Which animal is a fish that can effectively "taste" using receptors spread over much of its body surface?

Introduction / Context:
Different animals have evolved remarkable sensory adaptations that help them find food, avoid predators, and navigate their environments. Some fish have an especially well developed sense of taste, with taste receptors not only in their mouths but also on other parts of their bodies. This question asks you to identify which animal among the options is a fish that is famous for being able to taste with much of its body surface, including its whisker like barbels.

Given Data / Assumptions:

• The options include a tropical cockroach, an Arctic tern, a catfish, and a koala.
• We assume basic knowledge of which animals are fish and which are insects, birds, or mammals.
• The question refers to taste receptors distributed beyond the mouth.
• We focus on a well known example often mentioned in biology and general knowledge sources.

Concept / Approach:
Catfish are freshwater fish known for their whisker like structures called barbels, which contain many taste receptors. In addition, their skin can also contain taste buds, allowing them to detect chemicals dissolved in water over a large area of their body. This adaptation helps them find food in murky waters with low visibility. Cockroaches, Arctic terns, and koalas do not have this specific whole body tasting ability and are not fish. The correct approach is to recognise that catfish is the only fish in the list and the one commonly cited as being able to taste with its whole body surface.

Step-by-Step Solution:
Step 1: Identify which of the listed animals is a fish. Tropical cockroach is an insect, Arctic tern is a bird, and koala is a mammal, leaving catfish as the fish. Step 2: Recall that catfish have prominent barbels around their mouth that are rich in taste buds, functioning somewhat like sensitive fingers and tongues combined. Step 3: Remember that catfish also have taste receptors on their skin and fins, allowing them to detect food particles and chemicals in water across much of their body surface. Step 4: Understand that this widespread distribution of taste receptors leads to the common statement that a catfish can taste with its whole body. Step 5: Compare this specialised sense with the senses of cockroaches, terns, and koalas, none of which are known to taste with their entire body surfaces. Step 6: Conclude that the correct answer is catfish, the fish that can effectively taste with much of its body.

Verification / Alternative check:
Biology texts and popular science articles often highlight catfish as an example of an animal with an extraordinary sense of taste, noting that they can have tens of thousands of taste buds distributed over their body. Experiments show that catfish can locate food even in dark, muddy water where sight is limited, by relying heavily on chemical cues detected by their taste receptors. In contrast, the other animals listed have more typical distributions of taste buds mainly in the mouth. This consistent information confirms that catfish is the correct choice.

Why Other Options Are Wrong:
Tropical cockroach is an insect that may have chemosensory organs on its antennae and mouthparts, but it is not a fish and is not the species commonly described as tasting with its whole body, so this option is incorrect.
Arctic tern is a migratory seabird known for extremely long distance flights, not for whole body taste receptors. It is not a fish and does not match the description in the question.
Koala is an Australian marsupial that feeds mainly on eucalyptus leaves. It has normal mammalian taste receptors, primarily in the mouth, and is not the animal referred to in this well known example, so this option is also wrong.

Common Pitfalls:
Some learners may overlook the clue that the question specifically says the animal is a fish and may focus on unusual or exotic sounding names like Arctic tern or tropical cockroach. Others may not recall which species has widely distributed taste receptors and might guess at random. To avoid these errors, first narrow down the list to the fish and then recall that catfish are the classic example associated with the phrase tasting with the whole body.

Final Answer:
The fish that can effectively taste using receptors spread over much of its body surface is the catfish.