First zoeal stage of the crab Domecia acanthophora ( Desbonne , in Desbonne & Schramm , 1867 ) ( Decapoda , Brachyura ) and revision of the larval morphology of superfamily Trapezioidea

Th e morphology of the fi rst zoeal stage of Domecia acanthophora (Desbonne, in Desbonne & Schramm, 1867) was described from laboratory-hatched material obtained from ovigerous females collected at Vitória Island on the southeastern Brazilian coast. We compared the larval morphology orIgInal artIcle This article is part of the special series offered by the Brazilian Crustacean Society in honor to Nilton José Hebling in recognition of his dedication and contributions to the development of carcinology in Brazil.

In recent decades, several studies about the morphology of larval stages have been used to elucidate the taxonomic status of these crabs, of which there is still no consensus with respect to the superfamily Trapezioidea (e.g., Clark and Guerao, 2008;Clark and Ng, 2010).About 60 species of the superfamily Trapezioidea are known (see Ng et al., 2008), but the morphology of the first zoeal stage is described only for 14 species (see Tab. 1).
Considering the morphology of the first larval stage is unknown for most species of the superfamily Trapezioidea, new descriptions could contribute with knowledge of the relationship within this taxon.Thus, we provided here a detailed description of the first zoea of the crab D. acanthophora, hatched in the laboratory.Additionally, we reviewed and compared the larval morphology (zoea I) of Trapezioidea species (sensu Ng et al., 2008) in a comparative table, in order to facilitate the identification of these larvae.

MaterIal and Methods
Two ovigerous females of D. acanthophora were collected in September 2006 by scuba divers at Vitória Island (23°44'04"S 45°01'35"W) in the southeastern of the São Paulo State, Brazil.The crabs were kept isolated in aquaria filled with seawater from the collecting site, at constant temperature (24 ± 1°C), salinity (35 ± 1) and moderate aeration, until the larvae hatched.Newly hatched zoeae were preserved in a 1:1 mixture of 70% ethyl alcohol and glycerin.For detailed examination, the larvae and appendages were dissected under a Zeiss Stemi 200C trinocular stereomicroscope and prepared on semi-permanent slides with glycerin.
Drawings and measurements were done using a Leica DM750 microscope equipped with camera lucida.The illustrations and measurements were based on at least 10 specimens.The carapace length (CL) was considered from the eyes (base of the rostrum) to the posterolateral cephalothorax margin, and the rostrodorsal length (RDL) was considered from the tip of the rostral spine to the tip of the dorsal spine.The long terminal plumose natatory setae on distal exopod segments of the first and second maxillipeds were drawn truncated.
Antenna (Fig. 1d): biramous; well-developed and long protopod, with one row of short, equal spines in each lateral margin of similar sizes.Endopod absent.Exopod unsegmented, with three unequal terminal simple setae, the longest almost equal in length to exopod.
Third maxilliped: absent.Pereiopods: absent.Pleon (Fig. 3a, b): five somites.First somite smooth.Second to fifth somites with one pair of posterodorsal simple seta.Second and third somites with one pair of dorsolateral processes.Fourth and fifth somites with long and acute posterolateral processes; pleopods absent.
Telson (Fig. 3a-c): telson furcae distally spinulated and slightly curved outward, with 1 pair of welldeveloped lateral spines (spinulated only on the posterior margin), 1 pair of plumose setae posteriorly to the well-developed spines, and one pair of dorsal spines (spinulated only on the proximal inner margin); inner margin with 3 pairs of plumose setae.

dIscussIon
According to Clark and Ng (2010), the characters that separate the early stages of zoeae of the species of superfamily Trapezioidea are: the spinulation of the antennal protopod, the terminal setation of the antennule, the setation of the maxillule, maxilla, first and second maxillipeds, and medial and dorsolateral processes of the abdominal somites (see Tab. 1).The antennal morphology of D. acanthophora follows that observed for the other genera of the superfamily Trapezioidea (Tab.1).However, the distal spinulation of the antennal protopod in these genera is variable.The antennal protopod and its distal spinulation of D. acanthophora is similar to that of Domecia glabra Alcock, 1899 and Calocarcinus africanus Calman, 1909, which is formed by two rows of similar size spines.Other trapezioids have a distinct spinulation of the antennal protopod: Quadrella maculosa Alcock, 1898 and Quadrella serenei Galil, 1986 show an antennal protopod distally multispinulated (Clark and Ng, 2006); Tetralia cavimana Heller, 1861 and Tetralia rubridactyla Garth, 1971 present two rows of variable size distal spines (Clark and Galil, 1988;Clark and Ng, 2006); Trapezia cymodoce (Herbst, 1799) and Trapezia richtersi Galil & Lewinsohn, 1983 present two rows of distal spines arranged sparsely (Clark and Galil, 1988;Shikatani and Shokita, 1990;Al-Aidaroos, 1992;Clark and Ng, 2006).
The morphology of the larval stages of decapod crustaceans is used in studies to evaluate phylogenetic questions (e.g.Marques et al., 2003;Barros-Alves et al., 2013;Guerao et al., 2014).According to phylogenetic analysis, Clark and Ng (2010) suggested that the genera Domecia, Quadrella Dana, 1851, Tetralia Dana, 1851and Trapezia Latreille, 1828 are nested in one clade that is defined by the absence of seta 3.5 and seta 3.4 on the third endopodal segment of the second maxilliped (for details, see Clark and Guerao, 2008), and should be according to a synapomorphy defines the Domecia + Tetralia + Trapezia clade: the presence of one subterminal seta on the distal endopod segment of the maxillule (vs.two subterminal setae).Other synapomorphies define the sister group Domecia + Tetralia, including: the absence of a subterminal seta on the distal endopod lobe of the maxilla; and the absence of dorsolateral process on abdominal somites fourth and fifth (Clark and Ng, 2010).However, D. acanthophora presents two subterminal seta on the distal endopod segment of the maxillule and one subterminal seta on the distal endopod lobe of the maxilla.Thus, these features contradict the synapomorphies mentioned above, since they differ from observed by Clark and Ng (2010).
As previously discussed by Clark and Guerao (2008) and Clark and Ng (2010), Calocarcinus Calman, 1909 appears not to be related to the trapezioids.However, a similar morphological characteristic was observed for C. africanus and D. acanthophora: the presence of three pairs of lateral spines on the carapace.Therefore, the presence of this structure seems to be evidence that supports Calocarcinus relationship with the trapezioids (see Tab. 1), but further analysis is needed about this relationship.
Clark and Ng (2010) suggested, as autapomorphic features of D. glabra, the absence of setae on the proximal endopod segment of the maxillule, four terminal setae and one subterminal seta on the distal endopod segment of the maxillule, the basial setation Description of the first zoea of D. acanthophora Nauplius, 24: e2016021 of the first maxilliped arranged as 2, 2, 3, 2, the first endopod segment of the first maxilliped bearing only one seta, and the endopod of the second maxilliped with only four (two subterminal and two terminal) seta in the distal segment.These characters were also observed for the first zoea of D. acanthophora in this study, except the number of subterminal seta on the distal endopod segment of the maxillule (two for D. acanthophora vs. one for D. glabra).Thus, we suggest that other characters could be synapomorphies of the genus Domecia.
Some characters of the first zoeal stage that could be used to distinguish D. acanthophora and D. glabra are: the number of aesthetascs in the antennula exopod (three and four, respectively); the number of spines in the lateral carapace (three pairs and two pairs, respectively), wherein the lower pair is not ventrally deflected as in D. glabra; the number of setae in the basial endite of maxilla (4+4 and 5+3, respectively); the pairs of spines on the telson (two and three, respectively); and furcae distally spinulate in D. acanthophora and smooth in D. glabra (see Tab. 1).
The first zoeal stage of D. acanthophora exhibits some characters that differ from the other Trapezioidea species, such as the presence of simple setae at the basis of the first maxiliped (vs.plumose setae); the presence of only two pairs of spines on the telson furcae (vs.three pairs); and telson furcae with one pair of plumose setae posteriorly to the well-developed spines (vs.absent) (see Tab. 1).Thus, these characters can be considered as autapomorphy of D. acanthophora.Therefore, to prove this hypothesis, it is necessary further zoea I descriptions for the remaining species of the superfamily Trapezioidea.
The current study expands the number of species with first zoeal morphology known in Trapezioidea.Thus, we assert in favor of future studies to increase the number of larval descriptions, and to improve larval culture techniques in the laboratory, enabling the culture of larval stages for the species that the cultivation techniques currently used not guarantee survival and complete larval development, thereby enabling knowledge of a greater number of stages for larval species.This would certainly help to solve taxonomic and phylogenetic problems in the infraorder Brachyura.

acKnowledgeMents
The authors are indebted to Dr. Maria Lucia Negreiros-Fransozo, who gave us valuable suggestions for improving the manuscript.DFRA is grateful to CNPq -Conselho Nacional de Desenvolvimento Científico e Tecnológico (134950/2007-0) for his Master of Science fellowship.JAFP thanks Capes for a PhD scholarship.RCC is grateful to CNPq (PQ 305919/2014-8).We thank the "Omni Mare" Dive Center for the facilities provided during fieldwork.All sampling was conducted in accordance with applicable Brazilian state and federal laws with respect wild animals.

Table 1 .
Comparison of some larval characters of the first zoeal stage of Domecia acanthophora(Desbonne, in Desbonne & Schramm, 1867)and other species of the superfamily Trapezioidea.