Parastacus tuerkayi, Ribeiro & Huber & Schubart and Paula Beatriz Araujo, 2017

Parastacus tuerkayi View in CoL sp. nov. Ribeiro, Huber and Araujo

( Figs. 1–5 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 )

Type material. Holotype: male, Brazil, Santa Catarina, Penha, Beto Carreiro World (26°48’10”S 48°37’02”W), 04/IX/2013, leg. K.M. Gomes and F.B. Ribeiro ( MZUSP 34940 View Materials ) GoogleMaps . Paratypes: 1 ovigerous female, Brazil, Santa Catarina, Penha, Beto Carreiro World (26°48’11”S 48°37’01”W), I/2001, leg. H. Boos Jr. ( UFRGS 6376 View Materials ) GoogleMaps ; 1 male, Brazil, Santa Catarina, Penha, Beto Carreiro World, 2001, leg. K. Schaat ( UFRGS 3167 View Materials ) ; 1 male, same data as holotype ( UFRGS 6438 View Materials ) GoogleMaps .

Comparative material analyzed. Chile: P. pugnax – 1 male and 2 females, La Florida, Concepción , 19/I/1977 ( UFRGS 2407 View Materials ) ; 5 females, Rengo (cordillera), II/1984, leg. A.F. Neto ( UFRGS 726 View Materials ) ; 2 males and 3 females, Laguna San Pedro, Concepción, 18/VII/1970. Paratascus nicoleti – 1 male, Mehuim (next to Valdivia ), VIII/1997, leg. niños del Pueblo ( UFRGS 2405 View Materials ) . Brazil, Rio Grande do Sul: P.defossus – 1 male, Costa do Cerro, Lami, Porto Alegre , 19/ VII/2005, leg. L.C.E. Daut and J.F. Amato ; 1 female, Sítio do Mato, Zona Sul, Porto Alegre (30°4’10.27”S 51°5’10.46”W), 22/III/2014, leg. K.M. Gomes and F.B. Ribeiro. Parastacus caeruleodactylus Ribeiro and Araujo in Ribeiro et al., 2016 – 1 female, Morrinhos do Sul (29°17’13.7”S; 49°54’53.42”W), 12/XII/2013, leg. F.B. Ribeiro and K.M. Gomes ( UFRGS 5931 View Materials ) GoogleMaps .

Etymology. Named to honor Dr. Michael Türkay from Seckenberg Museum, Frankfurt am Main, Germany, who passed away in 2015. He dedicated several years of his life to the research of freshwater crustaceans, especially freshwater crabs from the Neotropical region, describing several new species and providing invaluable contributions to the taxonomy of freshwater decapods.

Diagnosis. Narrow front with short triangular rostrum. Rostral apex shaped as inverted “U”, with an upward blunt spine. Suborbital angle>90°. Postorbital carinae weakly prominent. Cervical groove V-shaped. Areola narrow and barely discernible.Telson subrectangular with sharp spines on lateral margins. Mandible with caudal molar process bicuspidate with one cephalodistal cusp and one small distoproximal cusp. S2 pleurae high and long with deep groove parallel to margin. Internal ventral border of basal article of antennule without sharp spine in males.

Description of the holotype. Rostrum: triangular, longer than wide (RW 83.4% of RL), short (10.2% of CL), reaching proximal portion of the second article of the antennular peduncle ( Fig. 1A–C View Figure 1 ). Dorsum straight, apex inverted “U”-shaped, ending in upward blunt spine ( Fig. 1B, C View Figure 1 ). Few plumose setae on lateral margins. Rostral sides slightly convergent and rostral basis parallel. Carinae almost straight, prominent and narrow, extending back to carapace, slightly surpassing rostral basis ( Fig. 1B, C View Figure 1 ).

Cephalon: carapace lacking spines or tubercles. CeL 67.4% of CL. Eyes small (CMW 51.6% of OW); suborbital angle>90°, unarmed ( Fig.3C View Figure 3 ). Front narrow (FW 41.2% of CW). Postorbital carinae longer than rostral carinae (RCL 51% of POCL) and weakly prominent. Lateral cephalic edge with moderate setation ( Fig. 1A–C View Figure 1 ).

Thorax: carapace laterally compressed, deep and narrow (CD 50.5% of CL; CW 45.4% of CL). Cervical groove V-shaped. Branchiocardiac grooves inconspicuous ( Fig. 1A View Figure 1 ). Areola narrow, 2.8x as long as wide (25.9% of CL) ( Fig. 1A View Figure 1 ).

Abdomen: lacking spines or tubercles, long and narrow (AL 78.2% of CL; AW 83.6% of CW), smooth, covered with small setae on pleural margins ( Fig. 1A View Figure 1 ). Pleural somites with rounded posterior margins. S1 pleurae with a large distal lobe not overlapped by S2 pleurae. S2 pleurae high and short with deep groove parallel to margin ( Fig. 1D View Figure 1 ).

Tailfan: telson uniformly calcified, subrectangular, longer than wide (TeW 76.6% of TeL),with sharp 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 dorsomedian longitudinal groove ( Fig. 1E View Figure 1 ). Uropod protopod bilobed, with rounded and unarmed margins; proximal lobe largest. Exopod lateral margin bears a small and sharp spine, mid-dorsal carina weakly prominent, ending in a very sharp spine. Transverse suture (diaeresis) straight, with ten dorsolateral spines (outer) and nine dorsolateral spines (inner) on right exopod and ten dorsolateral spines (outer) and eight dorsolateral spines(inner) on the left exopod. Endopod with mid-dorsal carina weakly prominent, ending in a very sharp spine; lateral margin with one sharp spine at level of exopod transverse suture ( Fig. 1E View Figure 1 ).

Epistome: anterolateral section with conical projection. Posterolateral section smooth and with deep lateral grooves converging to the basis of the anteromedian lobe and reduced median circular concavity. Anteromedian lobe pentagonal, 1.2x longer than wide, apex acute and straight with some serrated setae, reaching median part of antepenultimate article of antennal peduncle; dorsal surface straight, and basis with a shallow groove ( Fig. 2A View Figure 2 ).

Thoracic sternites: SLP4 smallest and close to each other, median keel present and not inflated; SLP5 small and very close to each other, median keel present and not inflated; SLP6 larger than SLP4, SLP5 and SLP8 and with a slightly concave surface, median keel inflated; SLP7 largest and with surface slightly concave, median keel inflated, bullar lobes absent; SLP8 small and slightly concave, median keel absent, vertical arms of paired sternopleural bridges close to each other, bullar lobes separated and clearly visible ( Fig. 2B, C View Figure 2 ).

Antennule: internal ventral border of basal article without sharp spine ( Fig. 2A View Figure 2 ).

Antenna: when extended back reaching S1. Antennal scale widest at midlength, reaching midlength of third antennal article, ASW 44.8% of ASL ( Fig. 2A, D View Figure 2 ), lateral margin straight, spine strong and distal margin straight. Coxa with prominent carina above nephropore and blunt spine laterally displaced. Basis unarmed ( Fig. 2A View Figure 2 ).

Mandible: cephalic molar process molariform, caudal molar process bicuspidate with one cephalodistal cusp and one distoproximal cusp. Incisive lobe with nine teeth.Third tooth from the anterior margin largest ( Fig. 2E View Figure 2 ).

Third maxilliped: ischium bearing few setiferous punctuations, but with some long smooth simple setae on outer margin ( Fig. 2F View Figure 2 ); dorsal surface without setae ( Fig. 2G View Figure 2 ). Merus ventral surface sparsely covered by long smooth simple setae in the median-proximal region ( Fig. 2F View Figure 2 ). Crista dentata bearing 29 and 26 teeth on right and left ischium respectively. Merus, dorsal surface sparsely covered with simple setae. Exopod longer than ischium, with flagellum reaching proximal margin of merus ( Fig. 2F, G View Figure 2 ).

First pair of pereiopods (chelipeds): large and subequal, laterally flattened (RPrT 25.6% of RPrL; LPrT 25.1% of LPrL) ( Fig.1A View Figure 1 ). Ischium ventral surface with 14 tubercles. Merus: right merus (RML) 53.5% of propodus length (RPrL); left merus (LML) 50.9% of propodus length (LPrL); ventral surface with two longitudinal series of tubercles: inner series with 17 tubercles, outer 16 and mesial 26, arranged irregularly on right merus; inner series bearing 17 tubercles, outer 16 and mesial 30, arranged irregularly on left merus. Dorsal and midventral spines present. Carpus with dorsomedial surface divided longitudinally by shallow groove ( Fig. 1A View Figure 1 ; Fig. 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% of length in right cheliped and 43.8% in left cheliped. Dorsal surface of palm with three rows of verrucous tubercles ( Fig. 2H, I View Figure 2 ). Inner margin without tubercles. Ventral surface bearing two rows of squamose tubercles, trespassing the beginning of the fixed finger ( Fig. 2H View Figure 2 ). Dactylus: moving subvertically, right dactylus (RDL) 62.8% of propodus length (RPrL), left dactylus (LDL) 60.2% of left propodus (LPrL); dorsal surface with squamose tubercles in the proximal portion ( Fig. 4I View Figure 4 ). Cutting edge of fingers visible. Fixed finger with eleven teeth, third and fourth teeth largest. Dactylus with 14 teeth, third tooth largest ( Fig. 2H, I View Figure 2 ).

Second pair of pereiopods: ventral and dorsal surface of carpus, propodus and dactylus with sparse cover of simple long setae ( 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 1.56 mm) with well-calcified membrane. Male gonopores rounded, opening onto apical end of a 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. 4B View Figure 4 ).

Branchial count: 20+ epr + r. Branchial arrangement as described by Huxley (1879) and Hobbs (1991), with the epipod of the first maxilliped with rudimentary podobranchial filaments.

Description of the female paratype: Differs from the holotype in the following morphological characters: rostrum less sharp at apex, RW 81.9% of RL ( Fig. 3A View Figure 3 ). Post orbital carinae shorter (RCL 65.8% of POCL) ( Fig. 3A View Figure 3 ). Areola 2.4x as long as wide, constituting 27% of CL ( Fig. 3A View Figure 3 ). S2 pleurae high and long ( Fig. 3C View Figure 3 ). Transverse suture (diaresis) with seven dorsolateral spines (outer) and five dorsolateral spines (inner) on right exopod and five dorsolateral spines (outer) and six dorsolateral spines (inner) on left exopod. Anteromedian lobe of epistome 1.1x longer than wide. Internal ventral border of basal article of antenulle with a sharp spine ( Fig. 3B View Figure 3 ). Antennal flagellum reaching S2. Crista dentata bearing 24 and 28 teeth on the right and left ischium, respectively. Chelipeds shorter than in male. Merus of chelipeds with up to two spines in the midventral region. Carpal spine present in both chelipeds, right cheliped bears two spines ( Fig. 3A View Figure 3 ). Female gonopores ellipsoidal (maximum diameter 1.21 mm) covered by a thin and non-calcified membrane.

Measurements. Holotype male, CL 33.52 mm and TL 66.81 mm. Paratype female, CL 26.45 mm and TL 54.93 mm. In type series, CL ranging from 18.72 to 33.52 mm (26.83 ± 6.16 mm). FW/CW: 0.4 ± 0.02 (min: 0.38; max: 0.43). RL/RW: 1.14 ± 0.05 (min: 1.08; max: 1.19). MCW/OW: 0.6 ± 0.1 (min: 0.51; max: 0.72). Postorbital carina longer than rostral carina in all specimens analyzed. CW/AW: 1.16 ± 0.09 (min: 1.08; max: 1.29). AreW/RW: 0.93 ± 0.05 (min: 0.89; max: 1.01).

Color of living specimens. Rostrum reddish brown. Cephalothorax anterior and lateral regions greenish brown to reddish brown. First pair of pereiopods reddish brown with dark reddish brown fingers. Pereiopod pairs 2–5 light brown to reddish brown. Dorsal abdomen light brown to dark reddish brown. Tailfan light brown to reddish brown ( Fig. 4E–G View Figure 4 ).

Remarks. All paratypes present both masculine and feminine gonopores in the same individual. Male paratypes also present female gonopores semi-ellipsoidal (average maximum diameter 1.18 mm) covered by a calcified membrane. Male gonopores are very similar in male and female paratypes.

Parastacus tuerkayi sp. nov. is morphologically similar to P. caeruleodactylus , P. defossus , P. nicoleti and P. pugnax in having the post orbital carinae weakly prominent, the areola narrow and barely discernible and the abdomen narrower than the cephalothorax. Parastacus tuerkayi sp. nov. is also similar to P. nicoleti in having the dorsal surface of dactylus with tubercles in the proximal portion. Parastacus tuerkayi sp. nov. differs from all other Parastacus species in having three well defined lines of verrucous tubercles in the dorsomesial margin of the palm of chelipeds and the internal ventral border of basal article of antennules without a sharp spine.

Phylogenetic position. The phylogenetic relationships based on 512bp of the 16S rRNA gene provide clear evidence for the separation of P. tuerkayi sp. nov. from other species of the genus Parastacus with high values of posterior probability ( Fig. 6 View Figure 6 ). Genetic distances estimated between P. tuerkayi sp. nov. and other Parastacus species range from 6.2% ( P. defossus ) to 13.1% ( P. nicoleti ) for the16S gene ( Tab. 2). Intraspecific genetic distance was not more than 0.03%.

Habitat and ecology. Parastacus tuerkayi sp. nov. was collected in a small fragment (approximately 500 m ²) of a swamp forest located inside the theme park “Beto Carreiro World” in the coastal region of the state of Santa Catarina. This physiographic region belongs to the Atlantic Forest Biome and the vegetation is composed predominantly by Myrtaceae , Poaceae , Piperaceae (genus Piper ) and some pterydophyta of the family Blechnaceae (genus Blechnum ) (P. Brack pers. comm.). Soil is mainly composed by clay and temporarily flooded with a large amount of organic matter derived from leaf decomposition (F. B. Ribeiro pers. obs.). Found in a flooded area, burrows of P. tuerkayi sp. nov. can be identified as type 2 according to Horwitz and Richardson’s (1986) classification.

Based on Hobbs’ (1942) classification, P.tuerkayi sp. nov. can be considered a primary burrower, in which the individuals spend almost their entire life underground and build deep and relatively complex burrows. Burrows can reach a depth of up to one meter, but with few branches and with long (up to 15 cm) and large (up to 12 cm) chimneys.

This burrow structure is very similar to the one of P. caeruleodactylus that is also found in swamp forests in the state of Rio Grande do Sul, near the foothills of the Serra Geral mountains and in the coastal region, and P. pugnax , found in small valleys or depressions between mountains or topographic depressions, usually associated with perennial forests in Chile ( Rudolph, 2013; Ribeiro et al., 2016). Parastacus tuerkayi sp. nov. is ecologically similar to P. pugnax , P. caeruleodactylus , P. defossus and P. nicoleti . These species share some morphological adaptations to the burrowing life style, as the narrow areola, which is indicative of one extended branchial chamber; carapace, abdomen and appendages covered by setae in some regions, reduced eyes and the abdomen narrower than the cephalothorax ( Horwitz and Richardson 1986; Richardson, 2007).

Regarding reproductive biology, the ovigerous female (paratype UFRGS 6376) bears approximately 20 eggs (average maximum diameter 2.4 mm) attached to its pleopods. The low fecundity is also a characteristic shared by strong burrowing species ( Richardson, 2007).

Distribution. Parastacus tuerkayi sp. nov. appears to have an extremely limited distribution, being found only in the municipality of Penha, state of Santa Catarina, southern Brazil ( Fig. 5 View Figure 5 ).

Conservation status. The EOO was estimated as comprising approximately 647.674 km ² based on the Otto Bacia shape level 4 ( ANA, 2006), indicating that this species can be included in the Endangered – EN category, in which the EOO is less than 5,000 km ² (IUCN, 2012). The species is categorized as EN under subitem “a”: for an EOO, which is severely fragmented; and subitem “b” (iii): continuing decline in quality of habitat. Both subitems are appropriate, due to the threats existing in the species occurrence area. Urbanization may be the main cause of habitat loss and fragmentation, since P. tuerkayi sp. nov. was found inside a theme park in a small fragment of a swamp forest (approximately 500 m ²). In addition, this region of the state of Santa Catarina is a target of intense urban real estate speculation and tourism. We therefore suggest that the conservation status of this species be classified as ENDANGERED B1ab(iii).