Larval development and post‐larval growth of Branchiomma bairdi (Annelida: Sabellidae) from a Mediterranean population

Abstract

Branchiomma bairdi is a Caribbean fan worm introduced in several localities worldwide, including the Mediterranean Sea, where the species’ range has rapidly expanded. Reproduction in B. bairdi was previously investigated in both extra‐Mediterranean and Mediterranean areas, but no information is available on larval development and post‐larval growth. In the present article, we examined these features for a population from the Mar Grande of Taranto (Ionian Sea). The species is hermaphrodite, and fertilization occurs in situ. Mucus seems to play an important role in fertilization, and also in preserving eggs before fertilization. The trochophore stage develops within the mucus and after hatching, larvae swim for about 3 d before settlement. The trochophore showed a distinct prototroch and two red dorsolateral larval eyes. The pelagic stage takes only 96 h even though prototroch is maintained after settlement, disappearing at 5 d, when larvae showed three chaetigers and branchial crown consisted of four radioles. Some interesting observations concerning changes in the morphology of chaetae and in the number of uncini during growth are also reported, together with discussion of the development of stylodes, an important diagnostic feature in Branchiomma species identification.

Clarifying the taxonomic status of the alien species Branchiomma bairdi and Branchiomma boholense (Annelida: Sabellidae) using molecular and morphological evidence

“…It is worth mentioning that biological data on reproduction and population dynamics concerning the Mediterranean form previously referred as B . bairdi [ 29 , 30 ] could probably be attributed to B . boholense .…”

“…boholense . Significant biological differences found between the Mediterranean populations and Mazatlán (Gulf of California) population were previously explained as adaptation to a new environment [ 29 , 30 ]. Results from the present study led to reconsider these biological differences due to the fact that the two examined taxa are actually different species.…”

“…Indeed, the two species differ in the reproductive features, with a different period and mode of reproduction. Brooding was reported for Malta and Mazatlán populations [ 26 , 45 ], while external fertilization occurs in Mediterranean specimens [ 30 ]. Moreover, no sign of asexual reproduction was found in the Mediterranean taxon contrary to what has been reported for B .…”

“…bairdi reported for the Italian coast should probably represent B . boholense [ 25 , 26 , 27 , 29 , 30 , 87 ]. Even though B .…”

“…luctuosum , and B . boholense [ 14 , 21 , 22 ] and since their spread in the Mediterranean the biological and ecological characteristic of these species have been deeply investigated [ 23 – 30 ].…”