Question

Neopilina galatheae exhibits the character of
A) Annelida and Arthropoda
B) Arthropod and Mollusca
C) Annelida and Mollusca
D) Mollusca and Echinodermata

Answer 1

Hint: Many organisms despite being clearly classified under one phylum have characteristics of a second phylum, providing a possible link between the two. Neopilina itself has internal segmentation as one of its features.

Complete answer:
Neopilina galatheae is a fairly newly discovered organism. It is a primitive species of animal, belonging to the phylum Mollusca. It is found in the mud in the ocean depths. Neopilina has a thin dorsal shell, a large, flat foot, a pair of ciliated lobes and pre-oral tentacles much like members of gastropoda. Overall, it has many similarities with chiton and gastropods, making it a mollusc.

However, Neopilina has body segmentation like that of an annelid. Its internal structures like gonads and nephridia are similar to annelids. Because of this, it is considered to be a link between the two phyla of Annelida and Mollusca, which means option C is correct.

Though it does have a segmented body structure and the arrangement of the organs is repeated serially, Neopilina is soft bodied without the typical arthropod exoskeleton. Also, though Neopilina does not have ganglia just like in echinoderms, it doesn’t have the typical mutable connective tissue of the echinoderms. As it does not contain the common features of Arthropods or Echinoderms, but does have many characteristics of molluscs and annelids, options A, B, and D are incorrect.

Hence the correct answer is option ‘C’.

Note: It has been suggested that via the intermediate species of a Nautilus like organism, Neopilina galatheae was a starting point in Gastropod evolution, including a reduction in gills and dorso-ventral muscles.