Plastic and POPs

Question 1

What are the different pathways of plastic falling to the seafloor?

Answer 1

1. Direct transport through carrion flow
2. 2-stage transport through carrion flow
3. Indirect transport through fragmentation
4. Direct transport in faecal pellets

Question 2

The visual function of colours can be divided into two broad categories:

Answer 2

: conspicuousness or camouflage.

Question 3

What are the different types of colour vision?

Answer 3

Trichromacy or trichromaticism is the possessing of three independent channels for conveying colour information, derived from the three different types of cone cells in the eye (humans = RGB).

Dichromacy or dichromaticism is the state of having two types of functioning colour receptors, called cone cells, in the eyes. Dichromats can match any colour they see with a mixture of no more than two pure spectral lights.

Monochromacy or monochromaticism among organisms is the ability to distinguish only one single wavelength of the light spectrum.

Question 4

Colour is produced by

Answer 4

Colour is produced by either a structural or pigmentary medium.

A pigmented material has selective absorbance properties
that determine the spectral reflectance of the incident light which are often contained in chromatophores.

Structural coloration involves materials that are themselves colourless because the colours are created by coherent scattering by iridophores and leucophores.

The main difference between pigment and structural colouration is that pigment colouration is the same from all angles.

Question 5

What are iridophores?

Answer 5

Iridophores are the cells that are made up of stacks of thin protein plates that function as multilayer reflectors that result in iridescence

Iridescence in cephalopods spans the whole of the visible spectrum, including the near-IR.

The angle of the iridophore dictates the colour which is reflected moving from red to yellow to green to blue with increasingly oblique angle.

Iridophores take longer to change than chromatophores but are still only in the order to several seconds.

Iridophores reflect polarised light, as a side product of iridescence, which may be used in communication.

Question 6

What creates the white part of the camouflage?

Answer 6

Changing colour

Leucophores contain spherical protein assemblages that scatter light equally well throughout the visible, IR and UV parts of the spectrum.

Leucophores create the white parts of camouflage and signalling body patterns of cuttlefish and octopus.

They provide a backdrop against which chromatophores (and iridophores) can create highly contrasting patterns.

Leucophores are not physiologically active (as some iridophores are), they do not polarize light and they look equally bright from all angles of view.

Leucophores reflect the ambient wavelengths of light (they look red in red light, blue in blue light, white in white, etc.)