I believe what you are seeing is the genital papilla, it's the female reproductive organ. The female keeps this tube retracted in their body while in adolescence; however, once the female reaches breeding age and is encourage by a suitable male they will often begin dropping their tube in preparation for breeding. Generally speaking you will often see them drag this appendage across breeding pots and other surfaces, it’s how they determine whether the surface is suitable for
Tutuapp 9Apps Showbox egg laying.