5b. The figures below show dogwhelk handling time (A) and the thickness of the m
ID: 189065 • Letter: 5
Question
5b. The figures below show dogwhelk handling time (A) and the thickness of the mussel shell at the site of the drill hole (B) for mussels exposed to dogwhelk cues and controls. What do these result tell us about the advantage of shell thickening in the presence of dogwhelks? What do the results in C and D tell us about the feeding behavior of dogwhelks feeding on mussels? (10 pts) 6000 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 5000 4000 3000 2000 1000 No dogwhelk cues Dogwhelk cues Dogwhelk cues No dogwhelk cues 0.5 0.5 0.4 0.3 0.4 0.3 S 0.2 0.2 0.1 0.1 0 Rnrahole Intart armas Intact areas Fig.4 (A) Handling time by dogwhelks (mean ± SE) and (B) shell thickness at the borehole of mussels previously exposed to dogwhelk cues and mussels not exposed to such cues. Shell thickness at the borehole and at intact shell areas of (C) mussels previously exposed to dogwhelk cues and (D) mussels not exposed to such cues. Asterisks indicate a significant difference (pExplanation / Answer
Dog whelks prey on mussels and barnacles. From figures (A) and (B) we can see that the mussels previously exposed to dog whelk cues have thicker shells at the bore hole. This translates into a greater handling time by dog whelks. Since, the dog whelk is an intertidal predator, the occurence of a tide within the handling time allows for the mussels to escape.
From figures (C) and (D), we can see that mussels previously exposed to dog whelk cues have thicker shells at the bore hole. The shell thickness at the intact areas is not very different among the ones exposed to and not exposed to dog whelk cues. This suggests that dog whelks prefer mussels with a specific shell thickness probably based on the profitability of mussels, predicted weight of flesh extracted to predicted handling time.
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