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BIOL 111 Study Guide - Final Guide: Ventral Nerve Cord, Pericardial Sinus, Telson

Biology (Sci)
Course Code
BIOL 111
Suzanne Gray
Study Guide

of 5
Lab 6 Invertebrates II
Phylum Arthropoda
The most diverse and complex of the invertebrate phyla
Exhibit cephalization (sense and control organs focused at the anterior end)
Also, exoskeleton and jointed appendages
Example: Crustaceans are highly adapted to aquatic life and very few live on
land (i.e. crayfish)
Phylum Arthropoda Crayfish
External Anatomy: bilateral symmetry
Body covering: the body of the crayfish is covered by a hard
cuticle composed largely of chitin
o The covering acts as a protective outer layer (exoskeleton)
to which muscles are attached
Body region: consist of the head and throax that are covered by
a fused dorsal shield called the carapace with a cervical groove
dividing the two regions. Together, the head and thorax are called
the celphalothorz
o Compound eyes on the head: separate anterior pointed
projection of the dorsal shield (called the rostrum)
o Abdomen: half the total length
Body Segments: covered by thin flexible chitin permitting
movement at the joints
Appendages: Crustaceans
o Basal stack: attached to the ventral surface of the body
o Two distal branches: exemplified by the swimmeret
o Biramous form: two branches
o Appendages are said to be homologous
o Serial homology: similar structures in different segments
8 segments in the thorax region and 6 in the abdomen region
Biramous form: antennules, maxillipeds, swimmerets, uropods
Serial homology: pharynx, esophagus, crop, gizzard, intestine
Lab 6 Invertebrates II
Table 8.1. Appendages of the crayfish. There are 19 segments with paired appendages.
1 Antennule (with statocyst in
base) Touch, taste, and equilibrium
2 Antenna (with excretory pore
at base) Touch and taste
3 Mandible (jaw) Crushing and chewing food
4 1st maxilla Food handling
5 2nd maxilla (with gill bailer) Food handling and draws water
over gills
6 1st maxilliped Touch, taste, and food handling
7 2nd maxilliped* Touch, taste, and food handling
8 3rd maxilliped* Touch, taste, and food handling
9 1st walking leg (cheliped)* Defense, food capture and
10 2nd walking leg* Walking and grasping
11 3rd walking leg* (with female
genital pore at base) Walking and grasping
12 4th walking leg* Walking
13 5th walking leg* (with male
genital pore at base) Walking
* gills attached to their bases Respiration
14 1st swimmeret male
1st swimmeret female Transfer sperm to female male
No function – female
15 2nd swimmeret male
2nd swimmeret female
Water circulation both sexes
Transfer sperm to female male
Carry eggs female
16 3rd swimmeret Water circulation both sexes
Carry eggs female
17 4th swimmeret Water circulation both sexes
Carry eggs female
18 5th swimmeret Water circulation both sexes
Carry eggs female
19 Uropod Backward swimming
Lab 6 Invertebrates II
Respiratory System:
Gills: some extend from the bases of the walking legs and others are
attached to the inner wall of the gill chamber (a lateral chamber
underneath the carapace)
Can respire on land for a short period of time, as long as there is water
trapped in the gill chamber
The gills featherey structure provides an enormous surface area for the
diffusion of gases
o Water enters under the carapace and is moved over the gills by
the beating activity of the gill bailer and the movement of the legs
o The stream of water after passing over the gills id laden with
carbon dioxide and depleted with oxygen, and is expelled from the
anterior end of the gill chamber
Circulatory System: consists of the heart (appears triangular, whitish structure
with a pair of small holes)
Open circulatory system: the heart lies in a dorsally located space (the
pericardial sinus) into which blood collects. No veins, blood enters the
heart via holes (ostia) and is pumped out through seven main arteries
The body cavity is called a hemocoel because it is filled with blood;
blood travels to the gills through the sinuses and exchanges carbon
dioxide for oxygen
The blood then travels back to the pericardial sinus and into the heart
where it is pumped to the rest of the body via arteries
The oxygen-carrying pigment in the blood plasma of arthropods is called
hemocyanin (contains copper)
Reproductive System:
Male: small pair of testes lie ventral and slightly anterior to the heart
o Colied seminal ducts carry the sperm from the testes to the genital
o The 1st pair of swimmerests are used to convey the sperm to the
seminal receptacle of the female
o Fertilization is external
Female: a pair of pinkish ovaries lay in position similar to the testes in the
male (small or large and full of orange eggs) granular appearance
o A pair of oviducts leads from the ovaries to the genital pores
o Females store the sperm in the seminal receptacle for several
o Mating occurs in the fall, but females do not release their eggs and
the stored sperm until the spring
o Fertilized eggs attach to the females swimmerets for
approximately six weeks until hatching and then for several more
weeks until the juvenile crayfish is large enough to survive