Aquatic Oligochaeta (Annelida: Clitellata) in wetlands and irrigated rice fields in the state of Rio Grande do Sul (Southern Brazil)

ABSTRACT The knowledge of the diversity and distribution of aquatic Oligochaeta (Annelida: Clitellata) species is scarce in southern Brazil. This study presents a list of the species of aquatic Oligochaeta in wetlands and irrigated rice fields in the state of Rio Grande do Sul. Collections were carried out in two large wetland remnants and seven irrigated rice fields distributed in three regions across the state. We recorded eight species from two families (Alluroididae and Naididae). We expanded the distribution ranges of two species (Brinkhurstia americana and Stylaria lacustris), which represent new records for the state of Rio Grande do Sul and registered their occurrence in non-documented environments. In specific, the present study increases to 24 species the aquatic Oligochaeta diversity for the state of Rio Grande do Sul. In addition, the spatial distribution of the species recorded suggests that rice fields support a subset of the wetland fauna of aquatic Oligochaeta. The results provide important information on the ecology and distribution of limnic Oligochaeta and are useful to inform on the diversity of this fauna in agroecosystems.

Checklist of Aquatic Oligochaetes Species in Tigris–Euphrates River basin

A total of 60 species of aquatic oligochaetes were identified in different sites within Tigris-Euphrates basin / Iraq, including River Tigris, River Euphrates, Southern marshes ( Al-Haweiza , Al-Hammar and Al-Chebaiesh ) , Shutt Al-Germa, and Shatt Al-Arab. In River Euphrates 39 species were identified, 40 species from River Tigris and 32 species from Shatt-Al-Arab and southern marshes.The identified species were classified as four species of Family Aeolosomatidae, 54 species of Naididae ( 31 Naidinae , 8 Pristininae and 15 Tubificid worms), one species of each of Lumbriculidae ( Lumbriculus variegates ) and Lumbricidae ( Eiseiella tetraedra). Among Aeolosomatidae , Aelosoma aquaternarium, A. Liedyi, A. variegatum and A. hemprichi, in which, A. variegatum was the most frequent species, found in Euphrates river. Naidinae community were represented by five species of genus Chaetogaster, two species of each of Paranais, Slavina, & Stylaria, four species of Allonais , and seven species of each of Dero and Nais, in addition to Stephensoniana trivandrana, Specaria josinae and Ophidonais serpentina. Nais variabilis was the most abundant and frequent species in River Tigris while Stylaria lacustris & Ophidonais serpentina are abundant in River Euphrates . Species of Pristininae were representative by four species of genus Pristina and three species of genus pristinella, among them Priatina longiseta is the most abundant species.Tubificid worms, Branchuira sowerbyi and Limnodrilus hoffmeisteri were the most frequent and abundant species in the surface sediments of Iraqi waters. Beside L. hoffmeisteri , other five species of Limnodrilus, two species of Potomothrix, and a single species of Tubifex tubifex , Embolocephalus velutinus, Aulodrilus piguetia, Psammoryctides moravicus and Rhyacodrilus coccineus were recorded.

Study of Naidid worms community associated with two species of aquatic plants in River Tigris inside Baghdad City / Iraq

The present study is concern with the interaction between the naidid worms diversity and the species of aquatic plant within which the worms found . For this purpose, two species of aquatic plant were used, Ceratophyllum demersum and Eichhornia crassipes. 12 samples of aquatic plants were collected , as one sample monthly for a period from September 2012 to September 2013 from different site on Tigris river within Baghdad City. From C. demersum, 1428 individuals, were sorted during the study period, related to 17 species. 12 species of subfamily Naidinae which are Chaetogaster limnaei , C. diastrophus , Ophidonais serpentine , Dero ( Dero) digitata. , D.(D.) evelinae , Nais pseudobtosa , N.simplex, N.stolci , N.Paradalis , N.elingius , N. variabilis and N. communis. In addition to five species of subfamily Pristininae, two species of Pristina , which are P. longiseta and . P. aequiseta, and three species of pristinella, which are P. . Jenkinae , P. sima , and P. osborni. Dero ( Dero) digitata was recorded the higher number of 430 individuals,with a percentage of 28.11% of the total sorted worms. About the aquatic plant Eichhornia crassipes, a total of 829 worms were sorted from it, which are related to six species of Naidinae , which are diaphanous , Ophidonais serpentine, Stylaria lacustris , Slavina appendiculata , N. variabilis and finally the species Allonais inaequalis. There was no any species of Pristininae sorted from this plant. The highest number of 467 individuals was recorded by the species Slavina appendiculata, with a percentage of 52.3% of the total number and 228 individual with a percentage of 25.5% was recorded by Allonais inaequalis.

Efectos de la temperatura sobre el crecimiento individual y formación de zooides en Stylaria lacustris (Linnaeus, 1767) (Oligochaeta, Naididae)

Los cultivos realizados con S. lacustris demostraron que la temperatura juega un papel de importancia en la tasa de la reproducción, en cuanto al número de zooides producido por individuo así como también al tamaño alcanzado por los mismos. Por otro lado, regularía la tasa de crecimiento y la reproducción sexual, dando lugar a la madurez de los individuos cuando aumenta la temperatura. El tiempo de vida promedio de los individuos inmaduros se estimó en 15 días, siendo este valor independiente de la temperatura utilizada en los cultivos. Los individuos maduros vivieron en promedio 37 días. La supervivencia en S. lacustris fue decreciendo gradualmente, según una curva de tipo lll. La expectativa de vida presentó su pico a la edad de 16 días y se mantuvo aproximadamente constante hasta una edad de 28 días a partir de la cual fue decreciendo en forma persistente hasta la última edad alcanzada. Se estimó el crecimiento individual, según la ecuación de von Bertalanffy, para los organismos mantenidos a 23 ± 2 °C y a 14 ± 1 °C. En aquellos individuos cultivados a mayor temperatura se registró una mayor talla, aunque su tasa de crecimiento fue menor que la de los individuos mantenidos a 14 °C.