International Journal of Aquatic Biology
Volume:7 Issue: 1, Feb 2019

Southern Gulf of Lake Tana is southern part of Lake Tana in Northwestern Ethiopia. Water samples were obtained from eight sites of the gulf for six months during November to April 2010/11 twice a month to determine temporal and spatial variation in phytoplankton biomass of the gulf. Phytoplankton biomass data was estimated following total chlorophyll-a concentrations determination methods. There was no significant difference in sampling sites and interactions between sampling sites and months (P>0.05). However, there is a significant difference in sampling months (P<0.05). The absence of significant difference in sampling sites and the interactions might be due to the similarity in human or natural impacts, and phytoplankton growth and decline. But, the presence of significant difference among sampling months might be due to the difference in growth/decline periods of the phytoplankton. Southern Gulf of Lake Tana subparts are similarly impacted naturally or by humans who passed their time around the gulf. The Ethiopian government and concerned non-governmental organizations in general and local communities, in particular, have better cooperate their efforts for conservation and sustainable use of the gulf. Similarly, they have to play in awareness creation for stakeholders to reduce natural/human impacts to the lake gulf.

The golden mantis shrimp, Lysiosquilla tredecimdentata was reported for the first time from Chennai coastal waters, Southeast India. One adult male specimen was found in the trawl by-catch near Kasimedu fishing harbour on September, 2014. The specimen was identified, described, illustrated and morphometrically measured.

The current study focused on the effect of administration of the neurotransmitter leucine enkephalin on ovarian maturation in the freshwater crab Travancoriana schirnerae. The crabs were administered with leucine enkephalin in multiple doses (10 µl/injection) and their dissected ovaries were processed for histomorphological analyses. Ovarian maturation was assessed by both macroscopic and microscopic observations such as ovarian index, mean oocyte diameter, oocyte proportion values and histological examinations of the ovaries of control and treated crabs. Our observations revealed significantly higher ovarian index, oocyte diameter and oocyte proportion values in treatments over controls. Leucine enkephalin treatment induced previtellogenic ovary to grow into primary vitellogenic, primary vitellogenic to secondary vitellogenic 1 secondary vitellogenic 1 and 2 to secondary vitellogenic 3 stage as evinced by the presence of a large number of primary previtellogenic ovaries in previtellogenic oocytes, larger proportion of secondary vitellogenic oocytes in primary vitellogenic ovaries and secondary vitellogenic stage 3 oocytes in secondary vitellogenic stage 1 ovaries of treated crabs over the controls. The conversion of previtellogenic ovary to early vitellogenic, early to middle and middle to late vitellogenic ovaries in treated crabs probably indicate the stimulatory effect of leucine enkephalin on ovaries either by triggering the release of the gonad stimulating hormone synthesized and released from the brain or thoracic ganglion or by blocking the release of the gonad inhibiting hormone synthesized and secreted by the X organ-sinus gland complex of the eyestalks or both. The results of the present study clearly indicate that leucine enkephalin has a stimulatory effect on ovarian maturation in T. schirnerae, thus shortening the period of maturation of ovary, which can be utilized in large-scale production of the species concerned. Further studies are needed to check the efficacy of this neurotransmitter as a supplement in diet to induce ovarian maturation of this species.

This study investigated the effects of different concentrations of probiotic Pediococcus acidilactici on the total number, specific growth rate, attached egg number and microbial count (lactic acid and total aerobic bacteria) in culture water and body of marine rotifer Brachionus plicatilis. The experiment was conducted as a completely randomized design in four groups: first group fed probiotic at 0.5×106 CFU ml-1 (P1), the second group fed probiotic at 1×106 CFU ml-1 (P2), the third group fed probiotic at 1.5×106 CFU ml-1 (P3), and the last group fed without probiotic (NP, control). Rotifers were cultured in standard conditions at an initial density of 30 ind.ml-1 using a 2.5×106 cell mL-1 of Nanochloropsis oculta. Based on the results, the maximum number (215±4.91 ind.ml-1) of rotifers were significantly obtained after ten days in the third group in comparison to other treatments (P<0.05). In addition, the highest growth rate (0.46±0.023 ind.ml-1) and shortest doubling time (1.5±0.14 days) were obtained in the treatment P3 but no significant difference was found between NP and other groups (P>0.05). Moreover, it was revealed that the total aerobic bacteria was significantly related to the 3rd group that found be 1.80×103 CFU rotifer-1 and 34.0×104 CFU ml-1 in rotifer body and culture water,respectively (P<0.05). Nonetheless, lactic acid bacteria of rotifer body and culture water was not concentration-dependent and the highest number of lactic acid bacteria in rotifer body (50.58±6.08 CFU rotifer-1) and rotifer culture water (4.43±3.28×103 CFU ml-1) was obtained in the treatments of P1 and P2, respectively. In conclusion, the present study showed that the bacteria P. acidilactici with N. oculta algae provide a higher growth rate and total aerobic bacteria in rotifer B. plicatilis.

As part of an ongoing study on the benthic macro-invertebrates of Chalakudi River basin, of the Southern Western Ghats of India, we establish a new record of a mayfly larva (Potamanthellus caenoides). Larva of Potamanthellus caenoides Ulmer, 1939 is recorded for the first time from the upstream of Chalakudy River. The specific location, sample and brief ecological notes are appended.

A total of sixty-one taxa of rotifer, belonging to 15 families, 3 orders were identified from the Phu Ninh Lake, Vietnam. Of these, five species were recorded new to Vietnam Rotifera fauna, including Lecane acanthinula (Hauer, 1938), L. sola (Hauer, 1936), L. thailandensis Segers & Sanoamuang, 1994, L. pyriformis (Daday, 1905), and Mytilina bisulcata (Lucks, 1912). The result raised the total number of rotifers known from Vietnam to 227 species. Moreover, the results showed that the number of species recorded increased with the increase of sample size, which followed the equation y=12.85+14.12log(x) (R2 = 0.99). Based on the estimators, the α-diversity of rotifers in Phu Ninh Lake might be up to 67±4 taxa (according to the Bootstrap index), 71±8 taxa (according to the Chao index), or even up to 79 taxa (according to Jacknife 2 index).

Benthic fish groups with low mobility are often restricted to a narrow range of a stream course, and their morphological characters tend to be affected substantially by the environmental conditions in their habitat. Due to morphological affectability of fishes by many factors in lotic ecosystems, a landmark-based hypothesis was used to investigate the effects of habitat hydrological conditions on morphological characteristics in freshwater benthic fishes; a case study on the genera Ponticola and Cobitis. A total of 216 gobies and 128 spined loaches specimens were caught from six rivers with different hydrological conditions, along the southern Caspian Sea basin. In discriminant function analysis (DFA), the overall assignment of gobies and loaches into their original groups were 95.7% and 80.5%, respectively. Discriminant analysis for pairwise groups shows a longer snout, shallow body/head, and elongated body for populations living in the large slope channel with faster water velocity versus relatively short snout and deep body/head for those living in small slope channel with slower water velocity. The results confirm the possibility of changes in the morphological characters of the benthic gobies and loaches, which should be considered in taxonomical and biological studies.