Lecture 15 - Squidgy deuterostomes Flashcards
Deuterostomes: what are they and what species do they include?
Animals that form their anus forming before their mouth during embryonic development
Chordata (e.g. vertebrates), Echinodermata (e.g. starfish), and Hemichordata (e.g. acorn worms)
Echinodermata: what are they, what are the key features, and what species are included?
Bilaterally symmetrical in early developmental stages, many can show radial symmetry with multiple arms
No brain or specific sense organs but have neurones and some (starfish) may have eyes (ie at end of arms)
Asteroidea, Ophiuroidea, Echinoidea, Crinoidea, and Holothuroidea
Bipinnaria larvae: where are these larvae present and how are they different to the adult form?
Found in some Echinodermata larvae (starfish)
It is the first stage in the larval development of most starfish. The bipinnaria is free-living, swimming as part of the zooplankton. Movement and feeding are accomplished by the bands of cilia.
Asteroidea: what are they, what are the key features, and what species are included?
Radially symmetrical organisms that belong to the Echinodermata phylum
Bilateral in the early stages of life, they have a flattened, star-shaped body with five arms, tube feet with suckers, they respire through papulae, comprised of calcareous plates and movable spines, and Pedicellaria (large numbers of minute pincers) is present
~ 1,800 species of starfish and sea fish
Ophiuroidea: what are they, what are the key features, and what species are included?
Pentaradially symmetrical organisms that belong to the Echinodermata phylum
Five skinny flexible arms, an internal calcium carbonate skeleton in the mineral form of calcite, and a water vascular system of fluid-filled vessels that end in tube feet
Over 2,000 species of Ophiurida (brittle stars), Euryalida (basket stars), and serpent stars
Echinoidea: what are they, what are the key features, and what species are included?
Radially symmetrical organisms that belong to the Echinodermata phylum
Bilateral in the early stages of life, a hard shell (a test) covered with small knobs (tubercles) which are attached to spines, triploblastic, exclusively marine, and benthic (bottom of the body of water)
~ 950 species of sea urchin and sand dollars
Holothuroidea: what are they, what are the key features, and what species are included?
Radially symmetrical organisms that belong to the Echinodermata phylum
Bilateral in early stages of life, found in abyssal depths (6000m down), display social behaviour (can group together), lack arms, body wall soft rather than calcareous, dioecious with a single gonad, sedimentary feeders, body surrounded by tube feet, interior madreporite, branched tentacles surrounding mouth that are lined with modified water vascular system
~ 1,200 species of Holothurians and sea cucumbers
Crinoidea: what are they, what are the key features, and what species are included?
Radially symmetrical organisms that belong to the Echinodermata phylum
Bilateral in early stages of life, cup-shaped body with five or more flexible and active arms. The arms, edged with feathery projections (pinnules), contain the reproductive organs and carry numerous tube feet with sensory functions. Using their arms they can swim, seemingly as an adaption to flee from predators (Echinoidea)
~ 600 species of Feather stars and sea lilies
Keystone species
Species that are integral to an ecosystem
Tunicates
Also known as ascidians or sea squirts
Can be sessile or planktonic
Planktonic forms (‘salp’) are often small and jelly-like or form huge trains of clones (pyrosomes); others (‘larvaceans’) make a jelly house
Ascidian
The larval form moves so CNS is needed but once the organism becomes sessile, the CNS is metabolised
Salp parasitism
This can occur if the Salp is hollowed out (while still alive) and this can be done by an amphipod, Phronima, which lives inside the Salp with protection until the Salp eventually dies
Pyrosome
May look like plastic bags, it also is the prey of turtles, explains why plastic bags are bad for turtles
