molluscs

Question 1

Solenogastres (molluscs class)

Answer 1

• Solenogastres (Aplacophora) is a small clade of
  marine, shell-less worm-molluscs with close to
  300 valid species.
• Most very small in size (<50 mm long)
• Their main morphological features are:
  
  • feature a narrow foot which lacks intrinsic
    musculature
  • mantle covered by a chitinous cuticle and by
    calcareous sclerites:
  • They do not possess plates (like chitons) or a shell
    (like gastropods)

Question 2

Caudofoveata (molluscs class)

Answer 2

-Caudofoveata (Aplacophora) is a small clade of
marine, shell-less worm-molluscs, mainly found in
the deep sea
-Most very small in size (1-30 mm long)
-Their main morphological features are:
-lack a distinct muscular foot
-feature scales and calcareous spines called
sclerites

Question 3

Polyplacophora (chitons) (molluscs class)

Answer 3

• Known as gumboots, sea cradles, coat-of-mailshells
• Greek – ‘poly’ (many), ‘pláx’ (plate), ‘phora’
  (bearing)
• Their main morphological features are:
  
  • Shell composed of eight overlapping
    plates/valves
  • A soft girdle that surrounds their overlapping
    shell plates

Question 4

Monoplacophora (mollusc class)

Answer 4

-Monoplacophora = ‘bearing one plate’
-~30 species known
-Thought to be among the most primitive of
molluscs
-Bilaterial symmetry, univalved, limited-shaped
(but not gastropods) and untorted
-Eight pairs of shell muscles are probably direct
homologues to those of the Polyplacophora

Question 5

Scaphopoda (mollusc class)

Answer 5

-Greek ‘káphē’ (boat) and ‘πούς’ (foot), also
known as ‘tusk shells’
-Vary in size from a few millimeters in length and
diameter, up to over 100, with a larger diameter
around 1 cm
-Shell tubular, cylindrical˗conical, more or less
curved, open at both ends!
-Feed mainly on foraminifers using captacula
(feeding tentacles)
-No gill! – gaseous exchange from mantle

Question 6

Cephalopods (mollusc class)

Answer 6

Greek ‘kephalópodes’ (headfoot)
-Encompass squid, octopus, cuttlefish, nautili
-Characterised by bilateral symmetry, prominent
head, tentacles modified from molluscan foot,
radula (beak)
-Considered the most cognitively advanced group
of invertebrates
-over 800 species, ranging from 10mm to 14m

Question 7

Bivalvia (mollusc class)

Answer 7

-Latin ‘bis’ (two) and ‘valvae’ (leaves of a door) –
paired shells
-Among the most diverse molluscan classes,
totalling almost 10 000 described extant species
-Culturally important – food (oysters), trade
(pearls), medical/bioengineering
-Include clams, oysters, cockles, mussels, scallops
and shipworms (the coolest)
-Laterally compressed bodies enclosed by a shell
consisting of two hinged parts, bilateral symmetry