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Life Sciences

University of Texas Rio Grande Valley

Theses/Dissertations

1999

Biological sciences

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The Ecology And Life History Of The Mexican Tetra, Astyanax Mexicanus, (Teleostei: Characidae) In The Lower Rio Grande Valley, Texas, Mario Estrada May 1999

The Ecology And Life History Of The Mexican Tetra, Astyanax Mexicanus, (Teleostei: Characidae) In The Lower Rio Grande Valley, Texas, Mario Estrada

Theses and Dissertations - UTB/UTPA

The Mexican tetra has been found to migrate from shallow waters in the spring and summer months into deeper waters during the winter months when temperatures are too cold for their survival. This fish is omnivorous with insect material being the major source of food. Its food types include green algae, nematoceran larvae, hemipterans, coleopterans, hymenopterans, dipterans, ostracods, fish eggs and amphipods. Furthermore, size classes showed that the Mexican tetras reached their largest size at the River site and smaller sizes at the Bridge and Gate sites and apparently breed year round. They are capable of producing from 300 to …


Sucrose Metabolism In Two Saccharum Species, Monica Ida Valdez-Garza May 1999

Sucrose Metabolism In Two Saccharum Species, Monica Ida Valdez-Garza

Theses and Dissertations - UTB/UTPA

S. officinarum is a thick-stemmed sugarcane which stores large amounts of sucrose, and S. spontaneum is thin-stemmed with very little sucrose. Sucrose synthase (SS), sucrose phosphate synthase (SPS), and invertase enzymes are thought to affect the accumulation of sucrose in the stems of sugarcane. This study was performed to determine if (i) differences between SPS and acid invertase activities account for the difference in sucrose content of sugarcane stems, and (ii) differences in SS activity influence sucrose concentration. The difference between SPS and acid invertase activities did not appear related to the low sucrose content in S. spontaneum. However, the …