Xiphinema Americanum - Morphology and Anatomy

Morphology and Anatomy

The length of the adult Xiphinema americanum ranges from 1.3 to 3.0 millimeters. The dagger nematode is characterized by a 100 μm odontostyle which is used for deep penetration of root tips with its spear-like stylet. The odontostyle is connected to the lining of the cheilostome by a folded membrane called the "guiding ring". The guiding ring is attached to a flanged odontophore.

Females: The body is usually in an "open C" conformation. The shape of the body tapers towards the extremities. The two rings of the odontophore are located 3 μm apart. The Xiphinema americanum esophagus is dorylaimoid with an enlarged posterior portion that occupies roughly 1/3 of its total length. The esophagus contains a muscular bulb which is 80 μm long and 20 μm wide. The valve between the esophagus and the intestine is amorphous. The vulva is 46-54% of the total body length, and is located equatorially with a transverse slit shape, with the vagina having a diameter of 1/3 of the body diameter. The ovaries normally occur in pairs, and are amphidelphic and relexed. The prerectum of X. americanum measures 120-140 μm long, with a rectum that is roughly the same length as the body diameter at the anus. The tail contains 2-3 pairs of caudal pores, is conoid, and curves dorsally with a subacute terminus.

Males: The males have a similar overall configuration as the females, but are slightly smaller in length. Males of X. americanum, however, are rarely found in nature. The male has diorchic testes that are connected to the cloaca, with one anterior branch and one posterior branch. It is common to find more coil in the posterior region. The males also have paired spicules but lack a gubernaculum and bursa.