The developmental transcriptomes of two sea biscuit species with differing larval types

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Genomics

Background:

• Larval development patterns exhibit significant diversity across and within phyla, yet the genetic underpinnings of this diversification remain largely unknown.
• Two sea biscuit species (Echinodermata: Echinoidea) with distinct larval development strategies were studied to investigate the evolution of life cycles.
• One species, Clypeaster subdepressus, has a feeding larva (3-4 weeks metamorphosis), while Clypeaster rosaceus exhibits facultative feeding, allowing metamorphosis in under a week using only egg reserves.

Purpose of the Study:

• To assemble and compare developmental transcriptomes of two sea biscuit species with differing larval development patterns.
• To provide a genetic resource for studying the evolution of alternate life cycles in echinoderms.
• To investigate the genetic mechanisms underlying variations in larval developmental periods.

Main Methods:

• Comparative transcriptome assembly for two sea biscuit species.
• Analysis of gene expression patterns during larval development.
• Identification of orthologous gene sequences and functional annotation.

Main Results:

• The two species' transcriptomes were highly similar, with predominantly orthologous contigs and comparable functional annotations.
• Significant differences in gene expression were observed: C. rosaceus (facultative feeder) showed earlier gene activation and less inter-stage expression differentiation.
• C. subdepressus (obligate feeder) displayed a greater degree of stage-specific gene expression.

Conclusions:

• This study presents the first genetic analysis of a species with facultatively feeding larvae.
• Results align with known developmental differences and suggest that earlier developmental gene onset may drive the evolution of reduced larval periods.
• The published transcriptome for the rare, intermediate larval type enhances genetic resources for echinoderm development and evolutionary studies.