NEW: Cane toads come to Dissection Connection

Introduction

To help satisfy the demand for whole animal specimens we’ve decided to stock cane toads. Mr Vivi has been collecting and packaging toads all summer and we now have a freezer full of the hoppers. They are packaged individually and identified by sex. So, consult the current price list and choose whether you want boys or girls. Available until they run out and collection starts again in spring.

male and female dorsal — Cane toads. Female on the left, male on the right. Notice the distinctive markings which can be partially used to sex a toad.

Dissection

A cane toad dissection allows the biology teacher to cover many aspects of body systems including, skeleton, musculature, heart and arterial, venous, digestive and respiratory, urogenital and nervous systems in a series of practicals using the same specimen. Dissection Connection stocks cane toads with a snout vent length (SVL) of over 80mm that have been sexed and packaged as individual male and female specimens. In stock soon, ‘The Zoology Coloring Book’ by Lawrence M. Elson to compliment your class.

You can also find dissection resources online:

http://www.biologycorner.com/bio2/notes-frog.html, and

http://www.rcs.rome.ga.us/hargett/biology/amphib/frogdis.htm

Euthanasia

Many methods have been suggested. Step-wise cooling and freezing was for some time the recommended method but recent work has found this method can cause distress and pain to the animal evidenced by behavioural responses to this and other methods. One of the mechanisms that cause pain in this method includes freezing in the blood, producing ice crystals that are transported around the vascular system and cause pain.

A joint project between The Australian Government, The New South Wales Government and The University of Wollongong (CAN001 Methods for the field euthanasia of cane toads, T. Sharp, A. Lothian, A. Munn and G. Saunders: 2011) found the preferred methods were:

stunning followed by decapitation
gassing with carbon dioxide (CO₂) for >4 hours

Due to the numbers handled and the requirement for an intact specimen for dissection, Dissection Connection has opted for method 2, gassing with CO₂.

This CO₂ euthanasia SOP is that recommended on the Queensland DETE animal ethics website and by Biosecurity QLD. We follow the procedures in the original scientific paper which outlines a number of extra steps that DETE don’t mention.

Specimen preparation

After successful euthanasia, toads are measured. Only those with minimum snout-vent-length (SVL) of 80mm are kept. Toads are sexed as per Narayan, Christi, Morely and Trevenen (2008) based on external morphological features and presence/absence of vocal sac openings in the mouth.

Toads are then set in trays, frozen overnight and vacuum packed.

Workplace health and safety

Use nitrile or chemical gloves to handle, NOT vinyl gloves for handling toads. I used vinyl gloves for about half an hour handling dead toads, my fingers were tingling for about an hour afterwards.

Nitrile gloves should be used when handling dead toads and conducting dissections as toxins may be present on the skin of the toad.

Have fun with this, it’s a great dissection!

References

Narayan, E., Christi, K., Morely, C., and Trevenen, P. (2008). Sexual dimorphism in the cane toad Bufo marinus: a quantitative comparison of visual inspection methods for sexing individuals. Herpetological Journal 18: 63-65.

Sharp, T., Lothian, A., Munn, A. and Saunders, G. (2011). CAN001 Methods for the field euthanasia of cane toads