Question

What is the type of holdfast characteristic of the order Cyclophyllidea?

Answer 1

A holdfast is a root-like structure that anchors aquatic sessile organisms to the substrate. Holdfasts vary in shape and form depending on both the species and the substrate type

Order Cyclophyllidea has scolex that usually contains four suckers; rostellum is present or absent (may be armed) with hook or adhesive glands present. One end anchored to intestinal wall by holdfast organ (scolex).On arrival to the intestine, most of the body has been digested away, leaving only the scolex and some undifferentiated tissue (neck), which begins to bud off segments (proglottids).4 radial muscular suckers on scolex. Most scolices also have a rostellum (dome-shaped projection at base of scolex, retractable and armed with small hooks)

Scolex (pl. scolices) is located at the anterior end and functions as an attachment structure. In some groups, the holdfast function of the scolex is lost early in life, and the anterior end of the stroblia becomes distorted into a pseudoscolex to function as a holdfast. To facilitate attachment to the host’s intestinal wall, tapeworms utilize several types of structures on their scolices, the most common of which are suckers. Muscles in the scolex make possible the holdfast action of this organ. The scolices of tapeworms are typically categorized as either acetabulate or bothriate, depending on the type of sucker present. An acetabulate scolex is characterized by the presence of 4 muscular cups sunk into the equatorial surface of the scolex; cups are radially arranged equidistant from each other. In addition to muscular cups, there may be accessory holdfast structures, such as hooks to help anchor the scolex to the host’s intestinal wall. In this case, the scolex is called an armed scolex. A bothriate scolex is characterized by the presence of 2, or rarely 4 to 6, longitudinally arranged, shallow depressions called bothria (sing. bothrium). These hooks are usually grouped at the apical end of the scolex on a protrusible rostellum. Various types of glandular secretions are associate with the scolex of many tapeworms. The function of these secretions has not been firmly established, although it has been speculated that they are proteolytic, adhesive, and/or stimulatory, depending on the species