Dendrocephalus carajaensis, Rogers, Christopher, Gomes, João Pedro Corrêa & Vieira, Fabio, 2012

Rogers, Christopher, Gomes, João Pedro Corrêa & Vieira, Fabio, 2012, A new species of Dendrocephalus (Crustacea, Anostraca) from Serra dos Carajás (Pará State, Brasil), Zootaxa 3363, pp. 52-58 : 54-57

Dendrocephalus carajaensis sp. nov.

( Figure 2 )

Etymology. The name “ carajaensis ” refers to the Serra dos Carajás where this species was discovered.

Type Locality. The type locality is a temporary wetland located in the extreme southern area of the National Forest of Carajás ( Figure 3 ). The area is part of Parauapebas river drainage, a major tributary of the river Itacaiúnas, which empties into the Tocantins River near the city of Marabá ( Santos, 1986). The substrate is primarily composed mostly of iron ore concretions (canga) and deposited organic matter. Pool depth during collection was 30-40 cm. The site is among the most diverse wetland areas sampled on the Serra Sul plateau (Golder Associates, 2010) with fifteen aquatic macrophyte species reported. Most of the habitat is colonized by Cyperaceae , particularly Eleocharis and Cyperus. The site is in seasonally dry forest: dry generally between June and September and wet from November to April, with an average annual rainfall of 1,930 mm ( IBAMA, 2003). Many macrophyte species on the Serra Sul plateau are drought adapted, which is most intense from June to August (Golder Associates, 2010). Data obtained in November 2007 and February 2008 indicated water temperature ranging from 29.9 to 30.1 °C, pH from 5.05 to 8.29; dissolved oxygen from 2.26 to 7.37 mg /L and conductivity from 29.7 to 39.6 µS/cm (Golder Associates, 2010).

Type Material. Holotype, male, data: Brasil: Pará: Canaã dos Carajás: ( Figure 1 ) Serra Sul, Carajás region, temporary pool, 06° 24’ 12.58” S, 50° 18’ 36.40” W, 700m elevation, 10 November 2008, F. Vieira & J. P. C. Gomes, deposited in Coleção de Crustáceos - Coleções Taxonômicas da Universidade Federal de Minas Gerais; accession number UFMG-0003. Allotype, female; same data as holotype; accession number UFMG-0004. Paratypes: same data as holotype, 49 females, 29 males; accession number UFMG-0001 and 0 0 0 2.

Diagnosis. ( Figure 2 ) Average length of preserved material: 13.1 mm from apex of head to apex of telson (males averaging 13.3, females averaging 13.1).

Male. Eye lacking a spine, frontal appendage basal trunk and primary branches lacking spines. Branch 1V posterior branch digitiform, smooth, lacking spines and apically rounded. Anterior branch twice length of posterior branch, apical portion broad with posterior margin serrate and anterior margin with a row of tumid projection ending in spines. Branch 2D sub-branch I, subcylindrical, with anterior surface bearing a row of spines and the apex tipped with single recurved spine. Branch 2D sub-branch II reduced, digitiform. Branch 2D sub-branch III with a lamellar basal projection, margined with spines, with two basal, spiniform projections. Branch 2D sub-branch III biramal, with the posterior ramus elongated, acute, and bearing spiniform projections. Posterior (superior) ramus distal half tumid, with anterior surface bearing two longitudinal rows of spiniform projections. Thoracopods I, II and III endopodites with the laterodistal corner, projecting as a short, rounded lobe, and bearing many large spines.

Female. The female does not have any specific distinguishing morphological characteristics.

Description. Male. Anteriolateral corner of head not projecting over base of eyestalk. Labrum covered with small evenly spaced spinules. Antenna-like appendage anteriobasal to eyestalk, filiform, slightly longer than eyestalk peduncle.

First antenna approximately 60% the length of second antenna.

Second antenna capable of extending to thoracomere II or III. Second antennal proximal antennomere subcylindrical, smooth, with length approximately 4.5 times distoapical width. Proximal antennomere distal end with medial antennal appendage. Antennal appendage subcylindrical, projecting medially, apically rounded, approximately 0.2 times length of antennomere, and with a few scattered setae. Second antennal distal antennomere subequal in length to proximal antennomere, round in cross section, broadly arcuate medially, distal third curving posteriorly, with apex spiniform and directed medially.

Frontal (cephalic) appendage prominent, typical of the genus. Proximal trunk subcylindrical, smooth, lacking spines. Primary branches smooth, lacking spines. Branch 1V well developed, peduncle subequal in length to the anterior branch, lacking spines. Posterior branch digitiform, smooth, lacking spines and apically rounded. Anterior branch twice length of posterior branch, apical portion broader than proximal portion, posterior margin serrate, anterior margin with a row of spines each borne on a tumid projection, apex with a single spine. Branch 2V thick, flattened, with numerous semiannulations. Apex bent approximately 70 degrees, bifurcate, each tip with a “knob structure” ( Pereira 1983) or “cell pad” ( Margalef 1961). Medial surface bearing a longitudinal row of projecting “knob structures”. Branch 2D sub-branch I, subcylindrical, with anterior surface supporting a row of long, recurved spines. Apex tipped with single recurved spine. Sub-branch II reduced, digitiform, tipped with a small spine. Subbranch III with basal projection. Basal projection lamellar, margined with spines, with two basal, recurved, spiniform projections. Sub-branch III biramal, with posterior (inferior) ramus elongate, apically acute, and supporting three spiniform projections, with a sub-basal spiniform projection. Posterior (superior) ramus distal half tumid, with anterior surface bearing two longitudinal rows of spiniform projections. Branch 2A (apical portion) with basal spine sinuate, apically acute. Basal cell pad produced. Anterior end, arcuate, apically aciculate and acute.

Maxillae lobiform and transverse, no setae visible.

Thoracopods with endites margined with long, plumose setae. Endopodites subquadrate, with distal margin bearing a row of plumose setae. Endopodites of all thoracopods, except thoracopod I lack setae on lateral and medial margins. Thoracopods I, II and III with endopodite distolateral corner thickened, produced, and bearing spines. Thoracopod I endopodite distolateral corner produced distally, with a suboblique row of stout, chitinized spines starting just medially of the distolateral corner and extending across the endopodite anterior surface to the lateral margin, at approximately the apical third. Medial margin edged with short, simple setae. Thoracopod II endopodite distolateral produced distally and laterally as a lobe, margined with stout spines curving distally. Marginal spines extend proximally, below produced lobe. Thoracopod III endopodite distolateral corner slightly produced, with a few stout marginal spines, curved distally. Exopodite elliptic, margined in long plumose, recurved setae. Epipodite elliptic and without marginal setae. Praepipodite broadly oval, lamellar, and without marginal setae.

Genital segments smooth. Retracted gonopod as for genus. Gonopod posteriomedial surface with a pyriform projection. Everted gonopods not observed.

Female. As typical for the genus. Head rounded, anterolateral corners not projecting over eyestalk base. First antenna 1.3 times as long as second antenna. Second antenna broadly elliptic, lamellar. Thorax smooth. Thoracopods as in male, except first three endopodites not modified. Thoracopod XI with exopodite narrowly elliptic, curving dorsally, and margined with plumose setae. Brood pouch fusiform, extending to distal margin of postgenital abdominal segment IV.

Egg. Subspherical, diameter approximately 250 μm, with broad pentagonal or quadragonal facies, each face diameter approximately 60μm.

Distribution and habitat. Dendrocephalus carajaensis sp. nov. is known only from the type locality in canga deposits on the Serra Sul plateau, in the municipality of Canaã dos Carajás, Pará State, Brasil. The canga deposits are not more than 5% of the 411,948.87 hectares of the Carajás National Forest ( Seco & Mesquita 1983, Ab’Saber 1986, ICMBIO 2012). Several of these canga formations were eliminated by iron ore mining. Thus, it is anticipated that the remnant habitat with appropriate conditions to support additional populations of this species are scarce.

The type locality will most likely be destroyed with the opening of a new iron mine (Golder Associates, 2010). Additional surveys need to be conducted to ascertain if this species occurs in any other habitats. Presently, this species meets the criteria under the IUCN Red List (IUCN, 2001) as Critically Endangered (CR), with the area of occupancy less than 10 km 2, known only to exist at a single site (B2), and projected decline in extent of occurrence, occupancy and quality of habitat (ab).

Figures

FIGURE 1. Map indicating Itacaiúnas river with adjacent drainage and the type locality (star) of Dendrocephalus carajaensis sp. nov.

FIGURE 2. Dendrocephalus carajaensis sp. nov., type, male. A, left side of head anterior view. Terminology follows Pereira, 1983: 1 V = first ventral branch (with anterior and posterior sub-branches); 2 V = second ventral branch; 2 D = dorsal branch (with sub – branches I, II and III); 2 A = apical branch. B, right thoracopod I, endopodite, anterior view. C, right thoracopod II, endopodite, anterior view. D, right thoracopod III, endopodite, anterior view. Scale bar represents 2 mm for A, 0.4 mm for B, C, and D.

FIGURE 3. Temporary flooded area located in the Serra Sul, extreme southern area of the National Forest of Carajás, type locality of Dendrocephalus carajaensis sp. nov.