Osornodella gabrielae, Pérez-Schultheiss, Jorge, 2013

Pérez-Schultheiss, Jorge, 2013, Osornodella gabrielae, n. gen. and n. sp., a new falklandellid (Amphipoda: Gammaridea) from freshwaters of the Chilean Coastal Range, Zootaxa 3599 (5), pp. 446-456 : 447-452

Osornodella gabrielae n. sp.

( Figs 1–6 )

Aff. Sternomoera sp. Pérez-Schultheiss, 2009: 150, fig. 3.

Type specimens: Holotype: undissected female ( MZUC N°37180) 4.48 mm, Los Riscos, Purranque, 21-VII-2005, Col. J. Pérez & A. Arriagada, Boca Vertiente Quebrada Pangal. Allotype: undissected male ( MZUC N°37181) 4.47 mm, same data as holotype

Paratypes: one dissected female ( MZUC N°37182) carcass and appendages mounted in a slide; dissected female and male ( MZUC N°37183), carcasses in a vial and right antennae mounted in slide MG-6; two undissected males and one female ( MZUC N°37184); one dissected male ( MZUC N°37185) carcass and gills mounted in a slide (MG-6); one dissected female ( MZUC N°37186); all paratypes from Los Riscos, Purranque, Osorno, 21-VII-2005, Col. J. Pérez & A. Arriagada.

Other material studied: Los Riscos, Purranque, Provincia de Osorno; 21-VII-2005; Col, J. Pérez & A. Arriagada:; 5 males, 8 females and 3 juveniles, all undissected ( MZUC N°37187); 1 male, 12 females and 3 unsexed specimens (JPS-55), vertiente en plantación de Eucalyptus a 2 m de camino; 5 ovigerous females, 5 females and 1 unsexed specimen (JPS-60), vertiente 1, sendero Jimmy, sedimentos; 1 male, 2 ovigerous females, 4 females and 2 juveniles (JPS-57), Vertiente a un m. de estero; 4 males and 4 females (JPS-61), borde estero Quebrada Pangal, entre sedimentos; 2 males (JPS-64), Riachuelo Bosque Nativo; 1 male, 4 females and 1 juvenil (JPS-65), boca vertiente quebrada Pangal; 1 dissected female (JPS-68), carcass and oostegites mounted in a slide, and 1 dissected male (JPS-74), all mounted in a slide, Vertiente 2, sendero Jimmy, sedimentos y bajo troncos y piedras; 1 dissected female (JPS-96), carcass and appendages mounted in a slide: vertiente a 1 m de estero; 1 male and 7 females (JPS-97), vertiente helechos vecina a quebrada. Los Riscos, Purranque, Provincia de Osorno; 12- VII-2005; Col, J. Pérez & A. Arriagada: 6 males, 3 ovigerous females and 5 unsexed specimens (JPS-58), vertiente 2, sendero Jimmy, sedimentos y bajo troncos y piedras. Tril Tril, Osorno; 12-X-2003; Col. Equipo CCULA 3° Campaña: 8 unsexed specimens and 1 ovigerous female partially destroyed (JPS-59), acantilados frente al mar, vertientes bajo piedras, entre sedimentos. Rucapihuel, San Juan de La Costa, Osorno; 25-VIII-2004; Col. J. Pérez: 2 females (JPS-63), sedimento grava fangosa-arenosa, riachuelo. Pucatrihue, San Juan de La Costa, Osorno; 12-II-2012; Col. J. Pérez: 1 female and 1 juvenile (JPS-69): riachuelo acantilado, orilla camino. Parque Pichimallay, San Juan de La Costa, Osorno; 8-VII-2005; Col. J. Pérez: 1 dissected male (JPS-62), carcass and appendages mounted in a slide: margen riachuelo sendero, sedimentos fango-arenosos.

Type locality: Los Riscos (40°53’S, 73°29’W), Purranque, eastern slope of Coastal Range, Osorno Province, Los Lagos Region, Southern Chile.

Diagnosis: as for the genus.

Description: Female: Total length: 2.98–4.67 mm (mean: 3.94 mm). Head: eyes absents; inferior antennal sinus well defined ( Figure 1 : H); antennula and antenna sexually dimorphic, articles tend to be slightly longer and slender than male, especially in flagellum. Antennula ( Figure 1 : bA1): about 30% longer than antenna; length of peduncular articles 1-3 between the ratios 1:0.8:0.7 and 1:0.6:0.4; peduncle articles narrowing progressively from 1 to 3; flagellum longer than peduncle, with 17–21 articles, every article with distolateral slender setae, slightly longer than in males. Accessory flagellum uni-articulate, vestigial, scale-like. Antenna ( Figure 1 : bA2): shorter than antennula, mean 62% (range 52 to 71%) of the antennular length; peduncular article 1 broad, rounded, gland cone slightly shorter than peduncular article 3, peduncular article 4 generally slightly longer than article 5, ratio as 1:0.8 (rarely slightly shorter, with ratio 1:1.08); peduncle and flagellum with distal slender setae; flagellum with 12–17 articles, first five articles in the ratio 1:0.7:0.5:0.6:0.6 or 1:0.8:0.5:0.5:0.6; articles 1 and 2 longer than wide, and articles 3-4 wider than long or as long as wide ( Fig. 1 : bA1 and bA2).

Labrum ( Figure 2 : bLa): without particular characters. Right mandible: incisor 6-denticulate, denticles blunted; lacinia mobilis bifid, sharp pointed, with margins slightly dentate and postero-proximal setulae; about 5 setulose rakers; molar strong, triturative, with one long marginal plumose seta; palp articles 1:2: 3 in the ratios 0.4:1:1, article 3 with about 6–8 D-setae, 2–3 E-setae and two B-setae (cf. Figure 2 : arM). Left mandible: incisor with 6 teeth; lacinia mobilis 4-dentate (cf. Figure 2 : alM). Paragnath ( Figure 2 : bPa): without distinct internal lobes; outer lobes distally covered with small and slender setulae and some truncated small and slender setae ( Fig. 2 : bLl). Maxillule ( Figure 2 : bM1): palp biarticulate, asymmetrical, article 2 longest, distally setose, left palp with 6 apical setae and one slender median subapical setae, right palp with 2 lateral subapical setae and 3 strong medial subdistal setae, basal endite with 9 distal comb-like strong setae; coxal endite with 6 apical plumose setae. Maxilla ( Figure 2 : bM2): endites distally with 2 rows of long setae, internal lobe with oblique row of 6 setae. Maxillipeds ( Figure 2 : bMp): basal endite with 3 strong short setae and several medial and distal slender setae, ischial endite with medial and distal setae, palp developed, carpal article longest, elongate and wide, with a row of long medial setae, propodus with distolateral lobe.

Gnathopods subsimilar, 1 smaller than 2; gnathopod 1 ( Figure 3 : Gn1): coxa subrectangular, longer than wide; basis with 5 long setae on posterior margins; merus with posterodistal setae; carpus subtriangular, shorter than propodus, with setae on posterior margin; propodus subrectangular, palmar margin slightly convex, defined by a small angular spine and 4 strong setae; dactylus with 1 seta on anterior margin, and 2 setae and 2 small recumbent teeth in posterior margin ( Figure 3 : PGn1). Gnathopod 2 ( Figure 3 : Gn2): coxa 2 subrectangular; basis with 5 long setae on posterior margin; merus with posterosubdistal setae; carpus subtriangular, shorter than propodus, and posterior margin produced in a posterior lobe longer than in gnathopod 1; propodus subrectangular, posterior margin with setae, palmar margin convex, defined by 4 strong spines, as in gnathopod 1; dactylus as in gnathopod 1. Propodus palm of both gnathopods with inclination of 50° in relation to anterior margin of article ( Figure 3 : PGn1).

Pereopods 3–4 subequal ( Figure 3 : P3 and P4), without sexual dimorphism; coxa 3 subrectangular, coxa 4 subquadrate, posteriorly excavate; basis elongate with long setae along posterior margin and slightly shorter along anterior margin. Coxae 5 bilobate; coxa 6 with posteroventral lobe. Pereopod 5 ( Figure 4 : P5): basis suboval, posterior margin feebly convex with 3 short spines, postero-ventrally not lobed, anterior margin with 4 groups of strong setae. Pereopod 6 ( Figure 4 : P6): longer than pereopod 5, basis suboval, postero-ventrally with a small lobe, posterior margin convex, with 11 small setae. Pereopod 7 ( Figure 4 : P7): similar to pereopod 6.

Epimeral plates ( Figure 5 : cAb): postero-lateral corner rectangular rounded in epimeron 1, acutely angled in epimera 2 and 3, with two or three setae in anteroventral margin of epimeron 1, no more than two submarginal setae, placed anteroventrally in epimera two and/or three. Pleopods ( Fig. 5 : Pl1 to Pl3): peduncle with a distolateral lobe and two mediodistal coupling hooks, ramus subequal, longer than peduncle. Uropod 1 (cf. Figure 5 : aU1): ramus shorter than peduncle, exopodite slightly shorter than endopodite; uropod 2 (cf. Figure 5 : aU2): rami near as long as peduncle, exopodite distinctly shorter than exopodite; uropod 3 (cf. Figure 5 : aU3): shorter than 2, rami longer than peduncle, endopodite uniarticulate, nearly as long as exopodite; endo and exopodite lined with short strong setae, single in lateral margin and paired in medial margin. Telson ( Figure 5 : cT): nearly as long as wide, divided in 20-30% distal forming two rounded lobes (with or without distal concavity); setal pattern variable, with one to 3 subdistal slender setae and 3–4 dorsally dispersed slender setae on each lobe. Coxal gills ( Figure 6 : bC2 to bC7): on segments 2 to 7. Sternal gills ( Figure 6 : bS2 to bS7): on segments 2 to 7, 3 to 6 bifid, 2 and 7 simple. In two females sternal gills exceptionally on segments 2 to 6, with 2 and 6 simple. Oostegites ( Figure 6 : aO2 to aO5): present from coxa 2–5, 2 broad and concave, 5 reduced and with scarce setae.

Male: Total length: 2.84 – 4.47 mm (mean: 3.77 mm). As female except by: flagellum of antennula with aestethascs present in flagellum articles 2, 3, 5, 7, 9, 11, 14 and last 1–2 subdistal articles (not seen in distal); and small calceoli of “gammarid” type in peduncular articles 3 (2 in some specimens, see Figure 1 : H) and flagellum articles 2, 3 and/or 5 (1 and 7 in some specimens, see Figure 1 : aA1). Flagellum of antenna with 14–17 articles, first five articles of antennal flagellum in the ratio 1:0.9:1.2:1.3:1.2 or 1:1:1.2:1.3:1.3; articles 1 and 2 wider than long. Small calceolus from flagellum articles 1 or 2, 3 and 4, 5 or 7 ( Figure 1 : aA2).

Etymology: This species is named for Gabriela, in recognition of her support and huge patience during all these years and for allowing me to work on this project in the lab at home, during our family time.

Ecological observations: Osornodella gabrielae n. sp. is a common inhabitant of small running freshwater springs, in zones covered by temperate forest on both eastern and western slopes of coastal cordillera of Osorno Province, Los Lagos Region, Chile. Some animals were obtained abundantly in a spring where the original forest was replaced by exotic Eucalyptus globulus plantations of at least 25 years old; and an additional specimen was collected in water film below the stones in a filtration of groundwater at cliff facing the sea. Individuals were scarce in deforested places surrounding the forest, but their presence in this unusual habitats suggests that the species would be an emergent-subterranean, as it seems occurs with other falklandellids ( Stock & Platvoet 1991). In general, the animals inhabit below stones and among fine sediments, with high organic matter content (leaf litter and other vegetal detritus), in the first several meters downstream, and especially in the emergence of the spring from the ground.

Figures

FIGURE 1. Osornodella gabrielae n. sp., male (JPS- 57): head, with detail of accessory flagellum. Male “ a ” and female “ b ” (both MZUC N ° 37183): antennae. Scale: 0.1 mm.

FIGURE 2. Osornodella gabrielae n. sp., female paratype (MZUC N ° 37182): mouthparts. Male “ a ” (JPS- 74): mandibles. Scale: 0.1 mm.

FIGURE 3. Osornodella gabrielae n. sp., female paratype (MZUC N ° 37182): gnathopods and pereopods. Scale: 0.1 mm.

FIGURE 4. Osornodella gabrielae n. sp., female paratype (MZUC N ° 37182): pereopods. Scale: 0.1 mm.

FIGURE 5. Osornodella gabrielae n. sp., male (JPS- 60): pleopods. Male “ a ” (JPS- 74): uropods; male “ b ” (JPS- 57): telson; female paratype “ c ” (MZUC N ° 37182): abdomen and telson. Scale: 0.1 mm except for cAb: 0.5 mm.

FIGURE 6. Osornodella gabrielae n. sp., female “ a ” (JPS- 68): oostegites; male “ b ” (JPS- 60): coxal and sternal gills. Scale: 0.1 mm.