The Perch: Inside and Out

A guided dissection and discussion of a perch.

Oren Pazgal

4/9/14

Vu-PAP Bio-1

Objectives

  • Students will be learning about the external and internal anatomy of a perch.
  • Students will focus on the organs, structures, and functions of the circulatory system.
  • Students will also understand the ecological role of the perch.

The genus Perca

Perches are a type of bony fish, which means that they have a rigid endoskeleton as well as scales covering their entire bodies. There are different species of perch in different parts of the world, but they all possess some common characteristics, as befits organisms in the same genus. A typical perch has a lifespan of 15-25 years, and a perch reaches sexual maturity at approximately 2-4 years of age. Perch only reproduce once a year in spring or early summer, but when they do reproduce all of the females release their eggs which settle to the bottom of whatever body of water they are inhabiting. Then the males release their sperm all at once, so that eggs can be fertilized by random males and achieve greater genetic diversity, which encourages natural selection. The eggs hatch around three weeks after fertilization, at which point they are known as prolarvae. The prolarvae mature and grow to adulthood, and so the cycle continues.

Ecology and Evolution

Since perches have such a varied diet from the prolarvae stage to adulthood, they function as both primary, secondary, and occasionally even tertiary consumers in their ecosystems. To help perch accomplish the task of consuming its food sourcesthey have evolved specialized teeth called palatines to eat smaller fish more easily. Not only that, but the perch has evolved gill rakers in the gills, which serve to filter out zoo-plankton from the gills and send them straight down the esophagus.
Below is a cladogram of the cursory evolutionary relationships of the genus Perca and other ray-finned fishes:
Big image

Dissection

Highlight: The Circulatory System

Although the circulatory system cannot easily be seen in the above pictures, it performs some absolutely vital tasks for perches' (and many other organisms') survival. The circulatory system is responsible for pumping blood throughout the body and carrying oxygen and other necessities to the body's cells. A perch's circulatory system consists of a single ventricle and atrium (the heart), an aorta, and all of the blood vessels in the body. In a perch, the circulatory system consists of only a single loop. The ventricle pumps out blood which then travels through the arteries to the gills, where the blood is oxygenated. The blood then moves through the long aorta and then through the capillaries that run throughout the body, supplying oxygen to all of the cells. The newly deoxygenated blood returns to the heart through the veins and enters the atrium before it is sent out on the loop again.

Works Cited