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Sea pens or pennatulaceans (Phylum Cnidaria, Order Pennatulacea) are colonial marine octocorals that typically anchor themselves into soft sediment. They make large colonies from the intertidal zone down to the abyssal plain that provide an important structural habitat to other organisms. In the present study, the morphological and histological characteristics of the dominant species of Virgularia gustaviana, the dominant sea pen species of the Persian Gulf, were surveyed. Samples of V. gustaviana were collected along the coastal intertidal zone of the Soru and Bandar Abbas beaches, located at the northeast of the Persian Gulf. The sea pens were then fixed in Bouin’s solution. Histological sections were prepared using routine histological techniques and stained with hematoxylin and eosin. V. gustaviana morphologically consisted of two major parts, including the rachis and peduncle, originated from the early polyp. Rachis with leaf-like plates consisted of autozooids and siphonozooids that were located at the ventral and dorsal surfaces of the rachis, respectively. The peduncle was the lower part of the sea pen with a smooth structure and the bubble-shaped end. The body wall (coenenchyme) of V. gustaviana consisted of three layers including the epithelium, mesogloea, and gastrodermis. There was a calcareous rod, with the dark and light concentric circles, called the axis at the center of the body of the sea pen. A layer of calcified sponge-like tissue called sclerite was observed around the axis. Sclerite was connected to the body wall of the sea pen by four thin tissue septa that divide the coelom into four water canals. Another water canal was found between the axis and the sclerite, which is considered [ABSTRACT FROM AUTHOR]

Non-native ascidians are becoming a global problem and several species have recently been used as models for studying invasion success in the marine realm. Despite a limited dispersal due to their short-lived larvae, they are often found in coastal habitats as a result of human activities. As one of the warmest waterways in the world characterized by heavy marine traffic, the Persian Gulf is particularly prone to invasive ascidians. This study is the first to have documented the occurrence of the colonial ascidian Didemnum psammatodes in natural and man-made substrates in intertidal zones at 15 study sites in Qeshm and Hengam Islands in the Eastern Persian Gulf. High densities of D. psammatodes were observed at several study sites located far from major ports, but close to human residences, which may be explained by the prevalence of hard-surface man-made substrates. [ABSTRACT FROM AUTHOR]

Shells in pearl oysters are produced by the mantle which is also used as a graft in pearl operations. Here, we investigate the mantle structure of a new pearl oyster species of the Persian Gulf,Pinctada persica, and compare it to two other pearl-producing species,Pinctada radiataandPteria penguin. The anterior, ventral and posterior segments of the mantle edge of each valve were fixed, and tissue sections were stained with haematoxylin and eosin. A new pentachrome method and PAS-alcian blue staining were used to characterise the different mucosubstances. The mantle edges were found to have an outer, middle and inner fold, which have different morphology in each species. The mantle edge is lined by cuboidal and columnar epithelia, and interspersed among these epithelial cells we found mucous cells and cells that contained brown granules. The outer and middle folds of the twoPinctadaspecies show different shapes to that ofPteria penguin. Most of the mucous cells in the mantle contain acidic mucosubstances and small amounts of mixed acidic-neutral mucosubstances were observed in the middle and inner fold ofPinctada persica. This study reveals that the mantle edges of the three species possess similar cellular structure, but vary in the shape of the folds. [ABSTRACT FROM PUBLISHER]