Systematic Zoology
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Diploma Thesis

“Specific dynamic action (SDA) and changes in organ size in turtles“

Spezifisch dynamische Aktion (SDA) und Organgrößenänderungen bei Schildkröten

The specific dynamic action (SDA) describes the increase of the metabolic rate according to the uptake of food. This circumstance is going along with physiological und morphological changes of the body. Organs involved in digestion change in size according to ingestion. To survey the mechanisms concerning organ size changes, the scientific focus is laid especially on the stomach, liver and intestine.

In this study the SDA and chages in organ size after food uptake are investigated in turtles with different feeding response. In this context it is shown that morphological- and physiological organ adaptations base on the same principles in snapping turles (Chelydra serpentina) and  yellow-eared (Trachemys scripta scripta) respectively red-eared slider turtles (Trachemys scripta elegans).

The oxygen consumption is quantified over an open respiratory system as a measure for the energy metabolism and the rate of the SDA. There is a strong increase of the mass specific oxygen consumption already 24 hours after the food uptake, which reaches his peak after 48 hours. This value is nearly 3 times the basic matabolic rate which drops back on the basic value in further progress. Morphological changes of the small intestine, especially the Tunica mucosa, are examined via ultrasonography but without new results. Sections of historesin embedded duodenums allow the examination on the histological and cellular level. There is a pseudostratified epithelium layer in turtles. Furthermore the wet weight, the dry mass and the nonfat dry mass of several organs of starving and non starving animals are quantified and compared, i.e. heart, lung, stomach, liver, intestine and the rest of the turtles body. 

Mophological mechanisms and adaptations are shown which have manifested within the organs after ingestion during evolution. The results are compared with published knowledge on other vertebrate groups and discussed in consideration of the evolutionary history of the SDA and mechanisms of organ size changes in vertebrates.