Question

5) Some crayfish species harbor small annelid worms that live in their gills. These worms keep the crayfish gills clean by feeding off of organisms that infest the crayfish gills. Thus, the worms potentially gain the benefit of food, transportation, and a site for reproduction and the crayfish potentially gain the benefit of reduced parasitism by other organisms. (24 pts)

a. These worms will consume crayfish gill tissue when there is not enough other food available. For each scenario, make a prediction (1-2 sentences) for whether crayfish individuals with worm partners or those without worm partners would have higher fitness. Provide a rationale for your prediction (1-2 sentences).

Populations living in waters with high levels of sediment harboring microorganisms that get trapped in gills when the water is filtered through.

Prediction:

Rationale:

Populations living in clear waters with very low levels of sediment harboring microorganisms that get trapped in gills when the water is filtered through.

Prediction:

Rationale:

b. The adult worms can live for short periods separate from a crayfish but developing young must reside in cocoons attached to crayfish gills to develop normally. Consider worms that consume the gill tissue of their hosts in addition to what they consume during cleaning of the gills. What are the potential benefits of such a strategy to the worms? What are the potential costs of such a strategy?

Potential Benefits:

Potential Costs:

Answer 1

5.a

Populations living in waters with high levels of sediment harboring microorganisms that get trapped in gills when the water is filtered through.

Prediction: crayfish species and the small annelid worms will both survive

Rationale: high levels of sediment harboring microorganisms ensures necessary growth of these organisms on the crayfish gills, which serve as food for the annelids as a result of which they dont consume gill tissues.

Populations living in waters with low levels of sediment harboring microorganisms that get trapped in gills when the water is filtered through.

Prediction: crayfish species population will decline whereas the small annelid worms will both survive

Rationale: low levels of sediment harboring microorganisms ensures less tha necessary growth of these organisms on the crayfish gills, so the annelids consume gill tissues along with microbes . consumption of gill tissues leads to reduced oxygen transfer which can cause death of the cray fish over time.

5b.

The adult worms can live for short periods separate from a crayfish but developing young must reside in cocoons attached to crayfish gills to develop normally. Consider worms that consume the gill tissue of their hosts in addition to what they consume during cleaning of the gills. What are the potential benefits of such a strategy to the worms? What are the potential costs of such a strategy?

Potential Benefits: The new worms will get sufficient nutrition due to the absence of adult worm and they will have a good and fast growth

Potential Costs: Because of the gill tissue eating habit along with cleaning of microbes, the host cray fish population will decline over time resulting in lack of space and nutrition for the developing young worms as they cannot stay separate from the cray fish.this will result in reduced rate of reproduction for the worms and a dwindling population in the near future.