Terebellides is a genus of polychaete worms in the family Trichobranchidae. They were first examined in 1984 by Susan J. Williams and were once thought to be found across oceans world-wide as a species with cosmopolitan distribution. The specimens first examined were located in the Eastern Pacific. In recent years, there has been a shift of focus to study them in the Atlantic Ocean, due to their complex DNA. Their geographic distribution emphasizes differences in nephridia size, the first characteristic identified in Atlantic Ocean specimens. This finding demonstrated the importance of comparing Atlantic taxa with those from the eastern Pacific. Current research focuses on a third stomach region that lacks certain internal anatomical characteristics found in other taxa.
Known species
Terebellides sepultura is named after the Brazilian heavy metal band Sepultura.Garraffoni, A. R. & Lana, P. C. (2003). Species of Terebellides (Polychaeta, Terebellidae, Trichobranchinae) from the Brazilian coast. Iheringia, Série Zoologia, 93(4), 355–363.
Physiology Terebellides are typically distinguished by their pale brown color. Developmental research on their known physiological features has led to further discoveries. Several elements have been noted in their stomach makeup and internal anatomy, with their proportionate stomachs connecting them to related species. Interest in studying the number of lamellae located in their digestive gland has increased. This composition includes two to five lamellate lobes. A specific characteristic of their anatomy is the single mid-dorsal branchia. They have a visible presence of eggs throughout the wall of their body. These worms are elongated and taper downwards with their ending segments being crowded and shorter in comparison. They have grooved tentacles around their head region, or prostomium, that aid in feeding and locomotion. The prostomium includes a lip-like structure that moves food to the cilia and into their mouth. They also have an abdomen and a thorax that contains 18 pairs of notopodia.
Feeding These worms are bottom-feeding detritovores that use their tentacles to obtain food particles from the surface of the ocean and from sediment. Mucus present on their tentacles helps them to trap food. They transfer food to a lip-like structure and move it into the mouth by the cilia. They reach out from their burrows with their tentacles and grasp onto nearby food in the benthic region of the oceans. A current study of their digestive system focuses on their digestive process and how their bodies break down ingested food.
Movement Terebellides have been noted to move along the Norwegian and Swedish continental shelf. They are sedentary and live within burrows in the benthic zone. They will rise to the surface when necessary to forage. They don't tend to leave their burrows and move only to obtain food and survive. Some species have limited movement abilities, specifically when disturbed. Their primary means of transportation are ocean currents, as they are not able to move their bodies sufficiently on their own. They also rely on these currents to disperse planktonic larvae.
Life cycle
Most of these worms start in planktonic larval stages, commonly known as planktotrphy, and grow into their adult stages. The planktonic larval stage is spent in open water where the marine worms feed and develop in the water column. As the larvae metamorphize into adults, they develop the segments used for feeding and begin to settle to the bottom of the ocean within the benthic region for the remainder of their lifecycle. As they grow into their final adult stage, they become more sedentary and reside in the burrows.
Some species have no larval form and go straight to the adult stage, but this is still being researched. This direct development stage involves parental care, an uncommon trait among invertebrates. Female worms lay their eggs in capsules inside of their burrows. Depending on the growth stage, the young worms may attach to the parent's body as they continue to grow throughout their lifecycle.
Ecology Terebellides play an important role in their benthic ecosystems. They have adapted to living in the harsh environments of hydrothermal vents, burrows, and cold seeps, which can range from near-freezing temperatures to surpassing 574 degrees Fahrenheit. The worms have a symbiotic relationship with bacteria that live within the worm burrows on the ocean floor. These bacteria produce energy through chemosynthesis, where they convert hydrogen sulfide into organic compounds. This process provides a shared food source in the nutrient deficient benthic regions of the ocean.
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