Invert. Zoology II

Midterm 2

Phylum Annelida

Lamarck 1802- “little rings”

spiralia (Lophotrochozoa)

20,000 species- 3 classes (polychaeta, oligochaeta, Hirudinea)

Class polycheata

-marine worms

-w/ parapodia

-13,000 species

Parapheletic (ancestral species→most descendants)

Class Clitellata (oligochates and leeches)

-w/ clitellum (thick reproduction band)

-7,400 species

Annelid Bauplan

-bilaternal symmetry

anterior-posterior axis → undirectional

-defined head region → cephalization

-triploblastic

-true coelomate- schizocoelous development

-spacious colem

-vermiform

-segmented→metamerism (linear serious of segments)

→ homonomous segmentation (same amount of space between)

→Heteronomous segmentation (different, odd)

-have appendages, parapodia- lobe like

-chaetae (chitin coating)

- 4 body regions (prostomium- head, peristomium-head, body segments-trunk, pygidium- tail)

Annelid Body Wall

-thin cuticle (non-living)

-epidermis→ often ciliated

-connective tissues (basement layers)

-circular muscles, longitudinal muscles

-peritoneum (membrane that lines coelom, body cavity, surrounds organs)

-coelom divided by septa

Annelid Coelom

Annelid Skeleton

hydrostatic→body wall muscles, coelomic fluid

-evert and retract proboscis, gills

-move parapodia

-rigid chaetae (aciculae- needle shaped structure, ,muscles, cats claws

Annelid Locomotion

polychaetes:

• errant :(longitudinal muscles, undulations, parapodia power-wavelength movement, burrowing- proboscis as shovel and anchor)

• OR sedentary: (weak body wall muscles, reduced parapodia, strong retractor muscles)

Clitellates:

• mostly errant

oligochates- strong circular+ longitudinal muscles, peristaltic motion

leeches- suckers, inch worming

Annelid Feeding

Diverse!

predators: homologous and fat, carnivores and omnivores, strong chemo/mechanoreceptors- use pharynx with jaws and teeth)

deposit: selective

suspension: tube worms, tentacles/gills→use currents, chaetopterus

blood: jaws, powerful pharynx, anticoagulant, anesthetic

Annelid Digestion

-complete gut→straight, specialized regions

foregut: mouth, buccal cavity, glands, pharynx, esophogus-, crop, gizzard-? mechanical pocessing

midgut: intestine (extracellular), cecae

hindgut: mucous glands, anus (terminal)

Annelid Circulation

Closed circulatory system (vessels, hearts(s) lacking

Blood= hemolymph (hemoglobin)

Annelid Gas Exchange

Specialized structures

often co-opted (parapodia, gills, tentacles)

highly vascular

Annelid Excretion/ osmoregulation

Metanephirdia→ nephrostome (intake)

Niphridioduct → selective resportion

nephridiopore→ waste removal

segmental arrangement

*marine polychaetes: osmoconfomer

*Estuarine, freshwater, and terrestrial: osmoregulator

Annelid Nervous System

Cerebral ganglion

circumenteric

longitudinal ventral nerve cord

ganglion in each segment, parapodia too

+tube worms have giant nerve fibers that bypass ganglia

Mechano/ Chemoreceptors: antennae, palps, tentacles, cirri

photoreceptors- oceili to eyes with lenses!

Annelid Asexual Reproduction

fragmentation

budding

regernation present but limited→ neoblasts (pluripotent- stem cells)

Annelid Sexual Reproduction

Polycheates: gonochorisitc, no gonads, gametes spawned out of metanephirdia- or body wall (epitoky)

Clitellates: Hermaphriditic, true gonads, cross-fertilization internal, clittelum (thick band)

Annelid Development and Life Cycle

Protosomes

spiral, holoblastic cleavage

gastrulation by invagination or epiboly

schizocoelous

Clitellates: direct development→juveniles crawl out of cocoon

Polychaetes: indirect or mixed→trochophore larve, gradual metamorphosis, teloblastic growth

Larval regions correlate to regions of adult worm (preprototroch=prostomium, prototroch=peristomium, pygidium-=pygidium-)

Phylum Mollusca

-Jonston 1650

-“soft nut with hard shell”

-80,000 species → 8 classes

polyplacophora (chitons)-850 species

gastropoda (slugs/snails)-70,000 species

bivalvia (clams/kin)- 9,200

Scaphopoda (tusk shells)- 500 species

cephalopoda (nautilus, squid, octopus, cuttlefish)- 700 species

Molluscan Bauplan

Diverse

bilateral

anterior-posterior→undirectional

defined head region - cephalization (not bivalves!)

triploblastic

true coelomate- → schizocoelous development

coelom reduced→replaced with hemocoel

not vermiform, not appendages

Body divided into: head, foot, visceral mass

Molluscan Bauplan II

Mantle: surrounds, visceral mass, secretes shell

Mantle cavity: ctenidia (respiratory/gill), cloacoa-like

torsion: viscal mass rotates 180 (switching head-foot areas)

Polyplacophora bauplan

Gastropoda Bauplan

Bivavlia Bauplan

Scaphopoda Bauplan

Cephalopoda Buaplan

Mollusca Body Plan

Cuticle (co-opted into shell)→conchin, not chitin

Epidermis- (ciliated, secretion)

Basement membrane

muscles (outside in): micrular, diagonal, longitudinal

Mollusca Skeleton

hydrostatic skeleton→ body wall muscles + epidermis

Shell: Calcium carbonate on protein matrix (outside in:epidermis, nacreous layer(s), prismatic layer, periostracum)

shell diversity

Mollusca Locomotion

Crawling; muscle aided gliding, muscle waves

burrowing: foot as shovel, plow, and anchor

Swimming: flapping foot, pteropods, heteropods, jet propulsion (scallops, Cephalopod), fins for hovering

Walking: octopi

Mollusca Feeding

radula; all but bivalves (gastropods and chitins)→toothed tongue (rasping, boring, cutting and piercing)

herbivores, predators, scavengers,

suspension (bivalves +gastropods→siphons, ctenidia)

deposit feeders (scaphopds +bivalves→captcula and siphons)

-Cephalopods: tentacles (extend to capture),arms (grab and manipulate), break (tearing→venom

Mollusca Digestion

Complete gut- straight/twisted, specialized regions

Foregut: mouth, buccal region w/ redula, esophagus, glands (extracellular)

Midgut: stomach (muscular), Digestive glands (cecae, extracellular), crystalline style

Hindgut: intensine (intracellular), Ink sac (Cephalopods), anus (mantle cavity)

Mollusca Circulation + Gas Exhange

Open circulatory system (vessels +sinuses, hemocoel)

chambered hearts

Blood: hemolymph (hemocyanin, sometimes hemoglobin)

Ctenidia (mantle cavity, cilated)

Cephalopods: closed circulation, branchial hearts

terrestrial molluscs: pneumostome (opening in slugs to breath) +lung

Gas Exchange- countercurrent exchange

fluids flow in opposite directions to enhance the transfer of a substance (like oxygen), is found in the gills of molluscs (with ctenidia). This mechanism is crucial for efficient gas exchange, maximizing the uptake of oxygen from the water into the molluscs blood.

Mollusca Excretion

Metaephridia- Mephrostome → intake

Nephridioduct →selective resorption

Nephridiopore→waste removal (opens in mantle cavity)

nephrostome in percardial coelom

*marine:osmoconformers

*fresh/terrestrial: osmoregulators

Mollusca Nervous System

Ladder like variation

cerebral ganglion circumenteric

ventral cord and ganglia

pedal cords (ventral)→ foot muscles

visceral cords (lateral)→visceral mass, mantle

cephalopods→ cranium, arms+tentacles, giant neurons

Mollusca Sensory Structures

Mechanoreceptors: lots of surface area

chemoreceptors: siphons, osphradia (sensory organ mantle cavity near gills), suckers, slime trails (“home scars”)

Photoreceptors-: shell eyes, pigment cup ocelli, eye with lenses, cephalopod eyes (no blind spot!)

Mollusca Reproduction

Asexual:

-parthenogenesis (virgin birth-rare)

-regeneration possible but limited

Sexual:

mostly gonochorisitc

(gastropods: herm. + protandrous)

true gonads

gonopores (mantle cavity, urogenital pores (gastropods))

spawning (indirect development)

shift to internal fertilization

Cephalopod mating: complex, Hectocotylus (mating arm- holds onto spermatophore- sperm packer)

egg sac or string

mixed-/ direct development

Mollusc Development + Life Cycle

Protostomes

spiral cleavage (64 cell stage)

Indirect development (chitons- broadcast spawning)

→trocchophore larva (annelids too)

→veliger larva w/ velum (secondary larval stage- calms +snails)

Mixed development (early dev. tp veliger stage)

→trophopore in egg, veliger free living (ciliated)

Direct Development

→cephalopods (no larval stage)

→mercoblastic cleavage (have large yolk)

→discoblastula (looks like disc on yolk-feed on yolk)

Phylum Bryozoan

Hatschek 1891

“moss animal”

Lophotrochozoa→ Lophaphorata

with phyla Phoronida + Brachuopoda

→Lophophore

→Epistome

→sessile

→U-shaped gut

~6,000 species- 2 classes

Bryozoan- class Hymnolaemata

marine

lack epistome

hard crystids

with heterozoids (cannot feed itself- bird beak)

Bryozoan- class Phylactolaemata

freshwater

with epistome

gelatinous cystids “dino snot”

lack heterozoids

Bryozoan Bauplan

bilateral symmetry

anterior-posterior axis- difficult to see

weak cephalization

triploblastic

true colemate- divided into 3 parts

colonial (flat, branching, gelatinous

Zooids (cystids, polypide-retractable)

Zooid types: autozoids (feeding), Heterozoids (vibracula, avicularia-bird beak)

colonial network; funiculus (connects stomach tract to body wall-shares food) , stolon (tube extensions), pore plates (connect zooids to colony)

Bryozaon Body Wall

Cystid- gelatinous, hardened/ calcified (Zoecia-protective)

Epidermis→secretes cystids covering

Muscle layers→longitudinal + circular

Muscle groups→specialized; retractors

peritoneum →lines abdominal cavity

Bryozoan Skeleton

Rigid zoecium

hydrostatic skeleton; coelomic fluid, muscles, membrane

Bryozoan Locomotion

Adults- sessile (retractions + extension)

some colonies crawl

Bryozaon Feeding

suspension feeders

ciliated phophore (circular or horseshoe shaped, mouth in middle)

lophore current

particle capture→ flicking!

food mostly protists

Bryozoan Digestion

Complete gut→U-shaped, specialzed regions, anus outside phophore (ectoproct)

Foregut: mouth (epistome), pharynx

Midgut: descending stomach, cardia, gizzard-like, extracellular, central stomach, cecum (extra+intracellular)

Hindgut: Pylorus, rectum, anus

sharingp funiculus (sharing nutrients with colony

Bryozoan Circulation, Gas Exchange, Excretion

no specialized structures

diffusion (surface area to volume, lophophore)

coelomic fluid, funicula, pore plates

Bryozoan Nervous System

Weak cephalization

cerebral ganlgion

circumoral nerve ring

nerves to viscera, muscles, tentacles

Bryozoan Sensory Structures

Mechanoreceptors: tentacles, avicularia

Bryozoan Asexual Reproduction

ancestrula

budding (distinct growth patterns, cystid→polypide)

regeneration possible

statoblast (like the gemmule- freshwater only- dormant stage)

Bryozoan Sexual Reproduction

Hermaphroditic colones

zooids male or female

no true gonads- peritoneum/funiculus

sperm spawned through tentacles

internal fertalization - capture

some fertilized eggs shed

brooding- ovicells, placental

Bryozoan Development + Life Cycle

Dueterostomes-?

molecular- protostomes

radical, holoblastic cleavage

coelo-or steroblastula

gastrulation by ingression

coelom formation is mystery

Indirect development: cyphonautes larva (planktotrophic)

Mixed development: Coronate larve (Lecithrotrophic)

Dramatic metamorphosis

+polyembryony-cleaves during development, becomes many indv.

Phylum Nemotoda

Lankester 1877

“threads”

Nematoida

Ecdysozoa- includes arthropods (cuticle, molt to grow)

~25,000 species: free living + parasitic, 2 classes

Nematoda- class Enoplea

bottle shaped pharynx

pocket-like amphids

Nematoda- class Chromadorea

bulbous pharynx

slit like, pore like, or coil like amphids

Nematode Bauplan

bilateral symmetry

anterior-posterior→unidirectional

defined head region→weak cephalization

triploblastic

blastocoelomate→Pseudocoelomate

spacious coelom

vermiform

unsegmented- no appendages

round in cross section- “roundworms”

lack locomotory cilia in all life stages

Nematode Body Wall

Cuticle- thick but flexible, multi-layered, collagen (no chitin)

textured

Epidermis: secretion, longitudinal cords (nerve cords + excretory canal)

longitudinal muscles; 4 groups, muscle cells with arms, unique

circular muscles lacking

large blastocoel (gonads)

Nematode Skeleton + locomotion

Hydrostatic skeleton (body wall muscles, coelomic fluid, elastic cuticle (high pressure!!)

whip like undulations

→crawling

→swimming

Nematoda Feeding

Free living species:

deposit, detritivores, microscavenger, predators, herbivores (have spines, teeth, jaws, stylets)

Parasitic:

important diseases; human parasites (Hookworm, Ascaris, Whipworm, Trichinella)

Nematoda Digestion

Complete gut→straight, specialized regions

Foregut: cuticle lining, mouth w/ lips and papillae, buccal cavity, pharynx

Midgut: intestine(not cuticle lined, extra + intracellular)

Hindgut: cuticle lined, males: cloaca + anus, females: recutum +anus (subterminal)

pressurized sphincters

Nematoda Circulation + Gas Exchange, Excretion

no specialized structures

diffusion (small and thin)

blastocoelom

lack proto- metanephridia

1-2 long renette cells (excretory canals, associated w/ epidermis)

ventral excretory pore

Nematoda Osmoregulation

marine; osmoconformers

fresh/terrestrial: osmoregulators

→water + cuticle

Nematoda Nervous System

weak cephalization

circumenteric nerve ring (nerve tissues that encircles the esophogus)

Nerve cords (dorsal and ventral, epidermal cords)

Nematoda Sensory Structures

Mechanoreceotors: papillae (head and tail- organs)

Chemoreceptors: amphids ANTERIOR (glandular- taste, smell= stimulate action potential), Phasmids POSTERIOR (send action pot., mating uses)

Photoreceptor: Ocelli (simple, no lens)

Nematoda Reproduction

Asexual: parthenogenesis (virgin birth)

Sexual: gonochoristic, true gonads, dimorphic

male system: testis, sperm duct, seminal vesticle, ejaculatory duct, cloaca, copulatory spicules + bursa

female system: 2 ovaries, oviducts, uteri, vagina + vulva

→internal fertilization, high pressure!

Nematoda Development + Life Cycle

zygotes coated- cysts

released as cysts

protostomes

cleavage holoblastic + unequal (neither radial or spiral, highly deterministic)

stereoblastula

gastrulation by epiboly and ingression

Eutely experiment→ C. elegans 959 cells

direct development

four juvenile stages : L1/L2- rhabditiform “larva”, L3- filaiform “larva”, L4- no name.

“duar”- rest, hiberation