Lecture 13 Flashcards
Mollusca; Diversity, taxonomy, systematics
1
Q
Mollusca species
A
- About 75000 species
- Largest marine phyla
- Approx. 23% of all marine species
- About 80% are gastropods
- Members of the bilateria
- Bilateral/secondarily asymmetrical
- Tripoblastic and true coelomates
2
Q
Protostomia
A
Mouth develops from blastopore
3
Q
Spiralia
A
Spiral embryonic cleavage pattern
4
Q
Lophotrochozoa
A
Trochophore larvae with ciliary bands
5
Q
The pre-phylogenomic “HAM” - hypothetical ancestral Mollusca
A
- Morphologist approach to understand ‘stem’ Mollusca
- Attempt to portray the most ‘fundamental’ morphology of molluscs
- Extremely speculative
- Many features lost or convergently evolved
- Does at least indicate some typical features to know
6
Q
Typical features
A
- Ventral body wall forms muscular foot
- Dorsal body wall forms the mantle and mantel cavity
- Secretes sclerites or shell, if present
- Houses the ctenidia/gills, if present
- Dorsally situated visceral mass
- Complete and specialized gut
- Open circulatory system
- Nephridia, if present
- Gonads
- Head region, if present
- Cephalisation
- Radula and odontophora
7
Q
Aculifera
A
Those lacking primary shells
8
Q
Sclerites
A
Spicules and scale-like structures embedded into or on top of Mollusca epidermis
9
Q
Caudofoveata (class: burrowing spicule worms)
A
- About 130 species
- Feeds on sediment-dwelling protists
- Gonochoristic, oral shield (unique) and single pair of posterior ctenidia
- No nephridia, eyes, tentacles, statocysts, osphradia, crystalline, style
10
Q
Solenogaster (class: epibenthic spicule worms)
A
- About 260 species
- Carnivorous, eats cnidarians
- Hermaphroditic
- No ctenidia
- Respiratory folds (unique)
- Sensory vestibule and ciliated pedal pit (unique)
- No nephridia, eyes, tentacles, statocysts, osphradia, crystalline, style
11
Q
Polyplacozoa (class: the deep-sea and intertidal chitons)
A
- About 930 species
- Unique features:
- 8 dorsal shell plates (valves)
- Thick gridle
- Mantle cavity lined with ctenidia
- Between 6 - 80 pairs of ctenidia
- Exhalant/inhalant water chambers
- Paired highly branched metanephridia
- Kidney-like analogous excretory organ
12
Q
Conchifera
A
Those with a primary shell
13
Q
Monoplacophora (class: deep-sea limpet-like molluscs)
A
- About 35 species
- About 3cm single cap-like shell
- Serially repeated organs
- 3 - 6 pairs of ctenidia
- 2 pairs of gonads, likely gonochoristic
- 2 - 7 pairs of metanephridia
- 2 pairs of heart atria
- Paired statocysts
14
Q
Cephalopoda (class)
A
- About 750 species
- Second branch of the conchiferan Mollusca
- Major division of nautiloidea and coleoidea
15
Q
Cephalopoda (general anatomy)
A
- Nautiloidea shells resemble many of the fossilised Cephalopoda
- Anti-predation system
- Chambered shell for buoyancy
- Coleoidea shells internalised or lost
- Camouflage/behavioural strategies
- Generally fast modes of locomotion
- Mostly visual sensory dependent
