Amazingly, half of the sponge's choanocyte
(filtration) cells had divided and the choanocyte
's cell division cycle was a phenomenally short 5.
These are: the presence of choanocytes
in sponges, the perceived simplicity of sponges relative to other animals, and comparisons of early embryological events (other characters, e.
The new sponge has neither choanocytes
nor a system for filtering water.
Differences between the structure of sponge choanocytes and the choanoflagellate cell, and the fact that many choanocytes are arranged within single chambers in a sponge (Fig.
In the calcareous sponge Sycon coactum, water enters through pores 10-20 [micro]m apart into long chambers lined by several thousand pumping choanocytes (Fig.
One view holds that the flagellated cells are transformed into the choanocytes of juvenile sponges (Borojevic and Levi, 1965; Boury-Esnault, 1976; Amano and Hori, 1994, 1996), but the opposing view contends that they are lost by exfoliation or phagocytosis during metamorphosis (Bergquist and Glasgow 1986; Misevic et al.
About 36 h after settlement, choanocytes are differentiated in the inner cell mass and formation of the choanocyte chamber begins.
piceus: the adjacent choanocyte
chambers are destroyed, and some of the choanocytes
As early as 1892, the inversion of these cells to form choanocytes
was proposed for some species of sponge (3).
Feeding in sponges has been well-documented, and with the exception of the two examples cited in the introduction, the Cladorhizidae and the Hexactinellida, particle uptake in sponges occurs at the choanocytes
in the flagellated chambers or at the pinacoderm-lined incurrent canals.
of Acanthochaetetes wellsi possess a periflagellar sleeve; a central cell at the apopyle of the choanocyte
chambers, as in the Hadromerida; and a spicule complement similar to that of the family Spirastrellidae in the order Hadromerida (Hartman and Goreau, 1975; Vacelet and Garrone, 1985; Reitner and Engeser, 1987; Boury-Esnault et al.
In the sections of sponge branches we were able to identify the following epithelial cells: exopinacocytes (covering the outer sponge surface), endopinacocytes (lining the water canals), and choanocytes
chambers in the canal system).
The fate of larval cells during metamorphosis and the origin of the choanocytes of juveniles have been debated for many years among sponge biologists (Fell, 1974; Simpson, 1984; Kaye and Reiswig, 1991; Woollacott, 1993).
In calcareous sponges, larval flagellated cells are transformed into the choanocytes of a juvenile during metamorphosis (Duboscq and Tuzet, 1937; Amano and Hori, 1992, 1993).
The chamber has a diameter of about 25 [[micro]meter] and is constructed of 3-[[micro]meter]-wide choanocytes