While trying to find out the characteristic of a newly found animal, a researcher did the histology of adult animal and observed a cavity with presence of mesodermal tissue towards the body wall but no mesodermal tissue was observed towards the alimentary canal. What could be the possible coelome of that animal?

The correct option is Pseudocoelomate.

Step-by-Step Explanation:

1. Understanding Coelom:
A coelom is the principal body cavity in most animals, located between the intestinal canal and the body wall. In triploblastic animals (animals with three germ layers: ectoderm, mesoderm, and endoderm), the nature of this cavity is a key diagnostic feature used in classification.

2. Analyzing the Researcher's Observations:
- The researcher observed a cavity.
- Mesodermal tissue was present towards the body wall (outer side of the cavity).
- No mesodermal tissue was observed towards the alimentary canal (inner side of the cavity, which is lined by endoderm).
- This means the body cavity is only partially lined by mesoderm. It is lined by mesoderm on the outer side (body wall) but not on the inner side (gut/alimentary canal).

3. Defining the Types of Body Cavities:
- Acoelomate: Blastocoel is completely filled with mesoderm; hence, no body cavity is present (e.g., Platyhelminthes).
- Pseudocoelomate: A body cavity (derived from the blastocoel) is present but is not completely lined by mesoderm. Instead, mesoderm is present as scattered pouches or only lines the outer body wall, leaving the gut lined by endoderm. This matches the researcher's observations exactly.
- Schizocoelomate (Eucoelomate): A true coelom formed by the splitting of the mesodermal mass. It is completely lined by mesoderm on both the body wall side (somatopleure) and the alimentary canal side (splanchnopleure).
- Spongocoelomate / Spongocoel: This is the central cavity of sponges (Porifera), which is not a true coelom and is lined by choanocytes rather than mesodermal tissue.

4. Conclusion:
Since the cavity has mesodermal tissue only towards the body wall and not towards the alimentary canal, it is a false coelom, specifically termed a pseudocoelom. Thus, the animal is a pseudocoelomate (characteristic of phylum Aschelminthes/Nematoda).