Download Mollusc lab

Class Polyplacophora
1. Chiton for Dissection i.e. Katherina sp.
External Anatomy – 8 valves, girdle, mouth, foot, mantle cavity,
ctenidia, anus
Valves - distinguish head and tail valve (what features distinguish
them? Insertion teeth, articulations, what distinguishes the tegmentum
from articulamentum in valves), intermediate valves (dissect out and
check for esthete channels)
Processes – check the chiton girdle for scale (papillae, granules, scale)
and hair (setae, spicules) processes
Internal dissection (cut from dorsal side after removing the valves) –
esophagus, stomach, gonad (can you distinguish sexes?), pericardial
cavity
2. Various chitons for observation – can you tell what environment
these animals may live in? how may they adapt to their environment?
Class Gastropoda
Subclass Prosobranchia (Eogastropoda)
= shelled gastropods, mantle cavity in the anterior position and figure
8 nerve cords
Order Archaeogastropoda
Haliotis sp. – abalone, 4-15 holes, oval, scalloping around edges
Limpets – true limpets are only marine, some produce home scars (why
might that be advantageous?)
Class Gastropoda
Subclass Prosobranchia (Eogastropoda)
Order Mesogastropoda (Pectinibranchia) – no nacreous layer to the
shell (mother-of-pearl layer), bipectinate gills
Crepidula fornicata – slipper shell, attached to stones, other shells and
each other, sequential hermaphrodites, oldest animals at the bottom of
a stack are females, youngest at the top are males, what about the
animals somewhere in the middle?
Strombus gigas – queen crown conch, cut shell to observe periostracum
and prismatic, technically no nacreous
Class Gastropoda
Subclass Prosobranchia (Eogastropoda)
Order Neogastropoda – long incurrent siphon and associated siphonal
structure (how do these animals feed?)
Busycon – whelks, marine gastropods, may be right or left handed
(twisting of the shell), observe the large operculum (what might be the
use of that), also see the whelk eggs
Class Gastropoda
Subclass Ophistobranchia – have at least one pair of tentacles they
cannot withdraw, rhinophores (detection of smell), many show shell
reduction (slugs)
Live sea slugs for observation, how do these animals eat? How do they
move?
Class Gastropoda
Subclass Pulmonata
Order Basommatophora – eyes at the base of non-retractible
tentacles
Heliosoma sp. – freshwater snail, bulbous, planispiral shell that may
contain an air bubble
Observe freshwater snails (live) for radula movement (what are these
organisms doing with the radula?)
Class Gastropoda
Subclass Pulmonata
Order Stylommatophora – order of air breathing land snails or slugs
Limax sp. – terrestrial slug, notice absence of the shell (how may
these organisms “defend” themselves from the onslaught of the
environment? How do they avoid dessication?)
Helix sp. – terrestrial snail, operculum lacking
External anatomy – mantle, foot, pneumostome (use?), anus, shell,
tentacles, eyes, genital aperture
Internal anatomy – see model of dissected snail
In some cases, it may be possible to remove the d ead animal from i ts shell
using curved forceps. If this is not possible, slowly break the shell from the
aperture backwards, following the whorls, until the animal can be removed from
the shell intact. (It is important to retain the broken pieces of the shell for
identific ation purposes). A pair of needle - nose pliers may be used depending on
the size of the animal’s shell.
Uncoil snail and make an incision above the mantle skirt. Slowly uncoil the
portion of the animal that was inside the shell to expose its contents. Mak e an
incision just above the mantle skirt. Be sure to make shallow incisions and angle
the scissors upwards, and away from the internal organs. Cut as far along the
skirt as possible. Cut along the length of the thin membrane. Peel
eel bac k the
membrane to exp ose the internal organs. Peel back the transparent membrane
to expose the internal organs. Continue with the incision all the way to t he end
of the coiled regions of the animal (portion that was retained inside the shell).
The animal may be invert ed to acc omplish this.
Slowly tease the ovotestis and the albumen gland away from the digestive
gland. Both organs can be carefully separated with a pair of tweezers. Once
dislodged, both systems can be separated. Cut forward into the mantle skirt to
expose the bas e of the r eproductive system. Rotate the animal unto the side
(may have to hold in hands) and cut into the mantle skirt going forward, towards
the head. Be sure to make the incision between the ocular tentacles. This cut
will expose the basal region of the reproductive system. Detach the
reproductive system.
Gently separate t he reproductive system from the digestive system. Make
incisions but be careful to avoid cutting through the atrium. This incision will
detach the entire reproductive system form the re st of the animal. Use an
insect pin to gently unravel the vas deferens, bursa
flagellum, and penis by following the connection to each.
copulatrix, oviduct,
Class Bivalvia
Subclass Lamellibranchia – ctenidia longer and folded back to form two
lamellae
Order Anisomyaria – one adductor muscle only
Crassostrea sp. – oyster, economical importance, shell thick, flattened
and variable in shape, contains concentric ridges
Aequipecten – scallop, shells are convex, shells variable in color, life
animals have distinct blue eyes lining the mantle
Mytilus edulis – blue mussel, shell inequilateral and roughly triangular,
shell shapes may vary, smooth with concentric lines
Class Bivalvia
Subclass Lamellibranchia
Order Heterodonta – marine bivalves, generally with two adductor
muscles
Mercenaria mercenaria – quahog, very thick shell which is available for
shell analysis
Larval slides – trochophore larva
Mya arenaria – steamer, softshell clam, long pronounced siphon which
may never be completely withdrawn between the shells
Live specimens for blood withdrawl and gill dissection
Preserved specimens for dissection
Geukensia dimissa – ribbed mussel, with a ribbed shell and a narrow
blunt pointed head, shells are olive brown
Class Bivalvia
Subclass Lamellibranchia
Order Schizodonta – teeth of the valves are large, amorphous and
variable
Representative freshwater bivalves and freshwater clam glochidia
Order Adapedonta – boring mussels
Ensis sp. razor clam
Class Cephalopoda
Subclass Nautiloidea
Nautilus sp. – internal chambers, siphuncle, sutures and septae, body
of the animal only contained in the last chambers
Subclass Coleoidea – primarily soft-bodied cephalopods
Order Teuthida – semi-gelatinous body, body is long and tapered,
tentacles (paired) and paired arms (4 pairs)
Loligo sp. – squid
Specimen for dissection (also
External anatomy – tentacles, head, eyes, funnel (siphon), mantle,
mantle-locking cartilage, fins (internal stiff pen), mouth with beak
Internal anatomy – organs of Verrill, cephalic retractor muscle,
articulating ridge, ctenidia, inc sack, kidneys, branchial heart, caecum,
gonad
Injected squid – anterior vena cava, posterior vena cava
Order Sepiidae – long, oval body, dorso-ventrally flattened, thick
internal shell
Order Octopoda – short compact body with only 8 arms with suckers,
funnel valve absent