Intermediate modes of larval development: bridging the gap between planktotrophy and lecithotrophy

Area of Science:

• Marine invertebrate larval biology
• Developmental ecology
• Evolutionary life history

Background:

• Marine invertebrate larvae display remarkable diversity in form and function.
• Larval nutritional strategies are often simplified into planktotrophy (feeding on plankton) and lecithotrophy (relying on yolk reserves).
• This dichotomy overlooks numerous intermediate larval forms, such as facultative feeders.

Purpose of the Study:

• To review studies on intermediate larval forms, particularly facultative feeders.
• To assess the significance of these forms for life-history evolution models.
• To advocate for a more detailed understanding of larval biology.

Main Methods:

• Literature review of studies describing intermediate larval forms.
• Analysis of recent descriptions of larval development.
• Assessment of the implications for evolutionary transitions.

Main Results:

• Intermediate larval forms, including facultative feeders, are not as rare as commonly assumed.
• Recent research highlights the prevalence of these less-categorized larval types.
• These findings challenge the simplistic planktotrophy-lecithotrophy dichotomy.

Conclusions:

• A more nuanced view of larval biology is essential to incorporate intermediate forms.
• Understanding the phylogenetic distribution and frequency of intermediate larvae is crucial for evolutionary studies.
• Intermediate larval types offer valuable opportunities for research in larval ecology and evolutionary developmental biology.