Reproductive condition of males and sperm storage in females spider crab Libinia spinosa (Majidae) in the Mar del Plata coast, Argentina.

M. P. SAL MOYANO; M. A. GAVIO

La Serena, Coquimbo

Congreso; The Crustacean Society Mid-year Meeting; 2007

Spider crabs exhibit morphological changes when attain sexual maturity. The chela of males enlarges while the abdomen of females becomes broadly oval. Libinia spinosa is found in the Mar del Plata coast (38°S), and earlier studies showed the presence of immature, adolescent and adult males in this population. Here, we present new findings on reproductive characteristics based on the condition of males’ vas deferens, presence of spermatophores and gonopod morphology while in females, they are based on the development of the ovary, the spermatheca content and morphology of gonopores. In this study we gathered information on morphometric and gonad maturity, gonopore condition and developed a staging scale for the spider crab Libinia spinosa. Samples were collected seasonally close to the fishing port at 3m depth. They included summer and fall 2004, spring 2006 and late summer-early fall 2007. We analyzed a total of 308 males and 172 females. Specimens were dissected to: (1) examine of the gonads, (2) check the presence of spermatophores by examining a squash of the vasa deferentia of males and of the spermatheca of females under a microscope, (3) assess the morphology of gonopods and gonopores using SEM. In males, four stages of development were observed: Stage 1: Not clearly differentiated. VD translucent, thin tubes, Stage 2: Differentiated. VD translucent to opaque. No spermatophores present, Stage 3: Clearly differentiated. VD white. Shape varies from a straight tube to a strongly coiled mass. Scarce spermatophores present, Stage 4: Clearly differentiated. VD white. Abundant spermatophores are present. In females, four stages of ovary development were characterized: Stage 1: Immature. Not clearly differentiated, Stage 2: Immature. Ovary white-translucent with filamentous aspect, Stage 3: Developing? Clearly differentiated, white, Stage 4: Mature. Clearly differentiated, orange. The first gonopod has an elongated endopodite, with the cuticula infolded ventrolaterally forming a tube that functions as an ejaculatory canal. The apical tip has two winglike processes with different setae types and tegumental gland pores. Gonopores were located on the sixth thoracic sternite communicates with the vagina. The form is biconcave, in immature females it bears an “operculum” while in mature ones it is absent. Conclusions: maturity of male Libinia spinosa is reached through 3 allometric steps, in coincidence with differentiation of primary sexual characters (vasa deferentia), and secondary sexual characters (chela morphometry) and gonopod development. At least four conditions are required for the females to reach sexual maturity: ovary maturation, pleon detachment, operculum loss and allometric growth of the abdomen.