Fine structure and immunocytochemistry of a new chemosensory system in the chiton larva (Mollusca: Polyplacophora)

Abstract

Combined electron microscopy and immunocytochemistry of the larvae of several polyplacophoran species (Chiton olivaceus, Lepidochitona aff. corrugata, Mopalia muscosa) revealed a sensory system new to science, a so-called "ampullary system." The cells of the "ampullary system" are arranged in four symmetrically situated pairs lying dorsolaterally and ventrolaterally in the pretrochal part of the trochophore-like larva and they send axons into the cerebral commissure. They are lost at metamorphosis. The fine structure of these cells strongly resembles that of so-called "ampullary cells" known from various sensory organs of other molluscs, such as the apical complex of gastropod and bivalve larvae, osphradia of vetigastropods, and olfactory organs of cephalopods, and nuchal organs of certain polychaetes. The ampullary cells and their nerves are densely stained by anti-FMRF-amide fluorescence dyes, whereas antiserotonin staining is only weak. While cytological homology of the ampullary cells with those of other organs is probable, the ampullary system as a whole is regarded as a synapomorphy of the Polyplacophora or Chitonida.

The simplicity of males: Dwarf males of four species of Osedax (Siboglinidae; Annelida) investigated by confocal laser scanning microscopy

“…There are no trochophore or metatrochophore larvae of annelids that have been studied in relevant detail that show this feature (Lacalli, 1984;Hay-Schmidt, 1995;Hessling, 2002;Hessling and Westheide, 2002;Voronezhskaya et al, 2002;Eeckhaut et al, 2003;McDougall et al, 2006;Brinkmann and Wanniger, 2008). Such crossing over is also unknown in putative annelids such as Sipuncula and non-annelid trochophores of molluscs and entoprocts (Haszprunar et al, 2001;Fuchs and Wanninger, 2008;Voronezhskaya et al, 2008). However, the crossing over does show some resemblance to the additional ventral fibers crossing in the middle part of the subesophageal ganglion of Trilobodrilus hermaphroditus (Mü ller and , which, while not suggesting they are homologous, does provide some support for our interpretation of an elongate first segment in Osedax males.…”

Expression of prohormone convertase 2 and the generation of neuropeptides in the developing nervous system of the gastropod Haliotis

“…within the larval nervous system (Croll and Voronezhskaya, 1996;Dickinson et al, 1999; Dickinson et al, 2000;Haszprunar et al, 2002;Dickinson and Croll, 2003; Croll, 2006). In the adult stages of these same animals, neuropeptides play a number of roles as local neurotransmitters and neuromodulators and as circulating hormones (Chase, 2002).…”

“…This is the first study to show a convertase is expressed early in molluscan development. While FMRFamide-like immunoreactivity has been reported widely in early larval stages of gastropod molluscs (Croll and Voronezhskaya, 1996; Dickinson et al, 2000;Haszprunar et al, 2002;Dickinson and Croll, 2003; Croll, 2006), neither the transcript for FMRFamide encoding genes nor the enzymes necessary for post-translational processing of the precursor protein have previously been demonstrated in such early larval stages. The results from this study suggest that HasPC2 is contributing to the proteolytic activity necessary for the synthesis of FMRFamide and related peptides.…”

“…Biol. 53: 1081-1088 (2009) Abbreviations used in this paper: DIG, digoxigenin; MALDI-MS, matrix-assisted laser desorption/ionization MS; PBS, phosphate-buffered solution; PC, prohormone convertase; RACE, rapid amplification of cDNA ends; WMISH, whole-mount in situ hybridization.within the larval nervous system (Croll and Voronezhskaya, 1996;Dickinson et al, 1999; Dickinson et al, 2000;Haszprunar et al, 2002;Dickinson and Croll, 2003; Croll, 2006). In the adult stages of these same animals, neuropeptides play a number of roles as local neurotransmitters and neuromodulators and as circulating hormones (Chase, 2002).…”

Novel, posterior sensory organ in the trochophore larva of Phyllodoce maculata (Polychaeta)

“…In polychaete trochophores, only the apical organ and ventral pretrochal sensory cell are known (Å kesson 1967;Lacalli 1981Lacalli , 1984Lacalli , 1986Hay-Schmidt 1995;Voronezhskaya et al 2003). In chiton larvae, transient dorsolateral sensory cells were described, but these cells are pretrochal, paired and FMRFamide immunopositive (Haszprunar et al 2002;Voronezhskaya et al 2002). Post-trochal peripheral neurons occur in larval gastropods, but they are solitary FMRFa IR cells, which appear at much earlier stages and have a different morphology and projection pattern (reviewed by Croll 2000).…”