Parastacus macanudo, Huber & Rockhill & Araujo & Ribeiro, 2020

Huber, Augusto F., Rockhill, Emily R., Araujo, Paula B. & Ribeiro, Felipe B., 2020, Pseudosesarma crassimanum, Zoological Studies (Zool. Stud.) 59 (47), pp. 141-149 : 2-7

Infraorder Astacidea Latreille, 1802 Superfamily Parastacoidea Huxley, 1879 Genus Parastacus Huxley, 1879

Parastacus macanudo sp. nov. ( Figs. 1–5) urn:lsid:zoobank.org:act:436143C1-7B31-42DF-B1C1-A6F96447A100

Type series: Holotype: adult male, Brazil, Rio Grande do Sul, São Leopoldo, Parque Imperatriz Leopoldina (29°45'40.7"S, 51°07'47.6"W) 20/VII/2018, coll. A. F. Huber & F. B. Ribeiro (MNRJcarcino 029877) . Paratypes: 1 male, same data as holotype (MNRJcarcino 029878); 2 males, same data as holotype ( UFRGS 6672).

Comparative material analyzed: Brazil, Rio Grande do Sul: P. brasiliensis : 1 male, Sítio do Mato, Zona Sul, Porto Alegre (- 30.114176S; - 51.1428W), 22/III/2014, coll. M. Pasolius, ( UFRGS 5868); three females, Mariana Pimentel (30°20'00"S, 51°22'39"W), coll. N. F. Fontoura ( UFRGS 2338); P. caeruleodactylus : 3 males and 4 females, Dom Pedro de Alcântara, RPPN Mata do Professor Baptista (29°23'06"S, 49°50'20"W), 12/ I /2019 ( UFRGS 6677); one male, Dom Pedro de Alcântara, RPPN Mata do Professor Baptista (29°23'06"S, 49°50'20"W), 16/IV/2014, col. D. C. Kenne & K. M. Gomes ( UFRGS 5934, PARATYPE); Santa Catarina: P. tuerkayi - male, Brazil, Santa Catarina, Penha, Beto Carrero World (26°48'10"S, 48°37'02"W), 04/IX/2013, coll. K. M. Gomes & F. B. Ribeiro ( UFRGS 6438), 2 males and 1 female, Brazil, Santa Catarina, Penha (26°47'50.2"S, 48°37'42.7"W), 12/ I /2019, coll. F. B. Ribeiro, K. M. Gomes & A. F. Huber ( UFRGS 6678).

Etymology: Named based on the regional expression “ macanudo ”, typical of the state of Rio Grande do Sul, which means powerful, strong and admirable. It refers to the large chelipeds of this species, which is an indicative of the strong burrowing capacity. We also suggest the common name “macanudo crayfish” for this species.

Diagnosis: Narrow front with short triangular rostrum. Rostral apex shaped as inverted “ U ”, with an inconspicuous and blunt spine. Suborbital angle> 90° and unarmed. Postorbital carinae inconspicuous. Cervical groove weakly V-shaped. Areola narrower than rostral basis and barely discernible. Telson subrectangular with sharp spines on lateral margins. Mandible with caudal molar process bicuspidate with one cephalodistal cusp and one small and sharp distoproximal cusp. S 2 pleurae low and long with deep groove parallel to margin. Internal ventral border of basal article of antennule without sharp spine.

Description of holotype: Rostrum. triangular, wider than long ( RW 85.4% of RL), short (12.8% of CL), reaching proximal portion of the second article of the antennular peduncle ( Fig. 1A–C). Dorsum straight, apex inverted “ U ”-shaped, ending in a tiny straight blunt spine ( Fig. 1B, C). Few plumose setae on lateral margins. Carinae almost straight, prominent and narrow, extending back to carapace, surpassing rostral basis; rostral carinae sides convergent and rostral carinae basis divergent. ( Fig. 1B, C).

Cephalon: Carapace lacking spines or tubercles. CeL 76% of CL. Eyes small ( CMW 57.6% of OW); suborbital angle> 90°, unarmed ( Fig. 3C ). Front narrow ( FW 34.6% of CW). Postorbital carinae longer than rostral carinae ( RCL 77% of POCL) and weakly prominent. Lateral cephalic edge with moderate setation ( Fig. 1A–C).

Thorax: Carapace laterally compressed, deep and narrow ( CD 58.1% of CL; CW 53.7% of CL). Cervical groove weakly V-shaped. Branchiocardiac grooves inconspicuous ( Fig. 1A). Areola narrower than rostral basis, 2.87x as long as wide (35.6% of CL) ( Fig. 1A).

Pleon: Lacking spines or tubercles, long and wide ( PL 83.9% of CL; PW 80.8% of CW), smooth, covered with small setae on pleural margins ( Fig. 1A). Pleural somites with rounded posterior margins. S 1 pleurae with a large distal lobe not overlapped by S 2 pleurae. S 2 pleurae low and short with shallow groove parallel to margin ( Fig. 1D).

Tailfan: Telson uniformly calcified, subrectangular, longer than wide (TeW 76.8% 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). 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 eight dorsolateral spines (outer) and four dorsolateral spines (inner) on right exopod and six dorsolateral spines (outer) and four dorsolateral spine (inner) on the left exopod. Endopod, mid-dorsal carina few prominent, ending in a very sharp spine; lateral margin with one sharp spine at level of exopod transverse suture ( Fig. 1E).

Epistome: Anterolateral section with small conical projection in both sides, the right side with small tubercle near the basis of the conical projection. Posterolateral section smooth and with deep lateral grooves converging to the basis of the anteromedian lobe. Median section with a longitudinal groove. Anteromedian lobe pentagonal, 1.1x longer than wide, apex acute and straight with some serrated setae, surpassing median part of antepenultimate article of antennal peduncle; dorsal surface concave and basis with a deep groove ( Fig. 2A).

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

Antennule: Internal ventral border of basal article unarmed ( Fig. 2A).

Antenna: When extended back reaching the posterior margin of the carapace. Antennal scale widest at distal to midlength, reaching proximal margin of third antennal article, ASW 51.1% of ASL ( Fig. 2A, D), lateral margin straight and distal spine well developed. Coxa with prominent carina above nephropore and two blunt spines with different sizes laterally distributed. Basis unarmed ( Fig. 2A).

Mandible: Cephalic molar process molariform, caudal molar process bicuspidate with one cephalodistal cusp and one sharp distoproximal cusp. Incisive lobe with nine teeth. The second tooth from the anterior margin is the largest ( Fig. 2E).

Third maxilliped: Ischium with few setiferous punctuations on outer margin and ventral surface ( Fig. 2F); dorsal surface without setae ( Fig. 2G); crista dentata bearing 22 teeth in both right and left ischia ( Fig. 2F, G). Merum, dorsal surface glabrous. Merum ventral surface sparsely covered by long smooth simple setae in the median region and with serrated setae on the inner margin ( Fig. 2F); Exopod longer than ischium, with flagellum reaching proximal margin of merum and with tuft of long and composed setae in the last articles ( Fig. 2F, G).

First pair of pereiopods (chelipeds): Large and subequal, laterally flattened (RPrT 28.3% of RPrL; LPrT 27.6% of LPrL) ( Figs. 1A, 2I). Ischium ventral surface with 11 and eight tubercles in the right and left respectively. Merus: right merus ( RML) 53.4% of propodus length (RPrL); left merus ( LML) 51.5% of propodus length (LPrL); ventral surface with two longitudinal series of tubercles: inner series with 16 tubercles, outer 12, plus 13 mesial tubercles irregularly distributed on right merus; inner series with 14 tubercles, outer 15, plus 14 mesial tubercles irregularly distributed on left merus. Dorsal and midventral spines present and blunt. Carpus with dorsomedial surface not divided longitudinally by groove ( Figs. 1A, 2I). Internal dorsolateral margin with row of tubercles, increasing in size distally; inner surface with 19 small mesial tubercles. Carpal spine present and blunt ( Fig. 2I). Propodus width (RPrW and LPrW) 38.1% of length in right cheliped and 41.9% in left cheliped. Dorsal surface of palm with a single row of verrucous tubercles irregularly distributed ( Fig. 2H, I). Inner margin without tubercles. Ventral surface bearing two rows of squamose tubercles, surpassing the beginning of the fixed finger ( Fig. 2H). Dactylus moving subvertically, right dactylus ( RDL) 64.5% of propodus length (RPrL), left dactylus ( LDL) 61.8% of left propodus (LPrL); dorsal surface with few squamose tubercles in the proximal portion ( Fig. 4I ). Cutting edge of fingers visible. Fixed finger with seven teeth, second and third teeth largest in the right cheliped. Dactylus with nine teeth, second tooth largest ( Fig. 2H, I). Ten teeth in both fixed finger and dactylus of the left cheliped.

Second pair of pereiopods: Dorsal surface of dactylus and ventral and dorsal surface of carpus and propodus with moderate covering of simple long setae ( Fig. 2J).

Gonopores: Presence of both genital apertures on coxae of third and fifth pairs of pereiopods. Female gonopores semi-ellipsoidal (maximum diameter 1.18 mm) with well-calcified membrane. Male gonopores rounded, opening onto the apical end of a small, fixed, calcified and truncated phallic papilla, close to the inner border of the ventral surface of coxae of the fifth pair of pereiopods. Male cuticle partition present ( Fig. 2B).

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

Measurements: Holotype male, CL 23.42 mm and TL 51.11 mm. In type series, CL ranging from 40.36 to 51.11 mm (45.83 ± 4.46 mm). FW /CW: 0.3 ± 0.02 (min: 0.33; max: 0.38). RL/RW: 1.10 ± 0.19 (min: 0.91; max: 1.33). CMW /OW: 0.7 ± 0.1 (min: 0.57; max: 0.79). Postorbital carina longer than rostral carina in all specimens analyzed. CW/ PW: 1.18 ± 0.06 (min: 1.09; max: 1.24). AreW/RW: 0.90 ± 0.08 (min: 0.83; max: 1.02) ( Table 1).

Color of living specimens: Rostrum dark brown or dark greenish brown. Cephalothorax anterior and lateral regions olive green to greenish brown with shades of light brown. First pair of pereiopods dark greenish brown externally and light brown internally. Pereiopod pairs 2–5 light brown. Dorsal pleon and taifan olive green to greenish brown with shades of light brown ( Fig. 3 ).

Variations in type-series: All paratypes present both masculine and feminine gonopores in the same individual. Male paratypes also present female gonopores semi-ellipsoidal (average maximum diameter 1.05 mm) covered by a calcified membrane. Male gonopores are very similar in all male paratypes. The apical spine of the rostrum and carpal spine are larger in the paratypes. The number of teeth in the crista dentata ranges from 20 to 22 in the left ischium and from 20 to 29 in the right ischium of the third maxilliped in the paratypes.

Habitat and Ecology: Parastacus macanudo sp. nov. was collected in a small fragment (approximately 500 m 2) of a swamp forest located inside the municipal park Imperatriz Leopoldina in the lower part of the SRB, in the state of Rio Grande do Sul ( Fig. 5 ). This physiographic region is an ecotone of the biomes Atlantic Forest (seasonal semi-deciduous forest) and Pampa (savanna), more precisely denominated as Ecologic Tension Area ( Mauhs 2013). The vegetation is composed predominantly by trees of Anacardiaceae (“Pau-Ferro”, Myracrodruon balansae ), Arecaceae (“Jerivá”, Syagrus romanzoffiana ), Fabaceae (“Grápia”, Apuleia leiocarpa ), Lauraceae (“Canela”, Ocotea spp. ), Meliaceae (“Camboatá”, Guarea macrophylla ), Moraceae (“Cincho”, Sorocea bonplandii ) and Sapindaceae (“ Camboatá Branco ”, Matayba elaeagnoides ) ( E. Rosseto pers. comm.). Additionally, some small-grasses and bushes ( Poaceae , Fabaceae , Asteraceae and Cyperaceae ) can also be found in the area. The soil is classified as Neossols Fluvic Eutrophic Ta (Santos et al. 2011) and is composed of clay and temporarily flooded depending on river level. According to the burrows and characteristics of the habitat, P. macanudo sp. nov. can be identified as a primary burrower following Hobbs’ (1942) classification. Burrows can reach a depth up to 1m and with 1–4 branches. Chimneys are huge and can reach up to 20 cm high and 10 cm wide ( Fig. 4C ). Burrows can be identified as type 2 according to Horwitz and Richardson’s (1986) classification.

Distribution: Parastacus macanudo sp. nov. appears to have limited distribution, being registered only in the municipality of São Leopoldo, state of Rio Grande do Sul, southern Brazil ( Fig. 5 ).

Conservation status: Data Deficient. The EOO was estimated as comprising approximately 1,312 km 2 ( B 1) and the AOO was calculated at 12 km 2 ( B 2). This species follows only the subitem b(iii): continuing decline observed in quality of habitat.

Figures

Fig. 3. Parastacus macanudo sp. nov., living specimens (holotype). A, habitus dorsal view; B, living specimen in the habitat; C, living specimen placed in aquarium. Scale bar: A = 10 mm.

Fig. 4. Parastacus macanudo sp. nov., habitat and burrows. A, swamp forest; B, single burrow opening (white arrow); C, chimney.

Fig. 5. Distribution and inferred EOO of Parastacus macanudo sp. nov. in the state of Rio Grande do Sul, southern Brazil. RS - state of Rio Grande do Sul, SC - state of Santa Catarina.