The deep-sea neogastropod Buccinum scalariforme: Reproduction, development and growth

Abstract

Specimens of the neogastropod Buccinum scalariforme (60–70mm shell height) collected between 700 and 1450m depth along the continental slope of eastern Canada were kept for 4 years in mesocosm settings. Their mating, spawning and development were assessed, thereby generating the first complete life cycle account of a deep-sea gastropod. Egg laying occurred in March and September, with a total of 9 egg masses laid in 2013 and 2015, coinciding with periods of maximum deposition of particulate organic matter (phytodetritus). Oviposition lasted 2–3 days and the female protected the egg mass for ~3 more days until it had hardened. Typically, egg masses contained 50–75 egg capsules, each measuring 5–8mm in diameter. A capsule contained between 100 and 150 spherical eggs (300–500µm) of which ≤50 developed into embryos. Potential fecundity calculated from the entire egg mass at spawning was between 1500 and 2250 propagules; it drastically decreased over ~4–5 months of development to an effective fecundity of 30–50 juveniles emerging from the mass (0–2 juveniles per capsule). Development went through early embryonic stages in ~15 days and reached the trocophore in 15–21 days, followed by intracapsular veliger larva (480µm) and intracapsular pediveliger (~1000µm) after ~90 days. Completion of development relied on oophagy and adelphophagy. The juveniles hatched at a shell height of 1–2mm and consumed the capsule membrane. Over 2.5 years, they reached a maximum size of ~8–10mm shell height at an average of 9.8µmday−1. Estimations indicate that B. scalariforme could require between 20 and 50 years to reach maximum adult size. Large gastropods like B. scalariforme are among the most abundant motile benthic invertebrates of the bathyal zone of eastern Canada. Knowledge of their reproductive biology constitutes a first step in assessing their vulnerability and resilience to ever growing anthropogenic pressures, including fisheries, and oil/gas exploration and exploitation.