Influence of Various Reproduction Substrates on the Survival, Health, and Reproductive Output of Broodstock Mediterranean Medicinal Leech (<i>Hirudo verbana</i>)

Principal component analysis and hierarchical clustering distinguished lethal substrates from viable substrates along an ionic and osmotic gradient driven by electrical conductivity up to 10.14 dS/m and high levels of sodium, copper, and zinc, indicating that the immediate cause of death was ionic and osmotic stress rather than organic richness. No cocoons were produced on the lethal substrates, whereas on the two viable substrates, the number of cocoons, cocoon morphology, number of offspring per cocoon, and offspring body weight were equivalent.

These findings reveal that commercially processed horticultural growing media pose an uncharacterized acute threat to captive reproduction and support the use of electrical conductivity as a low-cost, quantitative pre-use screening criterion; this principle is likely applicable to other exotic and wild species reared in semi-terrestrial breeding environments as well.</p>