LABORATORY 2: SHRIMP EXTERNAL AND INTERNAL ANATOMY

OBJECTIVES:

1) become familiar with gross external and internal anatomy of shrimp; and

2) examination of shrimp with respect to future necropsy methodologies.

SUPPLIES:

live shrimp, probes, scalpels, forceps, microscope slides, cover slips, compound

microscopes, dissecting microscopes, petri dishes, gram staining materials,

saline solution

PROCEDURE:

PART 1: EXTERNAL/INTERNAL ANATOMY

1) Remove one shrimp from the storage tank. Immobilize abdominal contractions by severing ventral nerve cord with scalpel.;

2) Identify and draw (for lab report) the following external anatomical features:

a) head;

b) thorax;

c) cephalothorax;

d) rostrum;

e) antennal scale;

f) first antennae (antennule);

g) second antennae;

h) stalked compound eye;

i) mandible;

j) maxillae/maxillipeds;

k) abdomen;

l) abdominal segments (1-6);

m) telson;

n) pleopods (1-5, paired);

o) pereiopods (walking limbs);

p) thelycum (female);

q) spermataphore (male);

r) petasma (male);

s) gonadapore (female).

The above structures should be drawn as one large side view (refer to Figures 2a-b). Students should also determine if specimen is male or female and draw relevant reproductive anatomy (note: a ventral view would be more appropriate for this drawing).

3) Identify and draw (for lab report) the following internal anatomical features:

a) ventral nerve cord;

b) branchial chamber;

c) primary/secondary gill filaments (remove a section of the gill, prepare as a wet mount and observe under low/medium power), Figures 2f-i);

Figure 2a. Simple External Anatomy of Penaeid Shrimp

Figure 2b. External Anatomy of Typical Decapod Crustacean

d) scaphognathite;

e) note various general regions of body: foregut, midgut, hindgut (foregut extends from mouth to hepatopancreas; midgut from posterior hepatopancreas to posterior midgut caecum; hindgut from posterior midgut caecum to anus);

f) mouth;

g) esophagus;

h) cardiac stomach (anterior foregut chamber);

i) pyloric stomach (posterior foregut chamber);

j) hepatopancreas (also referred to as midgut gland);

k) antennal gland (also referred to as green gland);

l) heart (just above the hepatopancreas);

m) ovary, oviduct, gonadapore (female);

n) testis, vas deferens, terminal ampoule (male);

o) brain;

p) lymphatic organ (small, hard to locate, anterior to hepatopancreas).

For the above, refer to Figures 2c-i. There should be one drawing made of a side view of a typical penaeid shrimp, showing the above internal organs. A ventral drawing of reproductive organ location should also be made.

Figure 2c. Simple External Anatomy of a Shrimp

Figure 2d. Internal Anatomy of Typical Decapod Crustacean

Figure 2e. Internal Anatomy of Litopenaeus vannamei Postlarva (University of

Arizona)

Figure 2f. Location of Gills, Penaeid Shrimp

Figure 2g. Normal Appearance of Lamellae

Figure 2h. Gill Fouling w/Filamentous Bacteria

and Diatoms

Figure 2i. Heavy Gill Fouling

4. Review Table 2a regarding functional anatomy of shrimp. Particularly make note of the function of the antennal gland complex, hepatopancreas and lymphoid organ.

Table 2a. Functional Anatomy of Shrimp

Organ/Structure	Principle Function
Abdominal striated muscle	Rapid backward movement, escape
Antennae	Tactile sense (predator detection)
Antennal gland complex	Excretion and osmotic balance
Antennules	Chemoreception
Anterior and posterior midgut cecae	Unknown (possibly water absorption)
Exoskeleton	External support, protective barrier
Foregut (mouth, esophagus, stomach)	Uptake, mastication, temporary storage
Gills	Respiration, excretion, osmoregulation, phagocytosis
Hepatopancreas	Digestion, nutrient absorption/storage
Lymphoid organ	Possibly antigen trapping, phagocytosis
Mandibles, mandibular palps, scaphognathite (gill baler)	Tactile sense, food particle pick-up, water movement over gills
Midgut	Absorption and excretion
Periopods and pleopods	Locomotion, chemoreception

REPORTING: Include 1) a description of the shrimp specimen you observed (source, body length, sex); 2) drawings of shrimp external anatomy, side view (with orientation, dimensioning, shading and labeling of anatomical structures); 3) drawings of shrimp internal anatomy, side view (with orientation, dimensioning, shading and labeling of anatomical structures/organs); and 4) drawings of gill structure.