Note
Female Euchaeta marina (Prestandrea, 1833) have one large, thin-walled lipid sac, whereas female Pleuromamma xiphias (Giesbrecht, 1889) have two separate and morphologically distinct lipid storage sites. One lipid site in P. xiphias corresponds to the mesenteric tissue that surrounds the anterior region of the midgut. The morphology of these cells resembles that of mammalian brown adipocytes. The cytoplasm is filled with extensive smooth endoplasmic reticulum, numerous mitochondria and several deposits of intracellular lipid. The second lipid site of P. xiphias lies in the posterior region of the metasome and resembles the thin-walled lipid sac of E. marina.