Eggshell formation in Bdelloura candida, an ectoparasitic turbellarian of the horseshoe crab Limulus polyphemus

Abstract

The marine triclad Bdelloura candida (Turbellaria) episodically deposits stalked eggshells onto the gill lamellae of the horseshoe crab Limulus polyphemus. Ultrastructural and biochemical analyses indicate that the eggshells consist of primary inner and secondary outer layers. Protein of the primary layer is rich in glycine, aspartate/asparagine, serine, and 3,4-dihydroxyphenylalanine (Dopa). In this regard it resembles the eggshell compositions of other members of the phylum Platyhelminthes. The primary layer appears to be derived from precursors produced in the vitelline cells of the flatworm. Each egg-laying episode consumes all of the precursor-containing vitelline cells. A Dopa-containing protein, vitelline protein 1 (Vp1), has been isolated from B. candida and resembles the primary eggshell layer in its composition. Vp1 has an apparent molecular weight of 34.4 and an acidic pI. Dopa-containing proteins are presumed to be directly involved in the cross-linking reactions that accompany quinone-tanning. The secondary outer layer of the eggshell may serve to adhere the eggshell to the gill. Its amino acid composition is unlike that of the primary eggshell and nothing is known about its precursors.

Jack of all trades: versatile catechol crosslinking mechanisms

“…Another natural example is the marine worm Bdelloura candida, producing a dopa-protein, which is believed to contribute to the curing of the primary inner layer of its eggshell. 120,121 During the hardening and darkening of the eggshell, the metal levels (e.g., iron, copper, zinc, and lead) increase, suggesting the occurrence of a metal-dependent curing process.…”

Oocyst wall formation and composition in coccidian parasites

“…The presence of dityrosine in vertebrate animal proteins is also seen in chicken aorta elastin, collagen and connective tissues from bovines, rats and cats, and in tissues of normal and diseased humans (LaBella et al 1968, Amado et al 1984, Davies et al 1999. DOPA-containing proteins are also widely distributed in nature and are involved in the synthesis of extraorganismic structural materials such as helminth worm and mosquito eggshells, egg capsules, cocoons, mussel byssal threads and various biological glues and cements (Waite 1990, Huggins & Waite 1993). In addition, phenol oxidase activity (catalyzing oxidation of DOPA to dopachrome) is detected only in homogenates of female Trichuris suis (a parasite inhabiting the intestines of pigs), not males, suggesting that the enzyme is likely to be associated with hardening of eggshell and that the eggshell proteins might consist of DOPA-containing proteins (Fetterer & Hill 1993).…”

Paternity in horseshoe crabs when spawning in multiple-male groups

“…Bdelloura candida is a triclad turbellarid flatworm that is found on most horseshoe crabs. As adults, the worms feed on scraps of food left around the crab's mouth (leg bases), but they also lay their eggs in the leaves of the book gills where they cause considerable damage (Huggins & Waite 1993) including degeneration and destruction of the gill cuticle (Groff & Leibovitz 1982). We combined these five measures of condition into a simple index: if the animal showed the poorest condition in all five categories, it received a rank of 5; if it showed the highest rank in all five categories it received a score of 25 (a middle rank in all five categories received a score of 15).…”