Redescription and notes on the reproductive biology of the sea anemone Urticina fecunda (Verrill, 1899), comb. nov. (Cnidaria: Actiniaria: Actiniidae)

Abstract

The externally brooding sea anemone Epiactis fecunda (Verrill, 1899) is redescribed as Urticina fecunda, comb. nov., onthe basis of preserved type material and anatomical and behavioural observations of recently collected animals. The sea-sonal timing of reproduction and aspects of the settlement and development of brooded offspring are reported. Preciselocality data extend the bathymetric range to waters as shallow as 10 m, and the geographical range east to the AvalonPeninsula (Newfoundland, Canada). We differentiate it from other known northern, externally brooding species of seaanemone. Morphological characters, including verrucae, decamerous mesenterial arrangement, and non-overlapping sizesof basitrichs in tentacles and actinopharynx, agree with a generic diagnosis of Urticina Ehrenberg, 1834 rather than Epiactis Verrill, 1869.

Brooding sea anemones (Cnidaria: Anthozoa: Actiniaria): paragons of diversity in mode, morphology, and maternity

“…The release of larvae and their locomotion to their eventual brood space upon the adult has been noted in U. fecunda as well (Larson et al. ).…”

“…Offspring of U. fecunda develop within pits on the column of the parent; adjacent and very closely set pits remain separated by a thin projection of the body wall in U. fecunda (Larson et al. ). While structures matching the above description of pit have been called by other names, the term pit has rarely been applied to other types of structure.…”

“…U. fecunda and E. georgiana are two externally brooding species in which a ciliated larval stage is present (Larson et al. ; Rodríguez et al. ) and is the mode by which offspring move from within the adult to upon it.…”

“…The mixed size and developmental state of those offspring was considered evidence of continuous reproduction (Dunn 1975b). On the other hand, individuals from relatively larger species of Epiactis and its relatives (i.e., E. japonica [VERRILL 1869], E. ritteri, U. fecunda [VERRILL 1899]) may hold hundreds of juveniles which are fairly uniform in size, at least at the beginning of their seasonal reproductive cycle, with the number decreasing and/or the diversity of sizes increasing over the reproductive season (Larson et al 2012;Larson & Daly 2015).…”

“…Subsequently, the number of species in which evidence for brooding has been reported has increased to 57 (Table 1). Furthermore, some of Carlgren's (1901) questions about the means by which externally brooded offspring reach their brooding location, and which stages of development they go through once there, have since been answered (Dunn 1975b;Ishimura & Nishihira 2002;Larson et al 2012).…”