Triops Longicaudatus - Structure

Structure

Triops longicaudatus is usually greyish-yellow or brown in color, and differs from many other species by the absence of the second maxilla. Apart from Triops cancriformis, it is the only tadpole shrimp species whose individuals display as many as three reproductive strategies: bisexual, unisexual (parthenogenetic), and hermaphroditic; see below. Triops cancriformis is easily recognizable by its yellow carapace with dark spots, whilst T. longicaudatus individuals have a uniform carapace. The species also appeared about 50 million years later, and, as its name suggests, its elongated tail structures (cercopods) are often nearly as long as the rest of the body; including the cercopods, the body may reach 75 mm (3.0 in) in length.

The head of Triops longicaudatus is typical of crustaceans and consists of five segments, but there is a tendency toward reduction of cephalic appendages. The trunk is not distinctly divided into thorax and abdomen. Most trunk segments bear appendages. Zoologists find it difficult to decide where the thorax stops and the abdomen begins; the debate is seemingly endless. The first eleven trunk segments each bear a single pair of limbs. They are followed by segments that are fused similarly to those of millipedes, and as a result, each segment bears up to six pairs of limbs. The trunk ends with a region of limbless segments. Some zoologists consider the thorax to consist of the two regions with appendages, and the abdomen the region without appendages. Others believe the region of fused segments to be part of the abdomen. For clarity, this article uses "thorax" to mean the two body regions with limbs.