Architectonics of crayfish ganglia

Abstract

The central nervous system of crayfish consists of a chain of segmental ganglia that are linked by cables of intersegmental axons. Each ganglion contains a highly-ordered core of longitudinal tracts, vertical tracts, commissures, and synaptic neuropils. We review from a technical perspective the history of the description of these ganglia, and recognize four episodes of progress. Each major innovation in anatomical methods has led to new insight into the structure and function of this nervous system, and new awareness of the structural patterns that are common to the CNS of all arthropods. Ganglia in different segments of the body differ in size, and appear to differ in anatomy. From a comparison of the structures of the cores of abdominal, thoracic, and subesophageal ganglia, we argue that this apparent difference is illusory. Rather, each of these ganglia is organized on the same plan, a plan also found in insect segmental ganglia. The apparent differences follow from longitudinal compression during development and from allometric growth of particular neuropils associated with innervation of the walking legs. Different authors have described the internal organization of ganglia in different segments, so we provide a cross-reference to the nomenclatures they have introduced. We compare the locations of cell bodies of motor neurons and accessory neurons that innervate different peripheral structures, and demonstrate double-labeling of certain GABAergic peripheral inhibitory neurons. Finally, we describe the construction of digital movies of serial sections of these ganglia, and discuss their utility.

Changes in the nitric oxide system in the shore crab Hemigrapsus sanguineus (Crustacea, decapoda) CNS induced by a nociceptive stimulus

“…Their physiology is similar to mammalian low-threshold mechanoreceptors (Byrne et al, 1974) or typical nociceptors (Illich and Walters, 1997) and their noxious-induced responses has been characterized in some invertebrate species (Shen et al, 2002), including crustaceans Barr et al, 2007;Elwood and Appel, 2009;Puri and Faulkes, 2010). In the sensory neuropils, fibers from cheliped receptors make synaptic contacts with dendrites of interneurons and motoneurons (Elson, 1996;Mulloney et al, 2003). In our study, these appeared to be the neurons that display maximum NADPH-d activity shortly after injury, and iNOS immunoreactivity thereafter.…”

Existence and distribution of gonadotropin-releasing hormone-like peptides in the central nervous system and ovary of the Pacific white shrimp, Litopenaeus vannamei

“…The anatomical nomenclature of the various parts of the supraesophageal ganglion (brain) was based on that described previously in three species of decapods by Sandeman et al (1992), whereas those of the subesophageal ganglion (SEG), thoracic ganglia, and abdominal ganglia were named according to the description of Mulloney et al (2003). The four ovarian stages in female white shrimps were visually evaluated based on the ovarian size, color, and histology as described by King (1948) and Bell and Lightner (1988).…”

Projection and local interneurons in the sixth abdominal ganglion of the sand crab Emerita analoga (Hippidae)

“…A6 in E. analoga contains roughly 360 neurons, about half the number in crayfish (Reichert et al, 1982;Paul et al, 1983;Kondoh and Hisada, 1986), of which fewer than 60 (again, half the number in crayfish; Reichert et al, 1982;Sigvardt et al, 1982) are bilateral pairs of intersegmental neurons with axons projecting into the connective between A5 and A6. A description of the architecture of A6 in E. analoga (Paul and Marx, in preparation) similar to descriptions available for crayfish Hisada, 1986, 1987;Mulloney et al, 2003) will facilitate interspecific comparisons of A6 neurons, but, even without comparable information on axon tracts, commissures, and neuropils, probable homologies of some individually identified neurons in E. analoga and crayfish can be suggested, based on analogous positions within A6 and strong similarities in morphological and physiological properties (Table 1). This is useful in discovering the behavioral roles of neurons, because the physiological properties of morphologically similar homologues are probably similar as well, unless there has been selection for altered function.…”