Another prediction (based on the assumption that the modification or elaboration of skeletal structures is an energetically expensive process (e.g., Palumbi, 1984, 1986)) is that a positive correlation should exist between sponge spicule or spongin concentrations, and predator presence or attack frequency.
varians, we found that sponges with spongin-fortified skeletons coexisted with predators, but sponges with low levels of spongin were restricted to predator-free habitats (Hill, 1999).
Injured areas were noticeably white (presumably because of increased spongin concentrations), and could be clearly demarcated from uninjured tissue.
Spongin formation begins soon after the appearance of the mesohyl, about 24 h after settlement.
Although the spicules are formed within the scleroblasts, the finished spicules free of cells are usually covered by spongin filaments (Jones, 1967; Garrone, 1985).
The concentration of reddish brown pigment granules is no longer evident and spongin
fiber formation has begun.
In addition, the sponge contains some spongin fibers.
It should be noted that the presence of spongin fibers in this species (as well as in the Negombata species mentioned before), which gives the species elastic properties, also supports the non-Hadromerid positioning of the Latrunculiidae, since this order is characterized by the absence of spongin fibers and therefore is finn but non-elastic (Bergquist, 1978; Hartman, 1982).