Parastacus bah, 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 : 51-56

Parastacus bah sp. nov.

( Figs. 32–34 , Table 1)

Holotype. male, Brazil, Rio Grande do Sul, Dom Feliciano, Camaquã Basin, Horto Herval (30°29’2.616"S 52°9'36.75"W), 05/X/2012, coll. K.M. Gomes ( MZUSP 45367 ).

Paratypes. Brazil, Rio Grande do Sul —­ 1: one male, Dom Feliciano, Horto Florestal Lageado (30°32' 6"S; 52°5 4.99"W), 05/X/2012, coll. K.M. Gomes ( UFRGS 5497 ); 2 : one juvenile, Dom Feliciano, Horto Florestal Xavier (30°32'54.6"S 52°7'30.72"W), 05/X/2012, coll. K.M. Gomes ( UFRGS 5493 ) .

Etymology. Named based on the regional expression “bah ”, typical of the state of Rio Grande do Sul, which is an interjection that is valid for almost everything, depending on the intonation, can be used as a surprise, rejection, approval, admiration; used as a noun in apposition. We also suggest the common name “bah crayfish” for this species.

Diagnosis. Wide front with short trapezoid rostrum wider than long with apex inverted “U”-shaped, ending in a straight blunt and small spine. Post orbital carinae obsolete. Cervical groove weakly V-shaped. Globose and short chelipeds.

Description. Rostrum: trapezoid, wider than long (RL 75.1% of RW), short (12.1% of CL), reaching the middle of the second article of the antennular peduncle ( Fig. 30A–C ). Dorsum straight, apex inverted “U”-shaped, ending in straight blunt and small spine ( Fig. 32B, C ). Few plumose setae on lateral margins. Rostral carinae angled, prominent and narrow, extending back to carapace not surpassing rostral basis; rostral carinae sides slightly convergent and rostral carinae basis slightly divergent ( Fig. 32B, C ).

Cephalon: CeL 69.2% of CL. Eyes large (CMW 74.7% of OW); suborbital angle>90°, unarmed ( Fig. 30C ). Front wide (FW 41.8% of CW). Postorbital carinae longer than rostral carinae (RCL 51% of POCL) and weakly prominent. Lateral cephalic edge with very sparse setation ( Fig. 32A–C ).

Thorax: carapace laterally compressed, deep and wide (CD 55.7% of CL; CW 48.7% of CL). Cervical groove weakly V-shaped. Branchiocardiac grooves inconspicuous ( Fig. 30A ). Areola wide, 2.2x as long as wide (31.9% of CL) ( Fig. 32A ).

Pleon: long and wide (PL 90.4% of CL; PW 80.3% of CW), smooth, not covered setae on pleural margins ( Fig. 32A ). 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. 32D ).

Tailfan: telson uniformly calcified, subrectangular, longer than wide (TeW 89.2% 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. 32E ). 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 very sharp spine. Transverse suture (diaeresis) straight, with nine dorsolateral spines (outer) and seven dorsolateral spines (inner) on right exopod and eight dorsolateral spines (outer) and seven dorsolateral spine (inner) on the left exopod. Endopod, mid-dorsal carina few prominent, ending in a small and sharp spine; lateral margin with one small and sharp spine at level of exopod transverse suture ( Fig. 32E ).

Epistome: anterolateral section with sharp conical projection. Posterolateral section smooth and with deep and setose lateral grooves converging to the basis of the anteromedian lobe, and reduced median circular conncavity. Anteromedian lobe hexagonal, 1.2x wider than long, apex straight with some serrated setae, reaching median part of antepenultimate article of antennal peduncle; dorsal surface concave at apex, and basis with a shallow groove ( Fig. 33A ).

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 a concave surface, median keel not 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 not visible ( Fig. 33B, C ).

Antennule: internal ventral border of basal article with small sharp spine ( Fig. 33A ).

Antenna: when extended back reaching the posterior margin of carapace. Antennal scale widest at midlength, reaching the end of third antennal article, ASW 57.1% of ASL ( Fig. 33A, D ), lateral margin straight, spine strong and distal margin emarginate. Coxa with prominent carina above nephropore and blunt spine above the nephropore. Basis unarmed ( Fig. 33A ).

Mandible: cephalic molar process molariform, caudal molar process bicuspidate with one cephalodistal cusp and one small distoproximal cusp. Incisor lobe with eight teeth. The third tooth from the anterior margin is the largest ( Fig. 33E ).

Third maxilliped: ischium glabrous in the middle, setose inner margin and sparse small and simple setae on outter margin ( Fig. 33F ); dorsal surface without setae ( Fig. 33G ). Crista dentata bearing 22 and 23 teeth in right and left ischium respectively. Merus ventral surface bearing few setae in the middle and densely setose inner margin. Exopod longer than ischium, with flagellum reaching proximal margin of merus ( Fig. 33F, G ).

First pair of pereiopods (chelipeds): small and subequal, laterally flattened (RPrT 28.1% of RPrL; LPrT 25.68% of LPrL) ( Fig. 32A ). Ischium ventral surface with 7 tubercles. Merus: right merus (RML) 68.8% of propodus length (RPrL); left merus (LML) 62.8% of propodus length (LPrL); ventral surface with two longitudinal series of tubercles: inner series with 12 tubercles, outer 16 and mesial 10, arranged irregularly on right merus; inner series bearing 13 tubercles, outer 16 and mesial 12, arranged irregularly on left merus. Dorsal and midventral spines present. Carpus dorsomedial surface not divided longitudinally by groove ( Fig. 33A ; Fig. 33I ). Internal dorsolateral margin with row of tubercles, increasing in size distally; inner surface with few mesial tubercles. Carpal spine absent ( Fig. 33I ). Propodus width (RPrW and LPrW) 47.32% of length in right cheliped and 47.1% in left cheliped. Dorsal surface of palm squamose tubercles irregularly distributed ( Fig. 33H, I ). Inner margin without tubercles. Ventral surface bearing two rows of squamose tubercles, trespassing the beginning of the fixed finger ( Fig. 31H ). Dactylus: right dactylus (RDL) 63.8% of propodus length (RPrL), left dactylus (LDL) 61.9% of left propodus (LPrL); dorsal surface with squamose tubercles in the proximal portion ( Fig. 33I ). Cutting edge of fingers visible. Fixed finger with three subequal teeth. Dactylus with four teeth subequal in size ( Fig. 33H, 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. 33J ).

Gonopores: Presence of both genital apertures on coxae of third and fifth pairs of pereiopods. Female gonopores semi-ellipsoidal (maximum diameter 0.74 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. 33B ).

Remarks. Parastacus bah sp. nov. was previously identified as P. brasiliensis in the UFRGS collection. Parastacus bah sp. nov. resembles small specimens of P. brasiliensis in having the squamose tubercles on the dorsal surface of the palm irregularly distributed. It differs from all other Parastacus species by the trapezoid rostrum.

Color of live specimens. No available data.

Habitat and Ecology. Streams. Burrows are simple and shallow and found in the stream margins. Burrows of P. bah sp. nov. can be identified as type 1a, b according to Horwitz and Richardson’s (1986) classification and the species can be considered a tertiary burrower based on Hobbs’ (1942) classification.

Distribution. Brazil: State of Rio Grande do Sul ( Fig. 34 ).

Figures

FIGURE 30. Parastacus guapo Huber, Araujo & Ribeiro, 2022: living specimen in nature.

FIGURE 31. Parastacus gomesae Huber, Araujo & Ribeiro, 2022: living specimen in nature.

FIGURE 32. Parastacus bah sp. nov., holotype (MZUSP 45367): A—­ habitus, dorsal view; B—­ cephalon, dorsal view; C—­ cephalon, lateral view; D—­ first to third male pleonal pleura; E—­ tailfan. Scale bars: A, D—­ 5 mm; B, C, E, 2.5 mm.

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.