Aegla manuinflata Bond-Buckup & Santos

Santos, Sandro, Bond-Buckup, Georgina, Pérez-Losada, Marcos, Bartholomei-Santos, Marlise Ladvocat & Buckup, Ludwig, 2009, Aegla manuinflata, a new species of freshwater anomuran (Decapoda: Anomura: Aeglidae) from Brazil, determined by morphological and molecular characters, Zootaxa 2088, pp. 31-40 : 35-39

Aegla manuinflata Bond-Buckup & Santos n. sp.

( Figure 2 )

Material examined. Holotype: male, TCL 23.48 mm, Taquara stream ( Fig. 3 ), northern part of the São Pedro do Sul municipal district, central region of Rio Grande do Sul (29º36’01”S, 54º10’37”W; altitude 158 m above sea level). Collected on 8 Dec 2001 (Sandro Santos, coll.) ( UFRGS 4438H).

Paratypes: 7 males, TCL from 16.76 to 21.49 mm; 4 females, TCL from 12.44 to 19.18mm. Same data as holotype ( UFRGS 4523).

Non-type material (utilized for morphometric and molecular analysis): Itaimbé stream: 5 males, TCL from 18.36 to 22.56 mm, 1 female, TCL 14.25 mm, São Martinho da Serra municipal district, also in the central region of Rio Grande do Sul, on the edges of the slopes of the Geral Range (29º30’39”S, 53º52’09”W), 424 m above sea level, material collected on 30 Mar 2007 (Sandro Santos, coll.). Água Negra stream: 2 males, TCL 19.69 and 15.13 mm, 1 female, TCL 15.30 mm, 29º35’23”S, 53º52’11”W, 222 m above sea level, collected on 31 Mar 2007 (Sandro Santos, coll.).

Diagnosis. Anterolateral spine of carapace reaching to base of cornea; protogastric lobes present; extraorbital sinus U-shaped. Rostrum triangular, carinate along its entire length, deflected. Cheliped hand inflated; proximal outer margin of dactylus with lobe; fingers without lobular tooth; palmar crest absent; inner margin of ventral face of ischium with 1 distal tubercle. Dorsal margin of carpus of second and third pereiopods with short slender setae. Anterior angle of ventral margin of epimeron 2 armed.

Description. Carapace moderately convex, area of gastric region more elevated than other regions, dorsal surface scabrous, covered with small scales and punctations.

Front large; PCW/FW ratio of male holotype 1.83.

Rostrum triangular, elevated along its entire length, deflected, of medium length, broad at base and tapered at extremity, indented in middle, carinate to apex. Subrostral process absent; in profile, rostrum with dorsal part higher than ventral part. Rostral carina beginning near protogastric lobes, with multiple parallel, closely set rows of pronounced scales extending to tip. Lateral margins of rostrum scaly.

Orbits moderately broad, shallow, bounded externally by an orbital spine. Orbital margin with few scales. Extra-orbital sinus U-shaped.

Anterolateral angle of carapace projecting anteriorly in a spine reaching to base of cornea. Outer margin of anterolateral lobe with scale-shaped tubercles; inner margin unarmed.

First hepatic lobe delimited anteriorly by deep fissure; lateral margin with subequal, scale-shaped tubercles; 2nd and 3rd hepatic lobes delimited with only modest incision; lateral margins with subequal, scaleshaped tubercles.

Epigastric prominences little defined, low, irregular in shape, elongated toward base of 1st hepatic lobe, with few scales. Protogastric lobes moderately elevated; anterior margin marked only by several scales.

Transverse dorsal line slightly sinuous. Areola quadrate, with margins subparallel along their entire length. AL/AW of male holotype: 1.37.

Epibranchial area triangular, well developed, with one apical tubercle followed by smaller, scale-shaped tubercles. Lateral margins of anterior and posterior branchial area with subequal, scale-shaped tubercles.

Anterior angle of ventral margin of epimeron 2 armed with tubercule; ventro-lateral margin slightly convex; posterior angle of ventral margin unarmed. Epimera of 3rd to 6th segments produced; on 3rd and 4th the lateral projection is ornamented with a small apical tubercle.

Telson divided by longitudinal sulcus.

Anterior extremity of third sternite acuminate, projecting between coxae of exopodites of third maxillipeds. Fourth thoracic sternum elevated, with a medial tubercle, lateral margins not recurved; anterolateral margin projecting, with one tubercle; tuft of long setae, transversely on anterior part of segment.

Cheliped unequal, hand quadrate. Major cheliped globose, palm inflated in medial and posterolateral region, covered by corneal scales. Minor cheliped more tapered. Palmar crest absent. Pre-dactylar lobe forming small step with anterior margin of propodus. Fingers thickened and covered with scales. Proximal outer margin of moveable finger without lobe. Prehensile margins of fingers with scale-shaped denticles along their entire length, with opposing, dovetailed lobular teeth. Dorsal face of carpus rugose, with scales; inner margin with 3 or 4 spines, the distal spine being the most robust of the group; these spines bear a few scales on the lateral margins; inner anterolateral angle subobtuse, with apical tubercle; anterodorsal margin with scales. Carpal crest modestly pronounced, especially at the proximal region, where there are scales in groups of 3–5 on the elevations of the crest; in the distal region, the crest is absent, with few scales; well-marked depression between carpal crest and inner antero-lateral angle; outer ventral angle of carpus with one spine; ventral face with 1 conical spine. Dorsal margin of merus of cheliped with one, more-pronounced, distal spine, the rest of the margin with scale-shaped tubercles; anterodorsal margin with scales. Lateral faces scabrous, with scales. Inner ventral margin of merus with distal scale-shaped tubercles; outer ventral margin with a prominent distal tubercle, followed by scale-shaped tubercles. Dorsal margin of ischium with elevation ornamented with tubercle; inner margin of ventral face with 1, more-prominent distal tubercle, and an elevation with scales arranged along the margin.

Dorsal margin of dactylus, propodus, and carpus of 2nd, 3rd, and 4th pereiopods with longitudinal rows of setae. Carpus of 2nd and 3rd pereiopods armed anterodorsally with one scale-shaped tubercle.

Variations: Specimens from Itaimbé stream have a shorter rostrum, and the tubercle on the 4th thoracic sternum is less pronounced.

Etymology. The specific name is an allusion to the cheliped propodus of the animals, which is relatively well developed, like a boxing glove. From Latin, manus means hand, and inflata means inflated.

Distribution. The Ibicuí-Mirim River rises north of the town of Santa Maria, in an area of the Geral Range, locally called the Pinhal Range. This river flows westward, and after about 130 km it joins the Santa Maria River to form the Ibicuí River. This last is the main affluent of the Uruguay River, and is nearly 290 km long with a drainage area of 46,850 km 2. (Source: Ministry of Transports of Brazil: http:// www.transportes.gov.br/bit/hidro/detrioibicui.htm - accessed on 08/20/2008).

Aegla manuinflata n. sp., was first recorded in Taquara stream, São Pedro do Sul municipal district ( Fig. 3 ). This stream is formed by three springs rising on the slopes of the Geral Range ( Fig. 3 ). The waters from these springs join to form the Taquara stream, which flows for about 20 km from north to south toward the right bank of the Ibicuí-Mirim River. This stream has boulders, cobbles, and gravel (pebbles) (>256; 256 to 64 mm and 64 to 4 mm diameter, respectively) in its stretch near the mountain slopes. As it flows farther from the mountains and enters the region known as the Central Depression, the larger particles become scarce and the bed is sandy. In this latter area, no specimens of A. manuinflata were found.

Besides the Taquara stream, the species was also recorded in the Água Negra stream, a tributary of the left bank of the Ibicuí-Mirim River. The mouths of these two streams are about 40 km distant from each other. In this section the Ibicuí-Mirim River flows in the transition region between the Central Depression (mean altitude 100 m) and the Geral Range (up to 500 m). The Itaimbé stream flows toward the Ibicuí-Mirim at about 5 km upstream from the mouth of Água Negra stream. Itaimbé stream is about 15 km long and is situated entirely on the slopes of the Geral Range. Its sources lie near the São Martinho da Serra municipal district, in an area of about 500 m altitude.

Both the Água Negra and the Itaimbé streams have similar physiographic features to those of the Taquara stream, only differing by being located in more uneven terrain.

In the Itaimbé stream, besides A. manuinflata , A. longirostri was also recorded. However, the latter occurred in smaller numbers, about one-tenth of those of A. manuinflata .

Besides Itaimbé stream, A. longirostri was also recorded in the sources of the Ibicuí-Mirim and Toropí rivers. The latter is a tributary of the left bank of the Ibicuí-Mirim. There is no record of A. manuinflata for these two areas.

Aegla platensis is also present in this hydrographic basin, specifically between the source of the Ibicuí- Mirim and the mouth of Itaimbé stream. This species is also recorded in tributaries of the Jaguarí River, whose mouth is on the right bank of the Ibicuí, about 30 km downstream from the confluence of the Ibicuí-Mirim and the Santa Maria, and 60 km from the mouth of the Toropí. In the Jaguarí River basin, A. singularis has been recorded in its middle stretch, and A. spinipalma Bond-Buckup & Buckup, 1994 in its sources.

Comparisons. Aegla manuinflata n. sp. resembles A. inermis Bond-Buckup & Buckup, 1994 in the absence of a palmar crest and the shape and ornamentation of the carpus of the cheliped. It differs from the latter by several features: the carapace is more elevated, with more marked and defined regions; the propodus of the chelipeds is strongly globose and inflated, and the dactyls are more elongated. The rostrum of the new species is much more elevated, and the rostral carina is more pronounced and has multiple rows of scales; whereas in A. inermis the rostrum is much lower and the carina is less pronounced in the apical region, with only one row of scales.

Aegla manuinflata lacks a palmar crest on its chelipeds, and so resembles in part A. inermis and also A. uruguayana . However, it differs in having an inflated propodus (hand), larger than those of the other two species.

Another distinguishing feature between A. manuinflata and A. uruguayana is the PCW/FW ratio. Whereas for the latter the mean value is 1.61 in males and 1.67 in females ( Bond-Buckup & Buckup 1994), the mean value for A. manuinflata is 1.75 in males and 1.85 in females. Aegla inermis shows an intermediate value for males (1.74) and a lower one for females (1.71). Thus, besides the differences in chelipeds, there is also a difference in relation to the front width.

Regarding the biogeography of these three species, A. manuinflata was recorded at only three localities, all in the sub-basin of the Ibicuí-Mirim River, which in its turn is a tributary of the Ibicuí. There is no record of A. uruguayana in that sub-basin. However, this species is present in streams that form the sub-basin of the Santa Maria River, which rises in the southern part of Rio Grande do Sul and flows to the central-west region, where it joins the Ibicuí-Mirim near the Cacequi municipal district, forming the Ibicuí. Aegla inermis is only present in the eastern part of the state, in the Sinos River basin (Cará stream). There is no communication between the basins in the east and west parts of the state. Our molecular data showed Aegla manuinflata to be closely related to A. platensis and A. singularis . These two species are present in streams near those where specimens of A. manuinflata were recorded. Nevertheless, up to now the latter species was only found sharing habitat with A. longirostri . Morphologically the chelipeds of these four species are very distinct. In all but A. manuinflata there is a well-developed palmar crest, although the proportions of cheliped size in relation to other dimensions are close, in both males and females.

Conservation outlook. This species can be considered “Vulnerable”, according to the criteria of the International Union for Conservation of Nature ( IUCN 2001), because it has been recorded in only three localities up to the present, and its populations can be considered as fragmented and with limited distributions. Moreover, agricultural activity in the hydrographic basin, mainly pig farming, whose effluents are usually discharged into streams, may impair the water quality, and hence the survival of these crustaceans.

Figures

FIGURE 2. Aegla manuinflata n. sp. a: male holotype (UFRGS 4438 H), dorsal view; b: pre-cervical portion of carapace, side view; c: ischium of cheliped, ventral view; d: third and fourth sterna, ventral view; e: second abdominal epimeron.

FIGURE 3. Collection localities (solid circles) of Aegla manuinflata n. sp., in the central region of Rio Grande do Sul. Arrow indicates type locality. BR 158, BR 287 and BR 392 are federal highways.