Parastacus longidactylus, Huber & Araujo & Ribeiro, 2024

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, Nauplius (e 20230496) 32, pp. 1-17 : 3-10

publication ID	https://doi.org/ 10.1590/2358-2936e20230496
publication LSID	lsid:zoobank.org:pub:D73CB1C7-AB83-4D4B-B654-AAB1A8E67888
DOI	https://doi.org/10.5281/zenodo.10926999
persistent identifier	https://treatment.plazi.org/id/ED31490A-FFA1-FFCB-4D89-7E9ABD8BFBCB
treatment provided by	Felipe
scientific name	Parastacus longidactylus
status	sp. nov.

Treatment

Parastacus longidactylus sp. nov.

( Figs. 1–4 View Figure 1 View Figure 2 View Figure 3 View Figure 4 )

Zoobank: urn:lsid:zoobank.org:act:EED4209E-8A29-4818-8137-98CBAC4805F7

Type material. Holotype: adult male ( MZUSP 45071 View Materials ), 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. GoogleMaps Paratypes: 1 female ( MZUSP 45072 View Materials ), same data as holotype GoogleMaps ; 1 male ( MZUSP 45073 View Materials ), 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 View Materials ), Mariana Pimentel , 09/X/1986, coll. N.F. Fontoura; 1 female ( UFRGS 5757 View Materials ), Porto Alegre, morro Santana , 06/IV/2013,coll. K. M. Gomes; 1 male ( UFRGS 5868 View Materials ), sítio do Mato, zona sul, Porto Alegre (30°07 ' 04 '' S 51°08 ' 47 '' W) GoogleMaps , 22/III/2014, coll. M. Pasolius; 2 juveniles and 3 males ( UFRGS 5947 View Materials ), Porto Alegre, Parque Natural do Morro do Osso (30°07 ' 07.7 '' S 51°14 ' 15.1 '' W) GoogleMaps , 22/III/2014, coll. K.M. Gomes, F.B. Ribeiro, M.F. Pasolius; 2 juveniles and 3 males ( UFRGS 5947 View Materials ), Porto Alegre, Parque Natural do Morro do Osso (30°07 ' 07.7 '' S 51°14 ' 15.1 '' W) GoogleMaps , 22/III/2014, coll. K.M. Gomes, F.B. Ribeiro, M.F. Pasolius; 1 male ( UFRGS 6025 View Materials ), rua Dona Francisca, Lomba do Pinheiro, Porto Alegre (30°08 ' 05.0 '' S 51°06 ' 11.9 '' W) GoogleMaps , 26/IX/2014, coll. K.M. Gomes, D.C. Kenne. — Parastacus buckupi Huber, Ribeiro and Araujo, 2018: 1 male ( UFRGS 3581 View Materials ), Maquiné, arroio Carvão , 25/X/2001, coll. F.S. Vilella; 1 female ( UFRGS 3895 View Materials ), Maquiné, arroio Carvão , 25/X/2001, coll. F.S. Vilella. — Parastacus gomesae Huber, Araujo and Ribeiro, 2022: 1 male ( MNRJ 30203 View Materials ), São Jerônimo, Horto Florestal Quitéria , riacho de primeira ordem (30°29 ' 05.8 '' S 52°04 ' 09.9 '' W) GoogleMaps , 21/X/2020, colls. A.F. Huber, K.M. Gomes, F.B. Ribeiro; 1 female ( MNRJ 30204 View Materials ), São Jerônimo, Horto Florestal Quitéria , riacho de primeira ordem (30°29 ' 05.8 '' S 52°04 ' 09.9 '' W) GoogleMaps , 21/X/2020, colls. A.F. Huber, K.M. Gomes, F.B. Ribeiro; 1 female ( UFRGS 5339 View Materials ), São Jerônimo (30°29 ' 05.0 '' S 52°04 ' 11.0 '' W) GoogleMaps , VII/2011, colls. K.M. Gomes, C. Sokolowicz. — Parastacus guapo Huber, Araujo and Ribeiro, 2022: 1 male ( MNRJ 30200 View Materials ), Pantano Grande, Horto Sanga das Pedras , zona alagada (30°13 ' 28.4 '' S 52°24 ' 44.1 '' W) GoogleMaps , 20/X/2020, colls. A.F. Huber; K.M. Gomes, F.B. Ribeiro; 1 female ( MNRJ 30201 View Materials ), Pantano Grande, Horto Sanga das Pedras , zona alagada (30°13 ' 28.4 '' S 52°24 ' 44.1 '' W) GoogleMaps , 20/X/2020, colls. A.F. Huber; K.M. Gomes, F.B. Ribeiro; 1 male, 3 females, 2 juveniles ( UFRGS 6932 View Materials ), Pantano Grande, Horto Sanga das Pedras , zona alagada (30°13 ' 28.4 '' S 52°24 ' 44.1 '' W) GoogleMaps , 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 View Materials ), São Leopoldo, Parque Imperatriz Leopoldina (29°45 ' 40.7 '' S 51°07 ' 47.6 '' W) GoogleMaps , 20/VII/2018, colls. A.F. Huber, F.B. Ribeiro; 1 male ( MNRJ 29877 View Materials ), São Leopoldo, Parque Imperatriz Leopoldina (29°45 ' 40.7 '' S 51°07 ' 47.6 '' W) GoogleMaps , 20/ VII/2018, colls. A.F. Huber, F.B. Ribeiro; 2 males ( MNRJ 29877 View Materials , MNRJ 29878 View Materials ), São Leopoldo, Parque Imperatriz Leopoldina (29°45 ' 40.7 '' S 51°07 ' 47.6 '' W) GoogleMaps , 20/VII/2018, colls. A.F. Huber, F.B. Ribeiro. — Parastacus promatensis Fontoura and Conter, 2008: 1 male ( UFRGS 4153 View Materials ), São Francisco de Paula, riacho Garapiá, CPCN Pró-Mata ( PUCRS) , 09/VII/2005, coll. L.C.C. Daudt; 1 female ( UFRGS 4157 View Materials ), São Francisco de Paula, riacho Garapiá, CPCN Pró-Mata ( PUCRS) , 15/I/2006, coll. L.C.C. Daudt; 1 male ( UFRGS 4159 View Materials ), 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 View Materials ), São Francisco de Paula, riacho Garapiá, CPCN Pró-Mata (29°29 ' 22.0 '' S 50°13 ' 04.0 '' W) GoogleMaps , 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 View Figure 1 ). Dorsum straight, apex inverted “U”-shaped, ending in straight blunt spine ( Fig. 1A–C View Figure 1 ). 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 View Figure 1 ).

Cephalon: Carapace lacking spines or tubercles. CeL 66.3% of CL. Eyes large ( CMW 84.5% of OW); suborbital angle 90°, unarmed ( Fig. 1C View Figure 1 ). 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 View Figure 1 ).

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 View Figure 1 ). Areola narrow, 3.14× as long as wide (27.7% of CL) ( Fig. 1A View Figure 1 ).

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 View Figure 1 ). 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 View Figure 1 ).

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 View Figure 1 ). 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 View Figure 1 ).

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 View Figure 2 ).

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 View Figure 2 ).

Antennule: internal ventral border of basal article with sharp spine in middle portion ( Fig. 2A View Figure 2 ).

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 View Figure 2 ), lateral margin straight, distal spine well developed. Coxa with weakly prominent carina above nephropore. Basis unarmed ( Fig. 2A View Figure 2 ).

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 View Figure 2 ).

Third maxilliped: ischium, ventral surface covered by tufts of composite setae with some sparse long and simple setae ( Fig. 2F View Figure 2 ); dorsal surface with few setiferous punctations on inner margin and dorsal surface and 2 short,serrated setae on proximal portion ( Fig. 2G View Figure 2 ); ‘crista dentata’ bearing 23 teeth on both right and left ischia ( Fig. 2F, G View Figure 2 ). 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 View Figure 2 ); 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 View Figure 2 ).

First pair of pereiopods (chelipeds): large and subequal, laterally flattened (RPrT 25.3% of RPrL; LPrT 23.9% of LPrL) ( Figs. 1A View Figure 1 ; 2I View Figure 2 ). 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 View Figure 1 ; 2I View Figure 2 ). Internal dorsolateral margin with row of tubercles, increasing in size distally; inner surface with 20 small mesial tubercles. Carpal spine absent ( Fig. 2I View Figure 2 ). 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 View Figure 2 ). Inner margin without tubercles. Ventral surface bearing 2 rows of squamous tubercles, surpassing the proximal part of fixed finger ( Fig. 2H View Figure 2 ). 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 View Figure 2 ). 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 View Figure 2 ); 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 View Figure 2 ).

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 View Figure 2 ).

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 View Table 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 View Figure 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 View Figure 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 View Figure 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).