Regulation of filter-feeding house components in response to varying food regimes in the appendicularian, Oikopleura dioica

Abstract

The frequent repetitive secretion of filter-feeding houses of the tunicate, Oikopleura dioica represents investment of a substantial proportion of total body carbon. Despite this investment, the filterfeeding strategy of pelagic tunicates has been proposed as an adaptation to oligotrophic environments. Here, we examined the capacity of O. dioica to modify its house renewal rate (HRR) and expression of component proteins, oikosins, as well as ingestion rates of different sized particles in response to varying food regimes. There were no significant changes in HRR (0.26 + 0.07 SD house h 21 ) with age or food concentration throughout the life cycle. Our data suggest that the complex pattern of endoreduplicating cycles in the oikoplastic epithelium probably limits the capacity to reduce the energetic output of house replacement as a response to a limiting food environment. On the other hand, at the molecular level, there was differential regulation of component house proteins when animals were cultured in standard versus limiting food regimes. Animals pre-conditioned in each of these regimes and subsequently challenged with an identical mixture of large and small particles exhibited different retention efficiencies of larger food particles. Taken together, these results raise the possibility that a limited ability to modulate house architecture may underlie the differential particle retention efficiencies observed.

Increased appendicularian zooplankton alter carbon cycling under warmer more acidified ocean conditions

“…In comparison, we measured DOC over an extended time period under conditions simulating natural ones more accurately, and allowing carbon mechanism processes to adapt and respond accordingly. Further, O. dioica houses are discarded up to 6 times per day (Troedsson et al ) and can be as high as 27 houses per day for other appendicularian species (Sato et al ) and contribute substantially to high POC export rates (Alldredge ; Dagg and Brown ; Deibel et al ), similar to dead fast sinking ctenophores and medusa species (Lebrato et al ).…”

Conservation and divergence of chemical defense system in the tunicate Oikopleura dioica revealed by genome wide response to two xenobiotics

“…Both BaP and Clo also resulted in down-regulation of oikosins that are components of the house [ 6 , 7 ]. Oikopleura invests a significant portion of energy in the synthesis of its food-filtering house, composed of more than 20 proteins [ 6 , 7 , 46 ]. It is possible that stress and reduced food intake (a likely consequence of reduced house production) triggers energy saving adaptive responses such as reduced muscle contraction and lower energy metabolism in Clo-treated animals.…”

The Evolving Proteome of a Complex Extracellular Matrix, the Oikopleura House

“…Thus, it is intriguing that a series of proteins with domains implicated in innate immunity are secreted from a region of the epithelium that produces this structure, and could indicate that they are an early defensive measure against the variety of marine bacteria the animal encounters in its pelagic environment. As O. dioica is known to be able to feed on bacteria [29] , and has a rapid gut passage time of several minutes, an alternative explanation could be that the oikosins containing PLA 2 domains serve a role in the pre-digestion of these particles through the disruption of bacterial cell walls.…”