Are my Cleaner shrimp reproducing?

[fma]

I have a 600 litre tank. The only invertebrates I have are 8 turbosnails and a pair of cleaner shrimp. I also have live rock. The tank was set up in November 2006.
I did not get live sand.
I have recently noted u-shaped tunnels on the side of the tank with small critters inside. They have a transparent colour and mearsure about 3 mm in length. They have about 6-8 legs which wave back and forth rapidly. The U shaped tubes are about 2 cm in length. Sorry for the vague description. I was perhaps wondering if they were passengers from the live rock I purchased.

[Ninong]

Cleaner shrimp, assuming you have a species in the genus Lysmata, are hermaphroditic. Any two will form a mated pair. Their cycle is approximately two weeks long and they will alternate so that a new brood of babies is released approximately every week. The larvae do not survive in a typical home aquarium.

Joyce Wilkerson describes the reproduction cycle of Lysmata amboinensis in this 1994 article.

[fma]

Many thanks for that link Ninong. Very useful and informative