Name:__________________

Fish 310 Spring 2015

#Shellfish Parasites & Pathogens

In today’s lab we will be looking at numerous shellfish species, some of which are host organisms for a particular parasite and some of which the parasite. A parasite is defined as any organism that is metabolically dependent on its host; relying on the host for energy and nutrition.

There are two types of parasites we will see today; those that live on the outer surface of the host (ectoparasite) and those that live within the tissues or bloodstream of the host (endoparasite). A tick would be considered a typical ectoparasite, while a tapeworm is an endoparasite.

While parasites negatively impact the host, the presence of a parasite does not always mean the presence of a disease. Below are some definitions you should become familiar with when talking about both parasites and diseases:

- Disease: an alteration from the normal state
- Parasite: an organism that is metabolically dependent on its host (gets its energy or food from its host) 
- Infectious: transmissible (e.g. virus, bacteria, protozoa, metazoa)
- Pathogen: an organism that is able to cause disease. Parasites, under certain conditions, may cause disease.
- Virulence: characteristics of the pathogen that allow it to infect, multiply and spread in or among hosts
- Pathogenicity: the ability to cause disease within a host 

 
##Ectoparasites

###Observe the preserved whale barnacle. Though not truly parasitic, they are detrimental to their host. For the barnacle, what is one advantage of this type of lifestyle? One disadvantage? (think of what gray whales do) Why is this species of barnacle not truly parasitic?
 

 

 

 

 

###Examine the preserved Rhizocephalan barnacle that has parasitized the body of a shrimp. What effect does this barnacle have on its host?
 

 

 

 

 
  
###Examine a preserved shrimp that is carrying a bopyrid isopod (Hemiarthrus abdominalis) parasite on its abdomen. What is the advantage for the parasite to be located on this part of the shrimp? 
 

 

 

 

 

###Observe the parasitic bopyrid isopod (Bopyroides hippolytes) located in the branchial chamber of the preserved shrimp. How do you think this relationship impacts the shrimp?
 

 

 

 

 

###Examine and compare a free living isopod and a parasitic isopod. How has the isopod adapted to life as a parasite (how are they different)?
 

 

 

 

 

###Now observe a parasitic branchiuran (fish louse). What morphological features make it well adapted as an ectoparasite on fish.
 

 

 

 

 

##Endoparasites

Because endoparasites live within the tissues or bloodstream of their hosts, the traditional method for detecting them is histology. Histology is the process by which tissue samples are fixed, sectioned, and stained for microscopic evaluation. Today we will be looking at a number of bacterial and protozoan parasites that have had huge impacts on the ecology and economic importance of valuable shellfish species.  

###Look at the healthy vs parasitized abalone tissue sections. What is the name of this endoparasite and what disease does it cause? From what you learned about this parasite, what type of tissue do you think you are looking at?
 

 

 

 

 

###Use a counter to score the level of infection of the abalone tissue provided using the semi-quantitative, log infection scale of Friedman et al. (1997). 0= uninfected, 1=1-10 inclusions per 20x field of view, 2=11-100 inclusions, and 3=>100 inclusions.
 

 

 

 

 

###We discussed two endoparasitic diseases; dermo in oysters and white spot syndrome in penaeid shrimp. Which of these diseases has a viral causative agent? How are Perkinsus marinus inclusions different from WSSV inclusions?
 

 

 

 

 

###While histology is considered the “gold standard” in pathogen detection it is very expensive, time consuming, and takes a well trained eye (as I’m sure you will agree). What is another method you could use to detect pathogens? How would you go about doing this?
 

 

 

 

 

###If you could be any parasite we saw today in lab, which would you be and why?
 

 

 

 

 


For more fun with parasites check out FISH404 Diseases of Aquatic Organisms