Invertebrate Biology Midterm 2

Phylum Nemertea

Ribbon Worms

What does Phylum Nemertea clustered with?

Annelids and Mollusca

Defining characteristic of the Phylum Nemertea

Eversible proboscis contained in the rhynchocoel

Features of the nemertea proboscis

Eversible and has a short point to stab prey and inject toxin

Muscles of the rhynchocoel

Longitudinal, circular (to push out), and retractor muscle (to pull in)

What does nemertea translate to and why?

“Unerring”; ability to accurately shoot proboscis to capture prey

Types of proboscis of nemertea

Stylet (common) and Sticky tip (multi-branched, less common)

Feeding strategies of nemerteans

Voracious predators with well developed chemical senses

Examples of Nemertea prey

Scyphozoan medusae carcasses, fish eggs

Nemerteans have coordination of ----- system and ----- system

Circulatory, Excretory

How does the circulatory and excretory systems of the nemerteans coordinate?

Flagellated flame bulbs lies in the middle of the of a circulatory vessel to filter blood and selectively reabsorbed and filter material into a collecting duct that leads to a nephridiopore

Phylum Annelida

segmented worms

lug worms

Arenicolidae

blood worms

Glyceridae

clam worms

Nereididae

fan worms

Sabellidae

Christmas tree worms

Serpulidae

Ice cream cone worms

Pectinariidae

Spaghetti worms

Terebellidae

Parchment tube worms

Chaetopteridae

earthworms

Crasciclitellata

leeches

Hirudinea

spoon worms

Thalassematidae

peanut worms

Sipuncula

hydrothermal vent worms

Siboglinidae

Pompeii worms

Alvinellidae

Traditional Annelid groups

Polychaeta, Oligochaeta, Hirudinea

metamer

single segment in a worm

coelomic compartmentation

each segment has a tiny coelom that is interconnected

1. Head
2. Trunk
3. Tail
4. Palp
5. Antennae
6. Prostomium
7. Peristomium
8. Parapodium
9. Setae
10. Pygidium
11. Anus

Prostomium

section before the mouth in Annelids

Pygidium

Tail segment in Annelids

Setae

Brittles that stick out of parapodia

Chaete

setae that are reinforced with chitin present in polychaetes, making them thicker and stronger

Skeletal structure of annelids

Muscular hydrostat (muscles themselves form skeleton they contract against)

Annelids have an X jaw and X pharynx

eversible, protrusible

Polychaete structures

1. Segment boundaries
2. Sensory structures
3. Median dorsal blood vessel
4. Gills
5. Parapodia
6. Cuticle
7. Chaete

Parapodial muscle

used to move parapodia back and forth

How are annelids able to move so quickly

musculature and segmentation

Circulation of Annelids

1. Capillary bed in parapodia
2. Median dorsal vessel
3. Capillary bed in intestine
4. Ventral dorsal blood vessel

Chloragogen cells

proto liver cells lining the outer intestine of annelids

Importance of coelomic compartmentation

Fluids in compartments get sloshed around because of muscle contraction which is important for excretion

Protonephridia

simpler/earlier nephridia in which ultrafiltration and reabsorption are together

metanephridia

nephridia in annelida where ultrafiltration and reabsorption are together

Podocytes

cells around blood vessels that complete ultrafiltration

Annelid digestive system

Podocytes complete ultrafiltration in coelomic cavity, then primary urine fluid is pushed toward nephrostome for reabsorption into a set of tube, final urine exits through excretory pore

Annelid Excretory System

1. Nephrostome draws in coelomic fluid
2. Blood vessels and capillaries
3. Site of reabsorption and tubular secretion
4. Excretory opening (nephridiopore)

How do worms burrow

Using segments to form penetrators and anchors

1. Penetration anchor
2. Terminal anchor

Larval development type of annelids

Trochophore larva

Members of Trochozoa

Annelids, Molluscs, Nemerteans

Apical tuft

tuft of cilia on top of trochophore

Prototroch

ring of cilia around trochophore

Indirect development

greater metamorphosis occurs, needs to travel for nutrients, larval stage

Direct development

larvae look like tiny adults and there is no real metamorphosis, do not need extra energy

Trochozoa is a subsection of

Lophotrochozoa

Main lifestyles of annelids

Herbivores-Omnivore/Scavengers

Carnivores

Surface deposit feeders

Subsurface deposit feeders

Suspension feeders

Muco-ciliary suspension feeders

Tube dwelling

Atoke

sexually immature, original worm

Epitoke

swimming stage that develops off the tail ends (Syllid)

Epitoky

reproduction of annelids in which a sexually immature worm it creates multiple copies o sexully mature worms on its tail ends, they swim up to the surface and release gametes

How is epitoky different than strobilation?

Epitokes are already mature and release gametes which then grow up

Examples of Herbivore/Omnivores Scavenger Annelids

Nereididae

Examples of Carnivorous annelids

Glyceridae

Example of surface deposit feeders

Terebellidae

Examples of Subsurface deposit feeders

Pectinariidae, Arenicolidae

Pectinariidae feeding

Arenicolidae feeding

Create a funnel depression and draw water in and fecal pile lies adjacent

Arenicolidae feeding

Sabellidae feeding

Large frilly appendages (radioles) with cilia collect particulate as water moves across gets captured, pre-sorted, and channeled down radial

Examples of Muco-ciliary suspension feeder annelids

Sabellidae, Serpulidae

Examples of Tube-Dwelling Annelids (subsurface suspension feeders)

Chaetopteridae

Chaetopteridae feeding

Secretes mucus bag from notopodium that sits in ciliated cup. Fan like parapodia generates a current.

Important features of annelids for predation/being an active hunter

Musculature and segmentation

Which annelids were previously not considered annelids and why?

Sipuncula, Thalassematidae, Sibolinidae because they lack segmentation

Former family of Family Thalassematidae

Phylum Echiura

Example of Family Thalassematidae

Bonellia viridis

Bonellia viridis (spoon worms) demonstrate ----

diomorphism

dimorphism

different sizes of male and female

Spoon worms dimorphism

Male are tiny and live on or in females, and sex is determined by if larva lands on a female. Females release bonellin (aphrodisiac) to attract larva, once they do the larvae turn into males. If larva remains on substrate it develops into a female.

Is bonellin toxic to other species

Yes

Thalassematid feeding

Trunk remains subsurface and use non retractable proboscis as a spoon to bring food towards mouth

Major characteristics of Siboglinidae

4 feet in length, live near hydrothermal vents, long gills

How do Siboglinidae derive energy

bacteria that live in their bodies and bacteria use chemosynthesis

Two broad types of Siboglinidae

Vestimentiferans and Pogonophorans

Main characteristic of Vestimentiferans

Tentacular Plume

Tentacular plume

utilized for respiration

Trophosome

Large bag with trillions of bacteria that undergo chemosynthesis

Opisthosoma

Ventral end of Vestimentiferan

Where do Vestimentiferans live?

Near hydrothermal vents

Pogonophorans differences from Vestimentiferans

live in anoxic basins where methane forms pools, have a tentacle bit and smaller trophosome.

why are Sipuncula called “peanut worms”

Squish into peanut shape when disturbed

Main characteristics of sipuncula

Introvert and tentacular ring used for feeding

Are sipuncula segmented?

Some segmentation of mesentaery bands internally, but not externally

Muscular system of Sipuncula

Large dorsal and ventral muscles to form peanut shape

What is in the coelomic fluid of Sipuncula

urns with cilia

What is the function of the urns with cilia in the coelomic fluid

filtering coelomic fluid of debris and particles

Taxonomy of earthworms

Phylum Annelida, Larger Group Crasciclitellata, and subgroup Lumbricidae

Characteristic structures of Lumbricidae

Clear segmentation, no parapodia on the side of the worms like the Polychaeta, but they has little bristles called setae, clitellum

 clitellum

Filled with secretory organs (mostly mucus)

Ultrafiltration in mollusks occurs in the

pericardium