Spermatophore of squid attaches for evagination using a spiral filament anchor and perforation.

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Recent reports of oral stinging after consuming cooked squid has led to inquiry of the reproductive mechanisms of the Teuthida order of cephalopods. The "stinging" was found to be attributed to the sperm carrier, or spermatophore, of the squid. What initially confounded scientists was the durability of the spermatophore to survive having been cooked. The spermatophore is encased in a membrane, i.e., cement body. It is believed that the free-floating spermatophore is able to attach to the surface of a female squid through a spiral filament on its side. This filament has stellate particles that scar the surface of the squid's skin, i.e., causes perforation. This is a new discovery; apart from chemical attachment, as found in most external reproduction, the spermatophore creates a mechanical form of attachment all on its own. The spiral filament also serves as an anchor in the perforated surface until the cement body is ejected into the deeper layers of the skin. Once ejected, the sperm is released and able to impregnate the female. Please see the attached page for better understanding of the spermatophore and its parts (there is a picture and video).

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"Although spermatophore attachment was long thought to be performed solely by adhesive substances from the cement body, several lines of evidence suggest that spermatophore attachment in squids is performed through a complex process that involves tissue perforation in addition to chemical adhesion. Recently, a tissue penetration mechanism was proposed to be intrinsic of the spermatophore structure in squids." (Marian et al. 2012:295)

"Male squid produce intricate spermatophores that, when transferred to the female, undergo the spermatophoric reaction, a complex process of evagination that leads to the attachment of the spermatangium, that is, the everted spermatophore containing the sperm mass. While this process is still not completely understood, the medical literature includes several reports of 'oral stinging' (i.e., punctured wounds in the human oral cavity) following consumption of raw male squid, which contains undischarged spermatophores able to inflict such wounds…spermatophore attachment generally involves tissue scarification, and…stellate particles play a vital role in the attachment process. Moreover, spermatophore attachment is confirmed to be autonomous (i.e., performed by the spermatophore itself) in another squid species…and the results strongly indicate that the attachment mechanism is not dependent upon a specialized epithelium, nor a mate’s specific chemical stimulus." (Marian et al. 2012:293)
 
"The undischarged spermatophore consists of a sperm mass…a cement body…and an ejaculatory apparatus…being enveloped by the outer and middle tunics. From the outside to the median axis of the spermatophore, the ejaculatory apparatus tube consists of the inner tunic, the middle and inner membranes, and the spiral filament...The cement body is divided into a conical oral region and a bulbous aboral region, apparently lacking an intermediate region. The cement body casing encloses a core of...granular material embedded in a more homogeneous matrix." (Marian et al. 2012:295)
 
"The spermatangium is composed of the everted inner tunic enclosing the sperm mass and of the burst cement body located on its base…The attached spermatangium’s base fits into a superficial depression in the oral epithelial tissue and the burst cement body occupies the space between the spermatangium base and the oral epithelium, possibly providing a means of chemical attachment." (Marian et al. 2012:295)
 
"Stellate particles found in the layer surrounding the cement body of the analyzed spermatophores are possibly closely applied to the inner membrane…The stellate particles from the spiral ?lament and from the layer surrounding the cement body were also hypothesized to take part in the tissue perforation mechanism." (Marian et al. 2012:297, 299)

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Journal article
SpringerMarian, JEAR; Shiraki, Y; Kawai, K; Kojima, S; Suzuki, Y; Ono, K

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