Related Experiment Video
Updated: Jul 12, 2025
08:02
Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton
Published on: May 7, 2016
9.9K
Evolution of reproductive modes in sharks and rays
Gergely Katona1, Flóra Szabó1, Zsolt Végvári2,3
1Department of Evolutionary Zoology and Human Biology, University of Debrecen, Debrecen, Hungary.
Journal of Evolutionary Biology
|October 27, 2023
Summary
Sharks, rays, and chimaeras evolved diverse reproductive modes from egg-laying to live-bearing. This evolution is linked to body size, offspring size, and habitat depth, revealing co-evolutionary patterns in vertebrates.
Area of Science:
- Evolutionary biology
- Ichthyology
- Reproductive biology
Background:
- The diversification of reproductive modes in early vertebrates remains incompletely understood.
- Chondrichthyes (sharks, rays, and chimaeras) exhibit remarkable reproductive diversity, making them a key model for studying evolutionary transitions.
- Investigating the ecological and life history drivers is crucial for understanding reproductive complexity.
Purpose of the Study:
- To reconstruct the evolutionary history of reproductive modes in Chondrichthyes.
- To identify ecological and life history factors predicting reproductive strategies.
- To understand the co-evolution of reproductive modes with environmental conditions and life-history traits.
Main Methods:
- Phylogenetically informed analysis of reproductive modes across 960 Chondrichthyes species.
- Reconstruction of ancestral reproductive states.
- Comparative analysis of life history traits (body size, offspring size) and habitat depth.
Main Results:
- The ancestral Chondrichthyes reproductive mode was egg-laying.
- Multiple independent transitions from egg-laying to live-bearing occurred, often via yolk-only live-bearing.
- Live-bearing species are characterized by larger body size, larger offspring, and a preference for shallower, pelagic habitats compared to egg-laying species found in deeper waters.
Conclusions:
- Reproductive mode in Chondrichthyes is not static and has evolved multiple times independently.
- Live-bearing is associated with specific life history traits and environmental conditions, particularly shallower, pelagic habitats.
- This study demonstrates how reproductive strategies co-evolve with ecological factors and life history traits in a basal vertebrate lineage.
Related Concept Videos
01:54Convergent Evolution
27.8K
Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.
27.8K
01:07Speciation Rates
21.2K
Overview
21.2K
02:35What is Evolutionary History?
36.5K
Scientists record evolutionary history by analyzing fossil, morphological, and genetic data. The fossil record documents the history of life on Earth and provides evidence for evolution. However, both fossil and living organisms offer evidence that outlines Earth’s evolutionary history.
36.5K
02:55The Evidence for Evolution
42.8K
Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.
42.8K
00:55Parental Care
11.7K
Many animals exhibit parental care behavior, including feeding, grooming, and protecting young offspring. Parental care is universal in mammals and birds, which often have young that are born relatively helpless. Several species of insects and fish, as well as some amphibians, also care for their young.
11.7K
02:32Osmoregulation in Fishes
49.7K
When cells are placed in a hypotonic (low-salt) fluid, they can swell and burst. Meanwhile, cells in a hypertonic solution—with a higher salt concentration—can shrivel and die. How do fish cells avoid these gruesome fates in hypotonic freshwater or hypertonic seawater environments?
49.7K