Parastacus longidactylus Huber & Araujo & Ribeiro 2024, sp. nov.
Creators: name: Huber, Augusto Frederico
name: Araujo, Paula Beatriz de
name: Ribeiro, Felipe Bezerra
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Parastacidae
Parastacus
Parastacus longidactylus

description: Parastacus longidactylus sp. nov.
(Figs. 1–4)
Zoobank: urn:lsid:zoobank.org:act: EED4209E-8A29-4818-8137-98CBAC4805F7
Type material. Holotype: adult male (MZUSP 45071), Brazil, Rio Grande do Sul, Amaral Ferrador, “Margem do Arroio Ladrão”, próximo da junção com o Rio Camaquã (30°52 ' 46.6 '' S 52°14 ' 33.0 '' W), VII/2015, coll. unidentified local residents, det. A.F. Huber. Paratypes: 1 female (MZUSP 45072), same data as holotype; 1 male (MZUSP 45073), Brazil, Rio Grande do Sul, Amaral Ferrador, 07/X/2013.
Comparative material. Brazil, Rio Grande do Sul: Parastacus brasiliensis (von Martens, 1869): 4 females and 1 male (UFRGS 2337), Mariana Pimentel, 09/X/1986, coll. N.F. Fontoura; 1 female (UFRGS 5757), Porto Alegre, morro Santana, 06/IV/2013,coll. K. M. Gomes; 1 male (UFRGS 5868), sítio do Mato, zona sul, Porto Alegre (30°07 ' 04 '' S 51°08 ' 47 '' W), 22/III/2014, coll. M. Pasolius; 2 juveniles and 3 males (UFRGS 5947), Porto Alegre, Parque Natural do Morro do Osso (30°07 ' 07.7 '' S 51°14 ' 15.1 '' W), 22/III/2014, coll. K.M. Gomes, F.B. Ribeiro, M.F. Pasolius; 2 juveniles and 3 males (UFRGS 5947), Porto Alegre, Parque Natural do Morro do Osso (30°07 ' 07.7 '' S 51°14 ' 15.1 '' W), 22/III/2014, coll. K.M. Gomes, F.B. Ribeiro, M.F. Pasolius; 1 male (UFRGS 6025), rua Dona Francisca, Lomba do Pinheiro, Porto Alegre (30°08 ' 05.0 '' S 51°06 ' 11.9 '' W), 26/IX/2014, coll. K.M. Gomes, D.C. Kenne. — Parastacus buckupi Huber, Ribeiro and Araujo, 2018: 1 male (UFRGS 3581), Maquiné, arroio Carvão, 25/X/2001, coll. F.S. Vilella; 1 female (UFRGS 3895), Maquiné, arroio Carvão, 25/X/2001, coll. F.S. Vilella. — Parastacus gomesae Huber, Araujo and Ribeiro, 2022: 1 male (MNRJ 30203), São Jerônimo, Horto Florestal Quitéria, riacho de primeira ordem (30°29 ' 05.8 '' S 52°04 ' 09.9 '' W), 21/X/2020, colls. A.F. Huber, K.M. Gomes, F.B. Ribeiro; 1 female (MNRJ 30204), São Jerônimo, Horto Florestal Quitéria, riacho de primeira ordem (30°29 ' 05.8 '' S 52°04 ' 09.9 '' W), 21/X/2020, colls. A.F. Huber, K.M. Gomes, F.B. Ribeiro; 1 female (UFRGS 5339), São Jerônimo (30°29 ' 05.0 '' S 52°04 ' 11.0 '' W), VII/2011, colls. K.M. Gomes, C. Sokolowicz. — Parastacus guapo Huber, Araujo and Ribeiro, 2022: 1 male (MNRJ 30200), Pantano Grande, Horto Sanga das Pedras, zona alagada (30°13 ' 28.4 '' S 52°24 ' 44.1 '' W), 20/X/2020, colls. A.F. Huber; K.M. Gomes, F.B. Ribeiro; 1 female (MNRJ 30201), Pantano Grande, Horto Sanga das Pedras, zona alagada (30°13 ' 28.4 '' S 52°24 ' 44.1 '' W), 20/X/2020, colls. A.F. Huber; K.M. Gomes, F.B. Ribeiro; 1 male, 3 females, 2 juveniles (UFRGS 6932), Pantano Grande, Horto Sanga das Pedras, zona alagada (30°13 ' 28.4 '' S 52°24 ' 44.1 '' W), 20/x/2020, colls. A.F. Huber; K.M. Gomes, F.B. Ribeiro. — Parastacus macanudo Huber, Rockhill, Araujo and Ribeiro, 2020: 1 male (UFRGS 6672), São Leopoldo, Parque Imperatriz Leopoldina (29°45 ' 40.7 '' S 51°07 ' 47.6 '' W), 20/VII/2018, colls. A.F. Huber, F.B. Ribeiro; 1 male (MNRJ 29877), São Leopoldo, Parque Imperatriz Leopoldina (29°45 ' 40.7 '' S 51°07 ' 47.6 '' W), 20/ VII/2018, colls. A.F. Huber, F.B. Ribeiro; 2 males (MNRJ 29877, MNRJ 29878), São Leopoldo, Parque Imperatriz Leopoldina (29°45 ' 40.7 '' S 51°07 ' 47.6 '' W), 20/VII/2018, colls. A.F. Huber, F.B. Ribeiro. — Parastacus promatensis Fontoura and Conter, 2008: 1 male (UFRGS 4153), São Francisco de Paula, riacho Garapiá, CPCN Pró-Mata (PUCRS), 09/VII/2005, coll. L.C.C. Daudt; 1 female (UFRGS 4157), São Francisco de Paula, riacho Garapiá, CPCN Pró-Mata (PUCRS), 15/I/2006, coll. L.C.C. Daudt; 1 male (UFRGS 4159), São Francisco de Paula, riacho Garapiá, CPCN Pró-Mata (PUCRS), 09/VII/2005, coll. L.C.C. Daudt; 1 male and 2 females (UFRGS 5949), São Francisco de Paula, riacho Garapiá, CPCN Pró-Mata (29°29 ' 22.0 '' S 50°13 ' 04.0 '' W), 2014.
Etymology. A combination of the Latin epithets “longus”, which alludes to a long size, and “dactylus”, which alludes to fingers. We suggest the common name “the long-finger crayfish” for this new species.
Diagnosis. Wide front with short triangular rostrum. Rostral apex shaped as inverted “U”, with straight, blunt spine. Suborbital angle 90°, unarmed. Rostral carinae prominent, wide, surpassing rostral basis, extending to proximal third of postorbital carinae. Postorbital carinae, rostral carinae prominent, with similar length. Cervical groove weakly V-shaped. Areola narrow. Telson subrectangular, longer than wide, with small blunt spines on lateral margins. Mandible with caudal molar process bicuspidate and incisor lobe with 10 teeth. S2 pleurae low and moderate with shallow groove parallel to margin. Chelipeds large and subequal, laterally f lattened, with long dactylus surpassing fixed finger. Carpus with dorsomedial surface not divided longitudinally by groove.
Description of the holotype. Rostrum: triangular, wider than long (RL 84.9% of RW), short (11.6% of CL), reaching middle portion of second article of antennular peduncle (Fig. 1A–C). Dorsum straight, apex inverted “U”-shaped, ending in straight blunt spine (Fig. 1A–C). Few plumose setae on lateral margins. Carinae almost straight, prominent, wide, extending back to carapace, surpassing rostral basis, extending to proximal third of postorbital carinae; rostral carinae sides convergent and rostral carinae basis slightly convergent (Fig. 1A–C).
Cephalon: Carapace lacking spines or tubercles. CeL 66.3% of CL. Eyes large (CMW 84.5% of OW); suborbital angle 90°, unarmed (Fig. 1C). Front wide (FW 53.7% of CW). Postorbital carinae and rostral carinae prominent and similar in length (RCL 96.3% of POCL). Lateral cephalic edge with moderate setation (Fig. 1A–C).
Thorax: carapace laterally compressed, deep, narrow (CD 42.4%of CL; CW 35.8% of CL).Cervical groove weakly V-shaped. Branchiocardiac grooves inconspicuous (Fig. 1A). Areola narrow, 3.14× as long as wide (27.7% of CL) (Fig. 1A).
Pleon: lacking spines or tubercles, short, wide (PL 72.9% of CL; PW 98.2% of CW), smooth, covered with small setae on pleural margins(Fig. 1A). Pleural somites with rounded posterior margins. S1 pleurae with large distal lobe not overlapped by S2 pleurae. S2 pleurae low and moderate, with shallow groove parallel to margin (Fig. 1D).
Tailfan: telson more calcified in proximal portion than in distal margin, subrectangular, longer than wide (TeW 80.2% of TeL), with small blunt spines on lateral margins;rounded distal margin with abundant long plumose setae and short simple setae. Dorsal surface with tufts of short setae and inconspicuous dorso-median longitudinal groove (Fig. 1A, E). Uropod protopod bilobed, with rounded and unarmed margins;proximal lobe largest. Exopod lateral margin unarmed, mid-dorsal carinae few prominent, ending in a sharp spine.Transverse suture (diaeresis) straight, with 8 dorsolateral spines (outer) and 8 dorsolateral spines (inner) on right exopod, and 7 dorsolateral spines (outer) and 8 dorsolateral spines (inner) on left exopod. Endopod, mid-dorsal carina weakly projecting, unarmed; lateral margin with 1 sharp spine at level of exopod transverse suture (Fig. 1E).
Epistome: anterolateral section with 4 marginal tubercles on both sides; anterior most tubercle biggest. Posterolateral section with simple setae and with deep lateral grooves converging to basis of anteromedian lobe. Median section with longitudinal groove. Anteromedian lobe irregularly septagonal, 1.04× as long as wide; apex acute,wide, with some small serrated setae, surpassing median part of antepenultimate article of antennal peduncle; apex concave, basis with shallow groove (Fig. 2A).
Thoracic sternites: SLP4 smallest and very close to each other, median keel present and not inflated; SLP5 small and close to each other, median keel present and not inf lated; SLP6 larger than SLP4; SLP5 and SLP8 with concave surface, median keel inf lated; SLP7 largest, with surface concave, median keel inflated, bullar lobes absent; SLP8 small, median keel absent, vertical arms of paired sternopleural bridges close to each other, bullar lobes not visible (Fig. 2B, D).
Antennule: internal ventral border of basal article with sharp spine in middle portion (Fig. 2A).
Antenna: reaching posterior margin of carapace when extended back. Antennal scale widest at distal to mid-length, reaching middle of third antennal article, ASW 36.6% of ASL (Fig.2A,C), lateral margin straight, distal spine well developed. Coxa with weakly prominent carina above nephropore. Basis unarmed (Fig. 2A).
Mandible: cephalic molar process molariform, caudal molar process bicuspidate with 1 cephalodistal cusp and 1 distoproximal cusp. Incisor lobe with 10 teeth; third tooth from anterior margin being largest (Fig. 2E).
Third maxilliped: ischium, ventral surface covered by tufts of composite setae with some sparse long and simple setae (Fig. 2F); dorsal surface with few setiferous punctations on inner margin and dorsal surface and 2 short,serrated setae on proximal portion (Fig. 2G); ‘crista dentata’ bearing 23 teeth on both right and left ischia (Fig. 2F, G). Merus, dorsal surface glabrous in proximal and middle portions, anterior outer margin portion with few long, serrated setae. Merus ventral surface sparsely covered by some long simple setae in median and outer regions (Fig. 2F); exopod longer than ischium, with flagellum surpassing proximal margin of merus and with tufts of long and composite setae in last and first articles (Fig. 2F, G).
First pair of pereiopods (chelipeds): large and subequal, laterally flattened (RPrT 25.3% of RPrL; LPrT 23.9% of LPrL) (Figs. 1A; 2I). Ischium ventral surface with 6 and 4 tubercles in right and left, respectively. Merus: right merus (RML) 60.2% of propodus length (RPrL); left merus (LML) 59.4% of propodus length (LPrL); ventral surface with 2 longitudinal series of tubercles: inner series with 17 tubercles, outer 11, plus 15 mesial tubercles irregularly distributed on right merus; inner series with 11 tubercles, outer 12, plus 14 mesial tubercles irregularly distributed on left merus. Dorsal and midventral spines absent. Carpus with dorsomedial surface not divided longitudinally by groove (Figs. 1A; 2I). Internal dorsolateral margin with row of tubercles, increasing in size distally; inner surface with 20 small mesial tubercles. Carpal spine absent (Fig. 2I). Propodus width (RPrW and LPrW) 46.3% of length in right cheliped and 45.5% in left cheliped. Dorsal surface of palm with irregularly distributed rows of squamous tubercles (Fig. 2H, I). Inner margin without tubercles. Ventral surface bearing 2 rows of squamous tubercles, surpassing the proximal part of fixed finger (Fig. 2H). Dactylus: articulating sub-vertically, right dactylus long (RDL) 69.4% of propodus length (RPrL), left dactylus long (LDL) 71.2% of left propodus (LPrL);dorsal surface with few squamous tubercles more concentrated in proximal portion (Fig. 2H). Cutting edge of fingers visible. Fixed finger with 10 teeth, fifth tooth largest in right cheliped. Dactyli with 12 teeth, third tooth largest in both chelipeds (Fig. 2H, I); right fixed finger with 11 teeth, left fixed finger with 9 teeth; fifth tooth largest. Second pair of pereiopods: dorsal surface of dactylus and propodus with tufts of long and simple setae. Dorsal and ventral surface of carpus with few sparse, simple and long setae in (Fig. 2J).
Gonopores: presence of both genital apertures on coxae of third and fifth pairs of pereiopods. Female gonopores semi-ellipsoidal (maximum diameter 1.35 mm) with well-calcified membrane. Male gonopores rounded, opening onto apical end of small, fixed, calcified and truncated phallic papilla, close to inner border of ventral surface of coxae of fifth pair of pereiopods. Male cuticle partition present (Fig. 2B).
Branchialcount:20+epr+r.Branchialarrangement follows the same described by Hobbs (1991) with epipod of first maxilliped with rudimentary podobranchial filaments.
Measurements: holotype male, CL 31.8 mm and TL 61.1 mm. In the type series, CL ranges from 27.8 to 31.8 mm (mean = 29.8 mm). FW/CW: 0.43 ± 0.12 (min: 0.29; max: 0.53). RL/RW: 0.82 ± 0.06 (min: 0.76; max: 0.87). CMW/OW: 0.75 ± 0.08 (min: 0.70; max: 0.85). Postorbital carina longer than the rostral carina in all specimens analyzed. CW/PW: 1.05 ± 0.05 (min: 1.02; max: 1.09). AreW/RW: 0.71 ± 0.11 (min: 0.64; max: 0.79) (Tab. 1).
Color of living specimens. Data not available.
Variations in type-series. All paratypes exhibit both masculine and feminine gonopores in the same individual. Male paratypes also exhibit semi-ellipsoidal female gonopores (average maximum diameter 1.36 mm)covered by a calcified membrane. Male gonopores are very similar in all male paratypes. The number of teeth in the ‘crista dentata’ ranges from 20 to 25 in the left ischium and from 19 to 26 in the right ischium of the third maxilliped in the paratypes.
Distribution. Parastacus longidactylus sp. n. appears to have a limited distribution, being registered so far only from the municipality of Amaral Ferrador, state of Rio Grande do Sul, southern Brazil (Fig. 4).
Habitat and Ecology. Parastacus longidactylus sp. n. was collected in the “Ladrão” creek near to the junction with the Camaquã River, in the Camaquã hydrographic basin, in the state of Rio Grande do Sul (Fig. 4). It is also part of the physiographic region of Serra do Sudeste region, bordering the Encosta do Sudeste region (IBGE 2004a; 2004b; UFRGS-IB-Centro de Ecologia, 2016).
Vegetation. The type locality of this species is in the Pampa biome. Types of vegetation in the area are Submontane Semideciduous Seasonal Forest, and Alluvial Semideciduous Seasonal Forest, commonly called gallery forest, or riparian forest, in the lower part, flat and prone to flooding in the rainy season (Beier et al., 2018; Rambo, 2015; SEMA, 2023).
Soil. The soil is classified as Dystrophic Red-Yellow Argisols (Santos et al., 2011). This soil usually occurs in areas of undulating relief, yet they may also be present in less steep areas. It has a characteristic yellowish-red color, which is related to higher levels of hematite and goethite iron oxides(Santos et al.,2023). Moreover, they are considered deep soils, with high drainage capacity, low fertility, nutrient limitations, strong acidity, and high susceptibility to degradation and erosion (Santos et al., 2011; 2023; Streck et al., 2002; 2008).
Burrowing behavior and burrow structure. Data not available.
Conservation status. Data Deficient. The extent of occurrence (EOO) was estimated as comprising approximately 6,968 km ² (B1) (Fig. 4). Considering the data concerning the Camaquã River Hydrographic Basin, this species can only be classified under subitem b(iii): continuing decline observed in quality of habitat (IUCN, 2019).Taking this into account, we classified this species as DATA DEFICIENT (DD).
description: Published as part of Huber, Augusto Frederico, Araujo, Paula Beatriz de & Ribeiro, Felipe Bezerra, 2024, A new freshwater crayfish species of Parastacus Huxley, 1879 (Malacostraca: Decapoda: Parastacidae) from southern Brazil, pp. 1-17 in Nauplius (e 20230496) (e 20230496) 32 on pages 3-10, DOI: 10.1590/2358-2936e20230496, http://zenodo.org/record/10716860