Generalist feeding behavior of the leech Helobdella austinensis (Clitellata: Hirudinae)

The glossophoniid leech, Helobdella austinensis, has been presented as a specialist species that feeds almost exclusively on snails (Mollusca). Nonetheless, laboratory populations have been maintained by others using frozen Chironomus sp. larvae (Arthropoda), suggesting that H. austinensis may be capable of feeding on a variety of other food sources. The primary goal of this study was to identify the chemical signal(s) that trigger feeding behavior in this leech. To approach this question, snail-conditioned water and snail mucus were tested as attractants, but a trend consistent with attraction was not found. Relative proportions of amino acids were calculated from liquid chromatography–mass spectrometry data of several food items. Aspartic acid was prevalent in all food items examined, whereas other amino acids had varying levels of prevalence. Amino acids were then tested for attractive activity but did not exhibit a significant attraction. To determine the extent to which H. austinensis behaved as a generalist feeder, a controlled testing chamber was used to challenge leeches with various food sources. Surprisingly, this species fed opportunistically on food sources across animal phyla. In addition to snails, shrimp, bloodworms, crickets, and superworms (Zophobas atratus) exhibited a trend consistent with attraction. Chicken liver drippings, blackworms (Lumbriculus variegatus), and live snails also exhibited a similar trend when controlled for outliers. The long-term effects of feeding H. austinensis on various food items were examined to determine if any could sustain a population. These data suggest that chicken liver and cherry shrimp are sustainable food sources for propagation of H. austinensis. Notably, bovine blood was also able sustain a single individual for an extended time period, consistent with current phylogenetic models of recent blood-feeding ancestry in this clade.