Transcript Brief Survey of Crustaceans

CHAPTER 20
Crustaceans
20-1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sally Lightfoot Crab,
from the Galapagos
20-2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Overview


Over 67,000 living species
Divided into 5 classes

We will study 3 classes, Branchiopoda and
Malacostraca, Maxillopoda
Branchiopoda = water fleas, brine shrimp
 Malacostaca = isopods, krill, crab, lobster, etc.
 Maxillopoda = barnacles

20-3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20-4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea
General Nature of a Crustacean

Main distinguishing characteristic of
crustaceans



Two pairs of antennae
Head also has a pair of mandibles and 2 pairs
of maxillae
One pair of appendages on each of the
additional segments


20-5
Some segments may lack appendages
All appendages, except perhaps first antennae, are
biramous
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea



Tagmata (segments) are usually head, thorax,
and abdomen
Some times one or more thoracic segments are
fused with the head as a cephalothorax
Arrangement of tagmata in Malacostraca is the
ancestral plan



20-6
Head has 5 fused segments
Thorax has 8
Abdomen has 6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20-7
Head (5) and thorax (8)- compose 13 cephalothorax segments
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea



Anterior end is a non-segmented rostrum
(covers eyes in some)
Telson, with the last abdominal segment and
uropods, forms a tail
Dorsal covering is the carapace

20-8
May cover most of body or just cephalothorax
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea
Form and Function

External Features


Secreted cuticle is made of chitin, protein, and
calcareous material
Heavy plates have more calcareous deposits


Telson

20-9
Joints are soft and thin, allowing flexibility
Bears anus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20-10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Appendages

20-11
Most have appendages on each segment, with
homology
Appendages of crayfish: 3 main parts to each appendage
Protopod = brown
Endopod = blue
Exopod = yellow
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20-12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Crawfish Appendage and Function
(Number if pairs)
Appendage
Function
# of pairs
Antenna
Touch, taste, equilibrium
2
Mandible
Crushing food
1
Maxilla
Handling food, drawing water
currents to gills
2
Maxilliped
Touch, taste, handling food
3
Walking legs
Offense, Defense, walking (cheliped
is 1st, with pincer)
5
Swimmeret
Transfer sperm, create water
currents, carrying eggs and young
5
Uropod
Swimming, egg protection in
females
1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Internal Features
 Coelomates  Open circulatory system

with blood (Hemocoel) -
Protostomes (mouth first)
 Complete Gut

20-14
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Muscular System
Striated muscles - most of body
 Most muscles arranged as antagonistic
groups
 Flexors draw a limb toward the body and
extensors straighten a limb out
 Abdominal flexors of a crayfish allow it to
swim backward

20-15
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Green Gland = Kidney
Internal Anatomy of the crayfish.
20-16
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Respiratory System



Smaller crustaceans may exchange gases across thinner areas of
cuticle
Larger crustaceans use featherlike gills for gas exchange
Circulatory



20-17
Open circulatory system
 No system of veins to separate blood from interstitial
fluid
 Hemolymph exits heart through arteries
 Passes to hemocoel to return to the heart via sinuses
Dorsal heart
 Single-chambered sac of striated muscle
Valves in the arteries prevent backflow
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hemolymph travel: Heart, Body, Sinus, Gills, Heart via Ostium (opening)
20-18
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Excretory System





20-19
Antennal or maxillary glands
Called “green glands”
End sac of green gland has a small vesicle and a
spongy labyrinth
Labyrinth connects by an excretory tubule to
dorsal bladder that opens to exterior pore
Hydrostatic pressure within a hemocoel provides
a force for filtration of fluid into the end sac
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20-20
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Nervous and Sensory Systems






20-21
Pair of ganglia connects to eyes and two pairs of
antennae
Nerves join this brain to the mouth, appendages,
esophagus, and antennal glands
Ventral nerve cord has a pair of ganglia for each
segment to control appendages
Tactile hairs occur on the body, especially on chela,
mouthparts and telson
Chemical sensing of taste and smell occurs in hairs
on antennae and mouth
Compound eye migrates pigments for day or night
vision
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Compound eyes work differently during day and night.
Pigment cells will expand or constrict to allow different amounts of light to hit the photoreceptor cells
20-22
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Reproduction, Life Cycles, and Endocrine Function
 Diversity of Reproduction
 Most crustaceans group eggs in brood
chambers, in brood sacs attached to the
abdomen, or attached to abdominal
appendages
 Crayfishes develop directly without a larval
form
 Most crustaceans have a larva unlike the adult
in form, and undergo metamorphosis
 The nauplius is a common larval form
 Appendages and somites are added in a
series of molts
20-23
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Life cycle of a Gulf Shrimp
Metamorphosis
20-24
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Ecdysis




20-25
Necessary for a crustacean to increase in size the
 Exoskeleton does not grow
Physiology of molting affects reproduction,
behavior, and many metabolic processes
Underlying epidermis secretes cuticle
Outermost epicuticle and 2 layer procuticle
dissolve and are discarded.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pre-molt Stage:
Protocuticle separates from epidermis.
Epidermis secretes new epicuticle.
Pre-molt Continued:
Molting fluid dissolves endocuticle, and
Solutions are rebsorbed.
New exocuticle develops
Ecdysis Stage:
Old epicuticle and exocuticle are discarded.
Post-ecdysis:
New cuticle is stretched and hardens.
Endocuticle is secreted.
20-26
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lobster Molt
A. Membrane between carapace and abdomen ruptures (2 hours)
B. Head Thorax and Abdomen withdraw (15 minutes)
C. Lobster continues rapid absorption of water to increase length by 20% and weight by 50%.
Tissue water will be replaced by protein later. (weeks)
20-27
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Hormonal Control of Ecdysis



20-28
Temperature, day length, or other stimuli trigger
central nervous system to begin ecdysis
Central nervous system decreases production of
molt-inhibiting hormone by the medulla region of
the brain
Promotes release of molting hormone from the
glands near mandible which promotes ecdysis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subphylum Crustacea

Feeding Habits
Suspension feeders generate water
currents in order to feed on plankton,
detritus, and bacteria
 Predators consume larvae, worms,
crustaceans, snails, and fishes
 Scavengers eat dead animal and plant
matter

20-29
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Brief Survey of Crustaceans
Class Branchiopoda

Over 10,000 species, 4 orders
 Order Anostraca, includes fairy shrimp and
brine shrimp


Order Cladocera, includes water fleas
(daphnia)

20-30
Lack a carapace
Carapace encloses the body but not the head
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20-31
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Brief Survey of Crustaceans
Class Maxillopoda

General body plan


No appendages on abdomen
Subclass Cirripedia - barnacles





20-32
Includes barnacles and three orders of burrowing or
parasitic forms
Adults are sessile
Carapace surrounds body and secretes a set of calcareous
plates
Head is reduced, abdomen is absent
Jointed feeding legs bear setae and extend from the plates
to feed on small particles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A. Acorn Barnacle
20-33
B. Gooseneck Barnacle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Barnacles on healthy grey whale
Contains commensalistic barnacles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Brief Survey of Crustaceans
Class Malacostraca


Largest and most diverse class of Crustacea with over 20,000
species
Contains three subclasses, 14 orders, and many suborders
Order Isopoda




Only truly terrestrial crustaceans
Also have marine and freshwater forms
Dorsoventrally flattened, lack a carapace, and have sessile
compound eyes
Common land forms include sow bugs and pill bugs (Rolly
Pollies)
20-35
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A. Pill Bugs
B. Freshwater Sow bug - aquatic isopod
ISOPODS
20-36
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Isopod Parasite
20-37
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Brief Survey of Crustaceans
Order Decapoda




5 pairs of walking legs
In crabs, first pair of walking legs form
pincers (Chelipeds)
Approximately 18,000 species
Includes crayfishes, lobsters, crabs, and
true shrimp (size of cephalothorax and
abdomen vary)
20-38
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A. Tropical Rock Crab
B. Hermit Crab
C. Male Fiddler Crab
D. Red Night Shrimp
E. Spiny Lobster
20-39
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sponge Crab - masks itself with materials from environment, sponge
20-40