Research Article |
Corresponding author: Damià Jaume ( damiajaume@imedea.uib-csic.es ) Academic editor: Tammy Horton
© 2017 Miguel Alonso, Damià Jaume.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Alonso M, Jaume D (2017) A new species of Hyalella from the High Andes of Ecuador (Crustacea, Amphipoda, Hyalellidae). ZooKeys 686: 1-13. https://doi.org/10.3897/zookeys.686.12223
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Hyalella cajasi sp. n. is described from high altitude shallow water lakes in southern Ecuador. This is the second representative of the genus recorded in the country after H. meinerti. The new species shares with nine South American species of the genus the display of a smooth, non-processiferous body, a male first uropod with a modified curved robust seta on the endopod, and six pairs of sternal gills. The new taxon can be distinguished from these species based on the presence/absence of eyes; relative length of antenna 1 with respect to antenna 2; presence/absence of short pointed robust seta distally on palp of maxilla 1; number of pappose setae proximally on medial margin of inner lobe of maxilla 2; elongation and curvature of the modified robust seta of endopod of male uropod 1; relative length of ramus of uropod 3 with respect to protopod; and armature and outline of telson, among other features. It seems to be a high-altitude endemic to the Cajas Massif in Azuay Province, being replaced in the same area at lower altitudes by H. meinerti.
Crustacea , descriptive taxonomy, high altitude lakes, Hyalella , new species, South America
Hyalella Smith, 1874 is the only genus of epigean freshwater amphipod known to occur in South America. The genus is the single member of the family Hyalellidae Bulyčeva, 1957, endemic to the Nearctic and Neotropical regions, where it is broadly distributed and diversified, to a current total of about 70 species (
Sampling was carried out during limnological surveys of 202 water bodies (lakes, lagoons and ponds) located between 3,150 and 4,460 m a.s.l. at Cajas National Park (Southern Ecuadorian Andes), in the framework of the project “Limnological Characterization of the lakes and lagoons of Cajas National Park”, funded by the University of Cuenca (Ecuador) and by Empresa Pública Municipal de Telecomunicaciones, Agua Potable, Alcantarillado y Saneamiento (ETAPA), of the municipality of Cuenca.
Samples were collected in 2015 in the littoral zone directly with a hand-held plankton net and fixed, in situ, in 95% ethanol. Once in the laboratory, specimens were dissected in lactic acid under the stereomicroscope, and appendages illustrated using a Leica DM2500 microscope equipped with Nomarski differential interference contrast and a drawing tube. Body measurements were derived from the sum of the maximum dorsal dimensions of body somites and exclude telson length. Type material is deposited in the Museo Ecuatoriano de Ciencias Naturales del Instituto Nacional de Biodiversidad, Quito, Ecuador [
The new species is known only from high-altitude (3,859 to 4,103 m a.s.l.) lacustrine water bodies at Cajas National Park, in the southern Ecuadorian Andes, where it is apparently endemic. It occurs both in the littoral zone of lakes and in shallow lagoons and temporary ponds. These water bodies are oligotrophic and low mineralized (Conductivity: 9.84-91.50 µS/cm), although they carry a significant amount of dissolved organic carbon (DOC) derived from adjacent terrestrial ecosystems, mainly Páramo grassland (“Pajonal”).
All collected by Henrietta Hampel at Cajas National Park (Azuay Province; southern Ecuador), 5th May 2015. Laguna Togliacocha (S2°47'55.90"; W79°15'02.13"); 3,859 m a.s.l. HOLOTYPE: male 9.0 mm, preserved in formaldehyde vial. PARATYPES: Five males and 5 females in formaldehyde vial. Holotype and paratypes registered under same registration number [
Body smooth, non-processiferous. Eyes normal. Antenna 1 much shorter than antenna 2. Incisor of mandibles multi-denticulate. Palp of maxilla 1 short, reaching to less than half distance between its insertion and distal margin of outer lobe, crowned with short robust seta. Inner lobe of maxilla 2 with two pappose setae proximally on medial margin. Coxal plate IV deeply excavated posteriorly. Six pairs of sternal gills, on pereionites II to VII. Uropod 1 sexually dimorphic, with male exhibiting a modified robust seta (“copulatory spine” sensu
Species name refers to Cajas National Park (Azuay Province; southern Ecuador), the type locality.
Body (not figured) up to 9.0 mm long, strongly pigmented, virtually black, smooth. Head (Fig.
Hyalella cajasi sp. n., male. A head with left antenna 1 and antenna 2 attached, lateral B inset of distomedial armature on posterior margin of articles 3-6 of antenna 1 C right epimeral plates D right pleopod 3, posterior. Scale bars: 0.2 mm (A, D); 0.1 mm (B); 0.5 mm (C, E, G–I); 0.05 mm (F).
Antenna 1 (Fig.
Antenna 2 (Fig.
Labrum (not figured) ordinary. Paragnaths (= lower lip; not figured) inner lobes absent.
Mandibles each with well-developed, triturative columnar molar; molar seta equally developed in both mandibles; palp lacking. Left mandible (Fig.
Maxilla 1 (Fig.
Maxilla 2 (Fig.
Maxilliped ordinary; basal endite (= inner plate) (Fig.
Coxal gills (Figs
Hyalella cajasi sp. n., male. A left gnathopod 1, medial (armature on palm margin of propodus and on dactylus omitted) B inset of carpal lobe, medial C inset of palm margin and palm angle of propodus, medial D inset of dactylus, medial E right gnathopod 2, medial (armature on palm margin of propodus and on dactlylus omitted) F inset of carpal lobe, medial G detail of palm margin and palm angle of propodus, and of dactylus, medial (submarginal armature along lateral side of palm margin omitted). Scale bars: 0.2 mm (A, G); 0.1 mm (B–D, F); 0.5 mm (E).
Gnathopod 1 (Fig.
Gnathopod 2 (Fig.
Pereiopods 3–4 (Fig.
Pereiopods 5–7 (Fig.
Pleopods (Fig.
Uropod 1 (Fig.
Uropod 2 (Fig.
Uropod 3 (Fig.
Telson (Fig.
Differing from male in smaller size (body up to 6.5 mm long); presence of oöstegites on pereionites II-V (Fig.
Of the approximately 70 species of Hyalella currently recognized (
Thus, Hyalella cajasi sp. n. differs from H. bonariensis Bond-Buckup, Araujo & Santos, 2008, described in
Diagnostic differences between H. cajasi sp. n. and H. brasiliensis Bousfield, 1996, from Paraná State (Brazil), include the short ramus of uropod 3, which is shorter than the corresponding protopod (versus ramus longer than protopod); the comparatively shorter propodus of male gnathopod 1, which is shorter than carpus (versus propodus about as long as carpus); and the male gnathopod 2 propodus with palm margin longer than the posterior margin (versus palm margin about as long as posterior margin) (see
The new species differs from H. carstica Bastos-Pereira & Bueno, 2012, a taxon known from Minas Gerais (Brazil), by the relative length of antenna 1, which is much shorter than antenna 2 (versus antenna 1 and antenna 2 about equal in length in H. carstica); by the presence of two pappose setae proximally on the medial margin of inner lobe of maxilla 2 (versus only one seta); by the broader than long telson (versus telson longer than broad); by the marginal armature of robust setae on telson, comprising a distal continuous series (versus single robust seta subdistally at each side); and by the much stouter male gnathopod 2 propodus, about 1.3 times as long as broad (versus 1.6 times, with palm margin much shorter than posterior margin) (see
Hyalella cajasi sp. n. differs from H. castroi González, Bond-Buckup & Araujo, 2006, a species from Rio Grande do Sul (Brazil), in the distal robust seta present on palp of maxilla 1 (versus palp pointed but devoid of armature in H. castroi); in the display of two pappose setae proximally on the medial margin of inner lobe of maxilla 2 (versus only one seta); in the condition of the modified robust seta on male uropod 1 endopod, which is hardly curved and only just surpasses the tip of endopod (versus seta elongate and strongly bowed); and in the stouter condition of male gnathopod 2 propodus, which is about 1.24 times as long as broad (versus 1.32 times) (see
Hyalella curvispina Shoemaker, 1942, known from Montevideo (Uruguay) and Rio Grande do Sul (Brazil), differs from the new species in the longer-than-broad telson, which in addition displays only 1+1 robust setae on distal margin, and the unarmed but pointed palp of maxilla 1. Furthermore, the modified setae on male uropod 1 endopod (sometimes it displays two instead of only one) are more elongate and curved than in H. cajasi sp. n. (see
Hyalella formosa Cardoso & Araujo, 2014 (described in
The new species differs from H. paramoensis Andres, 1988, a species known from a high altitude lake near Bogotá (Colombia), in the armature of the telson, which consists of a distal series of marginal robust setae (versus armature reduced to two long and slender robust setae in H. paramoensis); the presence of a robust seta on tip of the palp of maxilla 1 (versus palp unarmed); and in the relative length of the modified robust seta present on the endopod of male uropod 1 (versus seta extremely elongated in H. paramoensis) (see
Hyalella cajasi sp. n. differs from H. xakriaba Bueno & Araujo, 2013 (described in
Finally, H. cajasi sp. n. differs from H. veredae Cardoso & Bueno, 2014 (described in
With regards to H. meinerti, the only representative of the genus confidently known to occur in Ecuador until now, it differs from H. cajasi sp. n. in the display of a non-sexually dimorphic uropod 1, a 1+1 armature arrangement on distal margin of the telson, and in the presence of only one pappose seta proximally on the medial margin of the inner lobe of maxilla 2.
This study has been supported by a grant PROMETEO from Secretaría de Educación Superior, Ciencia, Tecnología e Innovación of Ecuador, to the first author, and partially financed by the Spanish State Research Agency (Agencia Española de Investigación, AEI) and the European Regional Development Fund (Fondo Europeo de Desarrollo Regional, FEDER) through the Project CGL2016-76164-P (AEI/FEDER, UE).