Bacillariophyta

Question 1

Answer 1

Volutin granules

Diatoms accumulate lipids and volutin.

Volutin granules accumulate in the cytoplasm and constitute a reserve of inorganic polyphosphates.
The number and position of the volutin granules constitute a systematic character.

Question 2

Answer 2

Pennate diatoms: two large chloroplasts, plate-like, parietal and often lobed

Question 3

Answer 3

Centric diatoms: many small discoid chloroplasts, lobed

Question 4

Answer 4

Red: epivalve: older and bigger than hypovalve

Green: Cingula: silicious rings (girdle band) located between the valves

Blue: hypovalve: younger and smaller than epivalve

Question 5

Answer 5

Differences in cingulum structure

Question 6

Answer 6

Small one:
Centric diatoms:
AA = radial
BB = valvar

Big one:
Pennate diatoms:
AA = apical
BB = valvar
CC = transapical

Valvar plane lies parallel to the valves, with an outline dependent on the shape of the valves in “valve view”

Apical plane traverses the long axis of the frustules from end to end (apex to apex)

Transapical plane lies perpendicular to the apical plane, traversing the frustules from side to side along the shorter dimension of the frustule

Question 7

Answer 7

pennate diatoms with raphe on both valves or only one

Question 8

Answer 8

the other valve may have a clear central area= pseudoraphe

Question 9

Answer 9

Raphe can be central or eccentric

Question 10

Answer 10

Central ends of raphe

Question 11

Answer 11

Polar ends raphe

Question 12

Answer 12

Loculate Areolae

Areolae of centric diatoms can assume the appearance of hexagonal chambers (LOCULAE) with a partially close outer surface (roof), characterized by the presence of a large round hole, called foramen

Question 13

Answer 13

tangential arrangement Areolae

Question 14

Answer 14

Radial arrangement Areolae

Question 15

Answer 15

The areolae in the pennate diatoms can be arranged in rows to form the STRIAE

Left to right: parallel, radiate, lineate parallel, lineate radial

Question 16

Answer 16

Most centric and Araphidean pennate diatoms have a RIMOPORTULA, a special wall organelle, represented by more or less elongate tube passing through the valve, which in the internal side of the valve shows an opening similar to two lips.

This structure is also called LABIATE PROCESS. Its function is related to the secretion of mucilaginous polysaccharides

Question 17

Answer 17

FULTOPORTULA that is not compressed internally

Question 18

Answer 18

ocellus = structure involved in the secretion of mucilaginous material. It consists of an elevated siliceous plate, finely perforated and surrounded by a hyaline rim.

In Centric diatoms and some Pennate diatoms

The mucilage secreted by the ocellus is used to anchor cells to the substrate or for adhesion of cells in a colony.

Question 19

Answer 19

A study carried out on the genus Skeletonema has shown the existence of numerous genetically and morphologically distinct species within what was considered a single cosmopolitan and opportunistic species, Skeletonema marinoi.

Question 20

Answer 20

benthic diatoms or periphyton

Single cells anchored to the substrate with whole valve

Question 21

Answer 21

benthic diatoms or periphyton

Erect cell colonies arranged to fan, anchored by mucilaginous pads

Question 22

Answer 22

Cells anchored to the substrate by long mucilaginous stalks

Question 23

Answer 23

benthic diatoms or periphyton

Cell chain

Question 24

Answer 24

meroplanktonic or ticopelagic diatoms

Temporary members of plankton
They are often pennate diatoms living loosely attached to the substrate.
With turbulence they are dragged into open waters and they continue to live like plankton