Dendrocephalus (Dendrocephalus) brasiliensis Pesta, 1921

Barros-Alves, Samara de Paiva, Alves, Douglas Fernandes Rodrigues, Jr, Eduardo Antônio Bolla & Hirose, Nicolas Rabet and Gustavo Luis, 2016, Morphological review of the freshwater fairy shrimp Dendrocephalus brasiliensis Pesta, 1921 (Anostraca: Th amnocephalidae), Nauplius (e 2016008) 24, pp. 1-10 : 3-9

publication ID	https://doi.org/10.1590/2358-2936e2016008
persistent identifier	https://treatment.plazi.org/id/706587B9-E67E-4D30-EA19-FF76FDE0FD8D
treatment provided by	Felipe
scientific name	Dendrocephalus (Dendrocephalus) brasiliensis Pesta, 1921
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Treatment

Dendrocephalus (Dendrocephalus) brasiliensis Pesta, 1921 View in CoL

Material examined. Alagoas – Porto Real do Colégio , fish tank, 15 males and 10 females, collected by M.F.G. Brito, 23 November 2012 (CARCINO 104); 11 males and 10 females, same data ( MZUSP 32913 View Materials ) .

Additional material examined. Rio Grande do Norte – Caicó , fish tank, 10 specimens, collected by N. Rabet, 6 August 1993 ( MNRJ 3000 View Materials ); Mossoró, ESAM , two specimens, collected by Lemos de Castro and P. Coelho, 27 February1980 ( MNRJ 3007 View Materials ) . Paraíba – João Pessoa : temporary pools, 10 specimens, collected by N. Rabet, 18 July 1993 ( MNRJ 3002 View Materials ) . Minas Gerais – Januária , temporary pool, two specimens, collected by W. Costa, G . Brasil and C. Campinha , 7 February 1994; two specimens, collected by J. Goma Pinto and D. Pillet, 6 February 2003 . Ceará – Brejo Santo, Açude Atalhos , four specimens, collected by U. Caramaschi, R . N. Feio and H. De Nieweyer , 6 December 1998 ( MNRJ 15893 View Materials ) .

Distribution. To date, this species was recorded in Brazil (Piauí, Ceará, Rio Grande do Norte, Paraíba, Bahia, Minas Gerais and São Paulo) ( Lemos-de-Castro and Lima, 1986; Rabet and Thiéry, 1998; Mai et al., 2008; Chaves et al., 2011) and northern Argentina ( César, 1989; César et al., 2004).

The occurrence of D. brasiliensis in fish-breeding tanks in the Porto Real do Colégio represents the first record of this species in the state of Alagoas. Two main hypotheses should be considered for the current record of these populations in Alagoas: 1) associated with the natural distribution of the species, even if it is not found yet in natural ponds in this state; or 2) introduced by human action in connection with aquaculture.

Dendrocephalus brasiliensis is typically found in temporary ponds in the Caatinga biome and in a coastal area (at João Pessoa, Paraíba, see Rabet and Thiéry, 1996). The distribution of this species appears to be interrupted in Bahia state ( Fig. 1 View Figure 1 ). This apparent gap should be confirmed by a precise examination of many dendrocephalid populations, because Dendrocephalus orientalis is clearly dominant in the center of Bahia, but we cannot exclude a sympatric distribution of the second species.

In addition to its natural distribution, the expansion of the geographical distribution of D. brasiliensis might be associated with fish-breeding tanks. Dendrocephalus brasiliensis and D. orientalis were collected twice in fish tanks ( Rabet and Thiéry, 1996; 1998; this study), and this activity might have a major impact on the distribution of the species. Particularly, this can generate predictions of the rapid expansion of D. brasiliensis into other hydrographic basins, which might cause problems related to the introduction of exotic species ( Rocha et al., 2005; Mai et al., 2008).

Redescription. Males (total length: 13.2–16.9 mm; mean length: 15.26 ± 0.71 mm). Eyes pedunculate, ovoid in lateral view, without posterior spines ( Fig. 2A View Figure 2 ). Antenna-like outgrowths slender ( Fig. 2B View Figure 2 ) lying between first antennae and second antennae. First antennae ( Fig. 2C View Figure 2 ) cylindrical, elongated, and smooth, almost as long as second antennae. Second antennae ( Fig. 2D View Figure 2 ) with proximal antennomeres fused basally on anterior region of head. Proximal antennomere bears stout and smooth digitiform process mediodistally. Distal antennomere weakly sclerotized, smooth, and evenly curved medially, with acute terminus. Basal part of arms frontal appendage ( Fig. 2E View Figure 2 ) lacking spines at anterior margin and with row of medial spines extending to terminal branches. Frontal appendage branch 1 V distally ramified into two sub-branches, both with longitudinal row of medial spines ( Fig. 3A View Figure 3 ). Posterior sub-branch with 0–2 short subterminal spines ending acutely in one hook-shaped spine ( Fig. 3a View Figure 3 1 View Figure 1 ). Anterior sub-branch longer than the posterior counterpart and broadening distally with 3–7 robust spines on posterior margin and 1–2 larger spines at tip ( Fig. 3a View Figure 3 2 View Figure 2 ). Frontal appendage branch 2D with three sub-branches: I, II and III (from posterior to anterior, respectively) ( Fig. 3B View Figure 3 ). Sub-branch I with row of short spines on anterolateral margin, ending acutely with 2–3 long spines in medial portion. Sub-branch II almost half size of sub-branch I, ending acutely with 0–1short sub-terminal spines, one long spine and 1–2 robust spines ( Fig. 3b View Figure 3 1 View Figure 1 ). Sub-branch III roughly equal to sub-branch I (sometimes shorter or longer) but with almost twice basal diameter, cylindrical proximally and flattened distally, bearing large spiniform process proximally. Distal flattened portion with row of 3–4 spines at posterolateral margin, 2–6 robust spines at anterolateral margin, 0–2 short subterminal spines and 0–1 minimal spine on tip. Frontal appendage branch 2A ( Fig. 4A, 4a View Figure 4 1 View Figure 1 ) cylindrical and heavily sclerotized on its anterior podiform end ( Fig. 4a View Figure 4 2 View Figure 2 ), presenting one bulging basal cell pad more laterally and one basal long spine ( Fig. 4a View Figure 4 3 View Figure 3 ). Frontal appendage branch 2 V cylindrical, abruptly narrowed, and usually bent distally ( Fig. 4b View Figure 4 1 View Figure 1 ), with 3–5 well-defined cell pads in median portion, another parallel medial-anterior row of 3–5 smaller cell pads, and anterior scattered minimal and shapeless cell pads ( Fig. 4b View Figure 4 2 View Figure 2 ); it ends at tip in cluster of 5–7 hand-like aligned cell pads ( Fig. 4b View Figure 4 3 View Figure 3 ).

Thoracopods with pre-epipods with finely serrated contours ( Fig. 5A View Figure 5 ). Endopods of thoracopods without basolateral lobe and without pronounced distolateral border. Endopods of limbs one, two and three marginally ornamented with, respectively, 5–7, 15–19 and 9–13 spines and 21–25, 26–29 and 27–33 setae, most of these plumose ( Fig. 5B, C and D View Figure 5 ).

Gonopod (retracted state) with basal part short, with slightly curved triangular lateral projection containing small spines and surface protuberances, as well as pointed end portion. Distal end of retracted gonopod globose and nude, with small groove at tip ( Fig. 6A View Figure 6 ).

Females shorter than males (total length: 11.9–14.5 mm; mean length: 13.27 ± 0.72 mm). Antennae short, flat and rounded at tip. Endopods of thoracopods morphologically similar. Brood pouch elongated ( Fig. 6B View Figure 6 ). Cercopods plumose. Brood-pouch length: 3.4–4.7 mm (4.15 ± 0.32 mm). Resting eggs (mean diameter: 208.4 ± 11.3 μm) polyhedral with rounded ridges ( Fig. 6C View Figure 6 ), intersecting to form large polygons with circular depressions, sometimes, with small polygons in addition to large depressions.

Remarks. Some features have been described here for the first time, such as antenna-like structures and the gonopod (retracted state). Furthermore, some morphological characteristics that were previously described superficially were examined in more detail (e.g., the endopod of thoracopods, the number of spines on branch 1 V and sub-branches I, II and III of branch 2D, the number of cell pads in branch 2 V).

When compared to other species of the genus, spines were not observed on the proximal anterior surface of the male frontal appendage arms, similar to Dendrocephalus carajaensis , Dendrocephalus geayi ( Daday, 1908) , Dendrocephalus sarmentosus Pereira & Belk, 1987 and Dendrocephalus venezolanus Pereira, 1984 ( Pereira, 1983; 1984; Pereira and Belk 1987; Rogers et al., 2012). Other species, such as Dendrocephalus affinis Pereira, 1984 , Dendrocephalus goiasensis , D. orientalis , Dendrocephalus spartaenovae Margalef, 1961 and Dendrocephalus thieryi , may have one or more spines on each arm ( Pereira, 1983; Rabet and Thiéry, 1996; Rabet, 2006; Cohen et al., 2014; Hirose et al., 2015). Furthermore, spines were not observed in the eyes of D. brasiliensis , similar to D. sarmentosus (see Pereira and Belk, 1987), D. carajaensis (see Rogers et al., 2012) and some individuals of D. orientalis (see Hirose et al., 2015).

In branch 1 V, the anterior sub-branch is longer than the posterior branch and the distal portion is swollen, as in D. affinis (see Cohen et al., 2014), D. carajaensis (see Rogers et al., 2012), Dendrocephalus cervicornis (see Pereira, 1983), Dendrocephalus cornutus Pereira & Belk, 1987 (see Pereira and Belk, 1987), D. geayi (see Pereira, 1983), D. orientalis (see Rabet and Thiéry, 1996; Hirose et al., 2015), D. thieryi (see Rabet, 2006) and D. venezolanus (see Pereira, 1984). This morphology differs from other species, such as D. goiasensis (see Rabet and Thiéry, 1996) and Dendrocephalus argentinus Pereira & Belk, 1987 (see Pereira and Belk, 1987), which display an acute distal portion. The main particularity of branch 2D is the presence of several small spines on the distal third of sub-branch III. This morphological characteristic is also shared with D. affinis , D. orientalis and D. thieryi (see Rabet and Thiéry, 1996; Rabet, 2006; Cohen et al., 2014; Hirose et al., 2015).

Branch 2A shows a strong column extending in one or two projections and a cell pad at the base, as already observed for other dendrocephalids; the distal end is podiform as in D. affinis (see Cohen et al., 2014), Dendrocephalus conosuris Pereira & Ruiz, 1995 (see Pereira and Ruiz, 1995), D. cornutus (see Pereira and Belk, 1987), D. goiasensis (see Rabet and Thiéry, 1996), D. spartaenovae (see Pereira, 1983) and D. thieryi (see Rabet, 2006), but differs from the hook-shaped projection described for other species, such as D. orientalis (see Rabet and Thiéry, 1996; Hirose et al., 2015) and D. carajaensis (see Rogers et al., 2012). Branch 2 V is typically bent at the tip and terminates in several well-defined cell pads (3–5), which are frequently found in the subgenus Dendrocephalus but differ in D. carajaensis (see Rogers et al., 2012) and D. sarmentosus (see Pereira and Belk, 1987), which share only two cells pads in the distal portion.

In D. brasiliensis View in CoL , the first two pairs of thoracopod endopods display no clear spinous laterodistal expansions and basolateral lobes, similar to D. sarmentosus View in CoL (see Pereira and Belk, 1987) and D. carajaensis View in CoL (see Rogers et al., 2012). The presence of basolateral lobes in the first two pairs of thoracopods is very common in the subgenus Dendrocephalus , as observed for D. orientalis View in CoL (see Rabet and Thiéry, 1996; Hirose et al., 2015), D. goiasensis View in CoL (see Rabet and Thiéry, 1996) and D. thieryi View in CoL (see Rabet, 2006).