- Figure 5 Movie
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Changing currents result in an upstream/downstream role reversal during crawling prior to mating.
Slug 1 initially heads upstream towards slug 2, but the currents change, leading slug 1 astray until it slows and stops crawling. Meanwhile, slug 2 is stationary until the current change, making slug 1 upstream. Slug 2 then turns, heads upstream, avoids a Ptilosarcus gurneyi, and eventually contacts slug 1, before mating begins (m). Flow is indicated by the dye plume generated from a fluorescein source (f). Black lines show slug movement tracks. Time-lapse speed indicated bottom left.
- Figure 6 Movie
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Initiation, alignment and copulation stages of mating in Tritonia diomedea.
A slug (1) crawls cross-stream and then turns upstream, when downstream of a second slug (2). Initiation: Slug 1 (the initiator) contacts the tail of slug 2. Slug 2 (the initiate) turns abruptly right, while slug 1 turns more slowly to the right. Alignment: Slugs 1 and 2 are now head-to-tail and continue circling clockwise. Copulation: Both slugs remain stationary for approximately 45 mins. Mating ends, with the initiating slug crawling away and the other slug remaining stationary. Black line shows slug movement track. Time-lapse speed indicated bottom left.
- Figure 8 Movie
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Tritonia diomedea browsing on a large Ptilosarcus gurneyi.
T. diomedea approaches from downstream (flow shown by suspended particles in the seawater) with rhinophores extended, oral veil lifted, and lips protruded. As T. diomedea nears its prey, it slows and then stops crawling, and lifts its head by raising the anterior portion of the foot off the substratum. The oral veil tips make brief contact with the P. gurneyi, and then the oral veil is immediately pulled back. Strike preparation follows, with the lips protruding even farther and continued retraction of the oral veil. The bite-strike consists of opening the jaws and extending the grasping radula out of the mouth as the entire buccal mass lunges forward. The radula grasps a pinnea and pulls it into the mouth, while the P. gurneyi retracts into the sediment. The jaws are used to cut part of the pinnea held by the radula, leaving a severed stump. Crawling resumes after the bite-strike is complete. The slug is 20 cm long.
- Figure 10 Movie
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Tritonia diomedea escape swim in response to contact with Pycnopodia helianthoides.
After P. helianthoides (p) approaches the T. diomedea(s), contact is made, and the slug begins an escape swim with a ventral flexion. Subsequent dorsal and ventral flexions lift the slug off the substratum, and the combined effects of the current and swimming begin to move the slug downstream, away from the predator. The flow eventually sweeps the swimming slug completely out of the field of view, at least a meter farther downstream from P. helianthoides. Black line shows movement tracks. Time-lapse speed indicated bottom left.
