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Author: Roxanna Smolowitz, D.V.M.
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OCW Zoological Medicine 2008
Exotic Companion Animal Practice (2009)
R. Smolowitz, PhD
Cummings School of Veterinary Medicine at Tufts University

1. Session Objectives and Goals

This session will highlight significant anatomical and physiological characteristics of some selected invertebrate species that may be seen by veterinarians with an exotic practice, as laboratory animal veterinarian or as veterinarian working with the commercial fishing and aquaculture industries. It will provide information concerning the environment potentiation of diseases commonly identified in invertebrates.

1.1. Learning Objectives

You will be expected to be familiar with the following:

  • Gain an appreciation for the key organ systems of:

    • Sepia officinalis (European Cuttlefish)

    • Asterias forbesi (Common Sea Star)

    • Homarus americanus (American Lobster)

  • Know the main physiological differences between three different groups of invertebrates

  • Gain a basic understanding of the importance of environment on disease in the invertebrates examined

  • Be able to develop a basic clinical approach for a diseased invertebrates presented for examination

2. European Cuttlefish

Link to basic information on Animal Diversity Web

2.1. Anatomy

  • Phylum-Mollusca, Class Cephalopod

    • Subclass COLLEOIDEA – Contain an inner shell or now shell

    • Cuttlefish – contain cuttle bones

  • Flexible muscular arms with suckers or hooks

    • Sepia and squid—eight arms and two tentacles

  • Specilized arms/tentacles - Hectcocotyli – Place sperm packets in the female mantle cavity

  • Specialized Skin

    • Chromatophores

    • Iridophores

  • Open Circulatory System

    • Three hearts (Cardiac and Branchial), Arteries, arterioles, sinuses

    • One cell type (hemocyte

    • Blood = Hemolymph

    • White body

2.2. Physiology

  • Exclusively Marine

  • SWIM BY JET PROPULSION-direction controlled by orientation of the muscular funnel

  • Poor Osmoregulatory Ability

2.3. Common diseases/conditions

  • BACTEREMIA-- Vibrio alginolyticus

  • Traumatic Lesions

3. Common Sea Star

Link to basic information on Animal Diversity Web

3.1. Anatomy

  • PHYLUM Echinodermata

    • Class ASTEROIDA-SEA STARS --Asterias forbesi

  • Pemtamerous Radial Symmetry

    • Central disk

    • Five arms

  • Surface Projections

    • Spines

    • Pedicellaria

    • Papula

  • “skin”

    • Columnar epithelium

    • Calcareous plates

    • Cuticle

  • Digestive System (carnivores)

  • Reproductive System (bilobed radial symmetry)

3.2. Physiology

  • Regeneration

  • Water Vascular System

    • Madeporite with pores

    • Stone canal

    • Circumoral water canal

    • Radial canal

    • Lateral canal

    • Ampulla

    • Tube feet

3.3. Common Diseases

  • Ulcerative dermatitis

4. American Lobster

Homarus Americanus link to basic information on Animal Diversity Web

4.1. Anatomy

  • Decopod Crustacean

  • External Skeleton – Cuticle

  • Digestive System

  • Reproductive System

  • Circulatory System

    • Structures: heart, Arteries, arterioles, sinuses, pericardial sac.

    • Cells: 3 types (granular, semigranular and agranular)

4.2. Physiology

  • Molting

  • Reproduction

  • Regeneration

4.3. Common Diseases

  • Shell disease

  • Bumper car disease (Mugardia sp.)

5. Invertebrate Medicine

5.1. “Hands-Off” Procedures

Just as body temperature, heart and respiratory rates are some of the most important data collected during the clinical exam in mammals, establishing water chemistry values and making simple observations of the invertebrate in the water are of paramount importance when assessing the patient. Observations from the tank side or from actually visiting the aquaculture site will frequently reveal important information that will help to understand the disease.

5.2. “Hands-On” Procedures

5.2.1. Scrapes of surface lesions

5.2.2. Phlebotomy

We still lack significant data regarding the blood values and hemodynamics in most invertebrates but examination of hemolymph can provide important data concerning the animal. Many parasites and bacteria proliferate in the hemolymph making examination of hemolymph an important diagnostic procedure.

6. Environmental Evaluations

6.1. Water Quality

Maintaining good water quality is the key to success in invertebrate health. Basic water quality parameters that need to be monitored include: temperature, dissolved oxygen, ammonia, nitrite, nitrate, pH, and water hardness. Other parameters such as levels of iron and other metals, and salinity are also important. While interactions and changes within the system, from small tanks to large estuary systems, are complex and very dynamic, the fundamentals of the water chemistry need to be understood in order to help resolve disease and to prevent or manage future disease occurrence. The ammonia cycle is the most important environmental component in enclosed aquatic system and will be discussed in detail.

7. Disease Etiology

Agents causing diseases in invertebrates are most often opportunistic and thus are multi-factorial in character, Therefore, identification of both the causative agents as well as any predisposing conditions are both important in disease control and long-term prevention. It is extremely important to consider the physio-chemical properties of the water since this is the primary environment of the invertebrates. Water transports many pathogens more efficiently than air, and water will also keep pathogens alive better than air (drying is one form of sterilization). Therefore consider that invertebrates are constantly immersed in a bacterial soup.

8. Stress

Stress is the sum of the biological reactions to any adverse stimulus, physical, internal or external, that disturbs the homeostasis of an organism. Should these stress reactions be inappropriate, they may lead to disease states. Examples of stressors are improper housing (lighting, humidity, temperature, water quality, improper hiding places), improper social structure, improper food, inadequate cleaning, etc. In order to avoid stress due to these factors it is of paramount importance to know your animals' natural history. Typical reactions to stress in fish are seen as decreased reproduction, decreased feeding, decreased immune function leading to disease and eventually death.

9. Common Problems

9.1. Husbandry

  • Providing an inappropriate environment.

  • Failure to establish the nitrogen cycle in the tank “new tank syndrome”.

  • Overstocking, leading to traumatic injury, territorialism, and cannibalism and oxygen shortage.

  • Overfeeding leading to ammonia overload in the tank.

  • Failure to properly quarantine new additions.

  • Failure to remove dead animals or decaying food and plants.

  • Failure to check the water chemistry on a regular basis (dynamic system).

  • Inadequate nutrition (underfeeding or inappropriate diet).

  • Misinterpreting reproductive or other normal behavior as aberrant.

10. Tarantula Medicine

Tarantulas are very unusual and not so popular pets, but people are fascinated by these strange and sometimes scary animals. Lately tarantulas are becoming more popular as pets and the demand for exotic veterinarians willing to treat these pets has also increased.

There are more than 34,000 species of spiders and some of these species may have a medical interest (research, potential human health hazard). Only a few species can be found on the market as pets.

This subject will not be covered in 2009, but please see Dr. Raffaele Melidone's journal article: Melidone R. Tarantula Medicine. UK Vet Vol 12 No 3 April 2007.

11. References and Resources

Supplemental Readings

11.1. Professional Organizations

International Association for Aquatic Animal Medicine ( )

World Aquatic Veterinary Medical Association ( ).

National Shellfish Association ( )

American Tarantula Society You can purchase their book, ATS Arthropod Medical Manual: Diagnosis & Treatment, at this site.

11.2. Websites

Aquaculture Dictionary - Aquatext

Saltwater Aquariums...

Synopsis of Infectious diseases and parasites of commercially exploited shellfish.

11.3. Water test kits

Gilford Instrument Labs, Inc.Ovelin, OH 44074 ; 216-774-1041 .

Hach Company P.O. Box 389, Loveland, CO 80539 ; 800-227-4224

La Motte Chemicals. P.O. Box 329, Chestertown, MD 21260 ; 301-778-3100

11.4. Texts and Articles

GOOD invertebrate anatomy text!

Carpenter, James W., Exotic Animal Formulary, 3rd Edition, W B Saunders Co. c2005.

Foelix, R. F., Biology of spiders (second edition), Oxford Thieme, New York, 1996.

Frye, Fredric L. Captive Invertebrates. Krieger Publishing Co., Malabar, FL, 1992.

Howard, D.W., E.J. Lewis, B.J. Keller and C.S. Smith. 2004. Histological Techniques for Maine Bivalve Mollusks and Crustaceans. NOAA Technicial Memorandum NOS NCCOS 5.

Journal of Invertebrate Pathology

Johnson-Delaney, C.A., Companion Medicine Handbook, Zoological education network, Lake Worth, 2000.

Kennedy, V.S., R.I.E. Newell, A.F. Eble. The Eastern Oyster Crassostrea virginica. 1996. Maryland Sea Grant College, College Park, Maryland.

Kinne. Editor. Diseases of Marine Animals. Volumes I to IV. 1990. Biologische Anstalt Helgoland, Hamburg, Germany.

Lewbart, Gergory A. Invertebrate Medicine. Blackwell Publishing, Ames, Iowa, c2006.

Melidone, R., Mayer, J., How to Build an Invertebrate Surgery Chamber, Exotic DVM, 7 (5), November 2005.

Pearse, V., J. Pearse, M. Buchsbaum and R. Buchsbaum. 1987. Living Invertebrates. Boxwood Press, Pacific Grove, CA

Ross, L.G. and B. Ross. Anesthetic and Sedative Techniques for Aquatic Animals. 1999. Blackwell Publishing, Oxford, UK.

Schultz, Stanley A. and Marguerite J., The Tarantula Keeper's Guide. Barrons Educational Series; 2nd edition, 1998.

Spider information

Verdez, J. M., Cleton, F. Mygales, Bornemann, Paris, 2001.

Veterinary Invertebrate Society Newsletter

Veterinary Clinics of North America. Exotic Animal Practice. Philadelphia, PA : W.B. Saunders Co., 1998- . Chapters on invertebrates in every volume.