Anatomical description of a tropical sea pen, Virgularia gustaviana (Herklots, 1863), from the Strait of Hormuz

The present investigation aimed to study the anatomical characteristics of Virgularia gustaviana (Herklots, 1863) from the Strait of Hormuz in the northwest of the Persian Gulf. In this regard, 25 sea pens, which were identified as V. gustaviana (Herklots, 1863), were collected from the intertidal zone of the Suru and Bandar Abbas coasts (the northeast of the Persian Gulf). The samples were fixed in the alcohol formalin glacial acetic (AFA) fixative for a week and were then studied using a stereomicroscope. According to the results, the body of V. gustavia anatomically consisted of two main parts (rachis and peduncle), both of which originate from a primary polyp. The rachis was the upper part of the body with leaf-like leaves. The peduncle, with a smooth, straightforward structure, was the lower part of the body. The caudal part of the peduncle was bubble-like. A mineralized axis was observed at the center along the body, surrounded by mesenteric septa. Although all sea pens share the same basic anatomical structure, colony shape varies considerably in different species in terms of evolution.