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The fat cells of females of Daphnia obtusa have a well developed rough endoplasmic reticulum, free ribosomes and small Golgi complexes. When the ovaries contain growing parthenogenetic oocytes, the fat cells show few scattered glycogen granules, whereas they show abundant glycogen when the ovaries contain one vitellogenic amphigonic oocyte. The latter case could be explained by the fact that the fat cells synthesize little vitellogenin since the yolk of amphigonic oocytes is mostly endogenous.

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The labral glands of Daphnia consist of three distinct functional units on each side: (1) several cells at the base of the head, (2) two large cells at the base of the labrum and one large cell (cell A) in the median part of the labrum and (3) one large cell (cell B) in the median part of the labrum. These gland cells do not form a syncytium, contrary to reports by previous investigators. With the exception of cell B, they have a well-developed rough endoplasmic reticulum and many active Golgi complexes. The Golgi activity changes during the molt cycle. The Golgi activity of the cells of the head base is different from that of the large cells of the labrum. Since clear exocytotic phenomena were not observed, the secretion can be assumed to flow into the hemolymph after accumulation in the enlarged intercellular spaces. Cell B has a distinctive cytoplasmic ultrastructure the function of which is not yet understood. The four large cells of the labrum are in contact with a duct cell (or several duct cells) characterized by a deep infolding of the plasma membrane. This delimits a narrow lumen, which contains no secretion. No passage of substance is visible from the gland cells to the duct cell(s).