Elemental analyses of Oikopleurids and factors affecting house production rate of Oikopleura vanhoëffeni (Tunicata, appendicularia) in coastal Newfoundland waters

Riehl, Michael Wilfred (1993) Elemental analyses of Oikopleurids and factors affecting house production rate of Oikopleura vanhoëffeni (Tunicata, appendicularia) in coastal Newfoundland waters. Masters thesis, Memorial University of Newfoundland.

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Abstract

Oikopleura vanhöeffeni and O. labradoriensis are cold-water pelagic tunicates that are abundant in coastal Newfoundland waters. The oikopleurid feeding apparatus or ‘house’ is a secreted structure which can be discarded and replaced in response to animal disturbance or house clogging. This study examined the energy costs associated with house production and factors that affect the frequency of house abandonment. -- The elemental content of O. vanhöeffeni and O. labradoriensis increased at about the third power of trunk and tail length. The mean C:N ratio of O. vanhöeffeni in this study was 3.51 (n=203) and for O. labradoriensis. 3.57 (n=12). These values are similar to others reported in the literature. -- Elemental analyses of 11 newly-secreted O. vanhöeffeni houses showed that ‘new’ houses had a mean carbon content of 8.38 μg C (7.5% of body carbon) and a mean nitrogen content of 2.60 μg N (20.1% of body nitrogen). No relationship was found between carbon measures of ‘new’ houses and of the animals that produced them; similar- sized animals showed a five-fold variation in house carbon content. Upwards of 88 μg C of natural particulate material were trapped within a single house. -- The mean house production rate (HPR) for O. vanhöeffeni was 1.7 houses day⁻¹ (n=104), and for the somewhat smaller O. labradoriensis. the average was 2.3 houses day⁻¹ (n=8). HPR between species was not significantly different. Food availability was the most important variable affecting HPR. No relationship could be determined for temperature vs HPR, and POC vs HPR. -- The O. vanhöeffeni house elemental content and HPR from this study indicated that a mean daily carbon investment of 14.3 μg C (13% of body carbon day⁻¹) was required for the house structure. Additional energy investment would be required for house secretion, expansion and other metabolic processes.

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