Anatomy of synganglia, including their neurosecretory regions, in unfed, virgin female Ixodes scapularis say (Acari: Ixodidae)

Abstract

The central nervous system of Ixodes scapularis is fused into a single compact synganglion. The esophagus runs through the synganglion and divides it into supraesophageal and subesophageal parts. The supraesophageal portion contains a single protocerebrum with four pairs of glomeruli, paired optic lobes and cheliceral ganglia, and a single stomodeal bridge. The subesophageal portion contains a centrally located network of commissures and connectives, a pair of palpal ganglia, paired olfactory lobes of the first pedal ganglia, four pairs of pedal ganglia, and a single opisthosomal ganglion. A retrocerebral organ complex (ROC) in close vicinity of the digestive tract, as described in some other tick species, apparently is lacking. Perhaps the function of the ROC is performed by the paired, large, ganglion-like bodies that lie anterolaterad to the cheliceral ganglia. The rind, which is formed from the neuronal somata and glial cells, surrounds the central fibrous core or neuropile. Neurosecretory cells (NSC) are distinct among rind cells due to their large size and concentration of cytoplasmic neurosecretions. NSC are present throughout the synganglion, although the subesophageal portion contains larger groups of these cells. Histological serial sections, stained with Meola's (Trans Am Microsc Soc 89:66-71, '70) paraldehyde fuchsin (PAF) procedure revealed 24 PAF-stained, putative neurosecretory regions in the synganglion of virgin, unfed females. All of these regions appear to be connected and associated with the nearest ganglion and are correspondingly named. Eighteen PAF-positive regions occur in the synganglion. In addition, PAF-negative (green-stained) cells occupy 6 distinct regions in the synganglion of unfed, unmated females.

Tick neurobiology: recent advances and the post-genomic era

“…This sheath encloses a periganglionic sinus allowing the synganglion to be supplied with fresh filtered haemolymph from the heart. In adult ticks, the dimensions of the synganglion are approximately 300-500 lm long by 275-550 lm wide (Prullage et al 1992;Szlendak and Oliver 1992). The basic arrangement of the synganglion is the same in the three main taxa of ticks that include the Prostriata, Metastriata and the Argasidae.…”

“…183-198 185 The suboesophageal region constitutes the largest part of the synganglion. The central region of this section is composed of a system of commissures and connectives (Szlendak and Oliver 1992). At the margin of the network of commissures and connectives are four pairs of large pedal ganglia which individually give rise to pedal nerves that innervate the four pairs of legs (Szlendak and Oliver 1992).…”

Localization of insulin-like immunoreactivity in the synganglion of nymphal and adult Dermacentor variabilis (Acari: Ixodidae)

“…Terminology of the neurosecretory regions in D. variabilis used in this paper follow Obenchain and Oliver (1975). More recent terminology of NSR in Ixodes scapularis (Szlendak and Oliver, 1992) is also provided in parentheses. RESULTS We found positive immunoreactive staining to an insulin antibody in five of the 18 PAF-positive neurosecretory regions (NSR) described by Obenchain and Oliver (1975) in the synganglion of D. variabilis adult unfed males and unfed females ( Table 1).…”

“…The posterior medial group of the protocerebral center [=posterior protocerebral in I. scapularis (Szlendak and Oliver, 1992)] contained two large immunopositive cells, one on each side of the esophagus, dorsomediad to the posterior region of the protocerebral neuropile, where the esophagus exits the synganglion (Fig. l a and 2b).…”

Immunocytochemical mapping of FMRFamide-like peptides in the argasid tick Ornithodoros parkeri and the ixodid tick Dermacentor variabilis

“…The wide distribution of FaRPs in the animal kingdom and the various biological activities of these peptides prompted us to look for an FMRFamide-like substance in ticks. Using classical staining techniques such as paraldehyde fuchsin, putative neurosecretory cells have been found in various regions of the synganglion (Binnington and Obenchain, 1982;Pound and Oliver, 1982;Szlendak and Oliver, 1992). In this paper, we report the distribution of FMRFamide-like immunoreactive cells, their axons, and possible areas for storage and release of these peptides in the synganglion of females of the argasid tick Ornithodoros parkeri and the ixodid tick Dermacentor variabilis.…”