I have a DNR question for ya…
Why do spider crabs hitchhike on cannonball jelly’s?
Do they feed on the jelly’s, or is it a symbiotic relationship?
Thanks!
2000 SeaPro 180CC w/ Yammy 115 2 stroke
1966 13’ Boston Whaler w/ Merc 25 4 stroke “Flatty”
excellent question…amazing how frequently they are on them…and there are a LOT of cannonballs out there right now, holy moly…
The Morris Island Lighthouse www.savethelight.org
that IS an excellent question… but i don’t know the answer! i wouldn’t think they’re eating them, but i will start asking around.
first guess is just like rudderfish and sergeant majors hang around big sharks and rays, they get a bit of whatever action there is… but i’m trying to think of what action a jellyball can bring to the table! possibly just floating at the surface near all the edibles? those cannonballs hardly filter or grab anything, so i can’t see a little crab picking off morsels from what it’s eating. also possible that all they get is safety- as long as a school of spades or a sea turtle doesn’t roll through, at least they’re not sitting on the bottom in plain view of a million sharpnose.
all conjecture. gotta go back to work outside for a while, will poke around and see what i can turn up.
ha! our own SCDNR website has everything we need, and somebody figured that one out and published it almost 100 years ago!
http://www.dnr.sc.gov/cwcs/pdf/Cannonballjellyfish.pdf
“Cannonballs are strong horizontal and directional swimmers (Shanks and Graham 1987). They are known for their symbiotic relationships with other marine species, specifically 10 species of fishes as well as juvenile longnosed spider crabs (Libinia dubia). These symbionts feed on both the zooplankton taken in by the jellyfish and on the hosts’ medusae. Symbionts may also use the bell for protection (Corrington 1927; Gutsell 1928; Phillips et al. 1969; Rountree 1983).”
so, they eat their food, eat their babies, and crawl up in there and use them as shelter. sounds fair to me.
Very cool! I knew you would dig up an answer for me. Ian will be interested in hearing the answer! Thanks!
2000 SeaPro 180CC w/ Yammy 115 2 stroke
1966 13’ Boston Whaler w/ Merc 25 4 stroke “Flatty”
Sounds kind of like modern day Democrats. Ooops, should I have put that in the politics section?
read in the article barbawang linked that the cannonball feed on red drum larvae.wonder if there is any correlation in low red drum number years to high number cannonball years.
certainly a possibility that they’d eat the larvae and eggs- red drum eggs are buoyant once fertilized, so they’re floating vulnerable at the surface for around 24 hours until they hatch, then they have a yolk sac stuck to them which impedes movement for the next 3 days or so. similar thing applies to trout eggs right now.
pretty much luck of the draw on what the jellyfish eat, but if a dense bunch of them happened to drift through water where reds/trout/etc had recently spawned (for reds, not likely to happen until at least late july) then they could probably pull out a good many eggs.
whether that has much effect on the population size of red drum, hard to say. people at DNR have been trying for a long time to tease out the individual factors such as rainfall, water temp, prey/predator interactions, etc that might influence the size/quality of any given year class.
my personal theory is that it has a good bit to do with the length of the spawning season (how many days that conditions are appropriate for red drum spawning may = roughly how many eggs are produced in a given spawning season), which could be somewhat dependent on the amount of time elapsed between when the water temp begins to drop in late summer (usu early to mid-august) and stays above about 77 degrees (sometimes around end sept/early oct).
just a theory 
that was post #777 for me… gotta go buy a scratch off lottery ticket.
quote:
Originally posted by barbawangthat was post #777 for me… gotta go buy a scratch off lottery ticket.
as scsuperfly says, “it is bad luck being superstitious” 
The Morris Island Lighthouse www.savethelight.org
i realized as a young person that the analogue to “there’s no such thing as an atheist in a foxhole” is that “there’s no such thing as a fisherman without superstitions”
too many variables for us to chalk it all up to luck. there’s gotta be a fish god, and he’s a vengeful one.