Mollusk

Mollusk

Horse Mussel

Submitted by lupo on Sat, 11/06/2010 - 22:15

 
Latin Name: 
Modiolus modiolus
Common Name: 
Horse Mussel
Description: 

A large solid, swollen and roughly oblong or triangular shaped shell. The hinged end is bluntly angled, with the rest of the shell being more gently curved.

In younger adults the outer shell is a dark blue or purplish color. As they grow older the perisostracum (the surface layer of shell) can lend a yellow glossy or dark brown hue. There is no ribbing but growth lines may be noticeable or may be evident in the unevenness of the outer layer of the shell. The inside of the shell is white except for the areas where muscles were attached. Adults are, typically, at least 4 in (10 cm) long but individuals may grow as large as 8.6 in (22 cm).

Biology: 

A large solid, swollen and roughly oblong or triangular shaped shell. The hinged end is bluntly angled, with the rest of the shell being more gently curved.

In younger adults the outer shell is a dark blue or purplish color. As they grow older the perisostracum (the surface layer of shell) can lend a yellow glossy or dark brown hue. There is no ribbing but growth lines may be noticeable or may be evident in the unevenness of the outer layer of the shell. The inside of the shell is white except for the areas where muscles were attached. Adults are, typically, at least 4 in (10 cm) long but individuals may grow as large as 8.6 in (22 cm).

These mussels are often found living among gravel and rocks, from just below low-tide line to water 600' (183 m) deep. Horse mussels us byssus threads to attach to the substrate and like blue mussels can form dense mats of live individuals.

underwater Modiolus modiolus mollusks.

These mollusks live below the tide line and attach themselves to a solid underwater substrate.

 

The small pea crabs Fabia subquadrata or Opisthopus transversus may be found living within the shells of living horse mussel.s

Life History: 

Adults are broadcast spawners, releasing eggs and sperm into the water column. The spawning season is not well defined and can vary with depth and location. It has been suggested that major spawnings occur at intervals of several years, with the possibility of partial spawnings one or more times each year (Wiborg, 1946; Rowell, 1967). Newly fertilized individuals live the first stage of their life as planktonic larvae. After 3 or 4 weeks they settle, attach to a substrate, and metamorphose into juveniles.

Distribution: 

A wide ranging species that lives in colder coastal waters. On both coasts of North America from the Arctic Seas to New Jersey, and from the Bering Sea to San Pedro, California. Also along the coasts of Japan, Iceland, Europe, NW Africa, and some Mediterranean areas.

Flotsam and Jetsam: 

Beds with high numbers of individuals form horse mussel reefs that serve a number of important functions. The filter feeding can collectively filter large volumes of water. The presence and actions of the mussel also enrich the benthos by drawing other organisms to the mussel reef. Local species richness is among the highest found in any cool water Atlantic benthos community. The young of many species use these areas as nursery grounds.

underwater horse mussel bed

Horse mussels can form dense beds.

 

The periostracum easily flakes off dry adult shells, and in young shells it is drawn out into triangular, pointed projections. This large mussel is frequently used as fish bait, and in some parts of Europe as food.

Abundance: 
Occasional
References: 
de Schweinitz, E.H. and Lutz, R.A. 1976. Larval Development of the northern horse mussel Modiolus modiolus (L.), including a comparison with the larvae of Mytilus edulis L. as an aid in planktonic identification. Biol. Bull. 150: 348-360.

Blue Mussel

Submitted by lupo on Mon, 11/01/2010 - 19:49

 
Latin Name: 
Mytilus edulis
Common Name: 
Blue Mussel
Description: 

A purple, blue or occasionally brown outer shell with an interior having a border of dark blue to violet surrounding a pearly white interior. The shell is smooth but typically has some growth lines. The shape is roughly an elongate triangle, up to 4 in (10 cm) at its widest dimension.

line drawing of the parts of a blue mussel shell.

A line drawing showing the parts of a Mytilus edulis shell

 

Biology: 

The blue mussel is a widely distributed and locally abundant bivalve mollusk found in the North and Mid-Atlantic regions. It is a semi-sessile species, anchored by byssus threads to firm surfaces in littoral and sub-littoral environments. Active suspension feeders, blue mussels derive their nutrition by filtering organic particles from the water column. The dominant food source for all their life stages is phytoplankton.

The geographical range of the species is limited by lethal water temperatures above 27 C in the south and by temperatures too low for growth and reproduction in the north. Larval and adult blue mussels are important prey items for many animals, including crabs, fishes, and birds.

a blue mussel shell.

The exterior of a blue mussel shell

 

In sheltered environments, large aggregations of mussels sometimes form dense beds that provide shelter for a variety of other invertebrates. In both these sheltered environments and exposed shores, blue mussel clumps sometimes become so thick that relatively few individuals are attached to the firm substrate. In such situations, storms occasionally wash away large sections of the mussel bed.

Life History: 

The blue mussel is diecious and oviparous. Eggs and gametes are released into the water column, where fertilization occurs. The timing of reproduction is dependent on local conditions that include nutrient availability and temperature. The planktotrophic larvae take about 3 weeks to develop and metamorphose. The juveniles grow to approximately 1.5 mm while attached to filamentous algae that are attached to a substrate. Then they are carried by water currents to a new location where they reattach to a firm substrate. This substrate may vary from large boulders to pebbles or, very frequently, other mussel shells.

Distribution: 

North Atlantic, Europe and other temperate and polar marine areas.

Flotsam and Jetsam: 

The blue mussel is a common item on seafood restaurant menus throughout the United States. In Canada and Europe the blue mussel is considered a quality seafood product and in Spain, France, Holland, and Italy, it forms the basis of an extensive commercial mariculture.

a pot full of blue musslesl

Blue mussels are on many menus.

 

Macroparasitic pea crabs can infest live mussels, living firmly attached by their rear legs to the gill of the bivalve. The crab feeds on food particles traveling in the food grooves and can cause severe gill damage.

Blue mussels tolerate low temperatures for extended periods, even surviving being frozen in ice for up to 8 months each year in Labrador populations.

Abundance: 
Common
References: 
Seed, R. 1976. Ecology. Pages 13-65 d B.L. Bayne, ed. Marine mussels: their ecology and physiology. Cambridge University Press, New York.

Angel Wing

Submitted by lupo on Sat, 10/23/2010 - 21:27

 
Latin Name: 
Cyrtopleura costata
Common Name: 
Angel Wing
Description: 

White shell, elongate oval-like in shape, thin, and very fragile. There are around 25 radiating ribs each half of the shell and a spoon-shaped brace under the "beak,", which is where the mollusc's foot muscles are attached.

Biology: 

Angel wings have long siphons which protrude from their burrow. This allows them to circulate water for their filter feeding diet. They are unable to retract their siphons into the protection of its shell hence the two valves can never shut completely. The muscles fusing the shell's valves together are weak, making it rare to find angelwings with both halves still intact. Angel wings live offshore and in estuaries. They sometimes burrow as much as three feet deep into the mud or clay.

Distribution: 

Cape Cod to the Gulf of Mexico.

Similar: 

Fallen Angel Wing

Abundance: 
Rare
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