M16 Vermes

Question 1

Linnaeus (1758)

Answer 1

Systema Naturae (animals in 6 classes, 2 for invertebrates). Insecta was all insects, arachnids and crustaceans. Vermes included all others.

Question 2

Lamarck (1793)

Answer 2

Vermes was broken down into multiple phyla, this has continued ever since.

Question 3

Vermiform phyla (main ones, bigger worms)

Answer 3

-Annelida are segmented worms
-Nemertea are ribbon or bootlace worms
-Platyhelminthes are flatworms
-Nematoda are round worms
-Priapulida are penis worms

Question 4

Phyla Annelida

Answer 4

23000 species, segmented/true worms (mostly)
-Referred to as polychaetes, bilaterally symmetrical
-Many are microscopic (<1mm), but up to 3m
-Hydrostatic skeleton (relies on fluid for muscle contraction) means there is independent movement of separate segments
-More highly developed nervous system to aid burrowing
-Varied feeding modes
-Reproduce asexually or sexually, can be gonochoristic (many marine) or hermaphroditic.

Question 5

Polychaete characters

Answer 5

-Bristle-like chaetae project from parapods on each body segment
-Pre-segmental prostomium and peristomium together make the head, and the last segment is made of the pygidium with segments in between.
-Components of all major body systems (excretory, circulatory, reproductive and nervous) are repeated in each segment apart from the gut.
-Closed circulatory system contains numerous different respiratory pigments
-Poor osmoregulators means excretion is via nephridia.
-Respiration is across general body surface or gills located either on segments or around the head.

Question 6

Sipuncula

Answer 6

Unsegmented, no setae, mouth with tentacles, U shaped gut, but still Annelid.

Question 7

Sedentaria

Answer 7

Static or slow-moving forms. Lack well-developed jaws/sensory apparatus. Specialised gill or tentacles to deposit or filter feeding and respiration (like fan worms).

-Clitellata (or clitellum) have collars that form a reproductive cocoon. No parapodia, less developed head forms.
-Echiura (spoonworms) are unsegmented as an adult, pair of ventral chaetae, live in burrows.
-Riftia are hydrothermal vent worms with no digestive systems. Trophosome contains symbiotic bacteria that can process the vent chemicals, providing energy for worms.
-Osedax are bone-eating zombie worms, symbionts breakdown inorganic bone, and they eat the symbionts.

Question 8

Errantia

Answer 8

Free-moving worms, well-developed jaws/sensory apparatus.

-Tomopteridae have well-developed eyes, transparent and good swimmers using parapods propulsion, voracious predators of plankton.
-Nereididae (ragworms) are slender with segments, eversible proboscis with jaws, can produce mucous tube, In sand, mud, under rocks, commensal.
-Eunicidae can get big, eversible pharynx with hard jaws, can burrow. Bobbit worm can get up to 3m long and ambush predators like fish and squid.

Question 9

Phyla Nemertea

Answer 9

1300 species (ribbon/bootlace worms).
-Unsegmented and often flattened, mainly carnivorous predators (through gut, mouth and anus are separate).
-Proboscis in a unique organ, separate to gut.
-Outer surface is ciliated and is moved by muscular action.
-Separate sexes gonads are repeated along body, external fertilisation and also asexual fragmentation.
-Closed circulatory system, with no specialised gas exchange surfaces, diffusion is across body and muscular contractions circulate fluid.

Question 10

Phyla Nematoda

Answer 10

Most abundant animal on earth (marine, freshwater and terrestrial).
-Mostly meiofauna, marine. Important in decomposition
-Unsegmented and cylindrical, pointed ends. Nerve ring around pharynx.
-Only have longitudinal muscles, so looks like they are thrashing when they move.

Question 11

Phyla Platyhelminthes

Answer 11

30,000 species (flatworms), some free-living (turbellarians).
-Bilaterally symmetrical dorso-ventrally flattened
-One gut opening, only feed on animal tissues. Most are hermaphrodites. Great regenerative example.
-Most move by ciliary gliding/muscular contractions
-Well-developed regenerative capacity

Question 12

Phyla Priapulida

Answer 12

22 species that are exclusively marine infaunal species (1mm-40cm).
-Bilaterally symmetrical, not dorsoventrally flattened
-Body consists of two parts; the prosoma/introvert, which is the mouth, covered in rows of spines that can be withdrawn into the rest of the body. Second part is the muscular trunk which is covered in a thin chitinous cuticle which is moulted as it grows.
-Burrow by extending the prosoma, gripping the mud with their spines and then dragging their whole body forward by withdrawing the prosoma into the trunk.