The most recently discovered phylum in the animal kingdom (1995) is the phylum Cycliophora. It includes three species of tiny organisms that live in large numbers on the outsides of the mouthparts and appendages of lobsters. The feeding stage permanently attaches to the lobster via an adhesive disk, and collects scraps of food from its host's feeding by capturing the scraps in a current created by a ring of cilia. The body is sac-like and has a U-shaped intestine that brings the anus close to the mouth. Cycliophorans are eucoelomate, do not molt (though their host does), and their embryos undergo spiral cleavage.
-If harboring large populations of cycliophorans neither helps nor harms their lobster hosts, then cycliophorans can be properly considered to be
1)parasites.
2)mutualists.
3)commensals.
4)symbionts.
5)endosymbionts.
A) 1 and 4
B) 2 and 4
C) 3 and 4
D) 2 and 5
E) 3 and 5

Question

Quizplus · Accepted Answer

Cycliophorans do not harm or benefit their host lobsters, therefore they can be classified as commensals. They form a symbiotic relationship by using the lobster as a habitat, but they do not have a significant impact on the lobster's fitness or survival, which eliminates the possibility of them being parasites or mutualists. Additionally, they are not endosymbionts since they live on the exterior of the lobster's mouthparts and appendages.

The Most Recently Discovered Phylum in the Animal Kingdom (1995)