What's For Lunch?

What's for Lunch?

Let's Do the Numbers

Level: Super Sleuth

Test your knowledge of the prey and predators of exotic species!

Characteristics	Knobbed Whelk, *Busycon carica*	Veined Rapa Whelk, *Rapana venosa*
Maximum size	9-10 inches (225-250 mm); males typically <166mm	6 - 7 inches (150 - 180 mm)
Age when it is able to produce young (reproduce)	Females 10+ years (males mature earlier; some later become female)	2 years
Lifespan	28+ years	10 - 15 years
Shell width for a given shell length (SL)	Less thick and broad	Thicker and very broad
# times that egg strings or mats are laid per year	One (fall, hatch in spring) in north Two (May-June and Sept-Nov) in south	Multiple times throughout summer (Chesapeake Bay)
# egg pouches or capsules per string or mat	40-160	50-500
# fertilized eggs/case	0 -100	200 - 1,000
Hatch time	3 to 13 months	14 -21 days
Pelagic larvae phase (amount of time the young float in the water before settling to bottom)	None	14 - 80 days
Water temperature range	4 - 25°C	4 - 30°C
Salinity (saltiness of water) range	> 18 parts per thousand (ppt)	> 15 parts per thousand (ppt)
Type of bottom preferred	Sandy/muddy bottom	Young - hard bottom Adults - sandy/muddy bottom
Growth rate	Newly-hatched: ~.7 mm/wk >36 mm by one year >144 mm by 10 years	Newly-settled: >1mm/wk 40-50 mm shell length (SL) by 5 months >60 mm SL by one year
How long until its size protects it from predation?	Snails less than < 1 yr old eaten by crabs	>100 mm shell length (SL)

Click on the column you think is the correct snail.

If your answer is correct, the box will turn Green. But if you get it wrong, it will turn Red.

	Knobbed Whelk	Rapa Whelk
Which snail matures faster?
Which snail lays egg strings or mats multiple times each year?
Which snail hatches more capsules or pouches per string or mat?
Which snail grows a thicker shell?
Which snail grows faster?
Which snail can tolerate a broader range of salinity? (Salinity measures the concentration of salt in the water; ocean water has the highest salinity while water from your faucet has the lowest.)
Which snail has a pelagic larval stage, meaning it floats around with the water currents when it is first hatched?
Which snail has more characteristics of an invasive species?

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