 3 or 4 times that of just the shell alone. When threatened, the snail pumps the water out of its body, pulling entirely inside the shell, and sealing the shell with a brown door-like operculum. Common in sandy and rocky intertidal. Up to 5.5 in (14 cm) high.  
 Food: This snail is one of the top predators of the intertidal environment. Chief among the moon snail's preferred foods are clams. The snail surrounds the clam with its foot, then drills into the clam shell with a radula, which is covered in tooth-like rasps. Weak acids also are excreted onto the shell, hastening the drilling process. Once the characteristic hole is made, near the clam's hinge, the snail injects digestive enzymes into the clam. When ready, the snail scrapes and sucks out the meat from the clam, leaving an empty clam shell behind. An adult moon snail can eat a clam every 4 days.  
 Reproduction: Female lays eggs in distinctive round molded sand collar. Made of a layer of sand, then a layer of tiny eggs, and then another layer of sand, the whole egg collar is held together with snail mucus. Eggs are laid in spring through fall, and the 500,000 eggs in each collar hatch out in about 6 weeks.  
 Fun Facts: Besides humans, gulls are the chief predators of the moon snail. A gull will pick up a snail and carry it aloft, and then drop it onto the rocks to break open the shell.  
   

 

Checkered Periwinkle

 

(Littorina scutulata)

 

 
checkered peri

Description: Brown or black elongated shell checkered with white spots. Found on seaweed or rocky shorelines in high intertidal zones. Can survive long periods out of water and are thought to be the ancestors of all land snails. Good eyesight, with eyes perched on long stalks. Length to about 0.5 in (1.3 cm).  
 Food: These snails use a long radula with up to 300 "teeth" to scrape algae off the rocks.  
 Reproduction: Separate sexes. Females lay eggs.  
 Fun Facts: It is said, when holding a periwinkle in ones hand, if one hums to the snail steadily for a minute or two, the snail will come out of its shell and begin crawling around.  
   

 

Purple Whelk

 

(Nucella lamellosa)

 

 Welk
Description: A relatively large, heavy bodied snail often with a shell covered by frilly ridges. Also known as a frilled dogwinkle.  In exposed areas the smooth form is encountered (shown at left). Color can vary from white, purple, yellow, orange, and others. Found throughout all intertidal zones on rocks, mussel beds and barnacles. Length to over 3 in (8 cm).  
 Food: Feed on mussels and barnacles, drilling a hole with a radula.  
 Reproduction: Females can lay up to 1000 eggs per year, with the eggs resembling yellow oat kernels, leading to their common name of "sea oats."  
 Fun Facts: These snails are eaten by the red rock crab, and mottled and ochre sea stars.  
   

 

Red Octopus

 

(Octopus rubescens)

 
 
Red Octopus
Description: A small octopus sometimes found exposed or under rocks in the intertidal zone. It has well developed eyes, a parrot-like beak under the mantle, and eight arms with suction cups on each arm. Very intelligent. Rough, unfolded skin. Color dull red, to reddish-brown, can be mottled with white. It can make its den under a rock, in an empty moon snail shell, or even in an empty bottle. Mantle grows to 4 in (10 cm). Arms can reach 16 in (41 cm) long.  
 Food: Hunts crabs and other invertebrates.  
 Reproduction: Separate sexes. Specially developed arm on males delivers sperm packet to female.  
 Fun Facts: This octopus can change color rapidly when disturbed. It can change between bright red, brown, white, speckled gray and black all within a matter of seconds. This ability to change color is useful for defense, and in hunting, but many researchers believe these color changes are an indication of emotional state of this intelligent little animal. This animal has a venomous saliva which it injects with its bite. If found on the beach, do not handle.  
   
   

Plate Limpet

(Tectura scutum)

 

 
plate limpet

Description: Often gray to greenish in color with off-white rectangular blotches radiating from top of flat, oval shell. Apex of shell is relatively low. Suction cup-like foot. Well developed eyes and tentacles. Highly territorial, and will defend home against competition. To 2 in (5 cm) long. 
 
 Food: Grazers.  Radula scrapes algae off rocks.  
 Reproduction: Lays eggs.  
 Fun facts: Some limpets will spend their entire lifetime, up to 20 years, on a single rock.  
   

 

Rough Keyhole Limpet



(Diodora aspera)

 

 keyhole limpet
Description: Color varies from light brown to gray, often with color banding.  Prominent off-center opening at apex of cone-shaped shell.  Ridges radiate from top.  Well-developed eyes and tentacles. Radula scrapes algae off rocks on which it makes its home. To 3 in (7 cm) long.   
 Food: Grazers. Radula scrapes algae off rocks.  
 Reproduction: Lays eggs.  
 Fun Facts: To protect itself from predators such as the ochre sea star, this limpet will erect a thin, soft mantle to cover its shell that prevents the sea star from attaching its tube feet.