Chlorophyll fluorescence assisted with image analysis in Antarctic clam: quantification of internal food intake

Abstract

The Antarctic soft-shelled clam, Laternula elliptica is one of the most common marine organisms inhabiting in shallow subtidal water around the Antarctic continent and surrounding islands. Seasonal changes in internal food intake of the clam were investigated over two years period from Feb 1998 to Jan 2000. Total chlorophyll in water column was obtained from a long-term monitoring programs conducted at the King Sejong Station. For analysis, clams were sampled at Marian Cove, King George Island using SCUBA, fixed in 10% neutral formalin in situ and transported to the lab. After recording sizes and weight, the middle part of the body was sectioned longitudinallly for histological preparation. Digested chlorophyll in digestive system on the paraffin block measured by actinic red light(650 nm) and periodic flashes using the kinetic imaging fluorometer. After the light exposure for 10 sec to the blockk in the fluorometer, fluoresced block image was directly captured in FluorCam software. The number of fluoresced pixels was counted using image analysis software. Fluorescence intensity was determined as a sum of the pixel's number, and expressed as an internal food intalke index (IFI). The monthly mean vallue of the IFI was used for quantification of monthly feeding status of the clam.