fish anatomy

[Gianluca Polgar]

Dear all,

I'm making some misurations on some gobiid (Perciformes: Gobiidae) 
specimens and I need some help about general ichthyological anatomy:

How should I count caudal fin procurrent rays (dorsal and ventral)?

I've found out that in some specimens a kind of "papilla" is visible 
immeadiatly posterior to the anus. In a specimen of about 15 cm it's almost 
triangular in shape and at 2.3 mm before attachment of anal fin. At M.O. it 
seems to be longitudinally sulcated and has got three smaller protuberances 
in an immediately anterior position: do you know what is it and what's its 
meaning? Does it relate with sexual dimorphism?

Please excuse my ignorance in fish anatomy, but It's not exactly my field.

Thank you for any kind of help.

Yours sincerely,

Gianluca Polgar

Gianluca Polgar
c/o prof L. Bullini
Università degli studi di Roma "La Sapienza"
Department of Genetics and Molecular Biology, "Charles Darwin"
Via dei Sardi, 70
00185
Roma, Italy