Fine structure of the CNS ganglia in the geometric spider Nephila clavata (Araneae: Nephilidae)

Abstract

As web spiders usually hang with their head downward, geometrical differences in body position could affect the organization of their central nervous system (CNS). Nevertheless, most of our knowledge of spider's CNS is dependent on what has been revealed from wandering spiders. To fill the gap, we describe here the fine structural organization of the ganglionic neurons and nerves in the geometric orb web spider Nephila clavata. Nerve cells in the supraesophageal ganglion in N. clavata are packed in the frontal, dorsal and lateral regions, but the nerve cells of the subesophageal mass are only restricted to the ventral and ventrolateral regions. High resolution transmission electron microscopy (TEM) reveals the fine structural details of the neuroglial cells and the neuronal cells which have a conspicuous Golgi apparatus, rough ER, free ribosomes and well‐developed mitochondria. Comparing fine structural characteristics of the CNS ganglia with those of wandering spiders in most respects, it has been revealed that the geometrical difference may affects to the arrangement of receptors in the central body known as an important association center for web building behavior. In particular, remarkable differences can be detected in the protocerebral area by the extraordinary development of the central body including absence of the globuli and associated mushroom bodies.

Exploration behaviour and behavioural flexibility in orb-web spiders: A review

“…Recently there has been a renewed interest in the otherwise neglected area of spider neurophysiology with a number of anatomical studies on brain size and structure (Quesada et al, 2011;Park et al, 2013). Similar methods could be used to compare structures in the supraesophageal ganglion between spiders with extensive site exploration to spiders with hardly any, such as the Darwin's bark spider (Gregoric et al, 2011), in order to estimate the possible computational requirements of the behaviour.…”

“…Volumetric measurements, however, failed to find any differences in relative size of the central body between the orb-web spider Nephila clavipes and three web-less spiders (Weltzien and Barth, 1991). Nonetheless, the central body remains at present the most likely candidate for the brain structure that governs web-building behaviour (Park et al, 2013). This is supported by older studies on the orb-web spider Araneus diadematus displaying disruption to normal webbuilding behaviour after its protocerebrum was damaged with laser light (Witt and Reed, 1964;Witt, 1969).…”

“…The subesophageal ganglion, which as the name implies is located below the esophagus, is the main centre for linking sensory input to motor output and consists of the fused ganglia of the appendages. The supraesophageal ganglion, also referred to as the 'brain', is the most complex part of the central nervous system and consists of several different structures including the protocerebrum, which contains the central body, and the optic nerves (Babu, 1975;Park et al, 2013). As the supraesophageal ganglion receives sensory input from the eyes, it is most highly developed in spiders with good vision such as jumping spiders and wolf spiders (Foelix, 2011).…”

Morphological and anatomical changes related to leg anomalies in Tegenaria atrica

“…The central nervous system of Poecilotheria and Argiope aurantia (Lucas) was described in detail by Babu (1965, 1969, 1975). It was also investigated by Babu and Barth (1984), Wegerhoff and Breidbach (1995), Barth (2002), Hwang and Moon (2003), Hill (2006), Park and Moon (2013), and Park et al (2013). The central nervous system of spiders can be described as a highly condensed organ consisting of two parts: the supraoesophageal ganglion (brain) and the fused suboesophageal ganglia, both located in the prosoma.…”

Fine Structure of the Neuroganglia in the Central Nervous System of the Harvestman Leiobunum japonicum (Arachnida: Opiliones)

“…Following fine work of the arachnid CNS (Babu, 1975), several other workers (Babu, 1985;Babu & Barth, 1984;Doeffinger et al, 2010;Hill, 2006;Hwang & Moon, 2003;Park et al, 2013;Weltzien & Barth, 1991;Weygoldt, 1985) have reported structural organization of the CNS of arthropod animals. However, most of our anatomical and histological understandings of Opilione CNS comes from only a few authors (Shultz & Pinto-da-Rocha, 2007).…”