Testisacs microanatomy and spermatogenesis of Helobdella simplex (Hirudinida: Glossiphoniidae)

ABSTRACT The aim of this study was to describe the testisac microanatomy and spermatogenesis of Helobdella simplex (Moore, 1911). The leeches were collected in the Sauce Chico River (Tornquist) during April 2012. The collection of material was carried out manually by checking rocks, logs, leaves and artificial substrates in the river bed. Helobdella simplex has six pairs of testisacs located between the gastric caeca. The testisac wall has two structurally and functionally differentiated cell types: the lining mesothelial cells and the germline cells. The lining cells are flat and form a continuous layer. In H. simplex no ciliated cells were observed into the testisacs, nor the formation of spermatogonia due to detachment of the testicular wall. Cell types were microscopically characterized, and five spermatogenesis stages are described, taking into account the maturation of germinal cells, the morphological changes in the cytophore and phagocytic activity. Testicular phagocytes actively participate during spermatogenesis. They are involved both in the removal of defective cells during the early stages of spermatogenesis and in the removal of the cytophore during the reacting reabsorption. Our study adds the knowledge of spermatogenesis in H. simplex and might be useful to differentiate the stages of development during the reproductive cycle, and to interpret aspects of its population dynamics.

Testisacs microanatomy and spermatogenesis of Helobdella simplex (Hirudinida: Glossiphoniidae)

The aim of this study was to describe the testisac microanatomy and spermatogenesis of Helobdella simplex (Moore, 1911). The leeches were collected in the Sauce Chico River (Tornquist) during April 2012. The collection of material was carried out manually by checking rocks, logs, leaves and artificial substrates in the river bed. Helobdella simplex has six pairs of testisacs located between the gastric caeca. The testisac wall has two structurally and functionally differentiated cell types: the lining mesothelial cells and the germline cells. The lining cells are flat and form a continuous layer. In H. simplex no ciliated cells were observed into the testisacs, nor the formation of spermatogonia due to detachment of the testicular wall. Cell types were microscopically characterized, and five spermatogenesis stages are described, taking into account the maturation of germinal cells, the morphological changes in the cytophore and phagocytic activity. Testicular phagocytes actively participate during spermatogenesis. They are involved both in the removal of defective cells during the early stages of spermatogenesis and in the removal of the cytophore during the reacting reabsorption. Our study adds the knowledge of spermatogenesis in H. simplex and might be useful to differentiate the stages of development during the reproductive cycle, and to interpret aspects of its population dynamics.(AU)

Testisacs microanatomy and spermatogenesis of Helobdella simplex (Hirudinida: Glossiphoniidae)

The aim of this study was to describe the testisac microanatomy and spermatogenesis of Helobdella simplex (Moore, 1911). The leeches were collected in the Sauce Chico River (Tornquist) during April 2012. The collection of material was carried out manually by checking rocks, logs, leaves and artificial substrates in the river bed. Helobdella simplex has six pairs of testisacs located between the gastric caeca. The testisac wall has two structurally and functionally differentiated cell types: the lining mesothelial cells and the germline cells. The lining cells are flat and form a continuous layer. In H. simplex no ciliated cells were observed into the testisacs, nor the formation of spermatogonia due to detachment of the testicular wall. Cell types were microscopically characterized, and five spermatogenesis stages are described, taking into account the maturation of germinal cells, the morphological changes in the cytophore and phagocytic activity. Testicular phagocytes actively participate during spermatogenesis. They are involved both in the removal of defective cells during the early stages of spermatogenesis and in the removal of the cytophore during the reacting reabsorption. Our study adds the knowledge of spermatogenesis in H. simplex and might be useful to differentiate the stages of development during the reproductive cycle, and to interpret aspects of its population dynamics.(AU)

Occurrence of Hirudinea species in a post urban reach of a Patagonian mountain stream / Ocurrencia de especies de Hirudinea en un tramo posturbano de un arroyo patagónico de montaña

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.(AU)

Se analizó la distribución temporal (mayo 2005 a febrero 2006) y espacial (pozones y rápidos) de las especies de hirudíneos en un segmento post urbano del arroyo Esquel (provincia de Chubut, Patagonia, Argentina). El sitio está localizado a 5,7 km aguas abajo de la planta de tratamiento de efluentes cloacales. Los valores promedio de nutrientes: amonio, nitratos y fósforo reactivo soluble, así como la conductividad del agua, turbidez y el total de sólidos suspendidos indican contaminación física y orgánica. Las especies de hirudíneos halladas fueron Glossiphoniidae: Helobdella scutifera Blanchard, 1900, H. michaelseni (Blanchard, 1900), H. simplex (Moore, 1911), Helobdella sp., H. hyalina Ringuelet, 1942 and H. obscura Ringuelet, 1942 y Semiscolecidae: Patagoniobdella variabilis (Blanchard, 1900). Helobdella hyalina and H. obscura representan nuevos registros para la provincia de Chubut. Helobdella hyalina (810 ind. m-2) y H. simplex (465 ind. m-2) fueron las especies claramente dominantes. Sólo H. simplex presentó una preferencia espacial siendo significativamente más abundante en los pozones que en los rápidos (p<0.001). El reclutamiento de las especies se observó principalmente en septiembre, diciembre y mayo donde los juveniles fueron muy abundantes. Aunque varias especies de Helobdella se registraron en este sector contaminado del arroyo, sólo H. simplex and H. hyalina presentaron poblaciones importantes y pueden ser consideradas como tolerantes al enriquecimiento orgánico. Esta información es de valor para futuros estudios sobre evaluación de calidad de los arroyos en áreas montañosas de la Patagonia y para otros donde estas especies están presentes.(AU)

Occurrence of Hirudinea species in a post urban reach of a Patagonian mountain stream / Ocurrencia de especies de Hirudinea en un tramo posturbano de un arroyo patagónico de montaña

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.

Se analizó la distribución temporal (mayo 2005 a febrero 2006) y espacial (pozones y rápidos) de las especies de hirudíneos en un segmento post urbano del arroyo Esquel (provincia de Chubut, Patagonia, Argentina). El sitio está localizado a 5,7 km aguas abajo de la planta de tratamiento de efluentes cloacales. Los valores promedio de nutrientes: amonio, nitratos y fósforo reactivo soluble, así como la conductividad del agua, turbidez y el total de sólidos suspendidos indican contaminación física y orgánica. Las especies de hirudíneos halladas fueron Glossiphoniidae: Helobdella scutifera Blanchard, 1900, H. michaelseni (Blanchard, 1900), H. simplex (Moore, 1911), Helobdella sp., H. hyalina Ringuelet, 1942 and H. obscura Ringuelet, 1942 y Semiscolecidae: Patagoniobdella variabilis (Blanchard, 1900). Helobdella hyalina and H. obscura representan nuevos registros para la provincia de Chubut. Helobdella hyalina (810 ind. m-2) y H. simplex (465 ind. m-2) fueron las especies claramente dominantes. Sólo H. simplex presentó una preferencia espacial siendo significativamente más abundante en los pozones que en los rápidos (p<0.001). El reclutamiento de las especies se observó principalmente en septiembre, diciembre y mayo donde los juveniles fueron muy abundantes. Aunque varias especies de Helobdella se registraron en este sector contaminado del arroyo, sólo H. simplex and H. hyalina presentaron poblaciones importantes y pueden ser consideradas como tolerantes al enriquecimiento orgánico. Esta información es de valor para futuros estudios sobre evaluación de calidad de los arroyos en áreas montañosas de la Patagonia y para otros donde estas especies están presentes.