Sexual and reproductive traits of the pearl oyster shrimp Pontonia margarita (Decapoda: Palemonidae), symbiotically inhabiting the mantle cavity of the rugose pen shell Pinna rugosa (Bivalvia: Pinnidae)

Abstract

Symbiosis between decapods and mollusks provides a unique opportunity to examine some of the evolutionary strategies employed by marine invertebrates. We describe the sexual and reproductive traits of the pearl oyster shrimp, Pontoniamargarita Verril, 1869, found symbiotically inhabiting the mantle cavity of the rugose pen shell, Pinnarugosa Sowerby, 1835. Solitary males and females (ovigerous and non-ovigerous) and heterosexual pairs (with ovigerous and non-ovigerous females) were found in a total of 47 rugose pen shells collected from a sandy area with seagrass meadows on the southeastern coast of the Gulf of California, Mexico. The body length (BL) of female P.margarita was correlated with the shell volume of their rugose pen shell host. The sex ratio was female-biased (0.85M:1F). Female P.margarita were larger than their male counterparts in terms of BL, cephalothorax length (CL), and the maximum chelae length of the second pereopod (MCL). The CL and MCL were more strongly correlated for males (r = 0.70, p = 0.01). The number and volume of eggs per ovigerous female varied from 95 to 1,571 and from 5.46 ± 0.48 to 8.85 ± 0.97 mm3, respectively. Our results indicate polygamous behavior and social monogamy among P.margarita, and a short-term pairing system for their association with P.rugosa.

<i>Euceramus transversilineatus</i> (Decapoda: Porcellanidae) living in the mantle lobe of the snail <i>Melongena patula</i> (Gastropoda: Melongenidae) in the south eastern Gulf of California: Inference of a biological association

“…Thus, their symbiotic association could be considered a short-term commensal relationship benefitting the guest E. transversilineatus, specifically, ensuring the survival and reproduction of the porcellanid crab in the shelter provided by the morphology of the snail. Similar observations were noted by Baeza et al (2013) and García-Ulloa et al (2019) for pontonid shrimps reproducing inside mollusks.…”

“…Among crustaceans, females of greater body length have a larger abdomen to contain more eggs (Salas-Moya et al 2014); however, in our study no significant correlation was observed between female body dimensions and number of eggs. This pattern has been reported by García-Ulloa et al (2019) for females of the pearl oyster shrimp Pontonia margarita in symbiosis with the rugose pen shell Pinna rugosa.…”

“…Its pearly white color would represent a disadvantage since it contrasts sharply against the dark muddy bottom (Carbajal Enzian et al 2018), which highlights the importance of a protective service acquired when this porcelain crab is living associated with M. patula. Corey & Reid (1991), Góngora-Gómez et al (2015) and García-Ulloa et al (2019) correlated the volume of bivalve shells with morphometric measurements of endosymbiotic crustaceans in terms of the space available for their accommodation. However, in the present study, no correlation was found between snail and crab measurements by crab pool and sex.…”