Lythrypnus dalli (Gilbert, 1890)

Size

Blue-banded gobies (Lythrypnus dalli) reach a maximum adult size of around 64 mm (roughly 2.5 inches), with standard adult sizes ranging from 18 to 45 mm (0.7 to 1.8 inches).

Coloration

They are brightly colored coral-red, with 5 to 9 blue bands on the front portion of their bodies.

Dorsal Fin Structure

They have two dorsal fins: a tall, spiny fin positioned near the head, and a longer soft-rayed fin that extends along the back.

Pelvic Fin Function

Like the round goby, they have a wide pelvic fin on each side of their body, which they use as a suction cup to cling to rocks in fast-moving currents.

Defense Toxin

As a defense mechanism, Lythrypnus dalli secrete a mild toxin that makes them irritating to eat.

Batesian Mimicry

Other goby species mimic this species' coloration and pattern to gain this same protection.

Habitat Type

Blue-banded gobies are most commonly found in rocky reef environments, and prefer hard substrates and sloped surfaces for their habitat.

Depth Range

They are often located in open rocky areas and caves near the ocean floor, and live at depths between 0 and 76 meters (0 to 250 feet) below sea level.

Threat Response

When approached or threatened, they typically retreat into small crevices, and will sometimes take refuge among the spines of sea urchins.

Reproductive Sex Change

The blue-banded goby has a regulated reproductive system that relies on bidirectional sex change.

Social Sex Determination

Individuals can function as either female or male, depending on their social environment.

Harem Structure

Blue-banded gobies usually form harems made up of one male and multiple females.

Sex Change Trigger

If the existing male is removed by predation or is otherwise absent, the largest female in the group will switch sex to take on the male role.

Courtship Behavior

Courtship behavior involves a male rushing toward a female, nipping her genital area, and locking jaws with her.

Egg Development Pre-Deposition

Prior to deposition, developing eggs are held along the walls of the brood chamber, until an appropriate shell is found for the eggs to be deposited into.

Male Nest Guarding

Males take on the dedicated task of guarding nests, using fanning motions of their pectoral fins to support egg development while driving off intruders.

Breeding Season

Their breeding season runs from approximately February to September.

Egg Hatching Timeline

At a temperature of around 21°C, blue-banded goby eggs hatch in 4 days, and juveniles reach maturity after 3 months.

Temperature-Dependent Hatching

Blue-banded goby embryos typically hatch between 4 and 10 days, with hatching time depending on environmental temperature.

6-Somite Embryo Development

By the 6-somite stage of development, the embryo has developed a distinct head bulge and tail bud.

Pharyngula Period Development

During the pharyngula period, small patches of pigmentation can be seen on the embryo; muscle movement and a heartbeat are also present by the 9-14 prim stage.

Hatching Period Development

The hatching period follows this stage, and is marked by the start of growth for pectoral fin buds and jaws.

Flexion Period Development

Caudal fin rays begin to develop during the flexion period.

Juvenile Stage Development

After the flexion period, individuals enter the juvenile stage, where both jaws extend forward.