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Marine Invertebrates > Lecture 10 > Flashcards

Lecture 10 Flashcards

Gnathifera

1
Q

Protostomia

A

Blastopore becomes the mouth; anus forms later

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2
Q

Spiralia

A

Spiral cleavage occurs curing developmental cell division

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3
Q

Four phyla within the clade (gnathifera)

A

1.) Chaetognatha
2.) Gnathostomulida
3.) Rotifera
4.) Micrognathozoa

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4
Q

Chaetognatha

A
  • Marine pelagic dwellers with a few benthic species recognised
  • About 130 extant species
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5
Q

Gnathostomulida

A
  • Marine sediment dwellers, often found in anoxic habitats of salt marshes and mudflats
  • About 100 extant species
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6
Q

Rotifera

A
  • Primarily freshwater dwelling, some brackish and coastal habitats are observed
  • About 3350 extant species
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7
Q

Micrognathozoa

A
  • Exclusively freshwater dwelling in Greenland
  • 1 extant species
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8
Q

Gnathostomulida (phylum) ‘jaw worms’

A
  • meiofauna - inhabits benthic marine and intertidal sediments
    • Especially common in anoxic and sandy (extreme) environments
  • Only given own phylum in 1969
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9
Q

Gnathostomulida (phylum) ‘jaw worms’ orders

A

1.) Long slender: filospermoidea
2.) Wider bodied: bursovaginoidea

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10
Q

Gnathostomulida jaws

A
  • Snapping pincer-like, located within the muscular pharynx
    • Scraping basal plate may be present in some species
  • Designed to scrape bacteria and detritus stuck to grains of sand and sediment
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11
Q

Gnathostomulida main body plan/anatomy

A
  • Simple sac-like elongated functionally incomplete gut, performs extracellular digestion
  • Anus may be present but sealed off
  • Gliding locomotion
  • No respiratory or circulatory systems present
  • Sexual reproduction, internal fertilisation; hermaphroditic
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12
Q

Gnathostomulida protonephridia excretory system

A
  • Network of blind tubules that line the body wall to an outer hole in the body
    • Flame cell cilia create current to drive body fluid into the tubules of tube cells through the gaps of interdigitation between the two cells
    • Wastes/ions are separated largely by molecular size and selectively eliminated
    • More valuable for osmoregulation than nitrogenous waste excretion
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13
Q

Flame cell cilia

A

Function like a kidney, removing waste materials through filtration

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14
Q

Interdigitate

A

An interlocking of things with fingerlike projections

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15
Q

Osmoregulation

A

The maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations

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16
Q

Diffusion

A

Helps in the movement of substances in and out of the cell; molecules move from high to low concentration until the concentration is equal throughout

17
Q

Gnathostomulida - sensory and nervous system

A
  • Cephalisation is clear
    • Brain with three commissures connecting hemispheres
  • Ciliary pit (primary sensory organ, head region) communicates with the brain
    • Cilia lining the pit contact prey and interact with the environment to inform the animal about prey proximity and gaps within the sediment
  • Buccal ganglion helps control feeding and contractions of the pharynx musculature
  • Separate dorsal and ventral nerve cords in body to help control locomotion and peristalsis
18
Q

Cephalisation

A

The concentration of sense organs, nervous control, etc. at the anterior end of the body, forming a head and brain, both during evolution and in the course of embryonic development

19
Q

Buccal ganglion

A

Sends nerves to the muscles of the jaws and radula and to the anterior salivary glands, buccal palps and oesophagus

20
Q

Rotifera (phylum) ‘wheel animals’

A
  • Most diverse gnathifera phylum
  • Most species reside in freshwater environments
  • Free living and endo/epizoic lives
21
Q

Acanthocephala (Rotifera)

A
  • Endozoic
  • Obligate parasite of many vertebrate guts
22
Q

Seisonidea (Rotifera)

A
  • Epizoic
  • Lives with gills of Nebalia crustaceans
23
Q

Endozoic

A

Living within or involving passage through an animal

24
Q

Epizoic

A

Growing or living non parasitically on the exterior of a living animal

25
Q

Planktonic

A

Floating or weakly swimming animal/plant life of a body of water

26
Q

Rotifera (protonephridia) - general anatomy

A
  • Possess a corona
    • Ciliated head structure creates water currents for feeding and locomotion
    • Can be modified as a trap in some monogonontas
  • Excretory protonephridia
    • Empty into a bladder that empties the waste into a cloaca
    • Diffusion of ammonia still occurs across body wall, protonephridia primarily used for osmoregulation (many Rotifera are freshwater tolerant)
  • Complete and regionally specialized straight gut
    • Gastric glands secrete enzymes for extracellular digestion beginning near mastax and ending within stomach
  • No respiratory or circulatory organs
27
Q

Rotifera - reproduction and development

A
  • Gonochorisitic; reproduce through asexual parthenogenesis (except for seinsoidea subclass)
    • Eggs grow and develop without fertilisation
    • Males usually smaller in size and complexity; bdelloidea males do not seem to exist at all
    • Insertion at gonopore or hypodermal injection through the body wall using specialized copulatry organs with stylets
28
Q

Chaetognatha (phylum) ‘arrow worms’

A
  • Almost exclusively pelagic zooplankton
    • Specialized jaws
  • Only resolved to the gnathifera clade in 2019
  • Mouth and anus exist; neither from blastopore
  • True coelom exists
29
Q

Gonochoristic

A

Those species with separate sexes

30
Q

Chaetognatha - jaws

A
  • Grasping spines on sides can move independently for dexterity
  • Designed to puncture, not chew
    • Prey is swallowed whole
  • Neurotoxins mix with fluid secreted by the pharynx and vestibular glands to quell prey
31
Q

Chaetognatha - musculature

A
  • Of the head is complex
    • Striated muscles for forceful contractions
    • Esophagus/pharynx musculature to swallow prey
  • Circular body muscles = weak myoepithelial cells
32
Q

Chaetognatha - body plan/anatomy

A
  • Simple, straightened gut; extracellular digestion
  • Basic hemal (circulatory) sinuses are present, peristalsis by muscle contractions
  • No discrete respiratory or excretory organs
  • Lateral and caudal fins reduce drag
33
Q

Chaetognatha - sensory/nervous system

A
  • Cephalisation is clear
    • Paired dorsal nerves to eyes and corona cilia
    • Ventral nerves innervate head, digestive tract and musculature as a loop
  • Large ventral ganglion, receives sensory information and controls movement
  • Ciliary receptors relay sensory input to ventral ganglion
34
Q

Chaetognatha - reproduction and development

A
  • Hemaphroditic
    • Paired ovaries within trunk
    • Paired testes within tail
  • Mature sperm filter into seminal vesicles
  • Seminal vesicles burst during mating rituals
  • Oviducts within the trunk collect sperm for internal fertilisation
    • Self-fertilisation occasionally occurs
  • Zygote released develops without larval stage within 48 hours

Marine Invertebrates (17 decks)

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