Diplostomum pseudospathaceum

Diplostomum pseudospathaceum is the parasite Aza describes to Davis as an image of life governed by an unseen author. Its cycle turns an infected fish’s apparent behavior into a means of the parasite’s reproduction, giving concrete, unsettling form to Aza’s fear that feeling and acting do not prove that the self is in control.

The Parasite’s Life Cycle

In Aza’s account, Diplostomum pseudospathaceum matures in the eyes of fish but can reproduce only in a bird’s stomach. Fish carrying immature parasites swim in deep water, where birds are less likely to spot them. Once the parasites are ready to mate, however, the fish begin swimming near the surface, exposing themselves to the birds that prey on them. The infected fish are, in effect, induced to make themselves easier to eat.

The cycle continues inside the bird. There the parasite breeds, and its offspring pass back into the water in the bird’s feces. They encounter fish, beginning the cycle again. The sequence binds the parasite’s reproduction to the fish’s consumption: what looks like the fish’s movement toward danger serves a process taking place within it.

Aza’s Explanation to Davis

Aza tells Davis about the parasite during a vulnerable conversation that has brought them close to kissing. Instead of remaining with that intimacy, she turns to the disturbing details of the parasite’s life cycle. She recognizes that she has carried their conversation far from its romantic beginning, but cannot stop: she wants Davis to understand why the fish frighten her.

Her fear is not simply that the fish are harmed. The parasite seems to author their story while they remain inside it, so that their actions appear to belong to them even as they serve another organism’s needs. Aza identifies with the fish because she worries that her own story, too, may be written by someone else. The parasite therefore supplies a biological image for a crisis of agency, rather than merely a macabre example of animal behavior.

Pain, Reality, and Agency

Aza connects this fear to a private habit she had not previously discussed with Daisy or Dr. Karen Singh. As a child, after her mother told her that pinching herself could show her whether she was dreaming, Aza began pressing her thumbnail into her fingertip whenever she doubted that she was real. The pain gave her a momentary assurance that she existed.

The fish complicate that test: they can feel pain, yet pain alone cannot establish whether they act freely or are serving the parasite’s purposes. Aza’s analogy unsettles the distinction between bodily certainty and self-determination. The parasite’s significance lies in that gap: sensation may confirm that an experience is real without proving who, or what, directs the life undergoing it.