Hopkins Marine Station Student Paper

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Title: Spatial distribution, physiological tolerances, and respiration rates of larvae of the intertidal fly, Oedoparena glauca
Student Author(s): Lopez, James
Faculty Advisor(s): Somero, George
%E Watanabe, Jim
Pages: 28
Location: Final Papers Biology 175H
Date: June 2001
Abstract: I quantified the spatial distribution, physiological tolerances, and respiration rates of larvae of the intertidal fly, Oedoparena glauca. O. glauca larvae consume the barnacle, Balanus glandula, and use the shell for protection and pupation. The percent of barnacles infested with larvae and pupae was greatest in a high-intertidal crevice (29%), moderate on upper north-facing intertidal walls (~3%), and zero at lower tidal heights and on south-facing walls. Thermal stress, high salinity, and submergence are physiological stresses imposed on the larvae and pupae due to life in the intertidal zone. In laboratory tests of thermal tolerance, all larvae died following 3 hours of exposure to 39 degrees C, but tolerated temperatures less than or equal to 38 degrees C. Pupae appeared more sensitive to thermal stress, with 0% eclosion by pupae treated at 35 degrees C, 38 degrees C, and 41 degrees C for four hours. Intertidal datalogger records and field measurements of internal B. glandula temperatures exceeded 36 degrees C, near the thermal limit of O. glauca larvae. In addition to this thermal stress, during periods of aerial exposure, B. glandula was significantly more saline in vivo than the surrounding seawater, perhaps due to evaporative cooling by the barnacle. In tests of submergence tolerance, larvae survived 8 days of submergence in filtered seawater held at 13 degrees C, but all died after 10 days. The pupae were apparently more sensitive to submergence; 40% of pupae submerged for two hours eclosed within 16 days, whereas there was only 12.5% eclosion of pupae submerged for 24 hours. The larvae were observed not to respire during six hours of submergence. However, the larvae respired at a rate of 0.4317 µmol O2/hr/g, over four days of submergence. This study illustrates that O. glauca larvae are hardy and capable of tolerating thermal stress and submergence. In contrast, the pupae may be more sensitive to these environmental conditions, perhaps restricting their geographical distribution .