Effect of diazinon on life stages and resting egg hatchability of rotifer Brachionus plicatilis

The effects of organophosphate pesticide, diazinon, on life history parameters and hatchability of resting eggs of rotifer Brachionus plicalitis were assessed. Newly hatched (<1h-old) neonates were individually cultured in six varying concentrations (0/control, 0.1, 1.0, 2.5, 5.0 and 10.0 mg/L) of diazinon. The life history parameters such as time (h) the rotifers bear first egg and release first neonate, reproductive period, net reproductive rate, mixis, intrinsic rate of population increase, and life span were evaluated. Results showed that among the life history parameters, the time the rotifers took to release neonates is the most sensitive, giving the lowest EC50 value of 1.24 mg/L. The fecundity of maternal females, amictic and mictic daughters was also investigated. Rotifers exposed to 10.0 mg/L produced significantly fewer amictic daughters, and at this concentration, rotifers did not produce any mictic daughter. At 5.0 mg/L, the number of male offspring was significantly lower than the control. Furthermore, the hatchability of resting eggs produced by the rotifers was evaluated when exposed to diazinon: from birth until they produced resting eggs (early development); during late developmental stage of resting eggs (before diapause); and during diapausing stage. The hatchability of the resting eggs was not affected when exposure was timed at late developmental and diapausing stages. Overall results showed that even though amictic females reproduced normally in the presence of low concentration of diazinon, sexual reproduction is severely affected, especially the hatchability of resting eggs when the exposure was timed on its early developmental stages. This provides another evidence that production of resting eggs is particularly sensitive to the presence of xenobiotics in the environment

Euryhaline rotifer Proales similis as initial live food for rearing fish with small mouth

The SS-type rotifer Brachionus rotundiformis is a common initial food for rearing fish larvae with a small mouth. However, there are commercially important fish species whose mouth sizes are too small to feed on SS-type rotifers. In 2004, we isolated a small (body length=82.7±10.9μm; body width 40.5±6.4μm), flexible, and iloricate rotifer, Proales similis from an estuary in Okinawa, Japan. Under laboratory conditions (25°C, 2-25ppt) P. similis produced its first offspring on 2.5 to 2.8days after hatching, and produced 4.3 to 7.8 offspring within 4.0 to 4.7days life span. Batch cultured P. similis fed Nannochloropsis oculata suspension at 28.8μg dry weight ml-1 and cultured at 25°C, 25ppt filtered seawater, increased exponentially from 25 to 2400ind ml-1 after 11days of culture with an overall intrinsic rate of natural increase (r) of 0.42day-1. The growth rate of P. similis was not significantly different when fed fresh N. oculata and super fresh Chlorella vulgaris-V12R. Total lipid per wet weight of P. similis fed by N. oculata and C. vulgaris were 2.4 and 2.6%, respectively. The compositions of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA) of P. similis fed N. oculata were 23.2, 0.0 and 5.3%, respectively, while these were 11.0, 17.5 and 0.5% respectively, when fed C. vulgaris. The use of P. similis to feed small mouth fish including seven-band grouper Epinephelus septemfasciatus, rusty angelfish Centropyge ferrugata, and humphead wrasse Cheilinus undulatus showed that it is an excellent starter food for these species because of their high selectivity index and improved survival. In addition, P. similis was ingested by Japanese eel Anguilla japonica larvae with a complicated digestive system. The use of P. similis as starter feed for small mouth fish larvae is highly recommended

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

The use of non-Brachionus plicatilis species complex rotifer in larviculture

Due to the expanding world aquaculture production, the demand for high quality and quantity of fish larvae has also increased. Up to date, the bottleneck in larviculture is the stable and ample production of appropriate live food such as rotifers and copepods. Among rotifers, Brachionus plicatilis species complex, which encompasses 15 species with varied sizes ranging from 100 to 400 μm, is commonly used in most hatcheries. The use of B. plicatilis species complex (B. plicatilis, B. koreanus, and B. rotundiformis) in larviculture is reported in several review papers. In this review, we first described rotifer species not classified under B. plicatilis species complex, some of which are already used in larviculture, while some have high potential for use based on their characteristics, life history, and distribution. Rotifers, Brachionus angularis, Brachionus calyciflorus, and Proales similis, are described in detail in comparison with B. plicatilis species complex. Furthermore, we discussed some characteristics of rotifers which can affect their predation

Phototactic behavior of the marine harpacticoid copepod Tigriopus japonicus related to developmental stages under various light conditions

Marine harpacticoid copepod Tigriopus japonicus is commonly distributed in the tide-pools and shows benthic behavior. To determine its phototactic behavior, the movement pattern was investigated with different light wavelengths (white, peaks at 460 and 570 nm; blue at 470 nm; green at 525 nm; and red at 660 nm) and intensities (0.5, 2.0, 3.5, 5.0, 15.0 W/m2)related to developmental stages i.e., nauplius and adult. The eyespot of the two developmental groups efficiently absorbed the light wavelength from 400 to 550 nm, while the level of absorbance was different. For the horizontal phototactic behavior, nauplii showed negative phototaxis with the all tested light wavelengths and intensities ranging 0.5?5.0 W/m2,while they lost phototactic movement at 15 W/m2 of all conducted light wavelengths except with the red light shown negative phototaxis. The adults showed negative phototaxis at 0.5 and 3.5 W/m2, while positive phototaxis at 2.0 W/m2 regardless of light wavelengths. The vertical phototactic movement was only monitored with adults. At 2.0 and 3.0 W/m2, >40% of adults showed planktonic behavior with the blue light. The results elucidate that T. japonicus has different patterns of phototaxis related to developmental stages which can be used to manipulate its distribution for dispersal

Molecular cloning and localization of GABAA receptor-associated protein in the rotifer Brachionus plicatilis

γ-Aminobutyric acid receptor type A-associated protein (GABARAP) and its homologs constitute a protein family found in many eukaryotes from yeast to human, and are known to be involved in intracellular membrane trafficking of GABAA receptors and autophagy. In this study, we cloned cDNA-encoding GABARAP from the monogonont rotifer Brachionus plicatilis and examined for its tissue distribution at the protein level in neonates, males and females. Using reverse transcription (RT)-PCR and rapid amplification of cDNA ends (RACE) techniques, we showed that like other GABARAPs, rotifer GABARAP was also composed of 117 amino acids and highly homologous to vertebrate GABARAP2 ortholog (74–76% identity). GABARAP was demonstrated with its specific antibody to be ubiquitously distributed, irrespective of neonates, males, and females, in the coronal area that covers brain and contains most mechano- and chemoreceptors. Rotifer GABARAP was also expressed in the mature eggs but not in immature eggs. Double immunostaining with mammalian anti-GABA γ receptor antibody showed that rotifer GABARAP co-localized with GABA receptor, suggesting the association of the two proteins. The presence of GABARAP in rotifer implies that it is highly conserved during evolution, and plays important roles in various biological processes.This study was partly supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS)

Occurrence and histopathogenesis of a didymozoid trematode (Gonapodasmius epinepheli) in pond-reared orange-spotted grouper, Epinephelus coioides

A didymozoid trematode encapsulated in the gills of orange-spotted grouper, Epinephelus coioides Hamilton, was observed in October 1997 and September 1999 among pond-reared fish in the Philippines. Capsule prevalence was 33% and 18% and mean intensity 2 and 1, respectively. The opaque-white and yellowish capsules were found only on the first gill arch and were attached lengthwise along the posterior surface of the primary gill filaments. When the capsules were opened, long thread-like worms were revealed, which were identified as Gonapodasmius epinepheli Abdul-Salam, Sreelatha and Farah. The parasites were encapsulated between the basement membrane of the epithelium and the efferent artery of the gill filament. The response of the host included mild hyperplasia of the interlamellar epithelium and an increase in the number of mucous cells

Phylogenomics and the rise of the angiosperms.

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods1,2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome3,4. Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5-7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade