1/30/2020 BIVALVE BIOLOGY Matt Griffin Adapted from Dale Leavitt 2019 PHYLUM MOLLUSCA • Invertebrates – no backbone - Millions of years old • High diversity > 85,000 living species > 60,000 species in fossil record • Habitat - Te rre s t r i a l - Freshwater -Marine • Represents 23% of all named marine organisms PHYLUM MOLLUSCA • Bilaterally symmetrical • Majority have a hard shell - exp: Nudibranchs & Cephalopods • Three distinct areas - head area - visceral mass -mantle • Primarily herbivorous 1 1/30/2020 PHYLUM MOLLUSCA Highly diverse - 7 classes Oyster drill Channel whelk Moon snail PHYLUM: MOLLUSCA CLASS: GASTROPODA • Spiral coiled shells – body can be withdrawn • Carnivorous – some predatory on bivalves PHYLUM: MOLLUSCA CLASS: CEPHALOPODA • Reduced shells - beak • Rival mammals in terms of complexity and function 2 1/30/2020 PHYLUM: MOLLUSCA CLASS: BIVALVIA • Two laterally compressed shells • Hinged together by elastic ligament and teeth • Head greatly reduced • Fleshy mantle encasing the visceral mass • Muscular foot • Loss of radula • Large gills used for feeding & respiration • Mostly sedentary BIVALVE • Lifestyles BIOLOGY • Anatomy • Growth • Respiration • Feeding and digestion • Nervous system • Circulatory system What do you need • Locomotion to know as a farmer? • Reproduction HABITAT - LIFESTYLES Epifaunal - Byssal attached (blue mussel) - Reclining (Giant clam) - Cemented (oyster) - Swimming (scallops) Semi-Infaunal - Byssally attached (ribbed mussel) Infaunal - Burrowing (quahog) - Boring (piddock) 3 1/30/2020 EPIFAUNAL - CEMENTED EPIFAUNAL – BYSSAL ATTACHMENT EPIFAUNAL - RECLINING 4 1/30/2020 EPIFAUNAL - SWIMING SEMI-INFAUNAL – BYSSAL ATTACHMENT INFUANAL - BURROWING 5 1/30/2020 INFUANAL - BURROWING Beak Bill EXTERNAL ANATOMY - OYSTER EXTERNAL ANATOMY - QUAHOG 6 1/30/2020 QUAHOG – TWO VARIETIES • Mercenaria mercenaria alba - White color - 98% of wild • Mercenaria mercenaria notata - “Charlie brown clams” - 1% - 2% of wild catch - May be common in hatchery stock BIVALVE SHELL LAYERS • Periostracum - thin - mostly made of protein - may or may not be present • Prismatic layer - thick layer - provides structure • Nacreous layer - AKA “pearly layer” - very smooth - protects bivalve soft tissue INTERIOR OF AN OYSTER resilium SHELL 7 1/30/2020 INTERIOR OF A QUAHOG SHELL WAMPUM (SUCKÁUHOCK) Shell beads of Eastern Woodland Tribes Mostly used in exchange in rights of honor and ceremonial gifts • Wampum – white beads • Suckáuhock – purple beads What is the purple from?? - slow growing - metabolic waste product deposited in shell BIVALVE CROSS SECTION Bilateral Symmetry 8 1/30/2020 SCALLOP QUAHOG OYSTER OPENING SHELLFISH OPENING AN OYSTER HINGE SHUCK OPENING AN OYSTER BILL SHUCK 9 1/30/2020 OPENING THE QUAHOG Gills 10 1/30/2020 BIVALVE MANTLE • First layer of tissue next to shell • Very thin (2 cells thick in some cases) • Muscles for movement (retraction) • Primary functions - Seals bivalve - Locomotion (in some cases) - SHELL FORMATION MANTLE FUNCTION Seals valves Locomotion 11 1/30/2020 MANTLE FUNCTION SHELL GROWTH Mantle controls chemistry within the extra pallial fluid 1. Mantle exeats periostracum to seals off extra pallial cavity 2. Protein matrix on leading edge 3. Calcium carbonate crystals deposited into protein matrix PEARL FORMATION 12 1/30/2020 PEARL FORMATION QUAHOG PEARLS SHELL GROWTH • Growth forms on leading edge - primarily linear growth - can force deeper cup • Ecotherms - metabolism depended upon water temperature - seasonal growth patterns 13 1/30/2020 HOW OLD IS THAT SHELLFISH? 1 2 3 4 5 6 7 8 9 10 11 12 13 SHELL CROSS SECTIONS “MING” WORLDS OLDEST ANIMAL 507 YEARS OLD 14 1/30/2020 OYSTER LENGTH AT AGE • Highly dependent upon - location - food flux - husbandry • Market Oysters (3”) ~ 18 – 36 months in SNE Understand growth cycles on your farm SHELL LENGTH VS. SOFT TISSUE MASS • Diploids - 2 sets of chromosomes - spawn in summer months - reduced condition • Triploids - 3 sets of chromosomes - increased growth (sometimes) - consistent condition - more expensive - harder to handle Always in season! 15 1/30/2020 RESPIRATION & FEEDING OYSTER RESPIRATION & FEEDING • Pumps up to 50 gallons of water a day • Filters down to 2-3 microns NUTRIENT CYCLING & REMOVAL N - removal by a single oyster 0.77 g N/yr. (if harvested) N - removal of 1-acre farm 231 kg N/yr. = 509 lbs. N - removal from RI oyster sales in 2018 = 14,500 lbs. 16 1/30/2020 RESPIRATION & FEEDING anterior dorsal EXHALENT CURRENT ventral INHALENT CURRENT posterior 17 1/30/2020 QUAHOG SOFT SHELL CLAM 18 1/30/2020 BLUE MUSSEL FEEDING – E. WARD 19 1/30/2020 LABIAL PALPS Crystalline Style 20 1/30/2020 DIGESTION • Free floating crystalline style • Cilia rotate crystalline style • Food ground against gastric shield • Digestive enzymes released • Food particles moved to digestive glands and intestine • Heart • Veins and arteries • No capillaries OPEN • Open sinus that blood (hemolymph) moves through CIRCULATORY SYSTEM OYSTER CIRCULATORY SYSTEM 21 1/30/2020 CLAM CIRCULATORY SYSTEM CIRCULATORY SYSTEM BLOOD CELLS • Ameboid phagocytic blood cells • Tr anspor t oxygen • Can ingest bacteria Normal cell morphology Abhorrent cell morphology HEMATOPOIETIC NEOPLASIA (AKA CLAM LEUKEMIA) • Proliferation of abhorrent blood cells • Displace tissue • Interfere with normal functioning of circulatory system 22 1/30/2020 NERVOUS SYSTEM No centralized nervous system Comprised of ganglia and nerves Mostly associated with mobile parts of the bivalve - Foot - Siphon SIMILAR ANATOMY THROUGHOUT BIVALVES 23 1/30/2020 LOCOMOTION • Swimming • Walking • Digging 1. Push foot into substrate 2. Balloon distal end of foot (anchor) 3. Retractation – liquifies substrate 4. Valves move toward foot JELLYBEAN CLAM (SOLEMYA) PISMO CLAM 24 1/30/2020 QUEEN SCALLOP RAZOR CLAM RACES SWIMMING AND BURROWING 25 1/30/2020 WALKING REPRODUCTION • Dioecious - separate sexes (mostly) • External fertilization • Free swimming planktonic larval stage • Settlement • Recruitment Temperature & chemical ques Clam Life Cycle Infuanal 26 1/30/2020 fertilized egg early cell division pediveliger D-stage larvae umboned larvae adult males & females Spat attached to substrate Epifaunal Cemented PROTANDRIC HERMAPHRODITISM • Development of male organs first • Switch sex to female • Females occur in larger (older) animals - energetics - avoid self-fertilization • Can switch sex back to female • E.g. oysters and quahogs SIMULTANEOUS HERMAPHRODTISM ripe unripe • Male and female gonads occur at the same time • Release of eggs or sperm is often delayed 27 1/30/2020 SEX DETERMINATION GONAD INDEX Size of gonad relative to the size of other soft tissue • Increase (March – Jun/Jul) • Decrease (Jul – Aug/Sep) • Increase (Sep – December) • Steady or slight decrease (Jan – March) Direct impact on meat quality SHELLFISH TERMINOLOGY Larvae (babies) • Free-swimming during first 2 – 3 weeks of life Metamorphosis • When larvae transform to their adult body shape Settlement • When metamorphosing shellfish occupies its adult-type of habitat Recruitment • When current cohort of larvae settle into a population Spat/Seed (Juveniles) • Spat: Juvenile bivalve after settlement • AKA Seed: terminology used in aquaculture 28.