MARC 主機 00000nam  2200337   4500 
001    AAI3470088 
005    20111205104800.5 
008    111205s2010    ||||||||||||||||| ||eng d 
020    9781124117140 
035    (UMI)AAI3470088 
040    UMI|cUMI 
100 1  Auker, Linda Ann 
245 14 The effects of Didemnum vexillum overgrowth on Mytilus 
       edulis biology and ecology 
300    132 p 
500    Source: Dissertation Abstracts International, Volume: 71-
       08, Section: B, page: 4589 
500    Adviser: Larry G. Harris 
502    Thesis (Ph.D.)--University of New Hampshire, 2010 
520    Didemnum vexillum is an invasive colonial ascidian in the 
       Gulf of Maine that readily colonizes hard substrates. 
       These substrates include hard-shelled organisms, such as 
       the common blue mussel Mytilus edulis. Preliminary 
       observations and short-term studies showed potential 
       effects of epibiosis on M. edulis growth, specifically lip
       thickness and tissue index. This dissertation study 
       further examined the effects of D. vexillum on growth and 
       reproduction of, and predation on, M. edulis. Shell 
       thickness index, tissue index, shell mass to tissue mass 
       ratio, lip thickness and mussel length were measured 
       throughout a 12-month period in control and overgrown 
       mussels. Additionally, histological preparations of the 
       mussels were used to determine reproductive condition of 
       the mussels in each of these treatments. These variables 
       were measured every three months (November 2008, February 
       2009, May 2009, and August 2009). Laboratory choice and 
       consumption experiments examined the effects of overgrowth
       of the ascidian on predation by Carcinus maenas. Finally, 
       mussel primary settlement was measured from summer 2008 
       through summer 2009 and compared to historical data. This 
       settlement was also correlated with the abundance of 
       neighboring D. vexillum 
520    Overgrowth had a negative impact on mussel growth. Tissue 
       index and lip thickness were negatively affected as the 
       mussel lip margin was overgrown. Overall mussel growth was
       significantly higher in control mussels by the end of the 
       experiment. The pattern of spawning and gonad development 
       was reversed in overgrown male mussels from the control 
       mussels. Predation studies showed a potential positive 
       effect for the mussel, as crabs consumed more control 
       mussels than overgrown mussels in both a choice study and 
       a consumption study. Finally, winter mussel settlement in 
       2008-2009 was lower than historical 1980-1981 settlement, 
       and there was a decrease in mussel plantigrades with  D. 
       vexillum recruits. These studies show tradeoffs in the 
       effects of overgrowth by D. vexillum; growth and 
       reproduction are inhibited, while predation is decreased. 
       As mussels are an important source of food and habitat for
       other Gulf of Maine organisms, overgrowth by  D. vexillum 
       has the potential to change ecosystem dynamics 
590    School code: 0141 
650  4 Biology, Ecology 
650  4 Biology, Oceanography 
690    0329 
690    0416 
710 2  University of New Hampshire 
773 0  |tDissertation Abstracts International|g71-08B 
856 40 |u