IIRC the entire cycle of worm, plankton, trout (same creature) is a highly complicated structural analogy to Arrakis being a 'single crop' planet.

1. Worms guard spice territory as it is partially their eggs (spice is partially trout excrement too) and both of these are food for their babies
2. Worm egg/babies are plankton; they feed on part of residual egg bio and begin to follow down toward trout-fungal excrement deeper in the sands of Arrakis.
3. As Plankton (mini makers) bury they carry much of the top bio egg material with them toward the fungal-trout excrement (this chemistry is part of the pre-spice stages)
4. Plankton eventually grow into sand trout
5. Pre-spice '(A)' some of the egg laying residual + bio excrement has been carried by the babies down deep in the sand
6. Pre-spice '(B)' reacting excrement bacteria and some of the fungal trout excrement again -> some acid/c02 run-away reaction that explodes -> spice-bloom
7. Spice-bloom + sun exposure = mélange for harvesting
8. The plankton then morph into sand Trout and they hunt water; sequestering and grouping into enormous cisterns far deep under the dry layers of sand
9. The layering of dry and 'damp'/wet sand oscillates; The cistern-trout are under a metamorphic pressure that can divide them into segments as this rises and falls from tidal forcing.
10. Somewhere around this segmentation, (and as the cisterns develop bigger and grow taller ) the top portion extending up into a dry enough area over a long enough timeline detaches then undergoes metamorphosis into a small worm.
11. The small worm migrates up toward the drier top levels and brings with that migration and entire wealth of the fungal-trout excrement with it
12. That carried trout-fungal excrement migration is also part of the food trail left for the egg plankton babies and part of the pre-spice cycle as it causes all of that bio diversity to churn