Bivalves and Cephalopods

one thousand species live in fresh water Zebra Mussel About one thousand species live in fresh water Zebra Mussel Zebras on native clams (Unionidae)

Best understood in the context of their Best understood in the context of their largely sedentary adult life style

umbo ctenidium Foot Adductor muscle Right valve Labial palps mouth Excurrent Incurrent siphons mouth Foot Mantle edge

distinguished by their Ctenidia Two principal types, distinguished by their Ctenidia and mode of feeding Class Bivalvia Protobranchia Llamellibranchia Filibranchia Eullamellibranchia

Ctenidia of Bivalves are modified for feeding except in one group: the Protobranchs

In most bivalves ctenidia are sheet-like with high S.A., and are used for feeding

Captured particles are moved to a ciliated ventral groove and then as a mucus strand to the mouth. http://www.biology.ualberta.ca/facilities/multimedia/index.php?Page=252

Summary of Water Flow and Feeding http://web.uconn.edu/jevanward/video/musselsum.MPG The sheetlike, arrangement of ctenidia in most bivalves is known as the Llamellibranch condition

There are two basic type of Llamellibranch ctenidia in bivalves Filibranch (in mussels) Eullamellibranch (most clams)

Living Cephalopods Squid Nautilus Cuttlefish Octopods --The class as a whole is adapted for swimming, suspended in the water by buoyancy mechanisms. -- all are carnivores, occupying the same niche as fishes

Architeuthys Mesonycheteuthis Colossal squid Dosidicus Giant squid up to 20 m long Mesonycheteuthis Colossal squid up to 14 m major prey item of sperm whales Dosidicus Humboldt squid, smaller but numerous (2 m) and comes to surface to feed

Ammonites Largest is 3 m in diameter

Sub Class Nautiloidea 5-6 species remain from diversity in geologic past Live in the last chamber of a multi-chambered shell Move by forcing water through a siphon.

Sub Class Nautiloidea How does a Nautilus adjust and maintain its buoyancy in water?

Cuttles, Squids and Octopuses tendency is reduction of shell. compensated for by selective ionic control; accumulate ammonium other adaptations to shell loss and life style

cuttle chameleons of the sea most specialized, agile and cryptic octopus

Specifically, compensation takes the following forms: Stealth and other defenses Acute sensory structures Speed Cunning

A. Stealth and other defenses Ink Sack : ink with melanin and mucus also dopamine, L-DOPA, tyrosinase L-Dopa is a precursor to catecholamines including dopamine which are involved in neurotransmitter function Tyrosinase is an oxidizing enzyme Pseudomorphs

A. Stealth and other defenses Chromatophores: each cell contains a different pigment which may be red, orange, brown, black, yellow or blue

Cephalopod Chromatophore The pigments in chromatophores can be black, brown, red, orange or yellow. They are not responsible for producing the blue and green colors seen in some species. Those are produced by iridiophores which are reflective cells. Cephalopods have several organs that allow them to hear high frequency sounds Black, brown, orange or yellow colors Also iridiophore reflective cells Most cephalopods are completely colorblind neurophilosophy.files.wordpress.com

B. Acute sensory structures -- Vision -- Lateral line analogs

C. Speed Rival fish in ability to swim, attaining burst speeds of 5-10 m second sustained for short distances at speeds of up to 40 km hr. Burst speed is achieved by jet propulsion More gradual swimming is fin undulation

complex nerve control of locomotion C. Speed : complex nerve control of locomotion Assures synchronized contraction of mantle muscles

C. Speed : circulatory system Hearts Requires a closed, elaborate circulatory system

D. Cunning -- Relative to body size, the brain is larger than that of most fish

Experiments with Octopus vulgaris show their ability to learn. They learn to choose colors not associated with shock. Observers choose properly colored objects after watching demonstrators