Title

EARLY THIRD INSTAR CRAYFISH ORCONECTES RUSTICUS RESPONSE TO MOVEMENT, ODOR, AND TACTILE CUES IN THE ENVIRONMENT

Date of Award

2006

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biological Sciences

First Advisor

John Graham

Abstract

An important step in the survival of juvenile crayfish is the avoidance of predation and the recognition of maternal odors. Attachment to the pleopods of the maternal crayfish is an important factor in the survival of juvenile crayfish as they receive protection against predation when in contact with the mother. Crayfish were reared from eggs and their abilities tested to detect, recognize, and respond to different odors of ecological relevance as determined by the preference for attachment to, or avoidance of test paddles bearing odors. It appears as if early third instar Orconectes rusticus crayfish are able to detect odors and recognize odors from their maternal sources. When movement is incorporated into the experimental design using an apparatus with test paddles for attachment, third instar juvenile crayfish are seen to avoid rather than being attracted to some odors. Some unfamiliar odors are avoided while familiar odors are not avoided. However, when test paddles with familiar and unfamiliar odors are presented with paddles containing no odor, attachment to the familiar odor paddles remains unchanged while attachment to the non-odor paddles increases and attachment to the unfamiliar odor decreases in an odor avoidance action that occurs in the presence of unfamiliar odors of potential predation. Chemical alarm cues from the brooding mother crayfish may not be a necessary component for the return of the juvenile crayfish to the brooding mother since the juvenile crayfish shows the ability to recognize potential predators and react by odor avoidance. The paddle attachment behavior seems to extend beyond odor preference or avoidance. Third and fourth instar crayfish were tested to determine their choice of substrate materials for attachment when presented paddles constructed from gauze, screen, and these materials in combination. The gauze is pliant, screen is firm, and gauze over screen is a combination of both qualities. The greatest preference by the third instar crayfish is the specific combination of gauze over screen while the least preference is gauze alone. The preference for material construction of the paddles starts to diminish in the fourth instar when odor preference seems to predominate.