Pufferfish Larva (Yolk-sac Stage)
Tetraodontidae (Family level identification)
Type: Saltwater / Estuarine (Demersal/Ichthyoplankton)
Physical Characteristics
The image shows a post-hatch yolk-sac larva. Key features include a highly bulbous, spherical yolk sac extending from the ventral side, a relatively short and stout body, and a developing caudal fin. At this stage, the body is semi-transparent to opaque with scattered melanophores (pigment cells). The heavy, rounded shape is characteristic of tetraodontids.
Habitat & Distribution
In Sri Lanka, these larvae are found in brackish lagoons and coastal estuaries. Adults inhabit reef and seagrass environments, but larvae are commonly part of the ichthyoplankton in shallow, nutrient-rich coastal waters.
Size & Weight
Larval size is typically 2.0 to 4.5 mm in total length during the yolk-sac stage. Adults of coastal Sri Lankan species can range from 10 cm to over 50 cm depending on the genus (e.g., Arothron or Lagocephalus).
Similar Looking Species
Boxfish larvae (Ostraciidae) are also spherical but often have a firmer, more armored appearance. Toadfish (Batrachoididae) larvae also possess large yolk sacs but typically have different pectoral fin development and pigment patterns.
Ecological Role
As larvae, they are part of the zoo-ichthyoplankton, serving as a food source for larger planktivores. As they mature, they become significant benthic predators, controlling populations of invertebrates.
Diet
In this yolk-sac stage, the larva does not feed externally, deriving all nutrients from the attached yolk sac. Upon absorption, they feed on micro-zooplankton like rotifers and copepod nauplii.
Behavior
Planktonic and predominantly buoyant or drifting with currents. Early stage larvae have limited swimming ability and rely on water movement to transport them into nursery areas within the lagoon.
Reproduction
Most pufferfish are demersal spawners, laying eggs on the substrate. After hatching, the larvae enter a brief planktonic phase before settling back to the benthos as juveniles.
Conservation Status
Diverse; most common lagoon species in the Indian Ocean are currently listed as Least Concern, though specific coral-dependent species face habitat-related threats.
Identification Tips
Identification in ichthyoplankton surveys is confirmed by the rotund body shape, the specific distribution of melanophores on the dorsal surface of the yolk sac, and the short pre-anal length.
Interesting Facts
Pufferfish larvae are born with the genetic blueprint to produce tetrodotoxin, an extremely potent neurotoxin, which can sometimes be found even in the eggs and early larval stages as a chemical defense against predators.
User Notes
From Sri Lankan lagoon ichthyoplankton survey
Identified on: 5/20/2026
Mode: Standard