Pauly et al.: Growth and related traits of Hippospongia lachne 
diameter in centimeters and the volume in cubic centime- 
ters, the expression of the diameter-to-volume relation- 
ship in the wool sponge becomes 
V = 0.055 x D®. (13) 
Therefore, the equation for the relationship between 
the age in years and the volume in cubic centimeters 
becomes 
3 
V, =1046(1- 1") (14) 
Opitz (1996), for her detailed food-web model of Caribbean 
reefs, used a ratio of dry weight to wet weight of 333:100 
and considered 22.5% of wet mass to be “inorganic skeletal 
material,” on the basis of a personal communication from 
a scientist working mainly on deepwater or cold-water 
sponges. 
Our own determination of the percentage of wet weight 
to dry weight for wool sponges collected in the Florida 
Keys (number of samples [n]=15) is 3.9% of wet mass. 
A larger percentage (11%) was estimated for another com- 
mercial sponge species that we collected in the same area 
(n=20): the grass sponge (Spongia graminea), which is the 
second-most valuable commercial sponge in Florida. 
Longevity 
The estimated longevity of the wool sponge, that is of 
its first, spherical phase, is as follows, given Equation 7: 
3/0.191=16 years, with uncertainty ranging from 12 to 
24 years. On the other hand, the values of production 
per unit biomass (which can be considered equal to Z) 
in Table 2, used with the inverse of Equation 8, lead to 
estimates of longevity of 2.5 years (for Z of 1.7 year”), 
4.8 year (for Z of 3.9 year+), and 22.3 years (for Z of 0.2 
year '). Only the last of these estimates 
appears realistic, whereas the first esti- 
mate of 16 years is compatible with 
that of Storr (1964, p. 18-19), whose 
longevity estimate includes the life his- 
tory phase during which wool sponges 
change shape (which was not considered 
in our study). In the meantime, however, 
experiments have been conducted, and 
their results indicate that the longevity 
of wool sponges is strongly influenced by 
environmental stress (e.g., stress caused 
by high temperatures, extreme levels 
of salinity, and phytoplankton blooms) 
(Butler et al., 2018). 
Also note that the value of Z that was 
based on estimates of production per 
unit biomass in Table 2 and was used 
to produce, through Equation 8, the 
only reasonable estimate of t 
leads to the following ratio for sponges: 
Z/K=0.2/0.191=1.1. In the absence of 
fishing (as was the case in the model 
developed with data from work in the 
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Pinkerton et al., 2008) (Table 2), Z/K is also M/K and 
M/K=1.1, which is a very plausible value for low-activity 
or sessile animals. Therefore, for example, although M/K 
is 1.5 for many populations of bony fishes (Taylor, 1958; 
Froese et al., 2016), the mean M/K is 0.76 for 16 pop- 
ulations and 13 species of bivalves (from Vakily, 1992, 
appendix 4) and is 1.1 for 11 species of sea urchins (see 
Longhurst and Pauly, 1987, figure 10.2, based on Ebert, 
1975), with both groups represented by both warmwater 
and cold-water species. 
Reproduction 
Butler et al. (2017) established that the number of gameto- 
cytes in tissue samples from 3 species of commercial 
sponges from the Florida Keys were positively and signifi- 
cantly related to sponge size, whether measured as sponge 
volume (F=4.762; df=1, 15; P=0.047; r7=0.254) or as diame- 
ter (F=9.270; df=1, 15; P=0.009; r?=0.398); the relationships 
explained ~40% of the variance in gametocyte number. 
van Soest (1978) concluded that wool sponges reach a 
size up to 18 cm in diameter in the waters of Curacao, 
where the waters are warmer than those of the upper 
Gulf of Mexico and where wool sponges reach diameters of 
over 30 cm (Storr, 1964). These numbers lead to Figure 3, 
which shows that maximum sizes reached by wool sponges 
decline with temperature (as indicated by the definition of 
the parameters of Equation 6) and which also illustrates 
the inverse relationship between minimum length at first 
maturity and water temperature, as has been reported for 
other WBE (Pauly, 2021a). This finding is supported by 
measurements of the growth of wool sponges in the Flor- 
ida Keys, where average growth rates varied 5-fold sea- 
sonally (Butler et al., 2017). 
Florida 
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Curacao 
a diameter at maturity 
3 4 5 6 7 
No. of months with SST>26.7°C 
Figure 3 
Apparent temperature dependence of size at first maturity (solid line) and 
max also maximum size (dashed line) for the sheepswool sponge or wool sponge (Hip- 
pospongia lachne) off Florida in the Gulf of Mexico (based on data from Storr, 
1964) and in the waters of Curacao in the Caribbean Sea (based on data from 
van Soest, 1978). SST=sea-surface temperature. 
