Question

part c: mutualism
the relationship between a boxer crab and sea anemones is an example of mutualism, in which both species benefit from the relationship. boxer crabs, also known as pom - pom crabs, carry small sea anemones in their claws, resembling pom - poms. the crab uses these anemones as a defense mechanism, waving them to deter predators with the anemones stinging cells. in return, the anemones benefit from increased mobility and access to a wider range of food sources as the crab moves around the reef. this symbiotic relationship enhances the survival prospects of both species.
it has been observed on reefs where boxer crabs are present that free - living individuals of this particular species of anemone are not present. they are only found in association with the crabs. so where do the crabs get the anemones? lab experiments have revealed that when a boxer crab is in need of an anemone, they will fight to steal one from another crab! at that point (when each crab only has one anemone), both crabs will split their anemone into two, creating identical clones.
in a field study, boxer crabs were collected from three reef sites of different depths. the data from these collections is shown below.

	reef a (depth = 5 m)	reef b (depth = 10 m)	reef c (depth = 15 m)
boxer crabs with one anemone	3	1	0
boxer crabs with two anemones	12	7	5
total boxer crabs	17	8	5

1. calculate the percent of boxer that have two anemones, for each location.

reef a ____ % reef b: __ % reef c: ____ %

1. suggest one reason why the percent of crabs with two anemones increases with depth.
2. suggest one reason why there are so few boxer crabs without anemones.
3. list three things that you do not know about the data collected in this table.
4. in order to accept this data as reliable (and therefore appropriate to compare between reefs), the data must have been measured constantly between all of the reef sites. list 3 things that the researchers could do to keep consistency within their collections.

Explanation:

Step1: Calculate Reef A percentage

Percent = $\frac{\text{Crabs with 2 anemones}}{\text{Total crabs}} \times 100 = \frac{12}{17} \times 100 \approx 70.59$

Step2: Calculate Reef B percentage

Percent = $\frac{7}{8} \times 100 = 87.5$

Step3: Calculate Reef C percentage

Percent = $\frac{5}{5} \times 100 = 100$

Step4: Reason for increasing percent with depth

Deeper reefs may have more predators, so crabs need two anemones for better defense.

Step5: Reason for few crabs without anemones

Anemones are critical for defense; crabs without them may not survive long.

Step6: Unknowns about the data

1. The time of data collection (e.g., season).
2. The size/age of the crabs sampled.
3. The specific species of anemone.

Step7: Consistency measures for reliability

1. Use the same sampling method (e.g., quadrat size) at all reefs.
2. Collect data during the same time of day/season.
3. Train all researchers to count crabs/anemones the same way.

Answer:

1. Reef A: ~70.59%, Reef B: 87.5%, Reef C: 100%
2. Deeper reefs have more predators, so two anemones improve survival.
3. Anemones are essential for defense; crabs without them die quickly.
4. 1. Sampling season/time; 2. Crab size/age; 3. Anemone species.
5. 1. Standardize sampling method; 2. Consistent data collection time; 3. Researcher training for uniform counting.