Chapter 17, Problem 25P

Summary Introduction

To analyze:

A sea slug Elysia chlorotica acquires chloroplasts by consuming an algal food source, Vaucheria litorea. The ingested chloroplasts in sea slug’s digestive epithelium carry out active photosynthesis for months after ingestion. The algal nuclear genome encodes more than $90\%$ but not all of the proteins needed for chloroplast metabolism. It is supposed that the sea slug actively maintains ingested chloroplasts, supplying them with photosynthetic proteins encoded in the sea slug genome.

Determine whether the sea slug has attain photosynthetic genes by horizontal gene transfer from its algal food source. Write down the steps required, and their plausibility, for heritable endosymbiosis to eventuate.

Introduction:

Elysia chlorotica is a small green slug, which shows kleptoplasty. Kleptoplasty is the phenomenon in which some slugs use chloroplast from the algae. Elysia chlorotica shows the symbiotic association with the chloroplasts of marine Vaucheria litorea.