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Biology of Invertebrates-Lectures > Poriferans > Flashcards

Poriferans Flashcards

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1
Q

What does poriferan mean

A

Pore bearing

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2
Q

Poriferan general overview/ history

A
  • simplest animal group among multicellular/metazoans
  • possess unique body forms from other animals but show genetic similarity
  • paraphyletic: members evolved from 2 or more ancestors
  • fossils exist since 580M years ago
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3
Q

Poriferans feeding

A

Pelagic feeders

-feed in floating/ drifting microorganisms

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4
Q

Poriferan habitat

A

98% marine, 2% fresh water, no terrestrial species

  • sessile: most are attached, few are mobile like protoplasmic Amoeboid movement
  • fork aquatic community among sedentary organisms
  • provide shelter for other aquatic organisms including Cyanobacteria and bacteria
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5
Q

Poriferan shape

A

Mostly shapeless and asymmetrical with few exemptions

-anterior, posterior or oral regions not clearly differentiated

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6
Q

Poriferan organs systems

A

Lack specialized organ system for reproduction, digestion, sensory, respiration and excretion

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7
Q

Poriferans possess redufferentiation capacity meaning:

A

Ability to reaggregate to reform when split

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8
Q

Poriferan general body Plan

A

-Body is rigid, perforated bag (porocyte), with flagella (known as choanocyte or collar cells) lining the interior.

Body divided into

  • Spongicoel (internal space of a sponge)
  • choancyte: used in capture of food and sperm for fertilization and generate current of seawater through and within the organism.
  • mesohyl: gelatinous, no living layer containing live and mobile Amoeboid cells called archaeocytes
  • epidermis: pinacocyte and nucleus
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9
Q

Archaeocytes move within the mesohyl by cytoplasmic streaming and perform important functions like:

A
  • differentiate into specialized cells when necessary
  • food digestion
  • stored digested food material
  • may give rise to flagellated sperm and eggs
  • non-self recognition when in contact with other sponges
  • become specialized into secreting supporting elements
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10
Q

Secreting supporting elements

A
  • may be calcareous or siliceous spicules or may be fibrous collagenous protein called spongin within the mesohyl layer
  • cells secreting spicules are called sclerocytes and those secreting spongin are spongicytes
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11
Q

Function of spicyles and spongin fibers

A

Maintain shape, scaring predators and classifying sponges

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12
Q

Gemmules

A

Seasonal dormant cells produced by freshwater and some marine poriferans to avoid harsh environmental conditions.
-hatch under favourable conditions releasing cells which differentiation into functional sponges

-also a means of asexual reproduction, releasing many identical offspring

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13
Q

How are gemmules formed

A

Formed by phagocytizing other cells and surrounding them with thick cells making them resistant to harsh environmental conditions (freezing, drying up and anoxia)

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14
Q

Tissue regression

A

Fresh water and some marine species in unfavourable conditions can reduce drastically into tiny mass with a protective coat

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15
Q

Pinacocyte

A

Outer covering arranged in layers called a pinacoderm

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16
Q

Ostia

A

Narrow opening/ channels allowing water into the sponge which are released by a single osculum

-some members are large (1m) and can filter several litres of water per day through Ostia for food captured by internal flagella

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17
Q

Diversity of the poriferans

A
  • differentiated into 3 levels of complexity of the choanocyte in the relation to the spongocoel
  • simplest to most complex = asconoid sponge, syconoid sponge, leuconoid sponge (largest group)
18
Q

Asconoid sponge

A

-vase-like-radially symmetrical, tubular, small (usually <4cm tall), with single osculum or opening from internal atrium

19
Q

Syconoid sponge

A

First stage of body wall folding

  • Invaginations (incurrent canals), and Evaginations (radial canals) but each of these are blind and do not meet, but are linked by prosopyles
  • produced by folding of pinacoderm and choanoderm: increase thickened of mesohyl-outer part=cortex
  • choanocytes now in chambers, not directly in atrium
  • connected to atrium and to outside with system of canals, but connection to outside may be via Ostia openings in thickens pinacoderm
20
Q

Leuconoid sponges

A
  • produced by further folding and thickening of mesohyl, flagellated canals become flagellated chambers: openings to these called prosopyles, water exits chambers via apopyle , excurrent canals lined by pinacocytes
  • increase complexity and increase surface area
  • regulation of water flow through sponge-it is not uniform
  • water speed function of cross sectional diameter of channels
  • permits choanocytes to move water through a small volume: achieve adequate exchange
21
Q

Classification of poriferans based on chemical composition and morphology of the support elements:

A
  • calcarea
  • desmospongiae
  • hexactinellida
  • homoscleromorpha (previously part of desmospongiae)
22
Q

Class Calcarea-calcareous sponges

A
  • spicules composed of calcium carbonate only!!!!!, no spongin
  • all spicules are of the same general size and shape, Monaxons with 3 (triactinate) or 4 (quadractinate) points
  • all 3 body types found in this class-asconoid, syconoid and leuconoid (this class only)
  • many have little colour but there are some brilliantly coloured totes found at shallow depths
23
Q

Class Hexactinellida (Glass Sponges)

A
  • Silica spicules (some have chitinous fibers as well) - Triaxon with 6 points (hexactinellid)
  • some species inhabit soft bottom sediment, supported by turf of spicules, others attach to substrate
  • complex in structure and symmetry
  • body canal may be leuconoid or syconoid
  • body layers have unique multinuclei within a cell cytoplasm
  • lack pinacoderm
  • basal long-thin silica fibers emits light through my to be for direction
  • osculum covered by a sieve plate of silica spicules
  • marine and usually grow in deep water
  • may provide protection and habitual for commensal shrimp.
24
Q

Differences of calcarea and Hexactinellida

A

Hexactinellida are

  • larger than calcarea (30-40cm)
  • less tendency to grow in clusters than calcarea
25
Q

Class Desmospongiae (Desmosponges)

A
  • most abundant group a month poriferans (80%)
  • include commercial sponges (spongiidae)
  • most are leuconoid
  • spicules composed of silica or spongin fibers (never calcium carbonate)
  • brilliant colours because of pigment granules and endosymbiosis organisms
  • spicules are never triaxon
  • include all fresh water species
  • possess contractile vacuole
  • marine species lack Ostia, no internal canal (spongocoel) and no choanocytes
  • marine species are carnivorous, body covered with long-thin filament for catching tiny crustaceans, digesting them externally within days.
26
Q

Spongillidae

A

Freshwater sponges with zoochlorellae (endosymbiotic protozoan with chloroplasts) that enhance sponge growth by transferring nutrients

Part of demospongiae

27
Q

Homoscleromorpha

A
  • most lack spicules
  • if present, are composed only of silica
  • possess basement membrane and ciliates epithelial cells
28
Q

Reproduction in poriferans

A

-sexual and asexual

29
Q

Sexual reproduction in poriferans

A

Involves meiosis to form gamete involving egg and sperm

30
Q

Asexual reproduction in poriferans

A
  • most members are haemaphrodites (single organism may produce eggs and Sperm and fertilize itself.
  • male gametes are expelled into the environment

Either brooding or oviparous

31
Q

Brooding

A

Eggs retained in the tissues and when fertilized, either related or brooded to larval stage which is then released through the oscula as a planktonic form

32
Q

Oviparous

A

Fertilized eggs or gametes of a few species are shed into the marine water body, to develop externally

33
Q

Poriferan larval forms

A
  • coelobladtula
  • amphiblastula
  • sterioblastula
  • parenchymella larvae
  • metamorphosis of larvae into adult sponges
34
Q

Coeloblastula

A

Some desmosponges and calcareous sponges develop into hollow blastula during larval stages

35
Q

Amphiblastula

A

Formation of flagellated large in calcareous sponges

  • rapid cell division can occur in some calcareous sponges resulting in formation of flagella at one end around blastocoel (internal).
  • inversion of blastula makes the flagella become external resulting in a free swimming larvae
36
Q

Stereoblastula larvae

A

Solidification of coeloblastula in some calcareous sponges

37
Q

Parenchymella larvae

A

Direct development of larval desmosponges from the stereoblastula into extensive flagellated sponges

38
Q

Metamorphosis of larvae into adult sponges

A

Larval sponges do not feed and typically last 24 hours before metamorphosing into adult

39
Q

Gemmule formation

A
  • occurs in response to adverse environmental conditions.
  • much more resistant than the sling itself
  • archaeocytes (stocked with nutrients from investing the other cells) surrounded by spicules and spongin-like protein (protective shell) form gemmule usually in the fall.
  • parent disintegrates
  • when good conditions prevail, the cells begins to divide, emerge through the micropyle, and a new sponge is formed.
  • can wait years!!!!!
40
Q

Can sponges use budding?

A

Yes, portion of parent develop bud, detach and develop into a new sponge

Biology of Invertebrates-Lectures (10 decks)

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