Figure 1.
Cell proliferation in eight marine sponge species after continuous BrdU-labeling.
Mean percentages (±SD) of BrdU-positive cells in the choanoderm (open bars) and mesohyl (solid bars) are shown. Significant differences between cell proliferation in the choanoderm versus mesohyl are indicated for each species (* p<0.001; 95%-CI are given in Table 2). All species were labeled with BrdU for 6 h except for C. reniformis which was labeled for 10 h.
Figure 2.
Cell proliferation and cell loss in a selection of four sponge species.
Sponge species from three benthic ecosystems; tropical coral reef, temperate Mediterranean reef, and mangroves. (A) In situ (H. caerulea, C. reniformis and M. microsigmatosa) and ex situ (C. caribensis) photographs of test species. (B) BrdU-positive choanocytes (arrows) and mesohyl cells (arrowheads) of sponges BrdU-labeled for 6 h (10 h for C. reniformis) in vivo as a measure for proliferation. Areas of non-specific BrdU-labeling are occasionally seen in the cytoplasm of cells or extracellularly. (C) High amounts of cell shedding (Sh) in the lumen of excurrent canals (Ca) in specimens of H. caerulea, C. caribensis and C. reniformis sampled in situ. Choanocyte chambers (Ch), oscula (Os), the mesohyl (Me) and pinacoderm (Pi) are shown. Minor amounts of cell shedding (arrows) in the tropical mangrove sponge M. microsigmatosa sampled in situ. (D) Active caspase-3 activity of in vivo tissue was found in cells located in the mesohyl (arrows) resembling spherulous cells and, occasionally, archeocytes.
Table 1.
Cell proliferation (choanocytes and mesohyl cells), cell loss (shedding and detritus production), and microbial abundance categorization (HMA/LMA) in eight demosponge species (Porifera: Demospongia) from three benthic ecosystems (tropical coral reef, temperate Mediterranean reef and mangrove).
Table 2.
Mean differences in the percentage of cell proliferation between the choanoderm and mesohyl (see Fig. 1 for percentages of cell proliferation in choanoderm and mesohyl).
Figure 3.
Histological investigations of cell shedding and identification of cellular debris in sponge-derived detritus.
Arrowheads indicate shed choanocytes and arrows indicate shed spherulous cells in H. caerulea (A), C. caribensis (B) and C. reniformis (C). Shed cells in H. caerulea are present as mucal sheets (arrows) of cellular debris when close to the outflow openings (D). Light microscopy of detritus samples shows the presence of degraded cellular material, indicated by arrowheads (E).
Figure 4.
TEM images indicating microbial abundances in two sponge species.
Arrows indicate selected bacterial symbionts. (A) Many associated microorganisms are present in the mesohyl (Me) of the high microbial abundance (HMA) species C. caribensis. (B) Choanoderm (Ch) and mesohyl (Me) of the low microbial abundance (LMA) species M. microsigmatosa. Only a few associated microorganisms are present.
Figure 5.
Daily detritus production of five tropical coral reef sponge species.
(A) Daily detritus production (mg) and controls (mean±SD). Significant differences were found between detritus collected from pots containing sponge and control pots without sponge (* p<0.001). (B) Percentage bodyweight produced in detritus per day in five tropical coral reef species.