Acta Histochemica 116 (2014) 487–492 Contents lists available at ScienceDirect Acta Histochemica jo ur nal homepage: www.elsevier.de/acthis Expression of carbonic anhydrase, cystic fibrosis transmembrane regulator (CFTR) and V-H + -ATPase in the lancelet Branchiostoma lanceolatum (Pallas, 1774) Aurora Pederzoli ∗ , Mauro Mandrioli, Lucrezia Mola Department of Life Sciences, University of Modena and Reggio Emilia, via Campi, 213/D, I-41125 Modena, Italy a r t i c l e i n f o Article history: Received 4 September 2013 Received in revised form 7 October 2013 Accepted 8 October 2013 Keywords: Amphioxus Osmoregulation pH regulation Skin Development a b s t r a c t Sequencing of the amphioxus genome revealed that it contains a basic set of chordate genes involved in development and cell signaling. Despite the availability of genomic data, up till now no studies have been addressed on the comprehension of the amphioxus osmoregulation. Using primers designed on Branchiostoma floridae carbonic anhydrase (CA) II, cystic fibrosis transmembrane regulator (CFTR) and V-H + -ATPase, a 100 bp long region, containing the protein region recognized by the respective anti- bodies, has been amplified and sequenced in B. lanceolatum indicating the presence of hortologous V-ATPase, CFTR and carbonic anhydrase II genes in Branchiostoma lanceolatum. Immunohistochemical results showed that all three transporting proteins are expressed in almost 90% of epithelial cells of the skin in B. lanceolatum adults with a different degree of positivity in different regions of body wall and with a different localization in the cells. The comparison of results between young and adult lancelets showed that the distribution of these transporters is quite different. Indeed, in the young specimens the expression pattern of all tested molecules appears concentrated at the gut level, whereas in adult the gut loses its key role that is mostly supported by skin. © 2013 Elsevier GmbH. All rights reserved. Introduction Teleosts and Chondrichthyes regulate body fluid pH and ionic composition mainly through the integument, gills, kidney and gut (Morris, 1960; Claiborne et al., 2002; Evans et al., 2005; Gilmour and Perry, 2009; Wood et al., 2010). In the early ontogenetic stages, before the development of gills and kidney, the skin is believed to be the major structure responsible for pH and osmotic regulation (Kaneko et al., 2002; Varsamos et al., 2002, 2005; Falk-Petersen, 2005; Lin et al., 2006; Bodinier et al., 2009). In larval and adult epithelia of the regulatory organs, principal cells and specific cells, such as mitochondria-rich cells (MRC) or ionocytes or chloride cells, express many ion transport-related transmembrane proteins and enzymes, including H + V-ATPase and carbonic anhydrase, that are involved in acid–base and ionic regulation (Piermarini and Evans, 2001; Claiborne et al., 2002; Marshall and Singer, 2002; Piermarini et al., 2002; Hirose et al., 2003; Lin et al., 2006; Grosell et al., 2009; Gilmour and Perry, 2009). ∗ Corresponding author at: University of Modena and Reggio Emilia, Via Campi, 213/D, I-41100 Modena, Italy. E-mail address: aurora.pederzoli@unimore.it (A. Pederzoli). Hagfish are considered the most ancient of craniates and, among marine fish, they are a unique living taxon that is exclusively marine and osmoconformer (Morris, 1960). They do not need osmotic regulation though they can compensate for volume loading in slightly hypo-osmotic environments or after hypo-osmotic fluid loading during feeding (Cobb et al., 2004). Nevertheless, their gill epithelium is rich in MRC cells, probably involved in pH regulation (Elger and Hentschel, 1983; Mallat et al., 1987; Choe et al., 2002; Tresguerres et al., 2006a, 2007a; Parks et al., 2007). Cephalochordata, commonly known as amphioxus or lancelet, represent a small taxon of Chordata consisting of about 30 marine species. It was traditionally considered the sister taxon of craniates (Holland et al., 1996), but more recently molecular phylogenetic analyses have indicated that tunicates, as the sister taxon of the vertebrates and cephalochordates as the most basal chordate group (Holland et al., 2008; Putnam et al., 2008). Up till now, the mechanisms of acid–base or ionic regulations have not been studied in amphioxus and specialized cells in transporting epithelia have never been described. It has been suggested that Branchiostoma nigeriense is isosmotic with the environment or osmoregulates since it can survive in salinities from 13 to 58 parts per thousand (Webb and Hill, 1958). Moreover, the morphology of the Branchiostoma floridae kidney does not change if lancelets are bred in artificial sea water at different salt 0065-1281/$ – see front matter © 2013 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.acthis.2013.10.005