PMC

(A) Satellite tracking locations for shark 4 (green), shark 5 (orange) and shark 6 (red) during camera tag attachment periods in 2019. Location of feeding events for each shark (squares in corresponding colours). Selected behaviours are highlighted with given locations (B-G). In (B) to (E) shark 4 is seen feeding at the surface following a second male shark. Shark 5 camera captures a second shark swimming slowly over the seabed in (F) as it swims towards the surface. (G) Shark 6 feeding at the surface.

(A) Shark 3 moving over sandy seabed, (B) shark 4 feeding while following a second feeding shark at the surface, (C) shark 2 moving over mixed ground with seaweeds (D) shark 5 trailed closely by a second shark, (E) shark 3 engaged in early morning group behaviour—three sharks visible; instrumented shark (centre) and two other sharks (far left and top right), (F) shark 4 rearward camera obscured by plastic sheet, (G) shark 5 rearward camera revealing defecation, and (H) shark 5 rearward camera revealing small horse mackerel following the tagged shark.

Shark photographs submitted by participants in the TSR where distinguishing characteristic were visible (A) and photographs that were classified as unknown (B-D). A) Confirmed sandbar shark with visible characteristics. B) Angler identified shark as bull shark, but identification could not be confirmed because shark was underwater. C) Angler identified shark as blacktip shark, but identification could not be confirmed because ruler covered most of the shark’s body. D) Angler identified shark as a sandbar shark, but species could not be identified because of photo scale, blurriness, and shark’s head covered by angler’s hand.

a–h NMJs of MN4-Ib in third instar larvae of non-ablated and Is ablated larvae in control, glia shark knockdown, muscle shark knockdown, and double knockdown backgrounds, labeled with GFP (green) and HRP (magenta). NMJ expansion was observed upon Is MN ablation (b), which is blocked by glia shark knockdown (d) or double knockdown (h). i Cartoon representation of a dissected larva (pink) and a hemisegment highlighted by dashed red rectangle. The target muscle examined in this figure is shown in blue. Cartoon is generated with Biorender. j Quantification of MN4-Ib bouton number in non-ablated and Is ablated larvae in control, glial shark knockdown, muscle shark knockdown, and double knockdown backgrounds. Control (N = 22 and 23 NMJs), t(43) = 3.598, p = 0.0008, unpaired t test, two-tailed. Glial shark knockdown (N = 21 and 22 NMJs), t(41) = 1.566, p = 0.1250, unpaired t test, two-tailed. Muscle shark knockdown (N = 23 and 19 NMJs), t(40) = 3.220, p = 0.0025, unpaired t test, two-tailed. Double shark knockdown (N = 16 and 22 NMJs), t(36) = 0.3390, p = 0.7366, unpaired t test, two-tailed. k Quantification of normalized EPSP of Is ablated larvae in control, glia shark knockdown, muscle shark knockdown, and double knockdown backgrounds. F(3, 71) = 5.533, p = 0.0018, One-way ANOVA. Is ablated control vs glia shark knockdown, p = 0.0062. Is ablated control vs muscle shark knockdown, p = 0.0105. Is ablated control vs double knockdown, p = 0.0093. Is ablated control vs Ib/Ib+Is, t(28.04) = 4.485, p = 0.0001, unpaired t test, two-tailed, with Welch’s correction. Is ablated in glia shark knockdown vs Ib/Ib+Is, t(30) = 2.798, p = 0.0089, unpaired t test, two-tailed. Is ablated in muscle shark knockdown vs Ib/Ib+Is, t(30) = 2.329, p = 0.0268, unpaired t test, two-tailed. Is ablated in double knockdown vs Ib/Ib+Is, t(25) = 2.254, p = 0.0332, unpaired t test, two-tailed. l Quantification of normalized quantal content of Is ablated larvae in control, glia shark knockdown, muscle shark knockdown, and double knockdown backgrounds. F(3, 71) = 4.437, p = 0.0065, One-way ANOVA. Is ablated control vs glia shark knockdown, p = 0.0466. Is ablated control vs muscle shark knockdown, p = 0.9470. Is ablated control vs double knockdown, p = 0.0214. For (k, l), N (NMJs) = 20, 20, 20, 15. Error bars indicate ± SEM, ns = non-significant, *p < 0.05, **p < 0.01, ***p < 0.001.