Date of Award

Winter 2004

Project Type

Dissertation

Program or Major

Zoology

Degree Name

Doctor of Philosophy

First Advisor

Jessica A Baker

Abstract

Squid embryos are able to contract their mantle early during the embryonic period.

This dissertation examines the onset of contractile capabilities and subsequent maturation of the main locornotor structures in embryos of two species of loligind squids with a focus on the mantle musculature. The functional implications of the differentiation and organization of the musculature is investigated.

The results of these series of studies indicate that the development and emergence of functional competence of the mantle musculature in loliginid squids is a dynamic process. Differentiation and organization of the musculature of the main locomotor structures does not occur simultaneously and has a precise sequence with the mantle developing first, then funnel and the fins developing and organizing last. The superficial mitochodria rich (SMR) fibers that drive respiratory contractions differentiate first at the inner and outer surfaces of the mantle. The central mitochondria poor (CMP) muscle fibers, which are active during fast and escape jetting, differentiate second and in the central region of the mantle.

The mantle of embryonic loligind squids is able to produce contractions in the absence of a completely developed and organized musculature. During subsequent stages, the mantle undergoes measurable ontogenetic kinematic changes as evidenced by an increase in the frequency and duration of the contractions. Moreover, mathematical modeling of these contractions indicates that the mantle in embryonic squids is capable of producing two distinct types of contractions. These different contraction types resemble the respiratory and locomotory contractions of the juveniles and adults.

When these data are examined in conjunction with the morphological data they show that mantle morphology and mantle functional ability appear to be developing in parallel. Additionally, stage 27 emerges as a morphologically and functionally significant point in development. Stage 27 embryos have a robust, differentiated mantle whose morphological organization and functional repertoire begins to reflect that of the adults. (Abstract shortened by UMI.).

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