Data from: Cell turnover and detritus production in marine sponges from tropical and temperate benthic ecosystems

This study describes in vivo cell turnover (the balance between cell
proliferation and cell loss) in eight marine sponge species from tropical
coral reef, mangrove and temperate Mediterranean reef ecosystems. Cell
proliferation was determined through the incorporation of
5-bromo-2′-deoxyuridine (BrdU) and measuring the percentage of
BrdU-positive cells after 6 h of continuous labeling (10 h for Chondrosia
reniformis). Apoptosis was identified using an antibody against active
caspase-3. Cell loss through shedding was studied quantitatively by
collecting and weighing sponge-expelled detritus and qualitatively by
light microscopy of sponge tissue and detritus. All species investigated
displayed substantial cell proliferation, predominantly in the choanoderm,
but also in the mesohyl. The majority of coral reef species (five) showed
between 16.1±15.9% and 19.0±2.0% choanocyte proliferation (mean±SD) after
6 h and the Mediterranean species, C. reniformis, showed 16.6±3.2% after
10 h BrdU-labeling. Monanchora arbuscula showed lower choanocyte
proliferation (8.1±3.7%), whereas the mangrove species Mycale
microsigmatosa showed relatively higher levels of choanocyte proliferation
(70.5±6.6%). Choanocyte proliferation in Haliclona vansoesti was variable
(2.8–73.1%). Apoptosis was negligible and not the primary mechanism of
cell loss involved in cell turnover. All species investigated produced
significant amounts of detritus (2.5–18% detritus bodyweight−1·d−1) and
cell shedding was observed in seven out of eight species. The amount of
shed cells observed in histological sections may be related to differences
in residence time of detritus within canals. Detritus production could not
be directly linked to cell shedding due to the degraded nature of expelled
cellular debris. We have demonstrated that under steady-state conditions,
cell turnover through cell proliferation and cell shedding are common
processes to maintain tissue homeostasis in a variety of sponge species
from different ecosystems. Cell turnover is hypothesized to be the main
underlying mechanism producing sponge-derived detritus, a major trophic
resource transferred through sponges in benthic ecosystems, such as coral
reefs.