Bettina Sandra Gullo

Macroinvertebrates associated with Limnoperna fortunei (Dunker, 1857) (Bivalvia, Mytilidae) in Rio de la Plata, Argentina

An analysis was made of specific richness (S), specific diversity (H), equitability (J), frequency (F), dominance (Dm) and density (D) of the macroinvertebrates associated with the invasive species Limnoperna fortunei (Dunker, 1857), was made.Limnoperna fortunei caused an increase in the specimen number on the rocky environment studied. The species richness and abundance of different taxa of macroinvertebrates, except mollusks was positively related to the presence and density of L.fortunei. Autochthonous gastropod species conversely, tended to be displaced.

Biodiversity and ecology of Hirudinea (Annelida) from the Natural Reserve of Isla Martín García, Río de la Plata, Argentina

The Island of Martin Garcia lies at the confluence of the Uruguay and Paraná Rivers (upper Río de la Plata). This island is an outcrop of the crystalline basement. Due to basalt exploitation the island exhibits several ponds covered by carpets of free-floating macrophytes. Seven major environmental variables were measured: water and air temperature, percentage of oxygen saturation, dissolved oxygen, electrical conductivity, total dissolved solids and pH. Eleven leech species were found, Helobdella striata, H. diploides, H. adiastola and H. hyalina were new records. UPGMA clustering of species based on their occurrence in different ecological conditions revealed three main species groups. Canonical Correspondence Analysis (CCA) explained 97.2% of the correlation between species and environmental variables. H. triserialis shows the widest range of tolerance, H. hyalina shows positive relationships to conductivity; H. diploides shows a high correlation with dissolved oxygen, H. striata, H. lineata, and S. similis are negatively correlated with water temperature, and H. simplex is positively correlated with pH. Relationships between the species richness (S) and the sampling sites were negatively correlated with water temperature and positively correlated with dissolved oxygen. Leech biodiversity from the water bodies of Martín García Island, shows a great diversity of species and a wide plasticity regarding the characteristics of the environmental factors considered.

Occurrence of Hirudinea species in a post urban reach of a Patagonian mountain stream

Temporal (May 2005 to February 2006) and habitat distribution (pools and riffles) of Hirudinea species was analyzed at a post urban reach from Esquel stream (Chubut province, Patagonia, Argentina). Site was located 5.7 km downstream a Waste Treatment Plant. Mean values of nutrients: ammonia, nitrates and soluble reactive phosphate, as well water conductivity, turbidity and total suspended solids indicated physical and organic pollution. Leeches assemblage was composed by the glossiphonids: Helobdella scutifera Blanchard, 1900, H. michaelseni (Blanchard, 1900), H. simplex (Moore, 1911), Helobdella sp., H. hyalina Ringuelet, 1942, H. obscura Ringuelet, 1942 and the semiscolecid Patagoniobdella variabilis (Blanchard, 1900). From these H. hyalina and H. obscura are new records for Chubut province. Helobdella hyalina (810 ind.m-2) and H. simplex (465 ind. m-2) clearly dominated the assemblage at the reach. Only H. simplex displayed a spatial preference being significantly more abundant in pools than in riffle habitats (p<0.001). Species recruitment occurred mostly at September, December and March when juveniles were very abundant. Although several species of Helobdella were able to live in the disturbed section of the stream, only H. simplex and H. hyalina sustained large populations at the site and can be considered as tolerant to organic enrichment. This information is valuable to future studies on stream condition assessment in mountainous areas in Patagonia, and in other areas in which these species are present.

First record of Helobdella hyalina (Hirudinea; Glossiphoniidae) in the mantle cavity of Planorbidae from lentic environments in a Buenos Aires province, Argentina

Pasante Div. Zool. Invertebrados, Cátedra Zoología Invertebrados I, Facultad de Ciencias Naturales y Museo – FCNYM, Universidad Nacional de La Plata – UNLP b Cátedra Zoología Invertebrados I, FCNYM, Universidad Nacional de La Plata – UNLP Div. Zoología Invertebrados, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Investigador Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Paseo del Bosque, s/n, 1900 La Plata, Buenos Aires, Argentina

Assessing the sensitivity of leeches as indicators of water quality

The objective of this work was assessing the sensitivity of leeches to several water quality attributes in lowlands streams. We used occupancy modelling that account explicitly for detectability, to estimate the influence of four variables (dissolved oxygen, 5-days biochemicals oxygen demand, conductivity, and dissolved inorganic nitrogen) affecting nine species. We described the sensitivity as a change in the occupancy along the range of water quality attributes. We found at least one species of Helobdella in 81% of sites and Helobdella, as genus, was detected along the entire gradient of each attribute. However, differences in the sensitivity were observed between species. For example, if we analyse the sensitivity of the genus Helobdella to dissolved oxygen, we can say that it is very tolerant. However, if we analyse the response to dissolved oxygen of each one of the species of Helobdella, we will realize that H. michaelseni, and H. simplex showed a high occupancy at high levels of dissolved oxygen; while H. hyalina and H. triserialis lineata showed high occupancy at low levels. Describe the sensitivity of the species in terms of occupancy, offers a new methodology to understand how the species behave along a stressor gradient.

Microanatomía de los testisacos y espermatogénesis de Helobdella michaelseni (Hirudinea, Glossiphoniidae)

espanolSe realizo un estudio histologico detallado de los testisacos y espermatogenesis de Helobdella michaelseni. El sistema reproductor masculino esta constituido por siete pares de testisacos esfericos localizados entre los somitos XIII/XIV a XIX/XX. Los espermiductos alcanzan los somitos XVII/ XVIII o XIX/XX. Atrio en forma de huso. Poro masculino localizado en el segmento XII a1/a2. La espermatogenesis se produce en el interior de sacos celomicos llenos de fluido. Cada testisaco esta tapizado por mesotelio. En su interior las celulas germinales permanecen unidas por el citoforo y desarrollan poliplastos germinales. Los espermatozoides maduros son liberados a la luz de los testisacos con posterioridad a la reabsorcion del citoforo. Se describieron cinco estadios durante la espermatogenesis teniendo en cuenta la maduracion de los elementos germinales y los cambios en el citoforo. EnglishA detailed preliminary histological analysis of Helobdella michaelseni Blanchard 1900 testisacs is described. The male reproductive system is composed of seven pairs of spherical testisacs found intersegmentally from somites XIII/XIV to somites XIX/XX. Spermiducts reach the back of somites XVII/ XVIII or XIX/XX. Spindle form atria. Male pore at somite XII a1/a2. The spermatogenesis occurs in the lu men of fluid-filled coelomic sacs. Each testisacs is clothed by mesotelium. Inside it, the germinal cells are connected to the cytophore and develop functional units called polyplasts. The spermatozoo are released into testisacs after the cytophore reabsorption. Five stages of spermatogenesis are described taking into account the successive maturation stages of germinal cells and the changes in the cytophore.

Testisacs microanatomy and spermatogenesis of Helobdella michaelseni (Hirudinea, Glossiphoniidae)

Se realizo un estudio histologico detallado de los testisacos y espermatogenesis de Helobdella michaelseni . El sistema reproductor masculino esta constituido por siete pares de testisacos esfericos localizados entre los somitos XIII/XIV a XIX/XX. Los espermiductos alcanzan los somitos XVII/ XVIII o XIX/XX. Atrio en forma de huso. Poro masculino localizado en el segmento XII a1/a2. La espermatogenesis se produce en el interior de sacos celomicos llenos de fluido. Cada testisaco esta tapizado por mesotelio. En su interior las celulas germinales permanecen unidas por el citoforo y desarrollan poliplastos germinales. Los espermatozoides maduros son liberados a la luz de los testisacos con posterioridad a la reabsorcion del citoforo. Se describieron cinco estadios durante la espermatogenesis teniendo en cuenta la maduracion de los elementos germinales y los cambios en el citoforo. Palabras clave: microanatomia, testisacos, Helobdella michaelseni , espermatogenesis.

Histologia del sistema reproductor masculino de Helobdella hyalina (Hirudinea, Glossiphoniidae) en Argentina

A detailed preliminary histological analysis of Helobdella hyalina Ringuelet, 1942 male system from Los Talas, Buenos Aires, Argentina is described. Six pairs of testisacs, located between the crop caeca, form the male reproductive system. Each testisac is clothed by the mesotelium. Inside it, the germinal cells are connected to the citophore and develop functional unit called poliplast. The spermatozoa are released into testisacs after the reabsortion of the citophore. Five stages of spermatogenesis are described taking into account the successive maturation stages of germinal cells and the changes in the citophore size. Lining cells and gland cells were found in the seminal vesicle. Five different types of gland cells are placed inside the ejaculatory ducts, as well as two kinds of cells are found in its distal portion: type 1, which produces eosinophilic granular secretion, type 2, with amorphous and slightly eosinophilic. Three distinct gland cells are located in the proximal portion of the duct: type 3, which produces a strongly eosinophilic granular secretion; type 4, with a negative eosinophilic amorphous secretion and type 5, with a basophilic granular secretion. Type 5 gland cells are described for the ducts of this species only.