PREPARATION OF DRY
SKELETONS
(skeletonization
follows a Ridewood preparation modified by G.J. Nelson)
1. Identify fish, locate Accession Number,
or assign Accession Number.
2. Record
Accession Number, other data (Name, Identifier, Tag No.).
3. Take
Standard Length (mm SL) or Total Length (mm TL) if appropriate.
4. Determine
sex and general stage of maturity.
—Preserve
in formalin stomach contents, parasites if desired.
—Save
skin, scutes, some scales if appropriate.
6. Remove the bones from the right side of
fish, including: right half of pectoral
girdle,
bones
of cheek (opercular bones, suspensorium, right half of lower and upper jaws,
infraorbital bones.
7. Gill arches are removed intact.
8. Pelvic girdle removed whole.
9. Remove both eyes.
To
remove gill arches:
a. Separate branchiostegal rays from
opercular bones by cutting membranes between the last ray and opercular bones.
b. Follow bones of operculum and lower
jaws forward to symphysis on insides of both sides with a knife/scalpel.
c. Locate and separate urohyal from
anterior part of pectoral girdle (where cleithra meet) with knife/scalpel,
following bones of pectoral girdle forward.
d. Locate interhyals and detach from
skull, carefully (frequently these bones are small).
e. Cut
through the esophagus, cut skin and muscles holding dorsal gill arch elements
to neurocranium, and pull gill arches out.
To remove bones of
right cheek:
a. Separate hyomandibular from skull.
b. Cut between parasphenoid and bones of
palate. Bones can be located by moving
cheek in and out.
c. Separate
infraorbital bones from skull (they
remain with bones of cheek).
d. Cut
through symphysis of lower jaw.
e. Separate
premaxillae.
f. Free
bones of upper jaw from head.
g. Nasals
remain with skull.
To remove pelvic
girdle:
a. Generally the pelvic girdle is removed
intact but the right half may be separated from the left by separating the
pelvic bones.
b. If
the girdle is being removed whole, separate it from pectoral girdle.
To remove half of
pectoral girdle:
a. Separate
cleithra at their base.
b. Locate
prongs of post-temporals (usually 2) and separate from skull (they vary in
size).
—One
generally lies flat along the top of skull.
—The other articulates with
posterolateral part of skull.
c. Separate ribs from tissue associated
with pectoral girdle.
—NOTE: The pectoral girdle is generally removed
whole in catfish.
NOTES
a. Remove flesh from fish to base of
caudal rays. A spoon works well after
filleting to scrape down to bones.
b. In fishes with bony plates or heavy
scales (gars), scutes (Carangids) scales or scutes are removed intact and
saved.
c. Open blood sinus along bottom of
vertebral column.
d. Remove eyes and puncture.
e. Open/remove any large muscle mass, in
particular large muscles of cheek, on inside of jaw, along top of skull,
associated with pectoral girdles.
f. Remove all internal organs and as much
of air bladder as possible as it will dry and be hard to remove later.
g. Wash well with water. Tag all parts with individual number, record
data on sheets supplied (see attached
example).
h. Air dry or soak in alcohol to
dehydrate, then air dry.
i. If specimen is greasy soak in
trichloroethylene and air dry until all trichloroethylene has evaporated.
j. Fins may be spread and pinned before
drying.
k. Feed to beetles (1 specimen per tray; try not to introduce similar fish to the same
colony at the same time).
—Leave
in colonies until well cleaned but not disarticulated.
—Fragile
areas may be "painted" with formalin to prevent disarticulation by
beetles.
—Spray with water to facilitate
feeding (2 times daily).
l. Remove to killing cases (with trays of
paradichlorobenzene) — leave for 3
days. Box and remove to freezer — 3 days.
M .Brush, clean, rebox, leave original
tag with animal.
n. Bones may be bleached by spraying with
hydrogen peroxide solution allowing skeleton to dry after each application to
prevent disarticulation.
—Large
specimens may be soaked in H2O2.
—Stop action of H2O2
with weak ammonia solution. Specimens
may be degreased now if necessary.
o. Specimens that are problematic for
beetles should be removed.
—If
too greasy they will kill beetles and should be degreased.
—If they contain toxins (some
puffers) they may be soaked in weak ammonia solution for 3 days changing the
solution daily and then soaked in water for a day and dried. Then return to the colonies.
p. Large specimens that will not fit in
colonies can be boiled in tubs in Osteology Lab, then flesh is removed by hand.
q. Put fish in final box, add box card and
box labels. Fumigate in fumigating
cases for 3 days; put into collection.
