Two-year survey of Alitta succinea (Annelida: Nereididae) in fouling communities with notes on morphology and reproduction

Abstract

Alitta succinea (Leuckart, 1847) is an errant segmented worm from the Nereididae family (Annelida) and is broadly distributed around the greater Atlantic basin. A. succinea is a resilient mobile omnivore that plays an important role in connecting lower and upper levels of the food web. Like many other nereidids, A. succinea metamorphoses into reproductive swimming forms, called epitokes, before entering the water column to spawn. In Galveston, Texas the species A. succinea is commonly found in fouling communities attached to artificial structures in marinas. This study presents a two-year survey of a population found in the Texas A&M University at Galveston Boat Basin. Over the two-year period, we collected over 2,000 A.succinea individuals for a gross comparison of population dynamics and morphometrics. During the summer, we found high numbers of small individuals, indicating a primary recruitment period. This was further corroborated by the high number of epitokes in the summer compared to the winter and spring. During the summer and fall, the observed epitokes were significantly smaller than those found in the winter and spring, which supports previous research that shows a positive relationship between temperature and developmental rates. The continual presence of epitokes indicates the existence of a recruitment process that occurs continuously throughout the year. In terms of morphometrics, atokes and epitokes, both females and males, had their own unique profiles. As we expected, epitokes have larger eyes and wider posterior segments compared to atokes. Interestingly, we found females to be significantly larger than males, no matter the season. This study presents an updated approach to staging sexually reproductive individuals to help standardize taxonomic descriptions.

Keywords:
Morphometrics; Metamorphosis; pileworm; Population Dynamics