Dendrocephalus xikrini Rabet & Lacau & Bozelli 2018, sp. nov.

Abstract

<i>Dendrocephalus xikrini</i> Rabet & Bozelli sp. nov. <p>urn:lsid:zoobank.org:act: D01C2A1B-75C2-4297-B1D3-B8B2564EB672</p> <p>Figs 1, 5–6, 7I</p> Etymology <p>Named in honour of the Xikrin, a subgroup of indigenous people from the Kayapó tribes living in the area of the Serra dos Carajás.</p> Material examined <p> <b>Holotype</b></p> <p>BRAZIL: mature Ƌ, total length 15.0 mm, cercopods 2.8 mm, Serra dos Carajás, Pará, 6°21′06.27″ S, 50°23′43.66″ W, pool S11-BC in an Amazonian savannah (Canga deposits), 25 Nov. 2013, R. Bozelli</p> <p>leg. (MNRJ 2973). In the same study period, approximately 30 phytoplankton species, 30 zooplankton species and 15 aquatic macrophyte species were recorded in the pool, but no fish were observed.</p> <p> <b>Allotype</b></p> <p> BRAZIL: mature ♀, total length 12.8 mm, brood pouch 2.9 mm reaching the extremity of the 6 th abdominal segment (including genital segments), cercopods 2.7 mm, same collecting data as for holotype (MNRJ 2974).</p> <p> <b>Paratypes</b></p> <p>BRAZIL: 8 ƋƋ, same collecting data as for holotype, total length 15.1 to 16.5 mm, mean = 15.75 ± 0.58 mm, cercopods 2.3 to 2.7 mm, mean = 2.56 ± 0.15 mm; 1 ♀, same collecting data as for holotype, length 13.5 mm, brood pouch 3 mm, cercopods 3 mm (2 ƋƋ, 1 ♀ MNHN (MNHN-IU-2016-3559); 2 ƋƋ in MNRJ (MNRJ 2975)). Other specimens are kept in personal collections of NR and RLB.</p> <p> <b>Type locality</b> (Figs 1, 7I)</p> <p> Pool S11-BC is the smallest (average area of 0.13 ha) among the previously studied lentic aquatic environments in the Serra dos Carajás inside the Carajás National Forest. Although very shallow (0.10 to 0.25 m) during our sporadic explorations from 2005–2013, the pool was never found completely dry, and during this period, its volume ranged from 56 to 140 m 3. Nevertheless, it is a temporary pool because it was possible to verify that the pool dried up in Google Earth images from August 2006. The electrical conductivity of the water varies between 4 and 64 μS/cm and pH varied between 4.89 and 5.63. The recorded turbidity values were between 1 and 64 NTU, but the water was always completely transparent.</p> Description <p> <b>Male</b></p> <p>Eye pedunculate, ovoid in lateral view with a prominent spine. Length of the spine relative to that of the eye between 10 and 20% (Fig. 5A). Antenna-like outgrowth slender, lying between the first antennae and second antennae. Second antennae with proximal antennomeres fused basally on the anterior of the head. Proximal antennomere mediodistally bearing a stout digitiform process ornamented with setae. Distal antennomere weakly sclerotized, evenly curved medially, and ornamented on the medial surface with scaliform transverse ridges; terminus acute. Frontal appendages with anterior margin of the base of the arms with three or four spines (Fig. 5B). Arms from the base to the terminal branches with spines (Fig. 5B). Frontal appendage complex with one ventral branch (1V) and three terminal branches (2V, 2D, and 2A). The terminal appendage in the medial position called branch 2A with a podiform apex and one well-developed cell-pad on the first third of the branch. A long spiniform process is present basally (Fig. 5C). Ventral branch called branch 1V with two sub-branches. Sub-branch I (most proximal) with one row of spines on the medial side with an acute extremity (Fig. 5D). Sub-branch II ¾ of the length of sub-branch I and with a row of short spines on the medial side with an acute extremity (Fig. 5D). Terminal ventral branch called branch 2V cylindrical and ending in a cluster of four to five cell-pads on a bulge and four rows of cell pads on the medial surface (Fig. 5E). Terminal branch in the dorsal position called branch 2D subdivided into three sub-branches. Sub-branch I (most proximal) with a row of short spines on the medial side and with three or four long spines (length of which is more than twice the diameter of the sub-branch) in the first half of the sub-branch (Fig. 6A). Sub-branch II longer than half of sub-branch I, with a row of small spines on the medial side and with two long spines (the length of which is greater than or equal to the diameter of the sub-branch) in the first half and half the length of the sub-branch (Fig. 6A). Sub-branch III slightly shorter than sub-branch I (80%) with twice the average diameter, proximally cylindrical and distally flattened and bearing a large spiniform process; distal flattened portion with two or three long spines (equalling the width of the sub-branch) on the posterolateral side (Fig. 6A). Endopodite of the first pair of limbs with a reduced basolateral lobe sharing small spines that form a row extending to the distal corner (Fig. 6B). Endopodite of the second pair of limbs with a border sharing large spines (Fig. 6C). Endopodite of the third pair of limbs similar to the second with slightly larger spines (Fig. 6D). No differentiation was observed in the fourth pair of limbs (Fig. 6E). Abdominal segments smooth. Cercopods margined with plumose setae.</p> <p> <b>Female</b></p> <p>Typical of the genus.</p> Resting egg <p> Similar to those of <i>D. aranai</i> sp. nov., subspherical with broad pentagonal or quadragonal facies.</p> Distribution <p> Known only from the <i>locus typicus</i>. Other pools prospected in the Carajás Mountains are inhabited by <i>D. carajaensis</i> only.</p>Published as part of <i>Rabet, Nicolas, Lacau, Sébastien & Bozelli, Reinaldo L., 2018, Richness of Dendrocephalus (Branchiopoda, Anostraca) in Brazil with the description of two new species, pp. 1-20 in European Journal of Taxonomy 478</i> on pages 7-12, DOI: 10.5852/ejt.2018.478, <a href="http://zenodo.org/record/3825236">http://zenodo.org/record/3825236</a&gt