Fig. 1

Morphoanatomical and histological sections of gonads from male, female and intersex red claw caryfish. a is a schematic representation of the reproductive system of male, female and intersex red claw crayfish; b-g are paraffin sections of gonads stained with HE. b is the testis from an adult male, which contains primary spermatocytes (PSC), secondary spermatocytes (SSC), spermatocytes (SC) and sperm (S); c is the ovary from an adult female, which has a dense arrangement with early vitellogenic oocytes (EVO). d is the sperm efferent duct of an adult male, and the spermatophore is full of sperm. e is testis from an adult intersex, and no sperm was observed. f shows ovaries from intersex adults; only primary oocytes (PO) were observed, and the oocyte perivascular space (OPS) was large and rich in follicular cells (FC) and was attached to the testis. g is the sperm efferent duct, which extends into the ovaries of intersex adults, and only empty spermatophores (ESP) were observed. SPW is the spermatophore wall, EI is the epithelial layer