Dale Leavitt 16-Jan-17
Shellfish Biology 1
Bivalve Biology Dale Leavitt
Shellfish Biology 101
Phylum Mollusca
Best known group of invertebrates
◦ animals without backbones
◦ well known because of shell collecting
Second largest Phylum
◦ >80,000 living species have been named
◦ 35,000 species in the fossil record
Majority of mollusks are marine
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Shellfish Biology 2
Phylum Mollusca
bilaterally symmetrical majority have a shell of
some kind three distinct areas
◦ distinct head area ◦ visceral mass ◦ large, muscular foot
mantle is present simple digestive
system => primarily herbivores
Come in a variety of shapes and sizes
Phylum Mollusca
Gastropoda single, usually spirally coiled shell into which the body can be withdrawn
There are seven Classes of Mollusca:
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Shellfish Biology 3
Phylum Mollusca
Gastropoda single, usually spirally coiled shell into which the body can be withdrawn
Bivalvia two laterally-compressed shells, hinged together by an elastic ligament and shell teeth
There are seven Classes of Mollusca:
Phylum Mollusca
Gastropoda single, usually spirally coiled shell into which the body can be withdrawn
Bivalvia two laterally-compressed shells, hinged together by an elastic ligament and shell teeth
Cephalopoda A funnel derived from the molluscan foot - circumoral arms - chitinous beaks.
There are seven Classes of Mollusca:
Class Bivalvia
Two shells (valves) with hinge
Laterally compressed Head greatly reduced Fleshy mantle encasing
the visceral mass and a muscular foot
Lost the radula Gills are large and used for
feeding Sedentary
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Shellfish Biology 4
Adult Biology What do you need to know as a shellfish farmer?
What does a shellfish farmer need to know about shellfish biology?
Life styles
Anatomy
Growth
Respiration
Feeding & Digestion
Nervous system
Circulatory system
Locomotion system
Reproductive system
Life Styles of the Shelled and Aquatic
Epifaunal ◦ Byssally attached
(blue mussel)
◦ Reclining (giant clam)
◦ Cemented (oyster)
◦ Swimming (scallop)
Semi-Infaunal ◦ Byssally attached
(ribbed mussel)
Infaunal ◦ Burrowing (quahog)
◦ Boring (piddock)
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Shellfish Biology 5
Epifaunal – Byssal attachment
Epifaual - Reclining
Epifaunal - Cemented
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Shellfish Biology 6
Epifaunal - Swimming
Semi-infaunal – Byssal attachment
Infaunal - Burrowing
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Shellfish Biology 7
Infaunal - Boring
External anatomy - oyster
Beak Bill
Exterior of the quahog
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Shellfish Biology 8
Two varieties of wild quahog
Mercenaria mercenaria var. alba ◦ White color ◦ Commonly found
Mercenaria mercenaria
var. notata ◦ Indian blanket or zig-zag pattern
◦ “Charlie Brown clams” ◦ 1-2% of the wild catch
The three varieties of farmed quahog
white
notata
???
Where did that third shell color come from?
Classic Mendelian genetic distribution ◦ ¼ white x ½ notata x ¼ stiped
Only see striped (mm) in hatchery stock??? ◦ Just one of those mysteries of Mother Nature!!
Mm x Mm M m
M MM Mm
m Mm mm
White
Zig-zag
Striped?
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Shellfish Biology 9
Shell layers
Periostracum
Nacreous
Pearl formation
Quahog pearl
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Shellfish Biology 10
Opening shellfish
Scallop Quahog Oyster
Soft Shell Clam
Opening an Oyster
Interior of an Oyster Shell
“Bill”
“Beak”
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Shellfish Biology 11
Opening the quahog
Opening a clam
Interior of a Quahog Shell
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Shellfish Biology 12
Wampum (Suckáuhock)
Clam in cross-section
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Shellfish Biology 13
Quahog mantle
Shell growth - Mantle
Shell growth - Mantle
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Shellfish Biology 14
Shell Growth in the Oyster
QuahogShell Growth
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Shellfish Biology 15
World’s oldest animal – 507yrs
“Ming”
Oyster growth (shell length)
Oyster growth
Condition Index ◦ Soft tissue/shell volume
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Shellfish Biology 16
Oyster internal anatomy
Quahog Internal Anatomy
LABIAL PALPS
Soft shell clam
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Shellfish Biology 17
Scallop anatomy
Oyster Internal Anatomy
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Shellfish Biology 18
Quahog mantle
Another use for the mantle
Respiration & Feeding in the mussel
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Shellfish Biology 19
Oyster filtering capacity (app. 4 h)
Feeding
Oyster feeding
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Shellfish Biology 20
Feeding
Oyster internal anatomy
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Shellfish Biology 21
Oyster feeding/respiratory current
Gills - Respiration & Feeding
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Shellfish Biology 22
Clam Gills
Respiration & Feeding
Gills - Respiration & Feeding
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Shellfish Biology 23
Mussel Filter Feeding
Oyster feeding
Oyster internal anatomy
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Shellfish Biology 24
Stomach
Clam Internal Anatomy
LABIAL PALPS
Clam Anatomy
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Shellfish Biology 25
Quahog Stomach
Digestion
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Shellfish Biology 26
Crystalline Style
Oyster Circulatory System
Clam Circulatory System
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Shellfish Biology 27
Circulatory system
Hematopoietic neoplasia (aka Clam leukemia)
Oyster Nervous System
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Nervous System
Locomotion
Digging
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Shellfish Biology 29
Digging (Jellybean clam)
Other bivalve movement
The Locomotion King!
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Shellfish Biology 30
Swimming then Burrowing
Walking
Reproduction in Bivalves
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Shellfish Biology 31
Shellfish Gender
Commonly separate sexes in the bivalves (dioecious) ◦ although hermaphroditism (monoecious) occurs
Sex is unknown until observed spawning ◦ Except scallops
ripe
unripe
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Shellfish Biology 32
Oysters & Quahogs
Protandric ◦ Protandry - development of male organs before female to avoid self- fertilization.
Most begin life as males and then may change over to female
As they grow, proportion of functional females in each size class increases
Females occur in larger (older) animals
Gonad Anatomy
Gonad Index of Quahogs
Gonad Index ◦ Size of the gonad relative to the size of the other soft tissue
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Shellfish Biology 33
Meat Quality