Does Odo really not have a sense of smell?

Question

In a scene in the episode Improbable Cause, Odo is questioning an assassin posing as a perfume seller, and during the questioning asks the assassin to describe the fragrances of some of his wares, claiming that he himself (Odo) doesn't have a sense of smell- was Odo lying about this (he obviously can see and hear in humanoid form, maybe he can smell too)?

Answer 1

"Improbable Cause" is the second episode in which Odo states that he has no sense of smell.

ODO: Ah. How fortunate. As it happens, I'm looking for a gift for a friend.

RETAYA: A lady friend?

ODO: Exactly. Unfortunately, I don't have a sense of smell. Perhaps you could describe this fragrance for me?

RETAYA: It has a somewhat floral bouquet.

_{Star Trek: Deep Space Nine - S03E20 - "Improbable Cause"}

He says the same thing in the prior episode, "If Wishes Were Horses."

QUARK: Neither had I until I made it my business to find out. With all these humans coming now, the true entrepreneur knows how to sniff the wind. Try it. Go ahead.

ODO: I have no sense of smell.

QUARK: You don't need one to detect the scent of opportunity.

_{Star Trek: Deep Space Nine - S01E16 - "If Wishes Were Horses"}

Granted, in each of those instances, Odo was talking to someone he didn't trust and wouldn't necessarily be inclined to be entirely honest with. However, I tend to think he was being truthful about that specific thing, for a couple of reasons.

Firstly, I've seen every episode of DS9, and as far as I know, there's never been any indication that Odo does have a sense of smell, outside of the period where he was forcibly locked into a humanoid form with humanoid biology by other Changelings. If we assume, for the sake of argument, that the writers of the show intended that he does have a sense of smell normally, it seems counterintuitive that they'd have him state otherwise in two separate episodes, and never contradict those statements in the entire run of the show.

Secondly, it's well-established that Odo isn't as skilled at shapeshifting as the Founders, especially when it comes to mimicking humanoids. In "The Adversary," a Changeling spy duplicated the form of a human ambassador so perfectly as to fool Starfleet sensors, which suggests that it must've perfectly duplicated not only that man's external features, but his internal features as well, including his sensory organs. In the same episode, Odo indicated that he couldn't duplicate a humanoid form that perfectly, and we never saw him perfectly mimic even the external features of another humanoid, never mind all the internal features as well.

EDDINGTON: I wish the internal sensors were online. It'd make it a lot easier to track down the changeling.

ODO: I'm not sure the sensors would help. If you scan me when I'm a rock, you'd detect a rock. I may not be able to duplicate a humanoid perfectly, but I'm guessing he can.

BASHIR: We scanned Ambassador Krajensky for tetryon particles. He registered as human.

KIRA: Well then right now the changeling could be anything or anyone on this ship.

_{Star Trek: Deep Space Nine - S03E26 - "The Adversary"}

In fact, when Odo was initially locked into the shape of a humanoid, in "Broken Link," Bashir scanned him and noted that he now had a heart, lungs, and a digestive system, suggesting that he didn't have those things normally.

SISKO: Odo, are you all right?

BASHIR: Captain, I'm getting some strange readings.

SISKO: What have you done to him?

FOUNDER: He has been judged.

BASHIR: Captain, I'm reading a heart, lungs, and a digestive system. It's as if he were human.

FOUNDER: We gave him what he wanted. We made him a solid. He's one of you now. Oh, poor Odo. Perhaps we should have killed you. It would have been far less cruel. He's yours. Take him and go.

_{Star Trek: Deep Space Nine - S04E26 - "Broken Link"}

In a prior episode, "Meridian," Odo told Kira that he has no taste buds.

KIRA: Odo, I know you don't need to eat but did you ever try anyway?

ODO: Once, not long after I was first able to assume the humanoid form.

KIRA: And?

ODO: And since I don't have taste buds, it was very unsatisfying. Not to mention messy.

_{Star Trek: Deep Space Nine - S03E08 - "Meridian"}

And in another prior episode, "The Way of the Warrior," he explained to Garak that he'd learned to simulate the act of drinking using mass from his own body, which reinforces the idea that his standard humanoid form lacks a functional digestive system.

GARAK: Fascinating. So both the cup and the liquid are merely extensions of your body.

ODO: That is correct. And if I want to, I can even drink the liquid, reabsorb it, and produce new coffee in the cup. This way I can give the illusion that I'm sharing in the dining experience.

GARAK: Very thoughtful.

_{Star Trek: Deep Space Nine - S04E01 - "The Way of the Warrior"}

This all suggests that while Odo's standard humanoid form looks relatively human (or Bajoran) on the outside, the imitation isn't that accurate internally, at least partly because he lacks the skill to perfectly duplicate a humanoid's internal physiology.

As I stated in a previous answer to a related question, I believe Odo likely is capable of replicating the functionality of real, humanoid eyes, as there's a fair bit of evidence suggesting that he does genuinely see things with his eyes, as humans do.

It's less clear to me that his ears work the same way as humanoid ears, since in "Chimera," his fellow Changeling, Laas, could apparently hear Odo speaking to him even whilst in the form of a blanket of fog.

Were Odo to put in sufficient time and effort, he could presumably learn to duplicate humanoid physiology perfectly, both internally and externally, as the Founders can, but it appears that he never reached the skill level required to do that within the span of the show.