Sampling of M. rhizophorae

The semi-terrestrial shrimp M. rhizophorae was originally described in the state of Alagoas, Brazil (Rathbun 1900). Since then, other studies have shown that M. rhizophorae is widely distributed in tropical Western Atlantic, Panama, Suriname, and Brazil (Figure 1 (a)) (Chace 1972; Almeida et al. 2006). In this study, shrimps were collected in the estuary region of the Vaza-Barris River (11°05 ʹ 47”S – 37°09 ʹ 30”W), Sergipe state, northeast Brazil (Figure 1 (a–e)). In this region of Brazil, mangrove forests are commonly observed in the estuarine regions, composed mainly of Rhizophora mangle L., Laguncularia racemosa (L.) C.F. Gaertn, Avicennia schaueriana Stapf & Leechman ex Moldenke and Avicennia germinans (L.) Stearn (Santos et al. 2012).

During a sampling of Upogebia omissa Gomes Corrêa, 1968 carried out previously (see Santos et al. 2018), specimens of M. rhizophorae were observed cohabiting burrows constructed by mud shrimps. Thus, the sampling sites in the present study were selected based on occurrence of U. omissa burrows along the fringe of the mangrove forest (Figure 1 (b–e)). During daytime samplings at low tide, in places where a dense concentration of burrows was observed (Figure 1 (c–e)), the sediment around burrows was manually excavated (or using a spatula) (Figure D) and M. rhizophorae (Figure 1 (f)) specimens were captured. All shrimps were captured in burrows inhabited by mud shrimps U. omissa. However, considering the large number of burrows in the substratum and their structural complexity (commonly ‘Y-shaped’ and possible connections with neighbouring burrows, see Coelho et al. 2000), it was not possible to verify (1) whether all burrows were inhabited by individuals of both species (M. rhizophorae and U. omissa), (2) the number of shrimps of each species per burrow, (3) if there were burrows of other crustaceans that were also occupied by M. rhizophorae individuals.

Shrimps were captured in two collections in September 2018, totalling five sampling hours. For each collection, a transect of approximately 20 m was outlined parallel to the mangrove forest fringe. All mud shrimps burrows were checked and the individuals of M. rhizophorae found in this transect were placed into individual plastic bags filled with seawater and transported to the laboratory. The specimens were preserved in 70% alcohol and kept for further analysis.