Assimilation of Bacteriophages by Marine Invertebrate Larvae (Annelida, Echinodermata, and Mollusca)

Studies on feeding for free-living, immature, developmental form of marine invertebrates known as larvae have focused on the capture of food particles (i.e. unicellular organisms) that are visible using light microscopy. However, there is an abundance of dissolved organic matter (DOM) that are too small to be detected by light microscopy and we know little about the ability of larvae to exploit DOM as a food source. Bacteriophages (hereafter phages), or viruses that use bacteria as hosts, are considered DOM because of their small size ( We tested the hypothesis that feeding larvae from the phyla Annelida, Echinodermata, and Mollusca consume phages by incubating larvae with phages labelled with the fluorescent tag DTAF (5-[{4,6-Dichlorotriazin-2-yl}Amino]fluorescein); larvae incubated in filtered sea water for the same amount of time were experimental controls. We used epifluorescence microscopy to detect the amount and distribution of fluorescence present in individuals. In every larval from tested, there was significantly more fluorescence in the digestive system of experimental larvae compared to control larvae ((one-way ANOVA Sabellaridae (Annelida) [F(1,12) = 40.801, p = 3.446×10⁻⁵], Chaetopteridae (Annelida) [F(1,7) = 58.052, p = 1.246×10⁻⁴], Ophuiroidea (Echinodermata) [F(1,12) = 22.603, p = 4.687×10⁻⁴], and Gastropoda (Mollusca) [F(1,6) = 32.01, p = 1.310×10⁻³]). These results indicate that phages enter the digestive system of the tested larvae and could represent a previously unrecognized source of nutrition for planktonic larvae