Hadrurochactas mapuera (Lourenço, 1988)

Ythier, Eric & Lourenço, Wilson R., 2024, A new species of Hadrurochactas Pocock, 1893 (Scorpiones: Chactidae) from the Mitaraka Massif in French Guiana, Faunitaxys 12 (59), pp. 1-9 : 2-4

Hadrurochactas mapuera (Lourenço, 1988)

Brazil

- Para,region of Mapuera river , 1 ♂ holotype, 23/II/1986 ( E.Baracuxi), MNHN .

Etymology. – The specific name is placed in apposition to the generic name and refers to the Tumuk Humak Mountains (Serra do Tumucumaque) where is located the Mitaraka Massif, the location in which the new species was collected ( Fig. 15).

Diagnosis. – Scorpion of medium size when compared to other known species of the genus, reaching a total length of 20.4 mm for the male holotype (see morphometric values after the description). Coloration yellowish brown, densely spotted on the carapace, the tergites and the appendages. Mesosoma yellowish, densely spotted with confluent brown to dark brown spots, with a yellowish longitudinal median stripe. Chelicerae yellowish. Legs tarsal segments yellowish. Metasomal segment V, telson and chela slender in comparison to the geographically closest species H. schaumii , H. cristinae and H. mapuera (Tab. 1). Ventral side of telson with two large spinoid granules under the aculeus and smaller size spine-like granules. Pectines with 10-10 teeth in male holotype; female unknown. Trichobothrial pattern of type C, neobothriotaxic (majorante) ‘major neobothriotaxy’.

Description based on male holotype

Coloration. – General coloration yellowish brown, densely spotted on the carapace, the tergites and the appendages. Prosoma yellowish with brownish variegated spots on anterior, lateral and posterior edges; eyes surrounded by black pigment. Mesosoma yellowish, densely spotted with confluent brownish spots, darker on the posterior edge of the tergites; the remaining yellowish coloration forming a confluent longitudinal median stripe. Sternites yellowish, the VII slightly darker; coxapophysis and sternum yellowish; genital operculum yellowish; pectines pale yellow. Metasomal segments reddish yellow with brownish spots. Telson reddish yellow with brownish spots; aculeus reddish. Chelicerae yellowish; fingers yellowish; teeth reddish yellow. Pedipalps reddish yellow with brownish longitudinal stripes on femur, patella and chela. Legs with femur, patella and tibia yellowish with brownish longitudinal stripes; basitarsus and telotarsus yellowish.

Morphology. – Carapace weakly granular to smooth; anterior margin very weakly emarginated; carinae absent; all furrows weakly pronounced; postero-median furrow finely granular; median ocular tubercle distinctly anterior to the centre of the carapace; two pairs of small lateral eyes and a third pair of lateral vestigial eyes in the back of the second pair. All tergites with minute granulation and a few indistinct bigger granules on the posterior margin. Pectinal tooth count 10- 10 in male holotype, fulcra absent. Sternites smooth and shiny except VI and VII which have some minute granulations; spiracles rounded; carinae absent; genital operculum longitudinally divided, each half with a sub-triangular shape. Dorsal carinae moderately granular on metasomal segments I-IV, absent on segment V; dorsolateral carinae moderately granular on all segments; ventrolateral and ventral carinae weakly pronounced or absent on all segments; dorsal surface smooth on all segments; lateral surfaces weakly granular to smooth on all segments; ventral surface smooth on segments I to IV; weakly granular on V. Telson with small-sized spine-like granules and two large spinoid granule under the aculeus; dorsal side smooth; aculeus relatively short and weakly curved. Pedipalp femur pentacarinate, weakly granular; patella and chela with weakly marked to unconspicuous carinae; fixed and movable fingers with seven rows of linear granules. Legs with long thin setae. Cheliceral dentition characteristic of the family Chactidae (Vachon, 1963) . Trichobothriotaxy of type C, neobothriotaxic (majorante) ‘major neobothriotaxy’ (Vachon, 1974).

Morphometric values (mm) of the male holotype.

- Total length (including the telson) 20.42. - Carapace length 2.79;

anterior width 1.72;

posterior width 3.12.

- Mesosoma: length 4.51.

- Metasomal segments

I: length 1.07, width 2.00, depth 1.63;

II: length 1.35, width 1.86, depth 1.53;

III: length 1.49, width 1.91, depth 1.53; IV: length 2.19, width 1.95, depth 1.53;

V: length 3.53, width 2.00, depth 1.44.

- Telson: length 3.49.

- Vesicle: width 1.05, depth 0.74.

- Pedipalp femur length 2.28, width 0.84;

patella length 2.56, width 0.93;

chela length 4.14, width 1.16, depth 1.30. - Movable finger: length 2.37.

Relationships. – Inrespecttoseveral characters, H.tumucumaque sp. n. shows similarities with H. schaumii , distributed in French Guiana, Suriname, Guyana and Venezuela ( Fig. 13-14). However, it can be readily distinguished notably by the following main features:

(i) metasomal segment V less rounded, narrower with length/width ratio 1.8 ( 1.4 to 1.6 in ♂ H. schaumii ; n=10) and thinner with length/depth ratio 2.5 ( 1.8 to 2.3 in ♂ H. schaumii ; n=10);

( ii) telson narrower with length/width ratio 3.3 ( 2.7 to3.1 in ♂ H. schaumii ; n=10) and thinner with length/depth ratio 4.7 ( 3.5 to 4.1 in ♂ H. schaumii ; n=10);

( iii) chela slender with length/width ratio 3.6 (3.0 to 3.3 in ♂ H. schaumii ; n=10);

( iv) ventral side of telson with two large spinoid granules under the aculeus and smaller size spine-like granules (one medium to large spinoid granule under the aculeus and smaller size spine-like granules in ♂ H. schaumii ; n=10);

( v) metasoma with dorsal and dorso-lateral carinae slightly less granular (better marked in ♂ H. schaumii ; n=10) and granulation generally less marked on body and appendages.

The new species can also be readily distinguished from the two other geographically closest species, H. cristinae described from eastern French Guiana and H. mapuera described from the region of the Mapuera river (tributary of Trombetas river) in the Amazon basin of Brazil ( Fig. 13-14), notably by the following main features:

( i) larger general size than H. cristinae with 20.4 mm ( 18.9 mm in ♂ holotype H. cristinae );

( ii) larger pectinal count than H. cristinae with 10-10 teeth (9-9 teeth in ♂ holotype H. cristinae );

( iii) confluent yellowish longitudinal median stripe on mesosoma (no stripe in ♂ holotype H. cristinae ) and no darker pigmentation on tarsal segments (diffused brownish pigmentation in ♂ holotype H. cristinae );

( iv) metasomal segment V narrower with length/width ratio 1.8 ( 1.5 in both ♂ holotypes H. mapuera and H. cristinae ) and thinner with length/depth ratio 2.5 ( 1.7 in ♂ holotype H.mapuera , 2.4 in ♂ holotype H. cristinae );

( v) telson narrower with length/width ratio 3.3 ( 2.8 in both ♂ holotypes H. mapuera and H. cristinae ) and thinner with length/depth ratio 4.7 ( 3.7 in ♂ holotype H. mapuera , 4.1 in ♂ holotype H. cristinae );

( vi) chela slender with length/width ratio 3.6( 3.1 in ♂ holotype H. cristinae , 3.2 in ♂ holotype H. mapuera );

( vii) ventral side of telson with two large spinoid granules under the aculeus and smaller size spine-like granules (one medium to large spinoid granule under the aculeus and smaller size spine-like granules in both ♂ holotypes H. cristinae and H. mapuera );

( viii) metasoma with dorsal and dorso-lateral carinae less granular and ventral surface of segment less granular than in ♂ holotype H. mapuera ;

( ix) trichobothria on ventral side of pedipalp patella situated at different positions than in H. cristinae with V3 equidistant from V2-V4 and V6 closer to V7 (V3 closer to V2 and V6 equidistant from V 5-7 in ♂ holotype H.cristinae ).

Biogeographic considerations: the disrupted pattern of distribution of Hadrurochactas species in forest formations of South America

Previous examples of scorpion groups restricted to particular types of vegetation cover in the Neotropical region have been outlined. A typical case is the one presented by the genus Rhopalurus Thorell, 1876 (here considered as a single genus), which shows a restricted distribution over open vegetation formations such as the Llanos, Cerrados and Caatingas ( Lourenço 1986 b, 1994). Other genera such as Ananteris Thorell, 1891 ( Ananteridae ) and Tityus C. L. Koch, 1836 ( Buthidae ) present much broader patterns of distribution, and are present in a large array of vegetation covers.

Contrarily to the Buthidae and Ananteridae , the elements of the family Chactidae are typical of forested formations, and largely present in rainforests, in particular those of the Amazon region and the Guayana lowland floristic Province as defined by Mori (1991). A singular exception is the model of distribution observed for the species of the genus Hadrurochactas . The species of this genus, like the majority of the chactid scorpions, are exclusively restricted to forest formations and their distribution was originally supposed to be limited to the Guayana Province where the group was represented by two species: Hadrurochactas schaumii (Karsch) and Hadrurochactas odoardoi González-Sponga.

Subsequently, new species were described from other regions outside the Guayana Province: Hadrurochactas mapuera Lourenço , collected in a forest formation located in a zone of possible contact between Amazonia and Guayana, just to the South of the Tumuk Humak Mountains (Serra do Tumucumaque), in the State of Pará, Brazil and Hadrurochactas polisi Monod & Lourenço collected in Central Amazonia. More remarkable was the description of Hadrurochactas brejo Lourenço , collected in a ‘Brejo’formation in the State of Ceará, Brazil, representing the first chactid element ever found outside of the Guayana-Amazon region (Lourenço, 1988). It seems important to recall that ‘Brejos’ are inselbergs recovered by humid forested vegetation which in the northeastern regions of Brazil are surrounded by xerophytic formations such as the Caatingas.These inselbergs are covered by forest because their elevation causes humid air to cool, forming consequent condensation leading precipitations to take place ( Andrade-Lima, 1982). The subsequent description of Hadrurochactas araripe Lourenço , once again from a ‘Brejo’ formation, confirmed this model of disrupted pattern of distribution presented by the genus Hadrurochactas . These two examples of disrupted distribution with isolation of populations in a today globally arid vegetal formation bring support to the theory of a possible past connection between the Amazon and the Atlantic forests (Lourenço, 1994), asstrongly suggested by palaeobotanists ( Bigarella &Andrade-Lima, 1982). The present description of one more new species from an inselberg equally suggests that these formations play a main role as refugia during past climatic vicissitudes.