Females floated first in bubble-rafting snails

Figure 1. Proposed evolutionary steps to rafting in Janthinidae. Left: Bayesian phylogram of Janthinoidea and seven potential sister families. DNA sequence data come from four loci: mitochondrial 16S rDNA, nuclear 28S rDNA, Histone-H3, Histone-H4. Bayesian posterior probabilities are followed by maximum likelihood bootstrap percentages above internal branches. Asterisks indicate support values of 100. Janthinidae and ‘Epitoniidae’ are represented in purple and green, respectively. Red letters indicate the evolution of four key rafting apomorphies, represented by photographs to the right of the topology. Right: (A) Tethered egg masses in Janthinoidea. Mature female Epifungium nielsi, a benthic ‘epitoniid’, on its coral host with egg capsules (e). An arrow indicates a small associated male. (B) Floating via modified egg masses in Janthinidae. Mature female Recluzia jehennei with bubble raft and husks of egg capsules (e), feeding on the cnidarian Physalia physalis. An arrow indicates a small associated conspecific. (C) Autonomous floating of juveniles and males in Janthina. Mature female Janthina exigua with bubble raft and egg capsules (e). (D) Loss of egg capsules from the float in ovoviviparous J. janthina. Mature female J. janthina with large bubble raft. (Scale bars in A–D: 1 cm.) Females floated first in bubblerafting snails