Predation patterns in heterobranchus longifilis Larvae: An analysis of their first exogenous feeding

Abstract

Two-day-old post hatch Heterobranchus longifilis larvae (4.06 ± 0.1 mm, 2.75 ± 0.06 mg and 0.35 ± 0.03 mm average
standard length, weight and mouth width, respectively) were introduced into glasswares and exposed to a wide
range of live zooplankton (prey size range: 42 to 876 µm) at a density of 2,944 individual/larva/day for 14 days. The
180 guts examined showed that food intake changed markedly with age and size. Larger preys were preferred as
larvae increased in age and size. Chilodonella uncinata and Lepadella ovalis (size range: 42 - 125 µm) dominated
the larval gut from day 2 - 4 post hatch. Brachionus quadridentatus, Alona monachanta and Chydorus sphaericus
(225 - 346 µm) were predominant at days 5 and 6, while Asplanchna priodonta, Bosmina longirostris and Daphnia
ambigua (485 - 876 µm) dominated from day 7 - 14 post hatch. Results from another 146 stomachs batch revealed
that 2 to 4 day old post hatch fry preyed on larger prey (225 - 876 µm) at disproportionate mouth-width to prey ratio
from 1: 1.2 to 2 when solely introduced and adequate. Initial recognition of prey by 2 - 4 day old larvae was longer
but thereafter feeding became more voracious and intermittent with shorter resting periods compared with older
larvae. Active feeding in H. longifilis larvae decreased with age while the length of feeding and rest period
increased with age.