The barnacle excretory organ

Abstract

The paired excretory organs or maxillary glands of the adult barnacles, Balanus balanoides and Balanus hameri, lie within the posterior part of the body below and to either side of the foregut. Each organ has an end sac linked to an efferent duct via a valve. The sac-shaped efferent duct connects with a relatively short terminal duct, opening out at the base of the second maxilla. The end sac consists of podocytelike cells having marked morphological and cytochemical similarities to the equivalent region of other Crustacea and to the vertebrate glomerulus. The main cells of the valve contain extensive apical secretion. They rest upon a series of modified end-sac cells projecting into the efferent duct. The efferent duct is composed of a uniform flattened epithelium which is cytochemically unreactive. The cells are lined by a short microvillous border, below which is a series of tubules which appear to be invaginations of the apical membrane. The morphology of efferent duct cells is not indicative of a highly active solute reabsorptive epithelium, but secretion of membrane-bound bodies into the efferent duct lumen was observed. The terminal duct is a relatively short, cuticle-lined ectodermal infolding. The parenchyma cells surrounding the efferent duct exhibit a marked affinity for certain dyes when injected into the haemolymph, indicative of a possible role in the elimination of material. The excretory organ is surrounded by a network of elastic fibres and is suspended within the body by strands of connective tissue and a complex series of tendon-muscle connexions. The end sac is well supplied with haemolymph from the scutal sinus but the supply to the efferent duct is more restricted.

Heavy metal depuration in flat tree oystersisognomon alatusunder field and laboratory conditions

“…According to the literature, the depuration rate of Zn in oysters is higher than in other bivalves [14]. In a study on barnacles Balanus balanoldes, during the first two months of depuration only 38% of Zn was lost [26]. Results reported on mussels also showed very slow depuration [27,28], compared to our findings.…”

Morphology of the Nervous System of Barnacles: the Median Ocellus ofBalanus Hameri (=Chirona Hameri)(Crustacea: Cirripedia)

“…The tergal and scutal plates were prized apart, thus tearing the adductor muscle of the scuta and pinned in this position. The cirri were pulled away from the scuta and pinned down so that the entire ventral surface (see White & Walker, 1981 for orientation nomenclature) of the body was exposed. The supraoesophageal ganglion was revealed by carefully removing the oral cone and then making an incision in the mid-line of the cuticle at this point and extending it anteriorly to the scutal adductor muscle.…”

Osmoregulation in Barnacles: An Evolutionary Perspective of Potential Mechanisms and Future Research Directions

“…The mantle provides a large surface area and is the tissue first in contact with the surrounding water, making this tissue a plausible site for osmoregulation in barnacles. Barnacles also have “branchiae” that are attached to the mantle and have been suggested to function as gills (White and Walker, 1981; Gohad et al, 2009). Since gills are considered the principal sites for maintaining salt balance in osmoregulating crustaceans (see above), the mantle along with these branchiae may provide the extensive surface needed for active ion transport during osmoregulation.…”

“…The antennal and/or maxillary glands of crustaceans are the excretory organs used to produce and excrete urine (White, 1987). They consist of three main regions – the end sac, the excretory canal, and the short efferent duct (White and Walker, 1981). Darwin (1851) first described the end sac complex in the anterior body of barnacles although an excretory function was not suggested until later (reviewed in Nilsson-Cantell, 1921).…”

“…Darwin (1851) first described the end sac complex in the anterior body of barnacles although an excretory function was not suggested until later (reviewed in Nilsson-Cantell, 1921). The end sac of the maxillary gland of adult barnacles consists of podocyte-like cells that have marked morphological and cytochemical similarities to the equivalent region of other Crustacea and to the vertebrate glomerulus (White and Walker, 1981). The striking similarity of such cells within animals of differing phylogeny indicates that the basic mechanism of primary urine formation is likely to be similar.…”