Cirripede Cypris Antennules: How Much Structural Variation Exists Among Balanomorphan Species from Hard-Bottom Habitats?

Abstract

Barnacle cypris antennules are important for substratum attachment during settlement and on through metamorphosis from the larval stage to sessile adult. Studies on the morphology of cirripede cyprids are mostly qualitative, based on descriptions from images obtained using a scanning electron microscope (SEM). To our knowledge, our study is the first to use scanning electron microscopy to quantify overall structural diversity in cypris antennules by measuring 26 morphological parameters, including the structure of sensory organs. We analyzed cyprids from seven species of balanomorphan barnacles inhabiting rocky shore communities; for comparison, we also included a sponge-inhabiting balanomorphan and a verrucomorphan species. Multivariate analysis of the structural parameters resulted in two distinct clusters of species. From nonmetric multidimensional scaling plots, the sponge-inhabiting Balanus spongicola and Verruca stroemia formed one cluster, while the other balanomorphan species, all from hard bottoms, grouped together in the other cluster. The shape of the attachment disk on segment 3 is the key parameter responsible for the separation into two clusters. The present results show that species from a coastal hard-bottom habitat may share a nearly identical antennular structure that is distinct from barnacles from other habitats, and this finding supports the fact that such species also have rather similar reactions to substratum cues during settlement. Any differences that may be found in settlement biology among such species must therefore be due either to differences in the properties of their adhesive mechanisms or to the way that sensory stimuli are detected by virtually identical setae and processed into settlement behavior by the cyprid.

Genomic insights into the sessile life and biofouling of barnacles (Crustacea: Cirripedia)

“…Unlike other crustaceans, the barnacle cyprid has a well-developed CNS and sense organs. This larva detects settlement cues and coordinates the substrate exploratory behaviors using a pair of antennules equipped with terminal and subterminal sensory setae ( Harrison and Sandeman, 1999 ; Chan et al., 2018 ). During metamorphosis, the CNS system is largely reconstructed in adult barnacles with a high diversity of sensory setae on the cirri for detection of prey and water currents ( Chan et al., 2008b ).…”

“…A previous study of A. amphitrite cypris revealed a complex connection between peripheral sense organs and the CNS by a large number (2,000) of neurons, and the antennular nerve is the major peripheral nervous system ( Harrison and Sandeman, 1999 ). Among the four antennular segments, the third segment contains an attachment disc with dense villi, and the fourth segment contains setae for detection of the physical and chemical properties of the substrate surface ( Chan et al., 2018 ). Given the common origin of insect and crustacean Lola and the conserved nervous system features between insects and crustaceans ( Osorio et al., 1997 ), the expansion of Lola genes and their expression in barnacles during different life stages are consistent with their purported roles in response to settlement cues and environmental signaling.…”

The Crustacean Antennule: A Complex Organ Adapted for Lifelong Function in Diverse Environments and Lifestyles

“…Some ostracods use their antennules in swimming, crawling, or digging (Hunt et al, 2007;Boxshall and Jaume, 2013). Barnacle cyprid larvae use their antennules in walking as they sense the quality of the substrate (Lagersson and Høeg, 2002); when these larvae decide to attach to a substrate, their antennular attachment discs and cement glands aid them (Chan et al, 2017). Parasitic rhizocephalan barnacles use their antennules to attach to a host (Boxshall and Jaume, 2013).…”

Μελέτη Των Αντιβιοεπιστρωτικών Ιδιοτήτων Δευτερογενών Μεταβολιτών Από Θαλάσσιους Οργανισμούς

“…To enable biometric analysis and examine any possible morphological abnormalities (Yamamoto, Kawaii, et al 1997;Yamamoto, Okino, et al 1997;Glenner and Brodin 2009;Al-Yahya et al 2016;Chan et al 2017) brought about by the presence of the chemical compounds listed above, cyprids were exposed to specific concentrations of compounds and then observed by scanning electron microscopy (SEM). In these experiments and for each compound, the concentration that did not result in mortality of the animals and gave the best positive or negative response in settlement bioassays was selected.…”

“…Acquired SEM images were subjected to biometrical analysis with ImageJ 1.48v (NIH, Bethesda, USA) and data were exported and statistically analysed with GraphPad Prism v.6 (GraphPad software Inc., San Diego, California, USA). Biometric measurements of the villi on the attachment discs of cyprids were taken from perfect lateral views (Al-Yahya et al 2016;Chan et al 2017) using stored micrograph images of the margins of the attachment discs. Counting was done by enumerating the length of villi visible in the test area as described (Al-Yahya et al 2016;Chan et al 2017).…”