Abergasilus facts for kids

Abergasilus amplexus is a tiny creature. It's a type of copepod, which is a small crustacean. This special copepod lives as a parasite. This means it lives on or in another animal, called a host, and gets its food from it. Abergasilus amplexus is found only in New Zealand. It lives in waters that are a mix of fresh and salt, called euryhaline habitats. It is the only known species in its group, called Abergasilus.

What is Abergasilus amplexus Like?

This tiny animal is very special. Most copepods have more legs. But Abergasilus amplexus has only three pairs of legs. Its fourth and fifth pairs of legs are either very small spines or are completely missing.

It also has very unique antennae. These are like feelers. The antennae on Abergasilus amplexus have hooks. These hooks make them look like tiny claws. This claw-like shape is even clearer on the female copepod.

The male Abergasilus amplexus lives freely in the water. It is part of the plankton, which are tiny organisms that float in the water. Both the male and female are very small. They are usually about 0.5 millimeters long. That's half a millimeter, smaller than the tip of a pencil!

Who Does Abergasilus amplexus Live On?

Abergasilus amplexus is a parasite, so it needs a host to live on. Its main host is the Short-finned eel (Anguilla australis). In a place called Lake Ellesmere / Te Waihora in New Zealand, almost all of these eels have this parasite. Sometimes, a single eel can have over 100 of these tiny parasites living on its gills!

This copepod can also live on other types of fish. Here are some of the other fish species it has been found on:

• New Zealand longfin eel (Anguilla dieffenbachii)
• Arripis trutta
• Goldfish (Carassius auratus)
• Common galaxias (Galaxias maculatus)
• European perch (Perca fluviatilis)
• Pseudophycis bachus
• New Zealand smelt (Retropinna retropinna)
• Yellowbelly flounder (Rhombosolea leporina)
• New Zealand sand flounder (Rhombosolea plebeia)
• Rhombosolea retiaria