Organization of the nervous system in the pygmy cuttlefish, Idiosepius paradoxus ortmann (Idiosepiidae, cephalopoda)

Abstract

The idiosepiid cuttlefish is a suitable organism for behavioral, genetic, and developmental studies. As morphological bases for these studies, organization of the nervous system was examined in Idiosepius paradoxus Ortmann, 1881, using Cajal's silver technique and immunohistochemical staining with anti-acetylated alpha-tubulin antibody. The nervous architecture is generally identical to that described in Sepia and Loligo, but some features characterize the idiosepiid nervous system. The olfactory system is highly developed in the optic tract region. The dorsolateral lobes show large neuropils, connected with each other by a novel well-fasciculated commissure. Each olfactory lobe is subdivided into two lobules. The neuropils of the anterior and the posterior chromatophore lobes are very poorly developed. Neuronal gigantism is not extensive in the brain; enlarged neuronal cells are visible only in the perikaryal layer of the posterior subesophageal mass. The giant nerve fiber system is of the Sepia type; the axons are not markedly thick and the first-order giant fibers do not fuse with each other at the chiasma. Three-dimensional images by whole-mount immunostaining clarified the innervation pattern in the peripheral nervous system in detail. Two commissural fibers link the left and right posterior funnel nerves ventrally and dorsally. The stellate commissure, which is absent in Sepia and Sepiola, connects the stellate ganglia with each other. A branch of the visceral nerve innervating the median pallial adductor muscle is characteristically thick. Tubulinergic reactivity of the cilia and axons reveals the presence of many ciliated cells giving off an axon toward brain nerves in the surface of the funnel, head integument, arm tips, and epidermal lines. Some of these features seem to reflect the inactive nekto-benthic life of the idiosepiid cuttlefish in the eelgrass bed.

Expression of serotonin (5-HT) during CNS development of the cephalopod mollusk, Idiosepius notoides

“…In the adult posterior subesophageal and periesophageal mass of I. notoides, 5-HTir cell somata seem to be located in the same relative position as in hatchlings. Neural cell somata of the perikaryal layer in the adult posterior subesophageal mass are at 10 μm rather large compared to the average of 5 μm in the sister species, Idiosepius paradoxus (Shigeno and Yamamoto 2002). In I. notoides, 5-HT-ir cell somata even exceeded this size at 8-16 μm length and 6-11 μm width (present study).…”

“…The nomenclature of each lobe in the CNS of I. notoides ( Fig. 1; Table 1) was adopted from previous studies (Young 1979;Shigeno and Yamamoto 2002;Yamamoto et al 2003;Wollesen et al 2010). Fig.…”

Comparative neuroanatomy of Caudofoveata, Solenogastres, Polyplacophora, and Scaphopoda (Mollusca) and its phylogenetic implications

“…Even though the central nervous system of cephalopods is well studied by immunohistochemical studies (Shigeno and Yamamoto 2002;Wollesen et al 2008), a comparison of scaphopods and cephalopods is complicated, because in cephalopods most of the major ganglia (cerebral, pleural, and pedal) are concentrated as lobes of a large brain. Cephalopods, especially the more derived Coleoidea, have highly developed optical lobes dominating the brain, which are entirely lacking in the blind scaphopods.…”

Evolution of the cephalopod head complex by assembly of multiple molluscan body parts: Evidence from Nautilus embryonic development

“…Whole-mount immunohistochemistry was completed according to a standard protocol as described by Shigeno and Yamamoto (2002) with some modifications. Fixed embryos were treated with 0.02 mg ml 21 proteinase K (GibcoBRL) in PBST (PBS, 0.3% Triton X-100) for 15 min at 378C, and postfixed in 4% PFA in PBST.…”