| dc.description.abstract | Freshwater sponges (Porifera, Spongillidae) owing to some of their characteristics, may be
exploited as bioindicators and, as such, are becoming increasingly interesting in ecological
studies. Earlier studies have shown that environmental factors have a fundamental impact on
Demospongiae spicule size and shape. However, data on spicule anomalies and possible causes
of their appearance are quite scarce. The present study aimed to assess the frequency of spicule
anomalies in sponges from 10 Serbian rivers, in relation to the species, physico-chemical
properties of the streams and presence of pollutants.
In autumn of 2017, 40 sponge samples were collected in ten tributaries of Sava and Danube
rivers (Velika Morava, Zapadna Morava, Juzna Morava, Tisa, Kolubara, Porecka River, Mlava,
Beli Timok, Crni Timok and Nisava). Basic physico-chemical parameters were registered at
every site where sponges were found. After spicule isolation by HNO3 digestion procedure, the
samples were subjected to morphological analysis by light and scanning electron microscopy,
and number of anomalies recorded. For other parameters such as heavy metals concentration,
nitrates, phosphates, carbonates, bicarbonates, dissolved silicates, etc. yearly values from the
Environment Protection Agency were taken into consideration.
Five species were found: Ephydatia fluviatilis, Ephydatia muelleri, Spongilla lacustris,
Eunapius fragilis, and Trochospongilla horrida. The most frequent anomalies were: spicule
bending near one end, both ends, or medially, spicules with bifurcations and spicules with
bulbous enlargements. The type and frequency of spicule malformations varied greatly within
the analyzed specimens. The frequency of anomalies ranged from 1 x 10-3
to 67 x 10-3
, with an
average number of 12 x 10-3
. Variations were noted in main physico-chemical parameters (the
conductivity ranged from 364 to 603 µS, the temperature from 12.3 to 21.9° C, the pH from 7.2
to 8.0 and the oxygen concentration from 7.07 to 11.3 mg/l). Similarly, the levels of different
metals and other pollutants surveyed in the ten rivers varied considerably, but the permitted
concentrations were not exceeded. The highest number of anomalies was found in a specimen
of E. fragilis collected at Markovac (Great Morava River) and the lowest number was found in
a specimen of E. fluviatilis from Kanjiza (Tisa River). Although the two “antipode” sites
exhibited some differences in concentrations of bicarbonates, Fe, Cr, Ni, Mg, etc., none of the
registered concentrations reached Intervention Values.io
From the present study it can be speculated that the propensity of sponges to display aberrant
spicules will mostly depend on the species. Besides species-specific intrinsic factors, some
exogenous factors are obviously also needed for the development of aberrant spicules, but it
remains unclear what these environmental factors are. Some species seemed more tolerant than
other to changes of water physico-chemical parameters. | sr |
