Anomura & Brachyura


Project: Mating systems and reproductive behaviour of marine crabs (Decapoda: Anomura & Brachyura)

Project title

Mating systems and reproductive behaviour of marine crabs (Decapoda: Anomura & Brachyura)

Mentor name

Alexandra Hiller, STRI research associate
Sabrina Amador, STRI staff scientist
Harilaos Lessios, STRI staff scientist



Field work is mainly conducted in the Pacific localities near Panama City (Punta Culebra, Veracruz and Isla Taboguilla) and Chiriquí (Boca Chica and Boca Brava), and the Caribbean localities of Galeta and Bocas del Toro. Sampling in some of the Pacific localities is limited to extreme negative tides.

Project summary and objectives

The evolution of mating systems in sexually reproducing animals is a consequence of natural selection acting on mate choice and on the optimization of individual reproductive success. Ecological traits, like type of habitat, also play an important role in the evolution of mating systems, as they may contribute to behavioural and morphological differences between males and females. Mating in animals is classified in two main general systems, both supported by controversial arguments on how they evolved: monogamous and polygamous. Why would it be advantageous for males or females to mate with one vs. several partners? Does the ecology of a species play a crucial role in locating sexual partners? Do free-living vs. commensal species (i.e., associated to other invertebrates) have different mating systems?

When crabs mate, males transfer spermatophores to females. These structures are capsules full of sperm, which females use to fertilize their eggs. Even if the reproductive behavior of a species suggests a polygamous mating system, the fate of sperm after copulation remains unknown to the naked eye.

In decapod crustaceans (shrimps, lobsters and crabs) there is evidence of offspring having a single sire (all eggs are fertilized by one male) or of a single clutch of eggs being fertilized by the sperm of multiple males. It is still poorly understood if all stored sperm is used to fertilize eggs, if the sperm of the fittest male fertilizes all eggs via sperm stratification, if sperm of the least fit is actively removed, or if sperm competition is involved.

Studying the evolution of different mating systems in marine crabs is a complex and often difficult task for two reasons: i) it involves understanding the ecology and population genetics of a species, and documenting the innate and learned reproductive behaviors of both males and females, and ii) it demands making long-term observations under water, which can be challenging, especially in the case of species inhabiting substrates exposed to heavy waves and currents.

We use ecological, behavioral, and genetic approaches to study the mating system of marine crabs. We make direct observations of the reproductive behavior of crabs by filming them in aquaria specifically designed for this task. We determine the successful fertilization of eggs by one or by several males by genotyping ovigerous females and their offspring (fertilized eggs or larvae reared in the lab).

Mentorship goals

We welcome motivated students to participate in fieldwork, laboratory, and computer work. Interns will learn fieldwork methods to document, collect and transport marine invertebrates, to maintain them in aquaria, and to document and analyze behavioral data. Interns will also assist in molecular work and analyses involved in genotyping. Students will be given scientific articles to discuss with their mentors and will have the opportunity to meet other students and researchers of the scientific community at STRI working on diverse research topics.

Desired Background

Students will work in demanding conditions because collecting crabs in the rocky intertidal during spring tides in the Pacific implies walking on slippery rocks. Snorkeling to collect some species may require swimming in areas with rocky bottoms where waves and currents may be strong. Maintenance of aquaria demands frequent cleaning of high loads of sediments. Mosquitoes and extremely hot and humid weather just add some fun to the lab work. Manipulating crabs requires patience and passion to learn their biology. Several hours a day of computer work is required to inspect videos and to code and interpret behavioral data. Interest in evolutionary biology, passion to work in the field under physically demanding conditions, experience in molecular work and basic understanding of genetics is desirable.

List of suggested readings

Christy JH (1987) Competitive mating, mate choice and mating associations of brachyuran crabs. Bulletin of Marine Science 41: 177-191.

Baggio RA, Pil MW, Boeger WA, Patella LA, Ostrensky A, Pie MR (2011) Genetic evidence for multiple paternity in the mangrove land crab Ucides cordatus (Decapoda: Ocypodidae). Marine Biology Research 7: 520-524.

Bailie DA, Hynes R, Prodöhl PA (2011) Genetic parentage in the squat lobsters Munida rugosa and M. sarsi (Crustacea, Anomura, Galatheidae). Marine Ecology Progress Series 421: 173-182.

Ellis CD, Hodgson DJ, André C, Sørdalen TK, Knutsen H, Griffiths AGF (2015) Genotype reconstruction of paternity in European lobsters (Hommarus gammarus). PLoS ONE 10: e0139585.

Hiller A, Viviani CA, Werding B (2010) Hypercarcinisation: an evolutionary novelty in the commensal porcellanid Allopetrolisthes spinifrons (Crustacea: Decapoda: Porcellanidae). Nauplius 18 (1): 95-102.

Hiller A, Lessios H (2017) Phylogeography of Petrolisthes armatus, an invasive species with low dispersal ability. Nature Scientific Reports 7: 3359.

Molenock J (1975) Evolutionary aspects of communication in the courtship behavior of four species of Anomuran Crabs (Petrolisthes). Behaviour 53: 1-30.

Toonen RT (2004) Genetic evidence of multiple paternity of broods in the intertidal crab Petrolisthes cinctipes. Marine Ecology Progress Series 270: 259-263.

Yocachonis T, McKeon CS, Windsor A, Stillman JH (2020) Multiple paternity in the intertidal zone porcelain crab Petrolisthes cinctipes Randall, 1840 (Decapoda: Anomura: Porcellanidae) is a life-history strategy that increases fitness during heat stress. Journal of Crustacean Biology 40: 684-691.

Werding B, Christensen B, Hiller A (2016) Three way symbiosis between a goby, a shrimp and a crab. Marine Biodiversity 46: 897-900.

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