Aegla charon Bueno and Moraes, 2017

Aegla charon Bueno and Moraes View in CoL n. sp.

( Figs. 4 View Figure 4 , 6–11 View Figure 6 View Figure 7 View Figure 8 View Figure 9 View Figure 10 View Figure 11 , 12C View Figure 12 )

Material examined. Holotype: male [20.40 mm CL or 23.91 mm CLR], Brazil, Ribeira de Iguape Hydrographic Basin, Alto Ribeira karst region, state of São Paulo, county of Guapiara , Intervales State Park , Lago Subterrâneo cave (cave entrance: 24°19’34.1”S 48°29’24.4”W), Sérgio L. S. Bueno, Adriana P. Bueno and Alexandre L. Camargo colls., 19.ii.2011 ( MZUSP 35193 View Materials ) GoogleMaps . Paratypes: 2 males [18.11–20.57 mm CL; 21.46–23.95 mm CLR] and 3 females [15.67–18.01 mm CL; 18.88–21.65mm CLR],same data as holotype ( MZUSP 35194 View Materials ) GoogleMaps ; 1 male [15.91 mm CL; 19.20 mm CLR], 1 female [16.02 mm CL; 19.13 mm CLR], same data as holotype, except Alexandre L. Camargo coll., 18.xii.2010 ( MZUSP 35195 View Materials ) GoogleMaps , 1 female [14.67 mm CL; 17.27 mm CLR], same data as holotype, except Alexandre L. Camargo coll., 18.xii.2010 ( CCDB 6140 View Materials ) GoogleMaps .

Diagnosis. Pigmented area of cornea slightly reduced. Rostrum long with fringe of setae subventrally on mid- and proximal third of lateral margins. Tuft of setae behind shaped subrostral process. Anterolateral spine curved upward and not reaching basal margin of cornea. Cardiac area trapezoidal. Areolar area subrectangular. Partially developed uniramous, one- or two-segmented pairs of pleopods on pleonal somites 2‒5 in adult male specimens. Posterolateral margin of telson concave mesially.

Description of the male holotype. Compound eyes: pigmented area of cornea slightly reduced (grade 1; see definition in the discussion section) as compared to epigean species, eyestalk well developed.

Anterior dorsal region of carapace ( Figs. 6 View Figure 6 , 7A View Figure 7 ): rostrum long, narrow base triangular shaped (ratio = 0.94), distal end slightly curved upward, apex overreaching distal end of cornea, lateral margins with row of corneous scales regularly distributed; fringe of long pappose setae evenly distributed subventrally on mid- and proximal third lateral margins of rostrum, and extending to margins of orbital and extraorbital sinuses as well. Rostral carina extending posteriorly to merge with general surface of carapace at level of protogastric lobes (in lateral view), reaching tip of rostrum anteriorly, elevated at mid-third, and punctuated with small scattered corneous scales. Sub-rostral process on proximal half of subrostral margin well developed, produced ventrally, triangular shaped, apex blunt, and with tuft of long pappose setae posteriorly. Orbital spine prominent, with spiny corneous tip; orbital and extraorbital sinuses well defined. Anterolateral spine acute, with cornified tip, curved upward (approx. 30°) and not reaching basal margin of cornea. Delimitation between posterior margin of anterolateral lobe and first hepatic lobe deeply demarcated, the latter tipped by blunt corneous scale at anterolateral angle. Lateral margin of the three hepatic lobes considered altogether and sequentially slightly concave in dorsal view and noticeably arcuate in lateral view, being more elevated at level of second hepatic lobe. Demarcation between first and second hepatic lobes weak, distinguishable as a small notch on lateral margin. Demarcation between second and third hepatic lobes rudimentary and noticeable as an incipient discontinuity on lateral margin. Dorsum of second hepatic lobe merging seamlessly with dorsum of gastric area. Epigastric prominences pronounced, round-shaped and ornamented with few corneous scales on summit. Protogastric lobes rudimentary, with few corneous scales on top. Posterior gastric pits not visible externally.

Posterior dorsal region of carapace ( Fig. 6 View Figure 6 ): Anterolateral region of epibranchial area slightly oriented upward, tipped by spiny corneous scale; anterior margin slightly concave; lateral margin straight, with corneous scales. Interior branchial area marked by elevated inner half area and depressed outer half area. Cardiac area trapezoidal (1.38). Areolar area sub-rectangular (1.93). Lateral margin of posterior branchial area with row of small corneous scales regularly distributed. Posterior margin devoid of corneous scales.

Third and fourth thoracic sternal plates ( Fig. 7C View Figure 7 ). Third sternite: anteromesial margin abrupt, with two spiny corneous scales terminally. Fourth sternite: anteromesial region unarmed, with few long setae subdistally; anterolateral angles produced anteriorly, curved upward, and with apical corneous scale.

Chelipeds (first pair of pereopods) ( Figs. 6 View Figure 6 , 7B View Figure 7 ). Unequal in size. Major cheliped. Dactylus (movable finger): dorsal margin and outer surface punctuated with small corneous scales, inner surface smooth; proximal lobe on dorsal margin with corneous scales; tufts of setae regularly distributed next to cutting margin on outer and inner surfaces; proximal third of cutting edge with wide lobular basal tooth covered by juxtaposed flat corneous scales of various sizes, the largest being the second distalmost one; remaining two-thirds of cutting edge with row of corneous scales changing width from wide proximally to narrow distally. Propodus: palm low (5.84), outer surface covered with corneous scales, longitudinal depression on upper section of proximal half near articulation with carpus; inner surface smooth, weakly excavated axially on lower-third section and accompanied by row of setal tufts; palmar crest rectangular, outer surface excavated, proximal half of dorsal margin with 4 tubercles tipped by spiny corneous scales, distal half lobulated, with row of corneous scales. Proximal third of cutting edge of fixed finger with wide lobular basal tooth covered by rows of juxtaposed flat corneous scales of various sizes; remaining two-thirds of cutting edge with row of corneous scales changing width from wide proximally to narrow distally; distal end with plate-like fused scales curved inward; tufts of simple setae distributed regularly along cutting margin on outer and inner surfaces of fixed finger. Carpus: dorsal margin with well-developed spiny subterminal lobe, and 3 spines decreasing in size proximally, and small tubercle devoid of corneous tip; subterminal lobe and spines on dorsal margin separated by large concave gap accompanied by 1 small, displaced spine next to carpal ridge; outer surface with carpal ridge adorned with groups of corneous scales and tiny setae regularly spaced; inner surface with three tubercles of unequal size near dorsal margin, accompanied by long simple setae, the distalmost tubercle being the largest one and surmounted by spiny corneous tip. Merus: dorsolateral edge adorned with row of low tubercles tipped by corneous scale, the distalmost one being the most developed; ventromesial edge with 6 tubercles gradually increasing in size distally, the distal one being the largest; ventrolateral border with 2 large tubercles subterminally near distal transverse groove followed by row of small tubercles proximally. Basi-ischium: dorsolateral edge with one heavy spine near articulation with merus; ventromesial edge with 5 spiny tubercles, the distalmost one being the largest; ventrolateral border smooth. Coxa: globose, unarmed.

Minor cheliped morphologically similar to major cheliped except as noted hereafter. Dactylus (movable finger): lobular basal tooth narrow covered by single row of spiny corneous scales; the remaining two-thirds of the cutting edge with row of narrow corneous scales. Propodus: inner surface excavated axially on both upper-third and lower-third sections, accompanied by tufts of simple setae, and producing an elevated area mesially ornamented by few tufts of simple setae; lobular basal tooth on proximal third of cutting edge of fixed finger rudimentary; cutting edge (lobular basal tooth included) with single row of narrow corneous scales. Carpus: dorsal margin with 5 spines, the largest being the second distalmost one; inner surface with 2 tubercles near dorsal margin, both surmounted by corneous tip. Merus: dorsolateral edge with one spine subdistally, followed by row of low tubercles tipped by corneous scale.

Second, third and fourth pairs of pereopods: morphologically similar, slender and laterally compressed. Row of spiny corneous scales regularly spaced along dorsal margin of dactyli, propodi, carpi and meri. General surface of dactyli covered with small pits from which tufts of simple setae sprout. Propodi with concentration of short simple setae on dorsal margin and long simple setae on ventral margin. Carpi trapezoidal, with concentration of short simple setae on dorsal margin. Dorsal margin of meri predominantly covered with pappose setae on proximal half and simple setae on distal half. Basi-ischii with group of pappose setae on dorsal margin. Coxa globose.

Fifth pair of pereiopods. Reduced, segments cylindrical in cross section, except ischium (laterally compressed on proximal half), and dactylus (small, dorsally flattened, highly setose, and form minute chela with fixed finger of propodus). Propodus highly setose (fixed finger included). Carpus as long as propodus; setae more concentrated on distal third. Merus longer than carpus. Ischium slightly curved axially. Sexual tube long and narrow on coxa. [ Fig. 8 View Figure 8 shows sexual tube from the left fifth pereopods removed for SEM (Scanning Electron Microscopy) preparation from male paratype MZUSP 35194; CL = 20.57 mm; CLR = 23.95 mm, with similar morphology to the sexual tube of holotype.]

Pleonal epimera (D). Anterolateral angle of second epimeron and ventral angle of second, third and fourth epimera unarmed.

Pleopods. Partially developed, uniramous, one- or two-segmented. Second and third pairs, and left fourth pleopod one segmented, showing as conical buds. Right fourth and fifth pair two-segmented, about one-third as long as corresponding pleopods in adult female specimens; proximal segment longest, with concentration of long simple setae at distal end near articulation with distal segment. Distal segment short, slender, approximately one-fourth of the size of proximal segment and with long, simple setae concentrated distally. [ Fig. 11 View Figure 11 from male paratype, 20.57 mm CL; 23.95 mm CLR (MZUSP 35194)]

Uropods ( Fig. 9 View Figure 9 ). Biramous, wide (1.01), with fringe of long, plumose setae along free margins.

Telson ( Fig.9 View Figure 9 ). Longitudinal suture well developed on dorsal surface, dividing the telson in two trapezoidal halves. Anterolateral margin with fringe of plumose setae on distal third; posterolateral margin concave mesially, with fringe of plumose setae which are longer terminally.

Variations. Cephalothoracic region . In all specimens examined of the type series, except the holotype, the subrostral process is subrectangular-shaped, slightly oriented anteriorly and with rounded apex in both sexes [ Fig. 10 View Figure 10 , from male paratype; 18.11 mm CL; 21.46 mm CLR ( MZUSP 35194 View Materials )]. Other morphological variations observed in the type series are as follows: lateral margin of the hepatic lobes considered together straight (in dorsal view) and elevation may be incipient (in lateral view); anteromesial margin of third sternite truncate .

Chelipeds.Major chelipeds: tip of dactylus of major chela with inward plate-like fused scale (absent only in the holotype, possibly worn out or missing). Dorsal margin of palmar crest may be lobulate in its entirety, being formed by evenly distributed tubercles tipped by corneous scales. Number of spines on dorsal margin of carpus of major cheliped may vary from 3 to 5, the largest one being either the first or the second distalmost one. Small displaced spine next to carpal ridge may be missing. Number of tubercles on inner surface of carpus may vary from 2 to 4. Number of tubercles on ventromesial edge of merus may vary from 5 to 6.

Pleon. Ventral angle of third and fourth pleonal epimera armed with one corneous scale each. Developmental stage of male pleopods 2–5 varies considerably, though none can be viewed as fully developed. Usually the 4 th and 5 th pairs are two-segmented, but similar morphological condition may be observed in the 2 nd and 3 rd pairs as well.

Females.Apart from the obvious sexually dimorphic condition with regard to the size of the first pair of chelipeds (they are smaller in females), the general morphology of this pair of appendages is similar in both sexes. In females, the elevation at middle-third section of rostral carina is less pronounced and uropods are narrower (0.90 ± 0.04; n = 5) than they are in males (1.02 ± 0.05; n = 4).