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  Foods & feeding
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  Absorption of DOM
 

An example of a study on absorption of DOM is presented here, while research studies on SUSPENSION-FEEDING and DEPOSIT-FEEDING are considered elsewhere.

NOTE Dissolved Organic Matter, including amino acids, fatty acids, and other substances. Also referred to as DOC (dissolved organic carbon)

 
Research study 1
 

drawing of a kelp plant Macrocystis integrifolia with a frond bagged to receive injection of radio-labelled substance for a study in translocation of DOM to tubeworms Schizobranchia insignisTubeworms Schizobranchia insignis often co-occur in beds of large kelp Macrocystis integrifolia. Studies at the Bamfield Marine Sciences Centre, British Columbia show that 14C-labelled carbon exuded by kelps can be absorbed or eaten and presumably used in the worms' own nutrition.  The study is of special interest in that all experiments are done in plastic bags in situ using SCUBA. Selected fronds of the kelp are bagged and injected with aliquots of Na214CO3 (see drawing on Right). After 48h the bags are removed and contents assayed for labelled material. After washing the fronds to remove residual isotope, they are re-bagged with live worms, again injected with isotope, left for 24h, and taken to the laboratory for tissue analysis.  In all cases, the worms are found to accumulate 14C-label to levels about 14-fold greater than untreated controls. The exuded material may be in the form of dissolved carbon photograph of a mixed cluster of sabellid tubeworms including Schizobranchia insignis (lower left), Eudistylia polymorpha (centre, left), and Eudistylia vancouveri (solitary, Left)or suspended particulate carbon, although which form is used by the worms is not known. The authors conclude by stating that their study is the first to show in situ accumulation of algal extracelluar products by a free-living marine invertebrate. Fankboner & Druehl 1976 Specialia 15: 1391.

 

Mixed cluster of sabellid tubeworms. Several specimens of
Schizobranchia insignis
are located at the lower Left of
the photo, a few Eudistylia polymorpha are scattered
throughout (see the tan-coloured individual near the
centre of the photo), and a single Eudistylia vancouveri
is located at the Left centre of the photo 0.2X

 
Research study 2
 

photograph of a fat inkeeper worm Urechis caupoA study on DOM (Dissolved Organic Matter) uptake and metabolism in larvae of fat inkeeper worms Urechis caupo by researchers at the University of Southern California shows that radioactively labelled alanine is readily absorbed from solution and catabolised for energy by 4d-old larvae. As such studies can only be done without risk of contamination from resident bacteria present in the larvae, the authors use axenic or bacteria-free cultures. Based on their measured uptake data and metabolic rates of the larvae, and on known concentrations of alanine in the culture vessels, the authors estimate that about 50% of a larva’s metabolic demand could be provided by transport and catabolism of this single amino acid (at 15oC). The study adds Urechis caupo to a growing list of marine-invertebrate larvae that can take up and metabolise DOM. Jaeckle & Manahan 1989 Biol Bull 176: 317. Photograph courtesy Brenna Green, California.

NOTE adult Urechis are handy in this regard, because before their release in each sex the gametes are stored in sacs in the upper part of the coelom. Bacteria-free gametes are obtained by aseptic removal of the sacs in vivo. Most or all studies on DOM uptake in larvae nowadays employ axenic-culture methodologies

 

 

Adult fat inkeeper worm at 3m depth
in Monterey Bay, California 0.75X

 
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