First zoeal stage of Macrocoeloma subparallelum ( Stimpson , 1860 ) ( Decapoda : Brachyura : Majoidea ) described from laboratory hatched material

Th e morphology of the fi rst zoeal stage of the decorator crab Macrocoeloma subparallelum (Stimpson, 1860) from Cuba is described and compared with the available descriptions for the genus. Among Macrocoeloma Miers, 1879 species, the fi rst zoea of M. subparallelum can be diff erentiated only by the number of aesthetascs and setae of the antennule (4 and 2, respectively). Recently, Macrocoeloma has been placed as an incertae sedis genus in Majoidea, closely allied to other Epialtidae and Pisinae members. Th e distinct spine in the distal segment of the endopod of the fi rst maxilliped in the zoeal stages of Macrocoeloma is similar to what we observe in other Epialtidae genera, a character that supports the recent phylogenetic fi ndings. keY words Cuba, Pisinae, Epialtidae, Mithracidae, larval development. orIgInal artIcle This article is part of the tribute offered by the Brazilian Crustacean Society in memoriam of Michael Türkay for his outstanding contribution to Carcinology CORRESPONDING AUTHOR William Santana william_santana@yahoo.com.br SUBMITTED 13 June 2016 ACCEPTED 25 July 2016 PUBLISHED 20 October 2016 Guest Editor Célio Magalhães DOI 10.1590/2358-2936e2016016


IntroductIon
Majoid crabs, commonly known as decorator or spider crabs, form one of the most diverse groups among brachyurans including nowadays six families with a total of 907 valid species (Davie et al., 2015).It is a superfamily that is distributed throughout nearly all oceans and is well represented, especially in warm regions, with about 239 species in the Americas, 124 species in the western Atlantic, and 115 species in the eastern Pacific (Griffin, 1966;Boschi, 2000).
Among majoids, the genus Macrocoeloma Miers, 1879 has been traditionally considered a member of the family Mithracidae; however, recent phylogenetic studies have suggested the exclusion of Macrocoeloma from this family, being now an incertae sedis group closely allied to other Epialtidae genera (Windsor and Felder, 2014).Currently, there are 14 described species of Macrocoeloma (see Ng et al., 2008), of which 10 are distributed in the western Atlantic from North Carolina to Brazil (Melo, 1996;Coelho et al., 2008).The larval development of only two Caribbean species belonging to this genus is known: that of Macrocoeloma camptocerum (Stimpson, 1871) and Macrocoeloma diplacanthum (Stimpson, 1860).Both have been partially described in the thesis of Yang (1967), and the latter has been re-described by Marques et al. (2003).
Macrocoeloma subparallelum (Stimpson, 1860) is a western Atlantic species found in the Gulf of Mexico, the Antilles, Venezuela, and in Brazil as far south as the Espírito Santo State, from shallow waters to 25 m deep (Rodriguez, 1980;Melo, 1996;Felder et al., 2009), and appears to prefer coral substrates (Rathbun, 1925).Despite being widely distributed, M. subparallelum is rarely collected, with only very few records in the literature (e.g.Rathbun, 1925;Rodriguez 1980;Scelzo and Varela, 1988).
We describe herein the first larval stage of M. subparallelum from Cuba and compare it with the available descriptions for the genus.

MaterIal and Methods
Two ovigerous females of M. subparallelum were collected in November 1994 in the beach of Jaimanitas, Havana, Cuba, between 1-2 meters of depth.The ovigerous females were held in an aquarium in a temperature-controlled room (24 ± 2°C) until hatching, which occurred at night.After hatching, the zoeas were fixed in 70% ethanol.Twenty specimens of the first zoeal stage were stained using methylene blue, acid fuchsin and/or chlorazol black, and then dissected in a light stereomicroscope Leica Wild M8 for morphological descriptions.For slide preparations polyvinyl lactophenol or Canada balsam were used as mounting mediums.The larval description follows the pattern used in previous works (e.g.Pohle and Marques, 2000;Santana et al., 2003;2004;Colavite et al., 2014) and the description of setae follows Pohle and Telford (1981), but here included only analysis by light microscopy (LM), using an Olympus CHA equipped with camera lucida.Some of the setae designated as plumose herein may be plumodenticulate due to the lower resolution limits of LM as compared to scanning electron microscopy (SEM).Description guidelines of Clark et al. (1998) were generally followed.A minimum of five zoeae were measured for carapace length (from the basis of the rostrum to the posterior margin of the carapace in lateral view) and total length (from the tip of the rostrum to the furcal shaft in lateral view).The adult females were measured for carapace width (CW) including branchiostegal spines.
Specimens of larval stages and the two spent female crabs (CW 24.1 mm and CW 23.95 mm) have been deposited at the GICUDONE -Grupo de Investigación in Carcinologia de la Universidad de Oriente, Escuela de Ciencias Aplicadas del Mar, Margarita Island, Venezuela (accession number # GIC-1001).
Mandible (Fig. 1D, E).Asymmetrical, with medial toothed molar processes uneven; enlarged lateral incisor processes; 2-3 marginal teeth between molar and incisor processes.Internal margin of incisor processes with a series of teeth, ending in a larger tooth in both mandibles.Palp absent.
Telson (Fig. 1K).Bifurcated, indistinct median notch, three pairs of plumodenticulate setae (Type 13-viii sensu Pohle and Telford, 1981) on inner margin; each furcal shaft proximally bearing a distinct lateral spine, furcal shafts covered with rows of spinules to just below the tips.

dIscussIon
Macrocoeloma subparallelum closely resembles congeners for which the first larval stage has been described.Macrocoeloma subparallelum, M. diplacanthum and M. camptocerum differ only in the number of aesthetascs and setae of the antennule; while the former has 4 aesthetascs and 2 setae, the latter two have 3 and 1, respectively.Another minor difference can be observed in the number of setae in the ventral margin of the carapace: M. subparallelum and M. diplacanthum have six to seven setae, while M. camptocerum has only six (Yang, 1967;Marques et al., 2003).
The larvae of the genus Macrocoeloma can be easily recognized through a combination of characteristics including the presence of a distended forehead with strong underlying muscle bands, a dorsal spine, and a distinct, strong spine in the distal segment of the endopod of the first maxilliped (Yang, 1967;Marques et al., 2003).All of these characteristics are present in M. subparallelum.As noted by Marques et al. (2003), this distinct spine can also be found in other Epialtidae species, such as Menaethius monoceros (Latreille, 1825), Pugettia Dana, 1851 and Huenia De Haan, 1837 (see Ko, 1998;Kornienko and Korn, 2004;Marques et al., 2003;Colavite et al., 2014).
Majoid crabs have a confusing taxonomic history due to several changes in the status of the families and subfamilies and the lack of substantial characters that support grouping of genera at higher taxonomic levels (Ng et al., 2008).A combination of adult, molecular, and larval characters could be the best way to find diagnostic characteristics for some groups.Despite the placement of Macrocoeloma as an incertae sedis group by Windsor and Felder (2014), this genus nested close to other Epialtidae and Pisinae members in their analyses.This is what we observe in the first zoeal stage of this genus, with the distinct spine in the distal segment of the endopod of the first maxilliped.This character is similar to what we see in other Epialtidae genera, which supports the recent phylogenetic studies (Windsor and Felder, 2014).However, Epialtidae is the most speciose family of Majoidea, with 452 recognized species (Davie et al., 2015), and shows a high degree of variability in several larval characters (see Clark and Cuesta, 2015).This could indicate that Epialtidae is not monophyletic in its present composition suggesting the taxonomic reevaluation and additional phylogenetic studies to better define Epialtidae in general and the position of Macrocoeloma in particular.acknowledgeMents