Aegla abrupta, Marçal, Ingrid Costa, Páez, Fernanda Polli, Silva, Priscila Frazato Da, Souza-Shibatta, Lenice & Teixeira, Gustavo Monteiro, 2021

Marçal, Ingrid Costa, Páez, Fernanda Polli, Silva, Priscila Frazato Da, Souza-Shibatta, Lenice & Teixeira, Gustavo Monteiro, 2021, Cryptic diversity among populations of Aegla Leach, 1820 (Decapoda: Anomura: Aeglidae) from Tibagi River basin, Paraná state, Brazil, with descriptions of three new species, Journal of Natural History 55 (33 - 34), pp. 2145-2171 : 2155-2161

Aegla abrupta sp. nov. Marçal and Teixeira

( Figures 7–10 )

urn:lsid:zoobank.org:act:8DC448C9-6106-447A-90E0-9B143E120783 Holotype

Male [ CLE 16.2 mm], Brazil, Paraná, Ortigueira, Paranapanema River basin, Tibagi River sub-basin, Formiga River , 24°11 ʹ 11.77”S, 50°56 ʹ 28.60”W, altitude 725 m, G.M. Teixeira, I.C. Marçal and R.S. Vieira coll., 10 March 2020 (MZUEL 515).

Paratypes

5 males [ CLE 12.8–24.4 mm] and 8 females [ CLE 12.5–18.2 mm], same data as holotype (MZUEL 499) .

Additional material examined

4 males [size not recorded] and 6 females [size not recorded], same data as holotype (MZUEL 504, genetic vouchers: Bold Systems access AEGLA 003-21, AEGLA 004-21) . 1 male [ CLE 16.7 mm], Brazil, Paraná, Ortigueira, Paranapanema River basin, Tibagi River sub-basin, tributary of the Formiga River , 24°10 ʹ 56.50”S, 50°56 ʹ 31.50”W, altitude 726 m, O .A . Shibatta coll., August 2014 (MZUEL 388). 1 male [ CLE 20.1 mm] and 6 females [ CLE 13.6–19.4 mm], Brazil, Paraná, Ortigueira, Paranapanema River basin, Tibagi River sub-basin, Piquira River , coordinates and coll . unknown, 2 February 2001 (MZUEL 440). 1 male [ CLE 20.1 mm] and 1 female [ CLE 19.2 mm], same locality, coordinates and coll . unknown, 25 April 2002 (MZUEL 441).

Diagnosis

Rostrum triangular, narrow base, extending beyond distal apex of compound eyes, carinate along entire length. Subrostral process well developed, occupying proximal half of subrostral margin, anterior and posterior margins forming acute angle. Orbital and extraorbital sinuses deep. Anterolateral spines reaching basal margin of cornea. Epigastric prominences pronounced. Protogastric lobes pronounced. Cervical groove trapezoidal. Areola subrectangular. Epibranchial area shortened. Lobe on proximal dorsal margin of dactylus rudimentary. Carpal ridge high on outer surface of carpus. Ventromesial border of cheliped ischium with 4 or 5 tubercles. Anteromesial region of third thoracic sternite abrupt. Anterior margin of second abdominal epimeron almost straight. Uropods wide.

Description of holotype

Carapace moderately convex, gastric region convex, dorsal surface scabrous, covered with punctations ( Figure 7A ). Rostrum triangular, narrow base (RBW/LMR = 0.79), extending beyond distal apex of compound eyes, carinate along entire length, small corneous scales on lateral margins and tip; ventral portion of rostrum much higher than dorsal in profile. Rostral carina beginning at level of protogastric lobes, with 2 rows of corneous scales extending next to apex. Subrostral process well developed, occupying proximal half of subrostral margin, triangular, tip rounded, anterior and posterior margins forming acute angle (88°) ( Figure 8A ).

Eyestalk and cornea well developed. Orbital and extra-orbital sinuses deep. Orbital sinus U-shaped. Orbital spines well developed, with small terminal corneous scale. Anterolateral spines acuminate apically with small corneous scales terminally, reaching basal margin of cornea.

Epigastric prominences pronounced, with corneous scales. Protogastric lobes pronounced, with corneous scales ( Figure 8A ). Gastric area elevated in relation to hepatic lobes and rostrum in lateral view. Demarcation between the first and the second hepatic lobes well defined, between the second and the third hepatic lobes weakly delimited. Lateral margins of hepatic lobes with small corneous scales and small setae.

Cervical groove trapezoidal ( Figure 8B ). Transverse dorsal linea sinuous along its extension. Areola subrectangular (AH/[(APM+AAD)/2] = 2.20). Cardiac area trapezoidal (TDL/PMC = 1.39). Epibranchial area shortened, triangular, anterolateral angle with corneous scale, lateral margin with row of corneous scales and small setae ( Figure 8B ). Lateral margins of anterior and posterior branchial areas with row of corneous scales and small setae.

Chelipeds unequal. Left cheliped largest ( Figure 9 (A,B)). Dactylus: dorsal margin and outer surface with small corneous scales, inner surface with setal tufts and scales. Proximal dorsal margin with rudimentary lobe. Cutting margin with well-developed lobular basal tooth, followed by row of corneous scales to distal end. Row of small tufts of long setae next to cutting margin. Pre-dactylar lobe well developed, rounded, without corneous scales. Propodus: outer surface granular, globose aspect. Palmar crest subdisciform with outer surface excavated, margin poorly serrated, covered by acuminate corneous scales. Cutting margin of fixed finger with well-developed lobular basal tooth, followed by row of corneous scales to distal end. Inner and outer surfaces of fixed finger with rows of long setal tufts next to cutting margin. Carpus: dorsal margin with 2 proximal tubercles, median spine, distal spine longest, each tubercle or spine with small setae and terminal corneous scale, subterminal lobe well defined, pointed, with small corneous scales and setae. Inner surface with large tubercle, long setae next to dorsal margin. Outer surface with carpal ridge high, with small corneous scales. Merus: dorsolateral edge with distal tubercle, with corneous scale terminally, followed by row of tubercles decreasing in size proximally. Ventromesial edge with distal spine, with corneous scale terminally, followed by 4 tubercles of similar size, with corneous scale. Ventrolateral border with distal tubercle, with terminal corneous scale, followed by row of small tubercles. Ischium ( Figure 7B ): dorsolateral edge with spine, with corneous scale terminally. Ventromesial border with proximal tubercle, 2 median tubercles and large distal tubercle, each with terminal corneous scale. Ventrolateral border smooth.

Minor cheliped (right) similar to major cheliped except as noted hereafter ( Figure 9 (C, D)). Dactylus: cutting margin with rudimentary lobular basal tooth. Propodus: cutting margin with rudimentary lobular basal tooth. Ischium: ventromesial border with proximal tubercle, 3 small median tubercles and large distal tubercle, each with terminal corneous scale.

Second, third and fourth pereiopods similar. Dactyli, propodi, carpi, meri and ischii with several rows of setal tufts and small scales on surface. Carpi and meri with row of small tubercles with terminal corneous scale along dorsal margin. Meri with row of small tubercles with terminal corneous scale along ventral margin. Meri and ischii with long setae concentrated along dorsal margin.

Anteromesial region of third thoracic sternite abrupt, projecting between coxae of third maxillipeds, with scattered setae ( Figure 7C ). Fourth thoracic sternite with anterolateral angles produced anteriorly, with scattered setae ( Figure 10A ). Pleopods 2–5 absent. Anterolateral angle of second abdominal epimeron well defined, unarmed ( Figure 10B ). Ventral angle of third abdominal epimeron well defined with small corneous scales apically. Ventral angle of fourth abdominal epimeron well defined, unarmed. Anterior margin of second abdominal epimeron almost straight ( Figures 7D , 10B ). Uropods well developed, wide (WU/HWT = 1.04). Telson divided by longitudinal suture. Anterolateral and posterolateral margins well differentiated.

Variations

The areola can be subrectangular (n = 10), trapezoidal (n = 2) or rectangular (n = 1). The cardiac area varies from subrectangular (n = 9) to trapezoidal (n = 4). The palmar crest may appear rectangular instead of subdisciform. The anteromesial region of third thoracic sternite can be abrupt (n = 8) or tapered (n = 5). The anterolateral angle of second abdominal epimeron may present apical corneous scales instead of being naked as in the holotype. In most specimens, the ventral angle of the third abdominal epimeron is devoid of corneous scales. The uropods are narrow in a few specimens (n = 2). All measurements are summarised in Table 1 .

Etymology

The specific epithet ‘abrupta’, from the Latin abruptus, refers to the abrupt third thoracic sternite of the species.

Distribution

The new species has been collected in three watercourses within the Tibagi River subbasin, Paranapanema River basin. These watercourses are located in the city of Ortigueira, Paraná state, Brazil.

Conservation status

We suggest that Aegla abrupta sp. nov. be assigned as ‘Vulnerable’ (VU) under criteria B1, B2ab(iii) as defined by the IUCN (2019). This species has been recorded in three localities (B2a) and the known extent of occurrence is estimated to be less than 500 km 2 (B1). The streams where the specimens of Aegla abrupta sp. nov. were found are in agricultural and urbanised areas (B2b(iii)).

Remarks

Aegla abrupta sp. nov. can be separated from its congeners, mainly by, among other characters, subrostral process well developed (undeveloped in A. strinatii ), occupying proximal half of subrostral margin (on proximal third of subrostral margin in A. lata , A. jacutinga , Aegla santosi sp. nov. and Aegla nanopedis sp. nov., and occupying median portion of subrostral margin in A. jaragua ); anterior and posterior margins of subrostral process forming acute angle (right angle in A. lata and A. jacutinga , and obtuse angle in A. jaragua , Aegla santosi sp. nov. and Aegla nanopedis sp. nov.); orbital and extra-orbital sinuses deep (shallow in A. odebrechtii ); epigastric prominences pronounced (poorly pronounced in A. lata and A. jacutinga ); protogastric lobes pronounced (poorly pronounced in A. odebrechtii , A. lata , A. jarai and A. jaragua ); cervical groove trapezoidal (U-shaped in A. lata and Aegla nanopedis sp. nov.); subterminal lobe of carpus well defined, pointed (poorly defined in A. strinatii ); outer surface of carpus with carpal ridge high (low in A. jacutinga ); dorsal margin of carpus and merus of second pereiopods with small tubercles with terminal corneous scale (with distal spine followed by tubercles decreasing in size proximally in A. jarai ); ventral margin of merus of second pereiopods with small tubercles with terminal corneous scale (one or two small spines in A. castro and A. schmitti ); anteromesial region of third thoracic sternite abrupt (tapered or truncate in A. lata , truncate in A. jaragua , and tapered in A. jacutinga , Aegla santosi sp. nov. and Aegla nanopedis sp. nov.); anterior margin of second abdominal epimeron almost straight (concave in A. castro and A. schmitti and slightly concave in A. jacutinga ); uropods wide (narrow in A. lata and A. jaragua ).

Our Bayesian tree based on the COI mitochondrial gene ( Figure 6 ) recovered Aegla abrupta sp. nov. as the sister species to Aegla nanopedis sp. nov., and both clustered in the same subclade as A. jacutinga . The interspecific genetic distances ( Table 2 ) reinforce the relationships evidenced in the Bayesian analysis.

Figures

Figure 6. Bayesian tree (HKY+I+G) for Aegla species based on partial sequences of the COI gene. The numbers above the branches represent the posterior probability (values <0.5 are not indicated), and the vertical line indicates the species delimitation assigned in the GMYC analysis.

Figure 7. Aegla abrupta sp. nov., male holotype, CLE 16.2 mm, Formiga River,Ortigueira, Paraná, Brazil (MZUEL 515). (a) dorsal view of the cephalothorax and anterior portion of the abdomen. (b) ventral view of ischium of major cheliped (left) showing four tubercles (arrows). (c) third thoracic sternite abrupt (arrow). (d) dorsal view of second abdominal epimeron (right side) showing anterior margin almost straight (arrow). Scale bars: a = 5.0 mm; b–d = 1.0 mm.

Figure 8. Aegla abrupta sp.nov., male holotype, CLE 16.2 mm (MZUEL 515). (a) external surface view of the anterior portion of the cephalothorax showing pronounced protogastric lobes (white arrow) and well-developed subrostral process (black arrow). (b) dorsal view of the anterior region of the cephalothorax showing trapezoidal cervical groove (black arrow) and shortened epibranchial area (white arrow). Scale bars: a = 1.0 mm; b = 5.0 mm.

Figure 9. Aegla abrupta sp. nov., male holotype, CLE 16.2 mm (MZUEL 515). (a) dorsal view of the dactylus, propodus and carpus of major cheliped (left) showing subdisciform palmar crest (thick arrow) and high carpal ridge (thin arrow). (b) ventral view of ischium of major cheliped (left) with four tubercles (arrows). (c) dorsal view of the dactylus, propodus and carpus of minor cheliped (right) showing subdisciform palmar crest (thick arrow) and high carpal ridge (thin arrow). (d) ventral view of ischium of minor cheliped (right) with five tubercles (arrows). Scale bars = 1.0 mm.

Figure 10. Aegla abrupta sp. nov., male holotype, CLE 16.2 mm (MZUEL 515). (a) third (thin arrow) and fourth (thick arrow) thoracic sternites. (b) dorsal view of second abdominal epimeron (right side) showing almost straight anterior margin (thick arrow) and unarmed anterolateral angle (thin arrow). Scale bars = 1.0 mm.