Throughout: Lymph nodes tend to cluster next to blood vessels that feed all the abdominal organs. There are hundreds of lymph nodes within the abdominal cavity, the retroperitoneum (the area by the spine behind the intestines), the pelvis, and the groin. In fact, there all lymph nodes throughout the body (except the brain and eye). ...Read more.
The various fish groups account for more than half of vertebrate species. There are almost 28,000 known extant species, of which almost 27,000 are bony fish, with 970 sharks, rays, and chimeras and about 108 hagfish and lampreys.
With somewhere around 1,500 species found in different oceans of the world, there is no questioning the diversity one gets to see in the starfish family, i.e., the Asteroidea class of kingdom Animalia. Sadly though, our knowledge about these organisms is mostly restricted to specimen that are washed ashore.