Behavioural analyses
Neophobia (number of contacts and inspections of a novel object) and
exploratory behaviour were assessed using a plastic test arena (7 cm
depth x 7 cm width x 30 cm length) filled with 0.7 L of water. The arena
was divided into six equally spaced zones: a covered acclimatisation
section (zone 0) with a sliding opaque door, and five open test zones (5
cm each) without cover (zones 1, 2, 3, 4 and 5) delineated by marks at
the top margins of the arena walls. A coloured toy block (0.5 cm depth x
0.5 cm width x 3.5 cm height) was glued at the middle of zone 3 to serve
as a novel object (Fig. S2). Nine-month old fish were placed
individually into zone 0 for 15 min acclimatisation, after which the
removable gate was slowly lifted, and the fish behaviour recorded for 20
min with an overhead camera fixed 0.5m above the arena. After the test
period, tanks were drained, rinsed with ethanol and distilled water.
Videos were analysed by the same person using BORIS v. 7. 1. 4
(Friard & Gamba 2016) to ensure
consistency. The following four behaviours were quantified for both
parents and offspring: (1) latency (s) to exit the acclimatisation zone,
(2) number of inspections within 3 cm of the novel object (i. e.
individual facing towards the novel for more than three seconds), (3)
number of contacts with the novel object, and (4) number of movements
between zones (activity).