Extending Darwin's investigations on the barnacle life-history

Abstract

Darwin's magnificent study of the stalked, sessile and fossil barnacles, perhaps his greatest work, was started not many years after the systematic position of cirripedes within the class Crustacea had been accepted. It was completed at a time when histology and microtomy were not developed and when living specimens could only be seen on occasional visits to the seaside. Yet 130 years later it remains the standard text.It was on a visit to Tenby that he observed that barnacles were sensitive to vibration and, in seeking an acoustic organ, he mistakenly seized upon the oviducal gland. This led to an ever increasing series of misinterpretations of the female generative mechanism. Associated with this error was the belief that the ovary and cement glands were homologous in both cyprid and adult. He later confessed to "having blundered terribly over the cement glands", but it was probably his search for examples of organs changing their function during evolution that led to this blunder. Similarly, he convinced himself mistakenly that the ovigerous fmna, which hold fast the egg masses to the mantle lining in stalked barnacles, became modified to gills in sessile barnacles.Darwin's interest in barnacle reproduction led to his discovery of complemental males attached to hermaphrodite individuals. He proved that they were dwarf cirripedes and not parasites. His knowledge that male and hermaphrodite flowers could co-exist helped him to accept that these apparently unnecessary beings could be present also in barnacles. We now know that complemental males are not confined to stalked barnacles but are also present in certain balanids. Though Darwin did not include the dioecious parasitic group, the Rhizocephala, in his studies, he recognized the wide repertoire of sexual arrangements from hermaphroditism to dioecy which now provides challenging material to our further understanding of sex allocation, control and evolution.Since Darwin dealt mainly with dried or preserved specimens he did not describe any of the details of the liberation of nauplii or the searching behaviour of the cyprid. Current investigators have shown that the former involves a prostaglandin which activates the embryos. Searching cyprids have been shown to be able to recognize their own and other species. Charles would have seen in this phenomenon a relevance both to survival and to the evolution of epizoic barnacles.Despite Charles' belief that his barnacle work would be "for ever unapplied" it has in fact been the foundation on which all studies of commercially important barnacle fouling have been based.

Dwarf males in the epizoic barnacle Octolasmis unguisiformis and their implications for sexual system evolution

“…A relationship between attachment site and sexuality can be explained by two possible proximate mechanisms: selective attachment by larvae with genetically predetermined sex, or environmental sex determination affected by the substratum type. Although sex determination among thoracican barnacles is largely unknown (Crisp ; Yusa et al. ), Callan () suggested that sex determination was environmental in Scalpellum scalpellum ( Linnaeus 1767), and Gomez () argued that it was genetic in Conopea galeata ( Linnaeus 1771).…”

Temperature Affects Adhesion of the Acorn Barnacle (Balanus amphitrite)

“…Cyprid locomotion, exploration and settlement has been well documented (Knight-Jones 1953;Crisp 1983;Yule and Crisp 1983;Crisp 1985;Crisp 1990;Mullineaux and Butman 1991;Glenner and Hoeg 1993;Konya and Miki 1994;Miron et al 2000;Dahlstrom et al 2004) use their antennae to "walk" along a substrate until a suitable location is found to settle. Faimali et al (2004) found that barnacle cyprids may perceive signals about the substratum surface or its biofilm, which plays a role in their settlement preference.…”

Perumegabalanus calziai gen. et sp. nov., a new intertidal megabalanine barnacle from the early Miocene of Peru

“…As a consequence of this, through geological time, cirripedes evolved peculiar solutions to cope with the disadvantages of a sessile lifestyle. Their ability to adapt to different environmental pressures, especially in the intertidal environment (CRISP & BOURGET 1985), inspired Darwin his view of organic evolution (CRISP 1983). The earliest confirmed cirripede is of Silurian age, while the earliest known modern neobalanoform is of Late Cretaceous age (BUCKERIDGE & NEWMAN 2006;KOČÍ et al 2017).…”