Three‐dimensional reconstruction and neural map of the serotonergic brain of Asplanchna brightwellii (Rotifera, Monogononta)

Abstract

The basic organization of the rotifer brain has been known for nearly a century; yet, fine details on its structure and organization remain limited despite the importance of rotifers in studies of evolution and population biology. To gain insight into the structure of the rotifer brain, and provide a foundation for future neurophysiologic and neurophylogenetic research, the brain of Asplanchna brightwellii was studied with immunohistochemistry, confocal laser scanning microscopy, and computer modeling. A three-dimensional map of serotonergic connections reveals a complex network of approximately 28 mostly unipolar, cerebral perikarya and associated neurites. Cells and their projections display symmetry in quantity, size, connections, and pathways between cerebral hemispheres within and among individuals. Most immunopositive cells are distributed close to the brain midline. Three pairs of neurites form decussations at the brain midline and may innervate sensory receptors in the corona. A single neuronal pathway appears to connect both the lateral horns and dorsolateral apical receptors, suggesting that convergence of synaptic connections may be common in the afferent sensory systems of rotifers. Results show that the neural map of A. brightwellii is much more intricate than that of other monogonont rotifers; nevertheless, the consistency in neural circuits provides opportunities to identify homologous neurons, distinguish functional regions based on neurotransmitter phenotype, and explore new avenues of neurophylogeny in Rotifera.

Serotonin immunoreactivity in the nervous system of the free‐swimming larvae and sessile adult females of Stephanoceros fimbriatus (Rotifera: Gnesiotrocha)

“…According to Montgomery (), who has performed histological research on S. fimbriatus , five sets of neurons project from the cerebral ganglion, three of which innervate sense organs: one pair innervates the dorsal sense organ; one pair innervates the lateral sense organ; and one unpaired median neuron innervates the hypodermis posterior of the dorsal sense organ. Our results could not confirm these observations, but in some respects this is not surprising since serotonergic innervation of sensory organs has only rarely been documented in rotifers (e.g., Hochberg ; Hochberg & Lilley ). Our observations do indicate that at least two of the neurons detected by Montgomery () are likely to correspond to a pair of 5HT‐IR neurites we detected in both larval and adult specimens.…”

4. Rotifera

“…4.20). ) Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 6/16/15 1:00 PM connections, and pathways between the cerebral hemispheres (e.g., Hochberg 2007Hochberg , 2009. The brain is of varying shape and size: rounded, sacshaped, quadrangular, or triangular, etc.…”

Adverse effects of the SSRI antidepressant sertraline on early life stages of marine invertebrates

“…including antennae and mandibula, the main limbs involved in swimming (Anderson, 1994). In rotifers, the corona is the main source of locomotion, where two concentric rings of cilia create different patterns of ciliary movement (Hochberg, 2009). In most of species belonging to class Monogononta such as Asplanchna brightwellii, the serotonergic system represents a complex network and includes sensory receptors located in the region of the corona although research studies focused on serotonin-modulated mechanisms lack in B. plicatilis (Hochberg, 2006(Hochberg, , 2009Hochberg and Hochberg, 2015; Leasi et al, 2009).…”

“…In rotifers, the corona is the main source of locomotion, where two concentric rings of cilia create different patterns of ciliary movement (Hochberg, 2009). In most of species belonging to class Monogononta such as Asplanchna brightwellii, the serotonergic system represents a complex network and includes sensory receptors located in the region of the corona although research studies focused on serotonin-modulated mechanisms lack in B. plicatilis (Hochberg, 2006(Hochberg, , 2009Hochberg and Hochberg, 2015; Leasi et al, 2009). In the absence of research studies focused on the mechanism of action of SRT and other SSRIs in marine organisms, we suggest that increasing and inhibition on swimming behavior could be regulated, at least partially, by high levels of serotonin in the synaptic cleft resulting in abnormal neurotransmission, duration and intensity, leading to possible behavior disruption (Cailleaud et al, 2011;Mesquita et al, 2011).…”