Prosobranchia: Veliger larvae of Taenioglossa and Stenoglossa

A number of features useful in the identification of prosobranch larvae are distinguishable only when they are alive and swimming. The delicate markings on the shell and some pigment of the soft tissues, however, are retained for some weeks in larvae fixed in Carriker’s fluid: 40%, formaldehyde 5 ml, sugar 50 g, borax 0.5 g, filtered seawater 500 ml.

Since there is  no close correspondence between larval and adult  appearance the  order in which species are described is  alphabetical  except for Rissoa spp. (figured on p. 21), Hydrobia ulvae, which  has  a brief larval life and is not planktotrophic, and a  larva of uncertain  identification (? Hacdropleura septangularis) ; the last two species are not in the keys. Terms used in the descriptions are given in the diagrams of a shell (A) and veliger (B).

The larvae considered in the keys are planktotrophic. Very young stages are often difficult to identify since the majority hatch with an unpigmented, bilobed  velum and lack pigmentation elsewhere, the foot is  a  simple lobe with no propodial region and any characteristic patterns on the shell surface are not readily visible. The keys are based on larvae of at least 1 1/2 whorls and where changes affecting identification occur during larval life, especially in the velum, foot and shell, these are indicated. In some cases identifications are made by alternative pathways through the keys.