Receptivity of Neohelice granulata (Brachyura: Varunidae): different strategies to maximize their reproductive success in contrasting habitats

SAL MOYANO M. P.; LUPPI T. A.; GAVIO M. A.; VALLINA M; MCLAY C

Atenas

Congreso; 10th Colloquium Crustacea Decapoda Mediterranea.; 2012

The Crustacean Society

RECEPTIVITY OF NEOHELICE GRANULATA (BRACHYURA: VARUNIDAE): DIFFERENT STRATEGIES TO MAXIMIZE THEIR REPRODUCTIVE SUCCESS IN CONTRASTING HABITATS Sal Moyano M.P.1, Luppi T.*1, Gavio A.1, Vallina M.1 and McLay C.2 1Instituto de Investigaciones Marinas y Costeras (IIMyC), CONICET. Universidad Nacional Mar del Plata, Funes 3350, Mar del Plata, Argentina. salmoyan@mdp.edu.ar 2School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand Introduction Mating systems depend on a set of ecological conditions characterized by limited abundance and distribution of resources and receptive females in space and time. Receptivity of female Neohelice granulata was studied including the form of the vulvae, different factors that influence the duration of receptivity, such as the presence of males, the size of females or the fullness of the seminal receptacle, by comparing two populations inhabiting contrasting habitats: Mar Chiquita Lagoon (MCL) and San Antonio Oeste (SAO). We also investigated the structure, histology and sperm storage in the seminal receptacle. Material and methods Sampling was carried out during the reproductive seasons of 2008-2011. The receptive period was monitored in laboratory by checking opercula mobility. The duration of female receptivity is defined as the time from the first day a female has mobile opercula up to the day it becomes immobile. Short-term studies were conducted: crabs were measured and placed in aquaria and subjected to two treatments: [1] four females, and [2] three females and one male. When a female became receptive, it was marked and examined daily until the opercula became immobile. Immediately after, females were killed, right and left seminal receptacles were dissected, weighed and processed according to standard histological techniques. For description of vulvae, receptive and unreceptive females were dissected and examined by scanning electron microscopy. Results Unreceptive females have immobile vulva opercula, while receptive females have a flexible hinge line. Duration of receptivity was dependent on the seminal receptacle load and the capacity to lay eggs, but independent of the presence of males or female size. Thus, females with empty seminal receptacles exhibited longer receptivity and did not lay eggs, while those with full seminal receptacles exhibited shorter receptivity and always laid eggs. Interpopulation differences showed that females from SAO had shorter receptivity, heavier seminal receptacles and were more likely to lay eggs than females from MCL. Histological sections of the seminal receptacles showed a multi-layered epithelium in unreceptive females and a two-layered one in receptive females that was probably involved in the maintenance of viable sperm. The existence of a special tissue at the junction of the oviduct and the seminal receptacle was found only in unreceptive females suggesting that it may be an internal mechanism influencing when females lay eggs. Discussion Neohelice granulata females appear to manipulate alternative mechanisms, including opercula mobility, the fullness of the seminal receptacle, changes in the thickness of the seminal receptacle epithelium and a special tissue at the junction of the oviduct and the seminal receptacle- to determine duration of receptivity and the timing of oviposition. An important consequence of this control is greater sperm competition.