التغاير الموسمي للافقاريات القاعية الكبيرة مع تسجيل جديد للنوع Nais raviensis Stephenson, 1941 (Oligochaeta : Naidinae)‎ من شمال محافظة البصرة

Abstract EN

The benthic macroinvertebrates in three stations at Euphrates and Shatt Al-Arab rivers have been studied for the period from July-2013 to June-2014 by monthly intervals.

Three replicates within each station have been chosen for sample collection using core tube.

During the study period, 25 Taxa belonging to three major invertebrates groups were recorded.

The five species, Potamothrix hammoniensis (Michaelsen,1901), Potamothrix bavaricus (Öschmann,1913), Psammoryctides moravicus (Hrabe, 1934), Psammoryctides moravicus (Hrabe, 1934), Nais stolci (Harbe, 1981) were recorded for the first time from southern Iraq, while the species Nais raviensis Stephenson,1941 considered as new record from Iraq.

A total of 4497 individuals of five groups of invertebrates (Gastropoda, Oligochaeta, Hirudinae, Polychaeta and Insecta) were colledes during the study period from all study stations.

From all three stations, the higher percentages were recorded by Oligochaeta with 85.2-90.6 %, while Ggastropoda with 6.3-8.8 %, Hirudinae with 0.25-1.8 %, Polychaeta with 0-0.15 % and Chironomidae with 2.7-4.2 %.

The dominations of each recorded species were studied.

Gastropoda was represented by four species, and the higher percentage was 55.2 % recorded by Melanoides tuberculata opposite to 9.7 % recorded by Physa acuta.

The Annelida was represented by 20 species.

The tubificids dominated by Limnodrilus hoffmeisteri with 98.6 % opposite to 0.1 % of Tubifex tubifex, while the naidids dominated by N.

stolci with 78.3 % opposite to 0.8 % of each of Pristina aequiseta and Dero nivea.

The monthly densities of the recorded species were ranged from 5430 ind / m² belonging to L.

hoffmeisteri to 11 ind / m² belonging to many species.

The study included the frequency percentage of all recorded species, which dominated by L.

hoffmeisteri with 100 %, opposite with 33 % recorded for many species.Results of statistical analysis showed significant differences between the first two and third stations.

The temperature was correlated positively with mean of each of pH and salinity, and negatively with each of number of species and densities of oligochaetes.

On the other hand the salinity was correlated positively with the total densities of oligochaetes.