Short story about exobiology during human exploration of an alien planet

Question

I have read a story long ago, where some explorers of an alien planet take an animal and use it like a boat (with a description similar to a very large Victoria.

Eventually, they have serious problems with the boat-animal (it begins to shake vigorously), and end up discovering it was just giving birth during the ride.

Earlier in the tale, some supposedly tame flying animal comes attacking them, and they discover that it is actually being neurologically controlled by a parasite, in a very similar way the Navi control their flying dragons in the Avatar Film: some animals in that planet evolved to "control" one another by a sort of lock-and-key neuro-anatomical structure.

Anyone knows the name and author of that story? I believe it's in some of Asimov's compilation books, but I'm not sure.

---

EDIT: actually the large boat-plant was not giving birth... But the accepted answer contains a link to the full text for the curious :o)

Answer 1

This sounds very much like Grandpa by James H Schmitz.

At the beginning of the story, the main character (Cord) discovers a new species of bug:

The thing was, in the free and easy terminology of the Sutang Colonial Team, a swamp bug. Concealed in the downy fur behind the bug's head was a second, smaller, semi-parasitical thing, classed as a bug rider.

Cord shoots the bug and the rider tries to attack him.

Later, Cord and 3 others use a large specimen of some sort of "plant animal" as a raft. They call this specimen "Grandpa".

They looked somewhat like exceptionally broad-brimmed, well-worn sugar-loaf hats floating out there, green and leathery. Or like lily pads twenty-five feet across, with the upper section of a big, grey-green pineapple growing from the centre of each.

I have it in the collection Decade the 1950's, edited by Brian W Aldiss and Harry Harrison.

It appears to be available online