Parastacus heterochaelis, 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 : 56-62

Parastacus heterochaelis sp. nov.

( Figs. 35–38 , Table 2)

Holotype. male, Brazil, Rio Grande do Sul, Viamão , Banhado dos Pachecos (30°5’40.95”S; 50°51’25.99”W), 20/ VIII/2013, coll. F. B. Ribeiro & K. M. Gomes ( MZUSP 43368 ).

Paratypes. Brazil, Rio Grande do Sul —­ 1 and 2: two males, Viamão, Banhado dos Pachecos (30°5’49.99”S; 50°51’7.02”W) ( UFRGS 5865 ) ; 3 and 4: one female and one juvenile, Osório, Morro da Borússia (29°53.63’S; 50°16.89’W), 22/IV/2015 ( UFRGS 6439 ) ; 5: one male, Osório, XI/1981, coll. L. Schirmer ( UFRGS 1359 ) .

Etymology. The name of this species is related to the heterochely, i.e. different sizes (left is larger) of chelipeds found in all specimens; used as an adjective. We also suggest the common name “the big claw crayfish” for this species.

Diagnosis. Rostrum wider than long. Rostral carinae short, not surpassing rostral basis when extending back to carapace. Postorbital carinae longer than rostral carinae and weakly prominent. Globose chelipeds with different sizes (heterochely). Anteromedian lobe of epistome with apex very acute.

Description. Rostrum: triangular, wider than long (RL 90% of RW), short (11.1% of CL), reaching the middle of the second article of the antennular peduncle ( Fig. 35A–C ). Dorsum straight, apex inverted “V”-shaped, ending in upward blunt and small spine ( Fig. 35B, C ). Few plumose setae on lateral margins. Rostral carinae straight, prominent and narrow, extending back to carapace not surpassing rostral basis; rostral carinae sides slightly convergent and rostral basis divergent ( Fig. 35B, C ).

Cephalon: Carapace lacking spines or tubercles. CeL 68% of CL. Eyes small (CMW 77.4% of OW); suborbital angle> 90°, unarmed ( Fig. 33C ). Front narrow (FW 33.5% of CW). Postorbital carinae longer than rostral carinae (RCL 47.7% of POCL) and weakly prominent. Lateral cephalic edge with dense setation ( Fig. 35A–C ).

Thorax: carapace laterally compressed, deep and wide (CD 57.8% of CL; CW 45.8% of CL). Cervical groove weakly V-shaped. Branchiocardiac grooves conspicuous ( Fig. 33A ). Areola narrow, 2x as long as wide (25% of CL) ( Fig. 35A ).

Pleon: lacking spines or tubercles, short and wide (PL 79.7% of CL; PW 80.9% of CW), smooth, covered with setae on pleural margins ( Fig. 35A ). Pleural somites with rounded posterior margins. S1 pleurae with a large distal lobe not overlapped by S2 pleurae. S2 pleurae low and short with deep groove parallel to margin ( Fig. 35D ).

Tailfan: telson uniformly calcified, subrectangular, longer than wide (TeW 82.4% 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. 35E ). Uropod protopod bilobed, with rounded and unarmed margins; proximal lobe largest. Exopod lateral margin bears a small and sharp spine, mid-dorsal carina few prominent, ending in a sharp spine. Transverse suture (diaeresis) straight, with six dorsolateral spines (outer) and four dorsolateral spines (inner) on right exopod left exopod. Endopod, mid-dorsal carina few prominent, ending in a minuscle and sharp spine; lateral margin with one sharp spine at level of exopod transverse suture ( Fig. 35E ).

Epistome: anterolateral section with blunt conical projection with tubercles. Posterolateral section smooth and with deep lateral grooves converging to the basis of the anteromedian lobe, and median concavity well developed. Anteromedian lobe pentagonal, 1.06x wider than long, apex very acute, reaching median part of antepenultimate article of antennal peduncle; dorsal surface straight in the middle and concave margins; basis with a shallow groove ( Fig. 36A ).

Thoracic sternites: SLP4 small and very close to each other, median keel present and not inflated; SLP5 smallest and separated to each other, median keel present and not inflated; SLP6 larger than SLP4 and SLP5, subequal to SLP8, with concave surface, 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 lobes visible ( Fig. 36B, C ).

Antennule: internal ventral border of basal article with sharp spine ( Fig. 36A ).

Antenna: when extended back reaching S3. Antennal scale widest at midlength, reaching the end of third antennal article, ASW 42% of ASL ( Fig. 36A, D ), lateral margin straight, spine strong and distal margin emarginate. Coxa with prominent carina and one blunt spine above nephropore. Basis unarmed ( Fig. 36A ).

Mandible: cephalic molar process molariform, caudal molar process bicuspidate with one large cephalodistal cusp and one small distoproximal cusp. Incisor lobe with eight teeth. The second tooth from the anterior margin is the largest ( Fig. 36E ).

Third maxilliped: ischium, ventral surface with tufts of small setae in the middle and inner margin and few single setae in the outer margin ( Fig. 36F ); dorsal surface with few small and simple setae ( Fig. 36G ). Crista dentata bearing 24 and 25 teeth in right and left ischium respectively. Merus ventral surface with tufts of long and small. Exopod reaches the end of ischium ( Fig. 36F, G ).

First pair of pereiopods (chelipeds): large and with different sizes, globose (RPrT 23.9% of RPrL; LPrT 31.2% of LPrL) ( Fig. 35A ). Ischium ventral surface with 4 tubercles. Merus: right merus (RML) 71.1% of propodus length (RPrL); left merus (LML) 48.3% 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 groove impression absent ( Fig. 36A ; Fig. 36I ). Internal dorsolateral margin with row of tubercles, increasing in size distally; inner surface with 20 small mesial tubercles. Carpal spine absent ( Fig. 36I ). Propodus width (RPrW and LPrW) 48.5% of length in right cheliped and 54.1% in left cheliped. Dorsal surface of palm with two rows of verrucous tubercles ( Fig. 36H, I ). Inner margin without tubercles. Ventral surface bearing two rows of squamose tubercles, reaching the beginning of the fixed finger ( Fig. 34H ). Right dactylus (RDL) 64.7% of propodus length (RPrL), left dactylus (LDL) 56.1% of left propodus (LPrL); dorsal surface with squamose tubercles in the proximal portion ( Fig. 36I ). Cutting edge of fingers visible. Fixed finger with nine teeth, third tooth largest. Dactylus with eleven teeth, second tooth largest ( Fig. 36H, I ).

Second pair of pereiopods: ventral and dorsal surface of carpus, propodus and dorsal surface of dactylus with moderate cover of simple long setae ( Fig. 36J ).

Gonopores: Presence of both genital apertures on coxae of third and fifth pairs of pereiopods. Female gonopores semi-ellipsoidal (maximum diameter 1.12 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. 36B ).

Remarks. This species resembles P. defossus in its small size, globose chelipeds, and the post orbital carinae being obsolete. Parastacus heterochaelis sp. nov. is distinguishable from all congeneric species by displaying heterochely (chelipeds with different sizes) with left cheliped larger and by the anteromedian lobe of epistome with apex being very acute.

Color of living specimens. Rostrum, cephalothorax anterior and lateral regions, dorsal pleon and tailfan brown to dark brown Pereiopod pairs 2–5 brown ( Fig. 37C–E ).

Habitat and Ecology. Peat bogs ( Fig. 37A ). Burrows are shallow with one or two tunnels and can reach up to 35 cm deep ( Fig. 37B ) Chimneys can reach up to 5 cm height and within the burrows can be found two adults individuals, including the female in the ovigerous stage. According to Horwitz and Richardson’s (1986) the burrows of Parastacus heterochaelis sp. nov. are of type 2 and it can be considered a primary burrower based on Hobbs’ (1942) classification.

Distribution. Brazil: state of Rio Grande do Sul ( Fig. 38 ).

abbreviations see Material and Methods section.

Figures

FIGURE 33. Parastacus bah sp. nov., holotype and paratypes: A—­ epistome (holotype, MZUSP 45367); B—­ thoracic sternites and gonopores (holotype); C—­ thoracomere 8, caudal view (holotype, MZUSP 45367); D—­ antennal scale, lateral view (holotype, MZUSP 45367); E—­ mandible (paratype 1, UFRGS 5497); F—­ third maxilliped, ventral view (paratype 1, UFRGS 5497); G—­ third maxilliped, dorsal view (paratype 1, UFRGS 5497); H—­ first pereiopod, lateral view (holotype); F—­ first pereiopod, dorsal view (holotype); G—­ second pereiopod, lateral view (holotype). Scale bars: A, C—­ 3.3 mm; B—­ 5 mm; D—­ 1.5 mm; E—­ 1 mm; H, I, J—­ 2.5 mm; F, G—­ 2 mm.

FIGURE 34. Parastacus bah sp. nov., distribution in the state of Rio Grande do Sul, southern Brazil.

FIGURE 35. Parastacus heterochaelis sp. nov., holotype and paratypes: A—­ habitus, dorsal view (holotype, MZUSP 45368); B—­ cephalon, dorsal view (paratype 5, UFRGS 1359); C—­ cephalon, lateral view (paratype 5, UFRGS 1359); D—­ female pleonal somites, dorsal view (paratype 4, UFRGS 6439); E—­ first to third male pleonal pleura (holotype); F—­ first to third female pleonal pleura (paratype 4, UFRGS 6439); G—­ tailfan (paratype 2, UFRGS 5865). Scale bars: A—­ 10 mm; B, C, D, E, F, G—­ 5 mm.

FIGURE 36. Parastacus heterochaelis sp. nov., holotype and paratypes:A—­ epistome (paratype 5, UFRGS 1359); B—­ thoracic sternites and gonopores (paratype 5, UFRGS 1359); C—­ thoracomere 8, caudal view (holotype, MZUSP 45368); D—­ antennal scale, lateral view (paratype 2, UFRGS 5865); E—­ mandible (paratype 2, UFRGS 5865); F—­ third maxilliped, ventral view (paratype 2, UFRGS 5865); G—­ third maxilliped, dorsal view (paratype 2, UFRGS 5865); H—­ first pereiopod, lateral view (holotype, MZUSP 45368); I—­ first pereiopod, dorsal view (holotype, MZUSP 45368); J—­ second pereiopod, lateral view (holotype, MZUSP 45368); Scale bars: A—­ 2 mm; B, H, I—­ 5 mm; D, F, G—­ 1,5 mm; C, J—­ 2.5 mm; E—­ 1 mm.

FIGURE 37. Parastacus heterochaelis sp. nov., habitat and living specimens. A—­ habitat, peatland in the municipality of Viamão, state of Rio Grande do Sul; B—­ chimney; C—­ male (right) and ovigerous female (left) living specimens caught in the same burrow; D—­ ovigerous female showing eggs attached to pleopods; E—­ living specimen. Scale bar: E—­ 1 cm.

FIGURE 38. Parastacus heterochaelis sp. nov., distribution in the state of Rio Grande do Sul, southern Brazil.