CAT 2022 Slot 2 · VARC · RC passage 3: How Cephalopods Camouflage

The full passage and all 4 questions (Q9–Q12) from CAT 2022 Slot 2, with answers and solutions.

The passage below is accompanied by a set of questions. Choose the best answer to each question.

[Octopuses are] misfits in their own extended families . . . They belong to the Mollusca class Cephalopoda. But they don’t look like their cousins at all. Other molluscs include sea snails, sea slugs, bivalves - most are shelled invertebrates with a dorsal foot. Cephalopods are all arms, and can be as tiny as 1 centimetre and as large at 30 feet. Some of them have brains the size of a walnut, which is large for an invertebrate. . . .

It makes sense for these molluscs to have added protection in the form of a higher cognition; they don’t have a shell covering them, and pretty much everything feeds on cephalopods, including humans. But how did cephalopods manage to secure their own invisibility cloak? Cephalopods fire from multiple cylinders to achieve this in varying degrees from species to species. There are four main catalysts - chromatophores, iridophores, papillae and leucophores. . . .

[Chromatophores] are organs on their bodies that contain pigment sacs, which have red, yellow and brown pigment granules. These sacs have a network of radial muscles, meaning muscles arranged in a circle radiating outwards. These are connected to the brain by a nerve. When the cephalopod wants to change colour, the brain carries an electrical impulse through the nerve to the muscles that expand outwards, pulling open the sacs to display the colours on the skin. Why these three colours? Because these are the colours the light reflects at the depths they live in (the rest is absorbed before it reaches those depths). . . .

Well, what about other colours? Cue the iridophores. Think of a second level of skin that has thin stacks of cells. These can reflect light back at different wavelengths. . . . It’s using the same properties that we’ve seen in hologram stickers, or rainbows on puddles of oil. You move your head and you see a different colour. The sticker isn’t doing anything but reflecting light - it’s your movement that’s changing the appearance of the colour. This property of holograms, oil and other such surfaces is called “iridescence”. . . .

Papillae are sections of the skin that can be deformed to make a texture bumpy. Even humans possess them (goosebumps) but cannot use them in the manner that cephalopods can. For instance, the use of these cells is how an octopus can wrap itself over a rock and appear jagged or how a squid or cuttlefish can imitate the look of a coral reef by growing miniature towers on its skin. It actually matches the texture of the substrate it chooses.

Finally, the leucophores: According to a paper, published in Nature, cuttlefish and octopuses possess an additional type of reflector cell called a leucophore. They are cells that scatter full spectrum light so that they appear white in a similar way that a polar bear’s fur appears white. Leucophores will also reflect any filtered light shown on them . . . If the water appears blue at a certain depth, the octopuses and cuttlefish can appear blue; if the water appears green, they appear green, and so on and so forth.

Question 9 · RC Inference Questions

Based on the passage, it can be inferred that camouflaging techniques in an octopus are most dissimilar to those in:

  1. A

    sea snails

  2. B

    cuttlefish

  3. C

    polar bears

  4. D

    squids

Pick an option, then check.
Answer & solution

Answer: Option A

The passage describes camouflage in cephalopods – octopuses, cuttlefish and squids – and compares leucophores to the way a polar bear's fur looks white.

Sea snails are other molluscs: 'shelled invertebrates with a dorsal foot'. They have a shell for protection and nothing is said about camouflage. Octopuses are 'misfits' because they are unlike these cousins. So the octopus's camouflage is most unlike that of sea snails – option 1.

Options 2 and 4: cuttlefish and squids are cephalopods with similar techniques (papillae, leucophores).

Option 3: polar bears share the white-scattering effect of leucophores.

Shortcut: the only creature in the options that the passage sets against octopuses is the sea snail.

Hence, the answer is option 1.

Question 10 · RC Detail and Fact Based Questions

All of the following are reasons for octopuses being “misfits” EXCEPT that they:
  1. A
    are consumed by humans and other animals.
  2. B
    do not possess an outer protective shell.
  3. C
    exhibit higher intelligence than other molluscs.
  4. D
    have several arms
Pick an option, then check.
Answer & solution

Answer: Option A

Octopuses are 'misfits' because 'they don't look like their cousins at all': other molluscs are mostly shelled with a dorsal foot, while cephalopods are 'all arms' and have large brains for invertebrates.

Option 2 is a reason: they lack the shell other molluscs have.

Option 3 is a reason: their large brains and 'higher cognition'.

Option 4 is a reason: they are 'all arms'.

Option 1 is not a reason. Being eaten by humans and other animals explains why they need protection; it is not what makes them different from their cousins.

Shortcut: 'misfit' means different from relatives. Being preyed upon does not set them apart.

Hence, the answer is option 1.

Question 11 · RC Detail and Fact Based Questions

Which one of the following statements is not true about the camouflaging ability of Cephalopods?
  1. A
    Cephalopods can blend into the colour of their surroundings.
  2. B
    Cephalopods can change their texture.
  3. C
    Cephalopods can change their colour.
  4. D
    Cephalopods can take on the colour of their predator.
Pick an option, then check.
Answer & solution

Answer: Option D

Option 1 is true: leucophores let them appear blue in blue water and green in green water.

Option 2 is true: papillae change skin texture to match the substrate.

Option 3 is true: chromatophores and iridophores change colour.

Option 4 is not true. The passage says they take on the colour of their surroundings, not of their predators.

Shortcut: camouflage in the passage is always about blending with the environment.

Hence, the answer is option 4.

Question 12 · RC EXCEPT and NOT Questions

Based on the passage, we can infer that all of the following statements, if true, would weaken the camouflaging adeptness of Cephalopods EXCEPT:
  1. A
    the number of chromatophores in Cephalopods is half the number of iridophores and leucophores.
  2. B
    the temperature of water at the depths at which Cephalopods reside renders the transmission of neural signals difficult.
  3. C
    light reflects the colours red, green, and yellow at the depths at which Cephalopods reside.
  4. D
    the hydrostatic pressure at the depths at which Cephalopods reside renders radial muscle movements difficult.
Pick an option, then check.
Answer & solution

Answer: Option A

Colour change depends on brain signals sent through nerves to radial muscles that open the pigment sacs, and on pigments matching the colours light reflects at their depth.

Option 2 weakens it: if neural signals cannot travel, the muscles get no message.

Option 3 weakens it: chromatophores hold red, yellow and brown pigments because those are the colours light reflects at that depth. If green replaced brown, the pigments would not match.

Option 4 weakens it: if radial muscles cannot move, the sacs cannot open.

Option 1 does not weaken it. The passage says nothing about how many of each cell type are needed. Having half as many chromatophores as iridophores and leucophores tells us nothing about how well they work.

Shortcut: an option that only gives a number, with no effect on how the system works, does not weaken anything.

Hence, the answer is option 1.

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