Parastacus rudolphi, Ribeiro & Araujo, 2024

Ribeiro, Felipe Bezerra & Araujo, Paula Beatriz, 2024, Taxonomic review of the genus Parastacus Huxley, 1879 (Decapoda: Astacidea: Parastacidae) with description of five new species, Zootaxa 5455 (1), pp. 1-84 : 73-80

Parastacus rudolphi sp. nov.

( Figs. 46–49 , Table 5)

Holotype. male, Brazil, Rio Grande do Sul, Osório, Morro da Borússia , 05/XI/2013, coll. K. M. Gomes ( MZUSP 45371 );

Paratypes. Brazil, Rio Grande do Sul —­ 1–5: two males, same data as holotype ( UFRGS 6441 ) .

Etymology. Named in honor of Professor Eric Rudolph from Universidad de Los Lagos, Osorno, Chile. He is a very important astacologist in Chile and dedicated several years of his life to the study of freshwater crayfish biology and taxonomy. We also suggest the common name “Borússia Hill crayfish” for this species.

Diagnosis. Narrow front with rostrum wider than long with an apex shaped as inverted “V’ ending in a straight blunt spine, rostral carinae angled. Carapace laterally compressed, deep and narrow. Telson subtriangular with very small lateral spines.

Description.

Rostrum: triangular, wider than long (RL 78.5% of RW), long (11.7% of CL), reaching the proximal portion of the third antennular peduncle ( Fig. 46A–C ). Dorsum straight, apex inverted “V”-shaped, ending in a straight spine ( Fig. 46B, C ). Few plumose setae on lateral margins. Rostral carinae angled, prominent and narrow, extending back to carapace, slightly surpassing rostral basis; rostral carinae sides slightly convergent and rostral carinae basis slightly divergent ( Fig. 46B, C ).

Cephalon: CeL 64.1% of CL. Eyes large (CMW 72.8% of OW); suborbital angle 90°, unarmed ( Fig. 46C ). Front narrow (FW 48.6% of CW). Postorbital carinae longer than rostral carinae (RCL 98.5% of POCL) and weakly prominent. Lateral cephalic edge with sparse setation ( Fig. 46A–C ).

Thorax: carapace laterally compressed, deep and narrow (CD 53.8% of CL; CW 36.5% of CL). Cervical groove U-shaped. Branchiocardiac grooves inconspicuous ( Fig. 42A ). Areola narrow, 2.5x as long as wide (25.04% of CL) ( Fig.46A ).

Pleon: long and narrow (PL 68.3% of CL; PW 97.1% of CW), smooth, not covered by setae on pleural margins ( Fig. 46A ). Pleural somites with rounded posterior margins. S2 pleurae low and short with shallow groove parallel to margin ( Fig. 46D, E, F ).

Tailfan: telson uniformly calcified, subtriangular, longer than wide (TeW 79.9% of TeL), with very small 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. 46E ). Uropod protopod bilobed, with rounded and unarmed margins; proximal lobe largest. Exopod lateral with a very small spine, mid-dorsal carina few prominent, ending in a sharp spine. Transverse suture (diaeresis) straight, with five dorsolateral spines (outer) and four dorsolateral spines (inner) on right exopod and six dorsolateral spines (outer) and five dorsolateral spine (inner) on the left exopod. Endopod, mid-dorsal carina few prominent, ending in a very small spine; lateral margin with one sharp spine at level of exopod transverse suture ( Fig. 46E ).

Epistome: anterolateral section with a blunt conical projection. Posterolateral section smooth and with deep lateral grooves converging to the basis of the anteromedian lobe, and with small median concavity. Anteromedian lobe pentagonal, 1.2x longer than wide, apex acute with serrated setae, surpassing median part of antepenultimate article of antennal peduncle; dorsal surface straight, and basis with a shallow groove ( Fig. 47A ).

Thoracic sternites: SLP4 and SLP5 subequal in size, close to each other, median keel present and not inflated; SLP6 larger than SLP4 and SLP5 and close to each other, median keel inflated; SLP7 largest and with surface slightly concave, median keel inflated, bullar lobes absent; SLP8 straight, median keel absent, vertical arms of paired sternopleural bridges close to each other, bullar not visible ( Fig. 47B, C ).

Antennule: internal ventral border of basal article with a blunt spine ( Fig. 47A ).

Antenna: when extended back reaching S3. Antennal scale widest at midlength, reaching the end of third antennal article, ASW 39.75% of ASL ( Fig. 47A, D ), lateral margin straight, spine strong and distal margin straight. Coxa with prominent carina and one blunt above the nephropore. Basis unarmed ( Fig. 47A ).

Mandible: cephalic molar process molariform, caudal molar process bicuspidate with one cephalodistal cusp and one small distoproximal cusp. Incisor lobe with ten teeth. The third tooth from the anterior margin is the largest ( Fig. 47E ).

Third maxilliped: ischium, ventral surface partially covered by tufts of short and simple setae ( Fig. 47F ); dorsal surface glabrous ( Fig. 47G ). Crista dentata bearing 25 and 26 teeth in right and left ischium respectively. Merus ventral surface covered by tufts of long and simple setae in the inner margin ( Fig. 47F, G ).

First pair of pereiopods (chelipeds): large and subequal, laterally flattened (RPrT 25.8% of RPrL; LPrT 25.8% of LPrL) ( Fig. 46A ). Ischium ventral surface with 14 tubercles. Merus: right merus (RML) 62.38% of propodus length (RPrL); left merus (LML) 60.1% of propodus length (LPrL); ventral surface with two longitudinal series of tubercles: inner series with 13 tubercles, outer 12 and mesial 13, arranged irregularly on right merus; inner series bearing 15 tubercles, outer 12 and mesial 13, arranged irregularly on left merus. Dorsal and midventral spines present. Carpus not divided by a shallow transversal groove ( Fig. 46A ; Fig. 47I ). Internal dorsolateral margin with row of tubercles, increasing in size distally; inner surface with few small mesial tubercles. Carpal spine present ( Fig. 45I ). Propodus width (RPrW and LPrW) 20.1% of length in right cheliped and 42.2% in left cheliped. Dorsal surface of palm with two lines of verrucous tubercles ( Fig. 47H, I ). Inner margin without tubercles. Ventral surface bearing two rows of squamose tubercles, reaching the beginning of the fixed finger ( Fig. 47H ), right dactylus (RDL) 59% of propodus length (RPrL), left dactylus (LDL) 66.9% of left propodus (LPrL); dorsal surface with rows of setiferous punctuations ( Fig. 45I ). Cutting edge of fingers visible. Fixed finger with five teeth, third tooth is slightly larger. Dactylus with six teeth, third tooth largest ( Fig. 47H, I ).

Second pair of pereiopods: ventral and dorsal surface of carpus, propodus and dorsal surface of dactylus with sparse covering of simple long setae ( Fig. 45J ).

Gonopores: Presence of both genital apertures on coxae of third and fifth pairs of pereiopods. Female gonopores semi-ellipsoidal (maximum diameter 1.26 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. 47B ).

Remarks. This species resembles P. pilimanus in the shape of chelipeds and rostrum. It can be distinguished from all congeneric species by the very small lateral spines on the telson.

Color of living species. Data not available.

Habitat and Ecology. Stream and wetlands associated with low order stream (1-5 order) (46A). Parastacus rudolphi sp. nov. also can be found under litter and entrances of tree roots or simple burrows in the banks, up to 40 cm deep ( Fig. 46B ). The accumulated sediment within and at the margin is also inhabited by adult individuals. Burrow with chimney was not observed during sampling (K.M. Gomes, personal communication). Species burrows can be identified as type 1 a and b, in wetlands of type 2 (Horwitz and Richardson, 1986). Parastacus rudolphi sp. nov. is considered a secondary burrower according to Hobbs (1942) classification.

Distribution. Brazil: state of Rio Grande do Sul ( Fig. 49 ).

An updated key for native South American crayfish genera (modified from Rogers et al. 2020)

1 Cheliped dactyl moving subhorizontally or obliquely, male genitalia articulated, slender, tubular phallic papilla, or complex uncalcified papilla.................................................................................... 2

1’ Cheliped dactyl moving subvertically, male genitalia, a fixed and slightly elevated ventromesial ridge bearing a small noncalcified papilla............................................................... Parastacus Huxley, 1879 (This genus is distributed in the central portion of Chile, north of Argentina, Uruguay and southern Brazil, in the states of Rio Grande do Sul and Santa Catarina).

2(1) Post orbital carinae well developed.................................................... Samastacus Riek, 1971 (This genus is monotypic and can be found in northern Patagonia between the provinces of Río Negro and Neuquén, in Argentina, and widely distributed in the central portion of Chile).

2’ Post orbital carinae obsolete......................................................... Virilastacus Hobbs, 1991 (This genus is endemic to Chile and it has four species)

An updated key for Parastacus (modified from Huber et al. 2024)

1 Telson with lateral spines, maxilliped III exopod flagellum reaching ischium proximal margin........................ 2

1’ Telson without lateral spines, maxilliped III exopod flagellum surpassing ischium proximal margin............................................................................................ Parastacus nicoleti ( Philippi, 1882) (This species is endemic to Chile and perhaps constitutes a species complex)).

2(1) Rostrum trapezoid................................................................. Parastacus bah sp. nov. (This species has an extremely limited distribution, being found only in the municipality of Dom Feliciano, state of Rio Grande do Sul, Brazil)

2’ Rostrum triangular or spatulated......................................................................... 3

3(2’) Postorbital carina proximal edge ending in a strong spine; uropod protopod proximal lobe bearing a spine; areola delimited by carinae............................................................................................. 4

3’ Postorbital carina proximal edge not ending in spine; uropod protopod lobe lacking spine; areola not delimited by carinae.. 5

4(3) Cheliped merus, carpus, and propodus medially with tufts of long setae; maxilliped III ischium ventral margin with longitudinal spine row............................................................... Parastacus varicosus Faxon, 1898 (This species is distributed in the states of Santa Catarina and Rio Grande do Sul — Brazil and Uruguay and Argentina).

4’ Cheliped merus, carpus, and propodus medially glabrous; maxilliped III ischium 386 ventral margin with longitudinal tubercle row...................................................................... Parastacus saffordi Faxon, 1898 (This species is distributed in the state of Rio Grande do Sul — Brazil and in Uruguay).

5(3) Cutting edge of cheliped fingers external face hardly visible, covered by tufts of long setae........................... 6

5’ Cutting edge of cheliped fingers visible, not covered by tufts of long setae........................................ 7

6(5) Cheliped carpus distally glabrous........................................................................ 8

6’ Cheliped carpus distally with tufts of long and simple setae....... Parastacus pilicarpus Huber, Ribeiro & Araujo, 2018 (This species is endemic to the state of Santa Catarina, Brazil).

7(5’) Epistome anteromedian lobe hexagonal or pentagonal........................................................ 9

7’ Epistome anteromedial lobe septagonal.................................................................. 10

8(6) Telson distal margin rounded.......................................................................... 11

8’ Telson distal margin acute.................................... Parastacus buckupi Huber, Ribeiro & Araujo, 2018 (This species is endemic to the state of Rio Grande do Sul, Brazil).

9(7) Chelipeds subequal in size............................................................................. 12

9’ Chelipeds with different sizes................................................ Parastacus heterochaelis sp. nov. (This species is found in wetlands from the central east to the northeast portion of the state of Rio Grande do Sul, Brazil, in the municipalities of Viamão and Osório.)

10(7’) Dactylus long.......................................... Parastacus longidactylus Huber, Araujo & Ribeiro, 2024 (This species is endemic to the state of Rio Grande do Sul, Brazil).

10’ Dactylus short............................................ Parastacus gomesae Huber, Araujo & Ribeiro, 2022 ((This species appears to have a limited distribution, being registered only in the municipality of São Jerônimo, state of Rio Grande do Sul, southern Brazil).

11(8) Postorbital carinae prominent.......................................................................... 13

11’ Postorbital carinae obsolete........................................ Parastacus laevigatus Buckup & Rossi, 1980 (This species has a limited distribution, being found only in the north of the state of Santa Catarina, the north limit of Parastacus distribution. It is probably extinct in nature).

12(9) Chelipeds with globose palm........................................................................... 14

12’ Chelipeds with flattened palm.......................................................................... 15

13(11). Telson subtriangular............................... Parastacus fluviatilis Ribeiro & Buckup in Ribeiro et al., 2016 (This species is found only in streams in the region of Campus de Cima da –RS up to 1.400 m of altitude).

13’ Telson surectangular............................................... Parastacus pilimanus (von Martens, 1869) (This species is widely distributed in the state of Rio Grande do Sul — Brazil, Uruguay and Argentina)

14 Cervical groove V-shaped............................................................................. 16

14’ Cervical groove U-shaped..................... Parastacus caeruleodactylus Ribeiro & Araujo in Ribeiro et al., 2016

15(12’) S3 longer than S2 and curved in lateral view....................................... Parastacus quasimodo sp. nov. (This species has an extremely limited distribution, being found only in streams in the Municipality of Caraá, the southwest portion of the state of Santa Catarina, Brazil).

15’ S3 and S2 with similar sizes and not curved in lateral view................................................... 17

16 Rostral carinae reaching postorbital carinae proximal edge.......................... Parastacus defossus Faxon, 1898 (This species is found in the south portion of Uruguay and its occurrence in Brazil is questionable since Brazilian populations can constitute a species complex).

16’ Rostral carinae surpassing postorbital carinae proximal edge..................... Parastacus pugnax (Poeppig, 1835) (This species is found only in the central portion of Chile and can constitute a species complex).

17 (15’) Mandible caudal molar process unicuspidate … Parastacus manezinho sp. nov. (This species has an extremely limited distribution, being found only in the island of Florianópolis, state of Santa Catarina, Brazil).

17’ Mandible caudal molar process bicuspidate................................................................ 18

18(17’) Rostrum apex V-shaped.............................................................................. 19

18’ Rostrum apex U-shaped.............................................................................. 20

19(18) Cheliped palm medial margin smooth.............................................. Parastacus rudolphi sp. nov. (This species has an extremely limited distribution, being found only in the municipality of Osório, state of Rio Grande do Sul, Brazil, in the Borússia Mountain)

19’ Cheliped palm medial margin tuberculate........................ .. Parastacus promatensis Fontoura & Conter, 2008 (This species has an extremely limited distribution, being found only in streams in the Municipality of São Francisco de Paula, state of Rio Grande do Sul, Brazil, up to 850 m of altitude).

20(18’) Cheliped palm dorsal surface with tubercles irregularly distributed............................................ 21

20’ Cheliped palm dorsal surface with three well-defined tubercle rows....................................................................................... Parastacus tuerkayi Ribeiro, Huber and Araujo in Ribeiro et al., 2017 (This species is endemic to the northern portion of the state of Santa Catarina).

21(20) Rostrum dorsal surface straight......................................................................... 22

21’ Rostrum dorsal surface concave..................................... Parastacus brasiliensis (von Martens, 1869) (This species is endemic to the central portion of the state of Rio Grande do Sul, Brazil).

22(21) Cephalon postorbital carinae prominent in anterior and middle portions.................................................................................................... Parastacus guapo Huber, Araujo and Ribeiro, 2022 ((This species appears to have a limited distribution, being registered only in the municipality of Pantano Grande, state of Rio Grande do Sul, southern Brazil)

22’ Cephalon postorbital carinae weakly prominent....... Parastacus macanudo Huber, Rockhill, Araujo and Ribeiro, 2020 (This species appears to have a limited distribution, being registered only in the municipality of São Leopoldo, state of Rio Grande do Sul, southern Brazil)

Figures

FIGURE 42. Parastacus manezinho sp. nov., distribution in the state of Santa Catarina, southern Brazil.

FIGURE 45. Parastacus quasimodo sp. nov., distribution in the state of Rio Grande do Sul, Brazil.

FIGURE 46. Parastacus rudolphi sp. nov., holotype:A—­ habitus, dorsal view (holotype); B—­ cephalon, dorsal view (holotype); C—­ cephalon, lateral view (holotype); D—­ first to third male pleonal pleura (holotype, MZUSP 45371); E—­ tailfan (holotype). Scale bars: A—­ 1 cm; B, C, D, E—­ 5 mm.

FIGURE 47. Parastacus rudolphi sp. nov., holotype and paratypes: A—­ epistome (holotype, MZUSP 45371); B—­ thoracic sternites and gonopores (holotype, MZUSP 45371); C—­ thoracomere 8, caudal view (holotype, MZUSP 45371); D—­ antennal scale, lateral view (paratype 2, UFRGS 6476, MZUSP XXXXX); E—­ mandible (paratype 2); F—­ third maxilliped, ventral view (paratype 1, UFRGS 6476); G—­ third maxilliped, dorsal view (paratype 1, UFRGS 6476); H—­ first pereiopod, lateral view (holotype, MZUSP 45371); I—­ first pereiopod, dorsal view (holotype); J—­ second pereiopod, lateral view (holotype MZUSP 45371). Scale bars: A, C—­ 2.5 mm; B, I—­ 5 mm; D, E—­ 2 mm; F, G—­ 5 mm; H, J—­ 1 cm.

FIGURE 48. Parastacus rudolphi sp. nov., habitat. A—­ habitat, stream in Morro da Borússia, state of Rio Grande do Sul, Brazil; B—­ single burrow opening (white arrow).

FIGURE 49. Parastacus rudolphi sp. nov., distribution in the state of Rio Grande do Sul, Brazil.