Reproduction and Development
Asexual reproduction occurs in this species in the form of paratomy, which is the budding of the posterior end of worm resulting in a genetically identical individual. During budding adult abdominal segments are transformed into the buds thoracic segments (Pernet, 2001).
Adult Filograna implexa undergoing budding
Photo by Bernard Degnan
During asexual reproduction as soon as bud is detached from parent it is able to move up and down in the parental tube, however within a few days must access external environment for settlement. Therefore, in order for new individual to escape tube there needs to be an “escape hatch”. Studies have observed when adult begins to bud hatch formation is initiated several days later, therefore suggesting that there is a linked pathway between bud formation and hatch development. Alternatively, there may be a hormonal signal released by bud at a specific developmental stage which signals to adult to build an escape hatch. Endocrine substances are famous for regulating reproductive and morphological changes hence; these may potentially be involved as a hormonal signal (Pernet, 2001).
Studies suggest that bud moves around inside tube testing for weakness in structure until the “escape hatch” is located. Escape hatch is held delicately in place by a thin membrane so as it requires little force to remove and is believed that the bud is capable of this. Often dispersal of individuals is minimal and exist point of parental tube may located in close proximity to newly fledged larvae secretion of their own tube (Pernet, 2001).
Filograna implexa larvae
Photo by Bernard Degnan
Sexual reproduction also occurs where gametes are spawned into water column and fertilised externally. F. implexa brood these resultant zygotes which undergo spiral cleavage e developing into trochophoric larvae. Gametes are produced and located in the abdominal cavity and are released from ciliated ducts of abdominal chaetigers adjacent to nephridia. F. implex is able to be either gonochronic which is most common in polychaeatas, simultaneous hermaphrodites with eggs and sperm separated into compartments or protandrous hermaphrodites, which basically means animal progresses from male to female, (Glasby, 2000; Ruppert et al., 2004).
Note: Oogenesis is known to occur in species (Glasby, 2000).