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Fine structure of the larval rhinophores of the nudibranch, Rostanga pulchra, with emphasis on the sensory receptor cells (1982)

Chia, Fu-Shiang ; Koss, Ron

Springer

Cell & tissue research 225 (1982), S. 235-248

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ISSN: 1432-0878

Keywords: Rhinophore ; Larva ; Nudibranch ; Sensory cell ; Ultrastructure

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary The rhinophores of the veliger larva of Rostanga pulchra are located in the intravelar field near the base of the velar lobes. Each rhinophore is a cylindrical structure, tapering distally, and covered with a dense meshwork of microvilli. A conspicuous row of ciliary tufts runs along each side of the rhinophore and several stiffer tufts, composed of fewer cilia, are positioned around the tip or at the base. The rhinophoral epithelium consists of supporting cells, ciliated cells (giving rise to the ciliary rows), dendritic terminals (giving rise to the tufts around the apex), and sinuses containing occasional amebocytes. The lumen of the rhinophore is occupied by the rhinophoral ganglion and muscle cells that are oriented in two perpendicular planes. Cell bodies of the dendritic endings are located within the rhinophoral ganglion, which in turn joins into the optic and cerebral ganglia. Rhinophoral ganglionic neurons do not synapse with each other, but numerous neuromuscular synapses are found in the lumen of the rhinophore. Morphological evidence suggests that the dendritic endings are chemoreceptors and the ciliated cells are possibly mechanoreceptors but are not functional at this stage in development. The functional role of the rhinophores is discussed in relation to larval behavior at settlement and metamorphosis.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00214678

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Fertilization in a chiton: Acrosome-mediated sperm-egg fusion (1988)

Buckland-Nicks, John ; Koss, Ron ; Chia, Fu-Shiang

New York, NY : Wiley-Blackwell

Gamete Research 21 (1988), S. 199-212

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ISSN: 0148-7280

Keywords: egg envelopes ; polyspermy ; mollusca ; polyplacophora ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology

Notes: Contrary to the widely accepted view that chiton sperm lack acrosomes and that fertilization in this group occurs via a micropyle, we demonstrate here that fertilization in Tonicella lineata occurs by acrosome-mediated sperm-egg fusion. The acrosome is a small vesicle containing two granules located at the tip of the sperm. The eggs have an elaborate hull (=chorion), which is formed into cupules that remain covered by follicle cells until maturity. When dissected ripe eggs were exposed to sperm in vitro, the sperm were attracted only to open cupules, inside which they swam through one of seven channels to the base where they penetrated the hull. The acrosome fired on contact with, or in, the hull, and during passage through it the apical granule was exhausted while the basal granule was exposed. If sperm contacted follicle cells between the cupules the acrosome did not react. The vitelline layer beneath the hull contains pores arranged in a regular pattern. Embedded in the base of each pore is an egg microvillus. Having penetrated the hull the sperm anterior filament located a pore and fused with the tip of the egg microvillus projecting into it. This created a membranous tube, through which the sperm nucleus was injected into the egg. The egg membrane appeared to be raised up into a small fertilization cone around the penetrating sperm, the vitelline layer became slightly elevated, and some cortical granules were released by exocytosis.

Additional Material: 13 Ill.