//
you're reading...

Ecology

Sex and parasitism on the open sea and in a fish’s mouth.

Paper: Cook, C. and Munguia, P. (2015), Sex change and morphological transitions in a marine ectoparasite. Marine Ecology, 36: 337–346. doi: 10.1111/maec.12144

 

Background

Parasites make a living off their selected host, using it as a food source or sometimes even as shelter. Parasitic organisms do not provide any benefit to their host and thus are required to adapt to environments where they are unwanted. Parasites must be able to spread to other hosts in order to survive or reproduce successfully. This complicated lifestyle can lead to creative strategies to get through life. As on land, parasites are common in the ocean. All types of animals suffer from parasites such as barnacles, snails, worms, leeches or even crabs. These parasites may harm or sometimes kill their hosts.

The parasitic isopod, Cymothoa excise, infects Atlantic croaker, Micropogonias undulates.  Isopods are a type of crustacean related to pillbugs (or roly polys) you may find in your garden. Some isopods are free living reaching over a foot in length in the deep sea. Some parasitic isopods infect the skin of fish. The isopods in this study live in the mouth of fish, attaching to the tongue or gills.

Our isopods must swim through the water to encounter a host fish to live inside, which can be quite a challenge. After securely attaching to the tongue, the isopod can focus on the next phases in its life – growth and reproduction. Male and female isopod are needed for sexual reproduction, but relying on luck to have both sexes float by at the same time is too risky. These isopods solve this problem by changing sex as needed to ensure there are males and females available. An isopod may be a juvenile, then a male, and then a female if one does not already live on their fish. This sex change over an individual’s life is known as sequential hermaphroditism.

The sex changes of the isopods are known, but not fully explored or understood. Researchers have observed the sex changes but what triggers them, or how prevalent it is was unknown. This study examined the morphology of the different stages, along with the reproductive output and explores the best timing for transitioning from male to female.

 

 

 

Seen at the National Museum of Natural History in Sofia in Bulgaria.

Isopods seen at the National Museum of Natural History in Sofia in Bulgaria. Credit: Orin Zebest.

The Study

The investigators collected Atlantic croaker over 22 months and examined the fish for parasites. Isopods were removed by hand, measured and identified based on stage and sex according to the following categories: juvenile, male, female or transitional (between sexes).

Over the length of the survey almost 100 croaker were caught through trawls (3 m depth) in the bay of Port Aransas, Texas. Overall 1 in 5 fish were infected by the isopod. Infection rate did not change with the season, but the intensity of infection (i.e. number of isopods per fish) changed throughout the year with spring having a low intensity increasing as summer went on and lowering in winter. Infected fish were home to a range of one up to six isopods.

The first isopod on a fish infected the tongue and was female or transitioning (except in one case when a small male was found alone in the gills), whereas all additional isopods were male. When two isopods are present they inhabited different areas of the tongue. Any more than two isopods were found in the gill arches.

 

maec12144-fig-0001

Fig. 1. (A) Seasonal frequency of isopods infecting fish as a function of fish size. Arrows indicate the median size of infected fish. (B) Seasonal frequency of infected fish as a function of the number of isopods per infection.

maec12144-fig-0002

Fig. 2. Location and frequency of isopod parasites occurring on Atlantic croaker (n = 70). Locations were divided into three areas – the gills, the tongue and a cavity behind the tongue next to the gills (T-G). Infected fish had one to four parasites.

 

 

 

As males transition to females they become larger. This study found larger females have higher reproductive success than smaller females. Larger fish can also support larger isopods. The researchers also determined six body traits that differ between males and females, showing morphological identification of sexes is possible.

 

Significance

This study helps us understand the fascinating life history of a parasitic isopod.  It raises questions about how the isopod undergoes sex changes and what controls these changes in the fish’s mouth. We still do not know what prevents more males from transitioning in this environment. Researchers can continue to study this relationship to determine what pheromones may be directing the transitions or to explore the competition occurring among males to determine which isopod has access to the female. Also, this study does not investigate the effect of the parasite on the host. Evolution of parasites is tied to evolution of the hosts and this paper helps to fill in part of the fascinating story while piquing our interest in learning more about the parasite and its relationship with its host.

 

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 3 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 4 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 5 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 6 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 9 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 9 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 10 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 11 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 11 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 11 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 12 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 1 year ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com