Starfish are fascinating marine animals that many people find both beautiful and mystifying. Their unique shape and behavior often lead people to wonder – do starfish have genders?

If you’re short on time, here’s a quick answer to your question: No, starfish do not have separate male and female genders. Starfish reproduce sexually, but they are hermaphrodites, meaning they contain both male and female reproductive organs.

In this article, we’ll take an in-depth look at starfish biology and reproduction to fully explain why starfish don’t have distinct genders. We’ll cover their anatomy, how they reproduce, differences between males and females in other species, reasons why distinct genders evolved in many animals, and more.

Read on to learn all about the sex lives of starfish!

Starfish Anatomy

Unique Body Plan

Starfish have a very unique and decentralized body plan that allows them to survive even after losing one or more arms. Their bodies are composed of a central disk surrounded by five or more arms that radiate outward.

The arms contain repetitions of internal organs such as the stomach, gonads, pyloric caeca (small tubular structures), and tube feet. This means starfish can regenerate lost arms and even grow an entirely new starfish from just one severed arm!

Their ability to regenerate body parts makes starfish truly amazing echinoderms.

Some key features of starfish anatomy include:

  • Central disk – contains most vital organs like the mouth, anus, and madreporite (entry point for water)
  • Arms – contain repeated vital organs, tube feet, and sensory organs
  • Endoskeleton – composed of calcareous plates, spines, and pedicellariae under the skin
  • Tube feet – tiny tube-like structures used for locomotion, sensation, and gripping prey
  • Water vascular system – unique water-filled canal system used to extend/retract tube feet
  • Sensory organs – eyespots detect light, touch receptors detect stimuli
  • Mouth/anus – on lower (oral) and upper (aboral) side for digestion

The decentralized nature of their organ systems allows starfish to keep functioning even after injury. Truly an incredible anatomical arrangement!

Decentralized Systems

In addition to their decentralized body plan, starfish also have decentralized nervous and vascular systems spread throughout their arms. This allows them to coordinate local responses in each arm without input from a central brain.

Some examples of decentralized systems in starfish include:

  • Nervous system – spread throughout body with radial nerves and nerve nets in each arm
  • Sensory organs – photoreceptors, chemoreceptors, and touch receptors in each arm
  • Digestive system – stomach and pyloric caeca repeated in each arm
  • Water vascular system – one madreporite but canal systems spread through all arms
  • Reproductive system – most species have gonads in each arm

This decentralized arrangement allows each arm to function independently if separated from the body. For example, an amputated arm can digest food, move using its tube feet, and even regenerate a whole new starfish over time. Simply amazing!

Starfish Reproduction


Most starfish reproduce through a process called spawning, where they release eggs and sperm into the water for external fertilization (Pawson, 2007). When starfish reach sexual maturity, triggered by environmental factors like water temperature, they undergo gametogenesis to produce mature eggs and sperm.

During spawning, the female starfish lift up their central discs to release the eggs through tiny openings called gonopores. Males similarly release clouds of sperm for fertilization. This phenomenon typically occurs in synchrony based on lunar or tidal cycles to increase chances of fertilization success (American Museum of Natural History, 2023).


Once starfish release their gametes, eggs and sperm fuse and mix together in the surrounding seawater. Fertilization occurs externally to form zygotes that later develop into juvenile starfish. The large numbers of eggs and sperm released are crucial since it allows for better likelihood of collision of sperm and eggs in the expansive marine environment.

Studies estimate a single female starfish may release up to 40 million eggs in one spawn! (Lumen Learning, 2023). The fertilized eggs hatch into larvae which float in the plankton as part of their early development before eventually settling on the seafloor.

Sex Differences in Other Species


Like humans, starfish exhibit sexual dimorphism, meaning there are physical differences between males and females of the species. The most noticeable difference is that male starfish tend to be smaller in size compared to females.

Males also have longer, thinner arms while females have shorter, stumpier arms. These size and shape differences likely evolved to facilitate mating positions.

Another key difference is that females have larger gonads along each arm that produce eggs. Males have smaller testes that produce sperm. During mating, the male will climb on top of the female and align his arms with hers to facilitate transferring sperm into her gonads to fertilize the eggs.

In some starfish species, males and females also differ in color. For example, male chocolate chip sea stars are reddish-brown while females are tan or cream colored. However, color is not a foolproof indicator of gender since some females can also be reddish in hue.

Courtship Behaviors

Courtship rituals are another way starfish communicate gender and initiate mating. Here are some fascinating starfish mating behaviors:

  • Males initiate courtship by climbing on top of or next to a female’s central disk area.
  • The male then begins waving his arms back and forth quickly to signal his interest.
  • If receptive, the female will respond by waving her own arms more slowly.
  • The male will keep waving until the female accepts and aligns her arms with his.
  • Some species like sea biscuits even take part in synchronized swimming during courtship!

This courtship dance allows the male and female to communicate before mating begins. The ritual exchange helps males identify appropriate mates and allows females to screen for desirable partners before expending energy on breeding.

Evolution of Distinct Sexes

Increased Genetic Diversity

The evolution of distinct sexes in starfish provided several advantages that increased the genetic diversity and survivability of the species over time. Here are some of the key benefits:

  • Sexual reproduction mixes up genes from two parents, creating more genetic variation in offspring. This makes populations more resilient to diseases and environmental changes.
  • Males and females develop specialized sex cells (sperm and eggs) that can find each other more efficiently for fertilization.
  • Separate sexes allow for sexual selection, where members of one sex (often females) choose mates based on desirable traits.

In particular, producing either sperm or egg cells optimizes each type for its reproductive function. Sperm can be produced in vast quantities and swim with flagella to seek out eggs. Eggs contain nutrients to support growth and develop receptacles to receive sperm.

Without distinct sexes, starfish would rely solely on external fertilization between individuals releasing eggs and sperm into water. Distinct sexes improve the odds of gametes finding each other, and sexual selection leads to fitter offspring.

Sexual Selection

Sexual selection occurs when individuals of one sex (usually females) are choosy about their mating partners. This selectivity drives the evolution of exaggerated traits in the other sex (typically males) to attract mates.

Some examples of sexual selection in starfish include:

  • Male sea stars growing larger body sizes to dominate areas with more females.
  • Male crown-of-thorns starfish developing more attractive colors to entice females.
  • Male bat stars evolving longer, flexible arms to transfer sperm packets to females more effectively.

These types of adaptations give certain males a reproductive advantage. Females produce healthier offspring by mating with robust, viable males displaying fitness indicators. This filtering of male traits leads to stronger, sexier starfish over generations!


While starfish may seem like simple creatures, their reproductive strategies are fascinating. Their ability to function as both male and female sets them apart from species with separate sexes. Understanding starfish reproduction not only sheds light on their biology but also allows us to appreciate the diversity of reproductive systems in the natural world.

The next time you see a starfish, take a moment to admire its alien beauty, knowing that each arm contains both eggs and sperm. Though you can’t tell a male starfish from a female, these amazing animals don’t need gender differences to pass on their genes and continue thriving in ocean ecosystems worldwide.

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