Phylum Nemertea and Phylum Mollusca.

1. Stella Maris Polytechnic University
Mother Patern College Of Health Science
Group One Members:
1. Chrisphine M. Mendimasa 11350
2. Elvis K. Goodridge 11269
3. B.k Adjaenehn Nyenpan 11306
4. Amosrine Young 11182
5. Yamah Paypay
11183
6. CourageGbolo
11253
7. Elaine P. Boakai
11258
8. Abraham S. Saysay 11064
General Zoology I (Zoo 201)
Presented to: Paul Zawolo Seamehn Phylum Mollusca
Phylum Nemertea

2. Objectives
By the end of this lecture session, students will be able to know:
• The phyla Nemertea and Mollusca
•Their Characteristics
•Classification
•Their distinguishing features

3. Overview of Nemertea (Rhynchocoela)
(Gr. rhynnchos, beak = koilos, hollow)
 A diverse group of worms, know
commonly as the ribbon worms or
proboscis worms.
About 1000 species
Exhibit different color patterns consisting
of yellow, orange, red and green.
They are usually found marine
environments, with some occurring in fresh
Drepnogigas albolinetus

4. General Characteristics
Triploblastic
Acoelomate
Bilateral symmetrical
 Unsegmented
Closed circulatory system
No Repiratory system
An eversible Proboscis, which in the
cavity above the alimentary canal.
Complete Digestive system
Most free living, burrowing in
sediments.
Distinguishing Features:
• Proboscis
• Rhynchocoel.

5. Characteristics cont’d
 The nervous system consists of an anterior
brain, made up of four Ganglia.
 Cerebral organs, pairs of organs associated
with the brain.
 longitudinal nerve cords, non-ganglionated
and runs parallel.

6. Cont’d
 Excretion : Some species posses flame cells
or protonephredia for excretion, which help
filter waste.
 Waste is often excreted through the body
surface, particularly the Epidermis.

7. Body Structure/Anatomy
Drepnogigas albolinetus

8. Cont’d
 Reproduction:
Nemertians are dioecious.
 Most Nemertians reproduce sexually, while
some reproduce asexually through
fragmentation.
 External Fertilization
 The larva stage is called pilidium.

9. Development in Nemertea
Lineus Ruber

10. Classification
 Nemerteans are classified into two
classes:
 Class Anopla
 Class Enopla

11. Classification cont’d
 Species from the class Anopla, possesa mouth
posterior to the brain and their proboscis lacks
stylets.
 Species from the class Enopla, posses a mouth
anterior to the brain and a stylet proboscis.
Lineus Sanguineus
Cerebratus lacteus

13. Overview of Mollusca
 Mollis- Latin “Soft”
 One of the Largest and most diverse
phyla in the animal kingdom.
 Containing over 90,000 living
species.
 Ancestral larva a trochopore.
 Members include: Octopuses,
mussels, clams, Garden sail (Helix)

14. General Characteristics
 Triploblastic
 Usually Bilateral symmetrical
 Soft and unsegmented
 Mantle and shell
 Organ Grade Organization
Primary locomotory organ is the foot.
 22
Coelemate
Mollusks are mostly free living
species.
 Cephalization
Aquatic & Terrestrial organisms
They are distinguished from other
organisms by the presence of a
Mantle and Radula

15. Body Plan /Anatomy

Head~ Foot Region

Contains the sensory organs and motor organs.

Mantle: a layer of overlapping skin, that protects the visceral
organs and secrets the shell in some species.

Visceral mass: Digestive organs, reproductive organs,
respiratory organs and excretory organs.

Radula: a tongue like structure that is essential for their feeding.

17. General Characteristics Cont’d
Mode of Reproduction
Most are Dieoecious; although some
are hermaphroditic.
Mode of Excretion
They consist of a pair of kidneys
(Metanephridia)
Anus
Mode of respiration
 Aquatic: Gills (ctenidia)
 Terrestrial: Lungs or Cutaneous

18. Nervous system
The nervous system structure
varies with classes.
Consists of pairs of Ganglia
Nerve cord
A chemo-receptive sense organ,
regulates the water currents in the
mantle cavity called Osphradium.
Ocelli- photo receptive sense
organ.

19. Conchifera
• Bivalvia
• Gastropoda
• Cephalopoda
• Scaphopoda
Classification
Aculifera
• Monoplacophora
• Aplacophora
• Polyplacophora

20. Class: Bivalvia (Pelecypoda)
 (Gr. Pelekys: hatchet; podos: feet)
 About 29,000 species, living in aquatic
enviroments.
 Characterized by two calcareous valves.
 Unique to the class is pearl formation
 Sp. Mussels

21. Class: Bivalvia (Pelecypoda)
 No head
 Bilateral Symmetrical
 Free living
 Parastic larva is glochidium.
 Organisms are filter feeders
Glochidium on fish gills.

22. Body Structure /Anatomy

23.  Protobranchs, primitive and leaf shape gills.
 Filibranchs, individual filaments are still more or
less separate.
 Eumalibranchs, gill in which the union of
filaments has developed further, so that the lamellae
actually consist of solid sheets of tissue.
 Septibranchs, forms a muscular septum.
Classification
• Bivalves are classified on the basis of their gills into three
subclasses:

25. Reproduction/ Lifecycle
 Dieocious, exhibiting external fertilization.

26. Class Cephalopoda
 (Gr. Cepha: head; podos: feet)
 Consists of highly intelligent species.
 Contains approximately 800 species.
 Exclusively Marine
 Closed circulatory system
 Head and arms are their distinguishing features.

27. Class Cephalopoda
 Bilateral symmetrical
 Complete Digestive system; the radula is found
with in the buccal cavity of the beak.
 Mostly Predators, utilizing their arms, tentacles,
suckers to capture.
 Lack external shells, except for Nautilus.
 Most Famous are the Octopus and squid.

28. Body Structure/ Anatomy

29. Nervous System
 The posses a well-developed nervous
system.
 Between two well developed eyes is a
large central Brain, which is further
divided into various lobes.
 Optic lobes are responsible for visual
processing, receiving information from a
pair of eyes, with complex lenses.
 Statocysts; balance organs.

31.  Locomotion
 Move using jet propulsion, fins,
and tentacle undulation.
• Squid are active swimmers,
while octopuses often walk
along the seafloor.
• Some species release ink
decoys (pseudomorphs) to
escape predators.

32. Reproduction
• Mating involves males transferring
spermatophores using a specialized arm
(hectocotylus).
• Females lay eggs in clusters, often attaching
them to substrates.

34. Class Monoplacophora
 ‘Bearing one plate’
 A super-class of mollusks with a cap-like
shell.
 Consisting of 37 species.
 Bilaterally symmetrical
 Detritivores

35. Reproduction/Lifecycle
 Dioecious, with external fertilization.
 - Spawning influenced by environmental
factors.
 - Long lifespan compensates for slow
growth.
 Image plz

36. Ecological and Economical
importance
 Part of Deep-Sea Ecosystems
 Indicator Species
 Evolutionary Research
 Biotechnological Potential

37. Contrasting Monoplacophora and Alpacophorans
 Shell
 Habitat
 Foot
 Body plan

38. Class Scaphopoda
 They're a class of marine mollusks
commonly known as Scaphopods, tusk shells,
or tooth shells.
 Benthic organisms.
 They're filter feeders, utilizing small tentacles.
 Sp. Dentalium Entalis, Terebralia Palustris

39. Class Scaphopoda
 They've no eyes or developed head; they
possess tentacles for sensing their
environment and capturing their food.
 Locomotion
 Muscular foot used for burrowing.
 Contain Nephridia as an excretory organ.

40. Body Structure/Anatomy

41. Reproduction
 Dioecious, with
external
fertilization.
 Stages
• Fertilization
• Larval stage
• Metamorphosis
• Juvenile stage
• Adult stage

42. Class Polyplacophora
 The class Polyplacophora are
also known as chitons and they
are common inhabitants of marine
rocky shore.
 Their body is oval and greatly
flattened dorsoventrally .
 Bilateral symmetrical.
 They contain eight overlapping
shell plate

43. Class Polyplacophora
 They have no cephalic eyes or tentacles.
 Contain muscular foot.
 They have a simple nervous system.
 Shell composed of eight overlapping
plates known as valves covered by a
mantle tissue

44. Body Structure/Anatomy

45. Reproduction/Lifecycle
 Dioecious, with
external fertilization.
 Stages
• Fertilization
• Larval stage
• Metamorphosis
• Adult stage

46. Class Aplacophora
 The entire marine, shell-less.
 Contains about 250 species.
 Vermiform animals which have
calcareous spicules, scales, or plate..
 They are separated into two principle
groups, sometimes considered as
independent.

47. Body Structure/Anatomy

48. Classification
 Aplacophora are classified into two
subclasses:
 SOLENOGASTRES
- are more elongated, have a narrow Foot and
typically live in association with cnidarians.
 CAUDOFOVEATA
- the body is somewhat separated into anterior,
medial, and possessing an anteroventral pedal
shied.

49. Classification
 SOLENOGASTRES
 Are more elongated, have a narrow foot and
typically live in association with cnidarians
such as hydroids and alcyonaceans
 They are found throughout the world and
live at depth between 18 and 6000+m
 They are hermaphrodites and their mating
occurs by gonad style
 This class is sometime called
neomeniomorpha

50. Classification
 CAUDOFOVEATA
 The radula and odontophore are strongly
develop, and the alimentary system is more
differentiated.
 They have pair of gill. They are dioecious
 The body of caudofoveata may have more
features in common with ancestors
mulluscs.
 This class is sometime called
chaetodermomorpha

51. Class Gastropoda
 (Gr. Greek: gaster, 'gut’, and podos, 'foot)
 They’re the largest and most varied
molluscan class with over 35,000 species.
 Found in marine, freshwater, and terrestrial
habitats.
 Locomotion structures includes a typical foot
and some species utilizes cilia and muscular
contraction
Helix aspersa (garden snail)

52. Classification

53. Class Gastropoda
Torsion, a counterclockwise movement exhibited in the lifecycle of
gastropods.
Torsion in Gastropods

54. Reproduction
 Dioecious, with external fertilization.
 Monoecious, with internal
fertilization.

55. Subclass Prosobranchia
 This subclass contains 20,000
species, mostly marine.
 Herbivores, deposit feeders, or
carnivorous.
 Heteropods use modified fins
for swimming.
 Marine snails, abalone,
heteropods.
Helix aspersa (garden snail)

56. Subclass Opisthobranchia
 Contains approximately 2,000
species, mostly marine.
 Unique traits: Reduced or lost shell,
mantle cavity, and gills.
 Use nematocysts from cnidarian prey.
 Pteropods: Foot modified into thin
swimming lobes.
 Sp. Sea hares, sea slugs, pteropods.
Notodoris minor (sea slug)

57. Subclass Pulmonata
 Contains about 17,000
species, primarily freshwater
or terrestrial.
 Dietary habits: Herbivores
with radula for scraping plant
material.
 Mantle cavity functions as a
lung (pneumostome).
 Terrestrial snails and slugs.
Limax maximus

58. Quote of the Day

59. References
Abbott, R. T., and P. A. Morris. 2001. R. T. Peterson (ed.). A fi eld guide to shells:
Atlantic coasts and the West Indies, ed. 5. Boston, Houghton Miffl in Company. An
excellent revision of a popular handbook.
Barinaga, M. 1990. Science digests the secrets of voracious killer snails. Science 249:
250–251. Describes current research on the toxins produced by cone snails.
Bergström, J. 1989. The origin of animal phyla and the new phylum Procoelomata.
Lethaia 22: 259–269. Argues that Caudofoveata are the only surviving members of
Procoelomata, putative ancestral sclerite bearing early Cambrian metazoan.
Fleischman, J. 1997. Mass extinctions come to Ohio. Discover 18 (5):84–90. Of the 300
species of freshwater bivalves in the Mississippi River basin, 161 are extinct or
endangered.
Images: Google