Additional references at end. 

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.

5.         Fillet fish removing as much flesh as possible, leaving both series of ribs on fish.

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.

Additional References:

Bartels, Th., and W. Meyer (1991): A rapid and effective method for the maceration of vertebrates. Dtsch. tierärztl. Wschr. 98, 407 - 409.