No Suitable Constructor Found For Thread

I have written a class that uses a thread and i am getting wierd error message saying no suitable constructor found for Thread(Tunnel) doesn not like this line, Thread lb = new Thread (tunnel);

import java.lang.*;
public class leftBound implements Runnable {
Tunnel tunnel;
public leftBound(Tunnel tunneler) {
tunnel = tunneler;
Thread lb = new Thread(tunnel);
lb.start();

[Code] .....

works fine if i do this though

import java.lang.*;
public class leftBound implements Runnable {
Tunnel tunnel;
public leftBound(Tunnel tunnel) {
this.tunnel = tunnel;
Thread lb = new Thread(this);
lb.start();

[Code] .....

But how do i get it to compile without using "this" method.