A new Limnocythere species in the Pampean region (Buenos Aires, Argentina)

Multiproxy paleolimnological research which includes the use of ostracods is in progress in several small lakes (lagunas) in the central plains of Buenos Aires province. Despite the great potential of ostracod-based reconstructions of past hydrological variations, such studies are still scarce. At least two syngamic species of Limnocythere have recently been recovered from Pampean Holocene lacustrine sedimentary cores. Correct identification of these species is of critical importance for the paleoenvironmental interpretation of the ostracod assemblages; however, the taxonomic status of the limocytherids reported from Holocene sediments in the area is far from clear. BERTELS & MARTÍNEZ (1990) mentioned two species of Limnocythere left in open nomenclature from Pampean sediments. CUSMINSKY & WHATLEY (1996) described some new species, including L. rionegroensis, from Patagonia and synonymized L. aff. L. bradburyi figured by BERTELS & MARTÍNEZ (1990) with this new species. FERRERO (1996) reported L. staplini from marginal marine deposits from Buenos Aires. BERTELS & MARTÍNEZ (1997) published a paper including the same two taxa of their previous work, without changes in their identification. CUSMINSKY et al. (2005) assigned L. aff. L. bradburyi of BERTELS & MARTÍNEZ (1990, 1997) to L. rionegroensis. LAPRIDA (2006) reported two extant limnocytherids, Limnocythere sp. and L. aff. L. staplini, and subsequently found them in sedimentary cores from Pampean lagunas (LAPRIDA & VALERO-GARCÉS, 2009). This account attests to the need of taxonomic revision of this genus in the area. In order to clarify its taxonomic status, we present the soft parts description of L. aff. L. staplini Laprida 2006 based on individuals newly collected from Arroyo Chico stream (37° 23´S- 57° 9´W). Lateral view: carapace fairly symmetrical; maximum length (ML) ~ 0.67 mm; maximum height (MH) ~ 0.28 ? 0.30 mm, occurring at ~1/3 ML. Dorsal view: anterior end beak shaped, posterior end rounded with left valve (LV) overlapping right valve (RV). Valve external ornamentation weak, presenting a light reticulate over the whole surface. A sulcus and two or three poorly developed tubercles occur slightly anteriorly of mid-length. Internal view: lophodont hinge of LV consisting of anterior and posterior teeth sockets flanking a central smooth bar; RV with corresponding smooth teeth and central groove. Marginal denticles absent. Marginal zone more developed anteriorly, with few straight, unbranched marginal pore canals. The four anteriormost appendages as for the genus; A2 lacks flagellated claws. Two setae on anterodistal edge of basal segment of the first walking leg (T1), one seta in the corresponding position of second and third walking legs (T2 and T3). Sexual dimorphism pronounced. Female: Dorsal margin rounded. Terminal claw of T1 about ¼ shorter than those of T2 and T3 (with T2 ≈ T3). Male: More elongated than female, carapace reniform, dorsal margin straight. T1 ≈ T2 in length, terminal claw of T3 ≈ 2.5 as long as terminal claws of T2 and T3. This species differs from L. staplini and L. bradburyi in the hinge (smooth vs crenulated elements); from both and L. rionegroensis in the slope of the dorsal margin of the female and shape of the male; and from L. staplini further in the sexual dimorphism in thoracopod size vs thoracopod size equal for both sexes (DELORME, 1970). The above combination of features is unique to this taxon, thus warranting the erection of a new species, Limnocythere sp. nov.Fil: Ramón Mercau, María Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Plastani, María Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Laprida, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina17th International Symposia on OstracodaRomaItaliaItalian Ostracodologists' GroupThe International Research Group on Ostracod

Implications of ostracod preservation in Holocene paleoenvironmental reconstruction of Lake La Brava (Argentina)

Peer reviewe

Mid-late Holocene lake levels and trophic states of a shallow lake from the southern Pampa plain, Argentina

Changes in trophic status of the shallow Lake La Brava (southeastern Pampa plain of Argentina) are evaluated based on geochemical, biological and sedimentological data. Based on a conceptual framework, we propose that the lake level defines the water column mixing conditions, affecting internal lake processes and determining the transparency of lake water. The shift between alternative states is reconstructed for the last ~4800 years. Four main lake stages have been recognized, although short term shifts characterize all stages. A turbid phytoplankton-dominated state prevailed between ~4700-4500 cal yr before present (BP). Drier conditions and low lake levels pushed the lake to a clear state until 2000 cal yr BP. Afterwards the lake switched back to a turbid state, and these conditions persisted until ~200 cal yr BP. In the last 200 years, the lake switched back and forth between clear and turbid states. The latter represents the modern conditions of the lake since ~1950 AD. These shifts can be attributed mainly to climatic drivers.We thank to Dr Juan Manuel Lirio and Lic Mario Núñez (Instituto Antártico Argentino) for field support. Nora Irene Maidana (Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina) help with diatom identification. Financial support was provided by PIP-CONICET 1265/08, PIP-CONICET 2142001100 100014, UBACyT 20020110100153 and CICYT project EROMED (CGL2011-25486). We thank the editor and two anonymous reviewers for their constructive comments, which helped us to improve the manuscript. This is the IDEAN contribution number R-112.Peer Reviewe

The role of Southern Hemispheric Westerlies for Holocene hydroclimatic changes in the steppe of Tierra del Fuego (Argentina)

The steppe of northern Tierra del Fuego is an important region for studying climate variability in the Southern Hemisphere, due to its position at the southern margin of the Southern Hemisphere Westerly Wind belt. Here we present a multiproxy analysis of a sedimentary sequence from Laguna Carmen (53°S, 68°W) which provides evidence of the progressive aridity and strengthening of the low-level Westerlies during the Late Holocene. We identified three prominent phases in the climatic record from Laguna Carmen: a cold and wet period between ~4000 cal. BP and ~2200 cal. BP, evidenced by a relative high lake level, periodic runoff into the lake, and oligohaline (mean: 2554 μS/cm) salinities; a step-change towards warmer and drier conditions after ~2200 cal. BP, reflected by limited runoff and oligo-mesohaline salinities (mean: 4799 μS/cm); and finally, the establishment of modern semi-arid conditions some time after ~1000 cal. BP, when the lake became a shallow lake that sometimes dried out during the summer. Our results coincide with paleoclimatic numerical models that suggest a progressive aridification of the southern Patagonian steppe since 6000 cal. BP due to stronger Westerlies and higher temperatures associated with changes in solar irradiance.Fil: Laprida, Cecilia. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Orgeira, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Fernández, Marilén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Tófalo, Rita. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Ramón Mercau, María Josefina. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Silvestri, Gabriel Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Berman, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: García Chapori, Natalia Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Plastani, María Sofía. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alonso, Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentin

Ostracods and paleolimnology of the southern Pampas: environmental and climatic reconstruction for the Late Holocene

Durante el siglo XX, la temperatura media de nuestro planeta se ha incrementado y las proyecciones indican un incremento adicional de ~2–6°C para el siglo XXI. En este sentido, el estudio de los climas del pasado puede ayudar a mejorar las proyecciones respecto de cómo el sistema responderá a cambios futuros, y también, ser un indicador de cómo los ecosistemas y las sociedades pueden ser afectados por estos cambios. Entre las distintas fuentes de información, la paleolimnología permite reconstruir la variabilidad climática y ambiental pasada en el medio continental con una alta resolución a partir de diferentes proxies biológicos, físicos y geoquímicos. En la presente investigación, el análisis de tres cuerpos de agua ubicados en diferentes áreas del sudeste pampeano ha permitido analizar la respuesta de estos ecosistemas a los cambios climáticos en distintas escalas temporales y espaciales. De estas reconstrucciones, se concluyó que el Holoceno medio-tardío presentó una disponibilidad hídrica algo menor que la actual para la región, manifestándose dentro de este periodo la Anomalía Climática Medieval (~800-1200 AD) como un período moderadamente más cálido y húmedo. Con posterioridad, la Pequeña Edad de Hielo(~1550-1850 AD) se presenta como un momento particularmente frío y seco en toda la región. La salida de esta fase climática fría marca el inicio de un mejoramiento climático y el restablecimiento de las condiciones húmedas y cálidas. Estas tendencias regionales muestran claros componentes subregionales y locales, por cuanto la respuesta individual de cada laguna, modelada por factores intrínsecos y fisiográficos, está sobreimpuesta a las tendencias generalizadas. El clima no sólo determinó la estabilidad de los ecosistemas, el nivel del agua, la estratificación, la salinidad y la estructura de las comunidades que habitan estas lagunas, sino también la alternancia de estados claros y turbios, que impactaron en todos los parámetros limnológicos. El impacto antrópico queda evidenciado desde 1950 AD. El incremento en las marcas térmicas y las precipitaciones registradas desde la década del 70 amplificaron esta señal, afectando el caudal ambiental de las lagunas pampeanas. Este impacto se percibe principalmente en el nivel de eutroficación de las mismas, el que se ha incrementado especialmente a partir de 1990 AD.During the XX century, the mean temperature of our planet has increased and projections estimate an additional rise of ~2–6°C for the XXI century. Therefore, the study of past climates can improve projections about how the system may react to future changes and also indicate how ecosystem and societies can be affected by these variations. Among the different sources of information, paleolimnology allows us to reconstruct the environmental and climatic variability of continental masses with high resolution issuing from different biological, geochemical and physical proxies. In the present study, the analysis of three different shallow lakes situated in different areas of the Southern Pampas has allowed to analyze the response of these ecosystems to climatic change at different spatial and temporal scales. From these reconstructions, it is inferred that the mid-late Holocene had a reduced water availability in comparison to the current standards for the region. Within this time, the Medieval Climatic Anomaly (~800-1200 AD) can be recognized as a warmer and more humid period. Later, the Little Ice Age (~1550-1850 AD) is represented by a particularly cold and dry condition along this region. The end of this cold climatic phase signals the beginning of a climatic amelioration and the onset of warm and wet conditions. These regional trends clearly present subregional and local variations, given that the individual response of each shallow lake, influenced by intrinsic and physiographic factors, is superimposed to the general tendencies. The climate controlled the stability of the ecosystems, water stratification, shallow lake salinity and structure of the biota, but also influenced the shifting between turbid and clear states, which had an impact on the limnological parameters. The human impact is evident since 1950 AD. The increment in temperature and precipitation recorded since 1970 amplified this signal. This impact is particularly strong in the eutrophication level of the shallow lakes in the Southern Pampas, and it has increased especially since 1990.Fil: Plastani, María Sofía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Cuatrocientos años de la historia hidroecológica de la laguna Chascomús

Los espejos de agua de la Encadenada del Salado, y en especial la Laguna Chascomús, tienen un papel fundamental para el desarrollo de la región. Su potencial económico, a partir del turismo, la pesca recreativa y otras actividades vinculadas, es una cuestión que desde el Ministerio de Desarrollo Agrario estamos comprometidos a atender y acompañar, sin descuidar el ambiente.En este sentido, este libro se propone difundir conocimiento para comprender, utilizar y preservarestos recursos; ¿cómo podríamos cuidar lo que no se conoce? Se trata de un intento de entender en profundidad las dinámicas ecosistémicas que suceden en estos cuerpos de agua y la forma en que la comunidad se vincula con ellos para habilitar nuevos la sociedad y la naturaleza.Esta publicación sobre la Laguna Chascomús resulta fundamental y emblemática. En primer lugar, porque con su belleza singular, admirada y reconocida por los y las bonaerenses, esta laguna forma parte, sin duda, de una parte importante de la historia de la región, de la Provincia y del país. En segundo lugar, el libro es un claro ejemplo del potencial del trabajo interdisciplinario en ciencias.Desde las diferentes disciplinas, los autores dan cuenta de la complejidad propia de los ambienteslagunares, abordando aspectos físicos, biológicos y también históricos, sociales, y económicos para conformar una mirada integral, que resulta fundamental para la mejor administración y gestión de los bienes comunes. Con una mirada interdisciplinaria, este libro apor ta formas de comprender a la laguna como un ambiente que es también un medio productivo, y que debe ser hoy valorado como tal por toda la población. Desde el Ministerio de Desarrollo Agrario sostenemos que el impulso a cualquier actividad productiva debe tener en cuenta desde su gestación que la misma debe ser sustentable. Por otro lado, el libro es resultado ulterior, no necesariamente buscado, de un trabajo cotidiano, incansable, de muchos años de dos investigadores, Gustavo Berasain y Leandro Miranda, que han teni do la iniciativa de convocar también a otros especialistas para su elaboración de este libro. Berasain y Miranda trabajan en la Estación Hidrobiológica del Ministerio de Desarrollo Agrario y en el INTECH (UN-SAM-CONICET), respectivamente, ambos en radicadas en la provincia de Buenos Aires con capacidad de estudiar en profundidad temas de la propia región. Por eso, más allá de las trayecto-rias personales, este libro también es expresión del potencial en materia de investigación e innovación tecnológica que tiene Chascomús. Nuestro compromiso con el conocimiento, el desarrollo productivo sostenible y el cuidado del ambiente requiere del esfuerzo mancomunado de todos los actores comprometidos con los valores y principios tendientes a preservar lo que pertenece a todos los bonaerenses. Necesitamos ahora profundizar estos estudios interdisciplinarios y replicarlos en otros ambientes lagunares para desarrollar nuestras fuerzas productivas en armonía con la naturaleza. Estamos convencidos de que con este libro, se está aportando conocimiento en el sentido indicado.Fil: Laprida, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Plastani, María Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin

A review of the genus Limnocythere (Podocopida: Limnocytheridae) in the Pampean region (Argentina), with the description of a new species, Limnocythere cusminskyae sp. nov.

Occurrences of Quaternary and extant limnocytherids in the Pampean region of Argentina are reviewed, particularly in relation with their use as paleohydrological indicators in environmental reconstruction research. In spite of its spread occurrence, the systematic of the genus in the area is still little known, which results in most records being left in open nomenclature and paleoenvironmental inferences being made on the basis of general considerations of the genus. We describe a new species, Limnocythere cusminskyae sp. nov., which we consider to be the taxon featured in several of these works, and discuss its morphological and ecological differences with coexisting Limnocythere species, particularly the proposed indicator species L. rionegroensis Cusminsky & Whatley.Fil: Ramón Mercau, María Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos ; ArgentinaFil: Plastani, María Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos ; ArgentinaFil: Laprida, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos ; Argentin

Limnocythere cusminskyae Ramón-Mercau, Plastani & Laprida, 2014, sp. nov.

Limnocythere cusminskyae sp. nov. 1990. Limnocythere sp. n. Bertels & Martínez, Fig. 11 1996. Limnocythere staplini. Ferrero, Fig. 4, 1a– 1 d 1997. Limnocythere sp. Bertels & Martínez, Plate V, Fig. 2–3; Plate VI, Fig. 16–17 1998. Limnocythere sp. 1. Bertels-Psotka & Laprida, Fig. 1 1998. Limnocythere staplini. Laprida, Fig. 14 2006. L. aff. L. staplini. Laprida, Fig. 3, J–L. Limnocythere sp. Laprida, Fig. 3, H 2009. L. staplini. Ferrero, Fig. 10, 5– 6 Type material. Holotype: One dissected male from the Arroyo Chico creek; soft parts mounted in a permanent slide with Hydromatrix® mounting medium, valves stored dry in a micropaleontological slide. Collection number: LM– FCEN 3200. Paratypes: One dissected male (LM– FCEN 3201.1) and two dissected females (LM– FCEN 3201.2 and LM– FCEN 3201.3) from the same sample as the holotype; soft parts mounted in permanent slides with Hydromatrix® mounting medium, valves stored dry in a micropaleontological slide. Supplementary material: One male (LM– FCEN 3202.1) and one female (LM– FCEN 3202.2) from depth 0–1.5 cm of La Barrancosa core; one male (LM– FCEN 3202.3) and one female (LM– FCEN 3202.4) from depth 4–5 cm of La Barrancosa core; valves stored dry in a micropaleontological slide. Type Locality: Arroyo Chico creek, Municipalidad de Balcarce, Provincia de Buenos Aires, Argentina (37 ° 23 ' 01'' S – 57 ° 09' 48 '' W). Diagnosis. Small to medium-sized, elongated limnocytherid of approximately 600 µm in length. Males with straight dorsal margin and evident cardinal angles, females with variably arched dorsal margin, clearly discernible anterior cardinal angle and variably expressed posterior cardinal angle; ventral margin markedly concave at midlength; dorsal and ventral margin subparallel. Overall shape of carapace in lateral view reniform (in males) to subreniform (in females). A sulcus and two or three smooth, poorly developed tubercles occur slightly anteriorly of mid-length; valve external ornamentation is weak. The hinge is modified antimerodont, consisting of one anterior small, smooth tooth, a central groove and a small, crenulated posterior tooth in the RV; LV with central bar smooth. A 1 with subapically flagellated setae on the third and fourth segments. Strong sexual dimorphism in thoracopod length: in females, the apical claws of T 2 and T 3 are of similar length, with that of T 1 being approximately ¼ shorter; in males, the apical claws of T 1 and T 2 are subequal while the apical claw of T 3 is approximately 2.5 times longer than either. The hemipenis has a well-developed distal lobe. The upper ramus of the clasping organ is a tentacle-like processus. The x 2 segment of the labyrinth is characteristically elongated and Y-shaped, with the bifurcated extreme adjacent to the vesica ejaculatoria. Derivatio nominis. In honor to Dr. Gabriela Cusminsky, in acknowledgment of her contributions to the knowledge of Quaternary Patagonian ostracods. Description. External view. In lateral view, the carapace is elongated; the anterior and posterior margins are simetrically rounded, with the latter more acuminate. The carapace of the male is reniform, with the posterior end slightly higher than the anterior one; MH situated approximately at anterior 1 / 4 of ML. The dorsal margin is straight, with marked cardinal angles, and subparallel to the ventral margin (Fig. 2 a–b). The female carapace is more compressed, with overall subreniform shape; the dorsal margin is slightly to broadly arched and sloping, with a well-defined anterior cardinal angle and posterior cardinal angle evident to weakly discernible; the ventral margin is broadly sinuous. MH occurs approximately at anterior 1 / 3 of ML (Fig. 2 c–d). In dorsal view, the anterior end is beak-shaped and the posterior end is rounded, with the LV overlapping the RV. External valve ornamentation is weak, presenting a light primary reticulation of muri and secondarily pitted fossae. A sulcus and two or three smooth, poorly developed tubercles occur slightly anteriorly of mid-length. Two rows of minute, similarly sized and shaped denticles occur in the anterior and posterior margins of both valves (only visible through SEM); the first row is located just over the free margin (Fig. 2 h). The valve surface presents scattered sieve-type normal pores. Internal view. The dorsal margin is straight, with the anterior cardinal angle marked. Muscle scars as for the genus with a vertical row of four scars. The hinge is modified antimerodont, consisting of one anterior small, smooth tooth, a central groove and a small, crenulated posterior tooth in the RV (Fig. 2 e–f); LV central bar smooth. The marginal zone is more developed anteriorly, approximately twice as broad anteriorly compared with the posterior margin, with few straight, unbranched marginal pore canals. Soft parts. The four anteriormost appendages are identical for both sexes, except for the morphology of a single seta in A 2 (see below); the three thoracopods, for their part, present strong sexual dimorphism, both in relative size and the chaetotaxy of the basal segment. The antennule (A 1) is 5 -segmented, with subapically flagellated setae on the third and fourth segments (Fig. 3 a). The basal segment bears no setae; the second and third segments bear 1 seta each; the fourth segment presents 6 setae; the fifth segment has 3 setae, one of them proximally fused with an aesthetasc. The antenna (A 2) comprises 5 segments plus the exopod, which is a long, articulated seta (the spinneret seta) (Fig. 3 b). The first four segments present bunches of setulae. The first segment is devoid of setae; the second presents the spinneret seta. The third segment bears 1 seta, smooth in the female and plumose in the male: its lower part is smooth, while the upper part presents numerous long flagella. The fourth segment presents 7 setae; 3 are plumose and 1, located medially, is an aesthetasc. The fifth segment bears 3 apical, unequally long claw-like setae. The mandible (Md) presents a 4 -segmented palp (Fig. 3 c). The first segment bears a respiratory plate with 7 rays and 2 ventro-apically inserted setae; the second segment bears a long plumose seta dorsally, plus 5 smooth + 3 plumose + 2 smooth setae. The third segment presents 2 setae, while the fourth segment bears 4 setae apically. The maxillule (Mx) presents 3 masticatory endites and bears a 2 -segmented palp and a respiratory plate (Fig. 4 d). The second segment of the palp is subrectangular and bears 4 setae. Between Mx and the first walking leg is a so-called sternum, an elongated structure consisting of a central plate and lateral extensions, associated with the masticatory apparatus. The first thoracopod (T 1) is a 4 -segmented limb which bears 6 setae + 1 apical claw in the female (Fig. 3 e), and 5 setae + 1 apical claw in the male (Fig. 3 f); the second seta of the basal segment is plumose in the male. The second thoracopod (T 2) is 4 -segmented; the female presents 4 setae + 1 apical claw (Fig. 3 e), while the male presents 5 setae + 1 apical claw (Fig. 3 f), of which 2 are plumose. The apical claw is about a quarter longer than the apical claw of T 1 in the female and subequal with the apical claw of T 1 in the male. The third thoracopod (T 3) is 4 -segmented as well, bearing 4 setae + 1 apical claw in the female (Fig. 3 e) and 5 setae + 1 apical claw in the male (Fig. 3 f), including 2 plumose setae. While in the female the apical claw of T 3 is approximately as long as the apical claw of T 2, in the male the apical claw of T 3 is strikingly long (≈ 2.5 x length of apical claw of T 2), amounting to about half the total length of the appendage. Genital lobe of the female without special features. The hemipenis (Fig. 3 g) has a well-developed distal lobe. The upper ramus of the clasping organ is a tentacle-like processus. The x 2 segment of the labyrinth is characteristically elongated and Y-shaped, with the bifurcated extreme adjacent to the vesica ejaculatoria. Measurements. Holotype (male; LM– FCEN 3200): ML = 627 µm; MH = 273 µm Paratype (male; LM– FCEN 3201.1): ML = 635 µm; MH = 283 µm Paratype (female; LM– FCEN 3201.2): ML = 565 µm; MH = 295 µm Paratype (female; LM– FCEN 3201.3): ML = 625 µm; MH = 330 µm Distribution. The species has been recorded both living and fossil in Southeastern Pampa, mostly in locations close to the Atlantic coast (Fig. 1). As most of the research involving Quaternary microfossils that has been carried out in the Pampean area is related to past sea level fluctuations reconstruction, and therefore most of those studies included only seaside locations, the fact that Limnocythere cusminskyae sp. nov. has been found almost exclusively in the coastal area is quite probably a sampling bias artifact rather than a reliable indication of the species’ (past) distribution. Laprida (2006) found live specimens of L. cusminskyae sp. nov. mostly in the shallow lakes Chascomús, Salada Grande, Los Horcones, Laguna del Monte and in the Arroyo Grande creek. Bertels & Martínez (1990; 1997) recorded the species in Holocene sediments from an exposed section along the margin of the Napostá Grande stream, at 2.5 km from its outlet to the ocean. The sediments, corresponding to the Bahía Blanca Formation, consist of shallow marine and transitional littoral-estuarine deposits. Ferrero (1996) reported it from a Holocene outcrop on the northern margin of the Quequén Grande river and in Late Pleistocene sediments ascribed to the Canal 5 Formation (Ferrero 2009) drilled near the Mar Chiquita Lagoon. Laprida (1998) found the species in samples taken from an outcrop on the right margin of the Canal Nº 15 channel, corresponding to the early Holocene Destacamento Río Salado Formation, while Bertels-Psotka & Laprida (1998) recovered a single valve from Holocene sediments outcropping near that location (at the junction of Provincial Route Nº 11 and Canal Nº 15 channel), corresponding to the Cerro de la Gloria Member of Las Escobas Formation. Remarks. Several limnocytherids recorded in the Pampean region have been likened to the well-known Neartic species L. staplini and, in one case, L. bradburyi Forester. Cusminsky& Whatley (1996) and Cusminsky et al. (2005) considered the material described as L. aff. L. bradburyi by Bertels & Martínez (1990; 1997) to consist of juveniles of L. rionegroensis. This would be the northernmost record of the latter species, and the only one outside the Patagonian region. L. rionegroensis is known both after bisexual and parthenogenetic populations. The valve outline of the male of L. cusminskyae sp. nov. differs from that of L. rionegroensis in the straight (vs curved) dorsal margin and from that of L. bradburyi in the ventral margin (reniform vs slightly curved). When comparing L. staplini and L. cusminskyae sp. nov., both sexes are very similar in external morphology; perhaps the most important difference between them lies in the hinge, with the anterior tooth of the RV being crenulated in the former and smooth in the latter. Likewise, the valves of the females of L. cusminskyae sp. nov. and L. rionegroensis are very similar in external view. The hinge of L. rionegroensis is described as lophodont with a smooth bar; this would imply that the teeth are smooth, in contrast with the crenulated posterior hinge tooth of L. cusminskyae sp. nov. Lastly, L. cusminskyae sp. nov. differs from L. bradburyi in having a smooth hinge bar (vs crenulated in the latter species). This suggests that careful examination of hingement details might allow distinction between the valves of these similar taxa. With regards to soft parts morphology, presently it is only possible to compare L. cusminskyae sp. nov. with L. staplini, whose appendages were described by Delorme (1971). This author makes no mention whatsoever of sexual dimorphism in thoracopod length; therefore, both species can be easily distinguished on the basis of soft parts analysis. Lastly, it can be mentioned that Kihn & Pall (2013) report a limnocytherid left in open nomenclature, Limnocythere sp., from a small shallow lake in the inland Pampean region; while the line drawings of valves illustrating their work show a certain resemblance to L. cusminskyae sp. nov., their poor quality and lack of description of the material prevent further comparisons.Published as part of Ramón-Mercau, Josefina, Plastani, María Sofía & Laprida, Cecilia, 2014, A review of the genus Limnocythere (Podocopida: Limnocytheridae) in the Pampean region (Argentina), with the description of a new species, Limnocythere cusminskyae sp. nov. in Zootaxa 3821 (1), DOI: 10.11646/zootaxa.3821.1.2, http://zenodo.org/record/22964

Limnocythere Brady 1867

Genus Limnocythere Brady, 1867 (Type species: Cythere inopinata Baird, 1843) Diagnosis. Carapace laterally elongated and sexually dimorphic, with the females being stouter and shorter than the males. When viewed dorsally, the anterior end of the carapace is usually beak-shaped, while the LV overlaps the RV posteriorly. Valves with marginal pore canals unbranched and often with tubercles of variable development. Flagellated claws present on the antennules of a number of species. Hemipenis with three uropodal setae, a movable trabecule, and a clasping organ with two rami; the lower ramus, consisting of a lateral process and a hooklike process, and the upper ramus, either reduced to an elongated tentacle or absent.Published as part of Ramón-Mercau, Josefina, Plastani, María Sofía & Laprida, Cecilia, 2014, A review of the genus Limnocythere (Podocopida: Limnocytheridae) in the Pampean region (Argentina), with the description of a new species, Limnocythere cusminskyae sp. nov. in Zootaxa 3821 (1), DOI: 10.11646/zootaxa.3821.1.2, http://zenodo.org/record/22964

The chironomids (Diptera: Chironomidae) of shallow lakes of the humid Pampa region, Argentina: An approach to paleoproductivity reconstruction

The Humid Pampa, center-east of Argentina, is the most important socio-economical area of the country. Several shallow lakes have been the focus of many studies due to the significant changes in their trophic status related to human activities and to global warming recorded since the beginning of the twentieth century. Although chironomids have been used extensively in paleoclimatic and paleoenvironmental research, they are rarely used for paleoenvironmental reconstructions of the Pampean shallow lakes. The aim of this paper is to contribute to the knowledge of the chironmids' community composition and distribution in the Pampa region, and to relate their distribution to selected climatic and limnological variables. The ultimate goal is to retrieve new ecological information for future paleoenvironmental and paleoclimate reconstructions by using chironomid-based inference models. In this study, chironomids head capsules were collected from surface sediments from 17 shallow lakes of the Humid Pampa. Our analyses indicate that the chironomid assemblages reflect the decreasing NE-SW rainfall gradient of the region as well as the land use intensity, which in turn affects the aquatic ecosystems, in terms of lake productivity. Some chironomids are associated with brackish conditions (e.g., Chironomus, Ablabesmyia, Tanytarsini D2). Additionally the occurrence of assemblages of detritivore taxa such as Goeldochironomus, Chironomus, Polypedilum, and Dicrotendipes reflect the natural eutrophic state of Pampean shallow lakes, whereas assemblages mostly dominated by Coelotanypus, Procladius, and Chironomus are indicative of hypertrophic conditions, which are usually the result of human activity. This is the first study of chironomids from surface sediments from the central temperate plains of Argentina, and our records extend the ecological information of the Diptera in temperate areas. Although more studies are necessary to fully understand the main factors determining the chironomid fauna distribution in the Pampa region, we conclude that chironomids are potentially good proxies for paleoproductivity and salinity reconstructions of Pampean shallow lakes.Fil: Montes de Oca, Fernanda. Administración de Parques Nacionales. Parque Nacional "Nahuel Huapi"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tonello, Marcela Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Massaferro, Julieta. Administración de Parques Nacionales. Parque Nacional "Nahuel Huapi"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Plastani, María Sofía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Laprida, Cecilia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin