Megalagrion xanthomelas facts for kids
Quick facts for kids Megalagrion xanthomelas |
|
|---|---|
.jpg) |
|
| Conservation status | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Order: | |
| Family: | |
| Genus: |
Megalagrion
|
| Species: |
M. xanthomelas
|
| Binomial name | |
| Megalagrion xanthomelas (Selys, 1876)
|
|
The Megalagrion xanthomelas is a special type of damselfly also known as the orangeblack Hawaiian damselfly. It's an insect that belongs to the same group as dragonflies. This damselfly was first discovered in 1876.
It is an endemic species, which means it can only be found in the beautiful forests of the Hawaiian Islands. The Megalagrion group, which this damselfly belongs to, came from ancestors that lived in fresh water. These damselflies can grow to be about 33 to 37 millimeters long.
You can often find the orangeblack Hawaiian damselfly near calm water sources in Hawaii. These include small streams and ponds. Sadly, this species is in danger because its habitat is being lost. A common home for them is in special places called anchialine ponds. Here, they have learned to control their body fluids when the water's saltiness changes. This ability helps them find places with less salt. It has also led to different groups of the damselfly adapting. Those on the western coast can handle saltier water better than those on the eastern coast.
Amazing Adaptations
Different Colors
Since the Megalagrion damselflies are native to the Hawaiian Islands, they have changed a lot over time. This is called adaptive radiation. It means they have developed many different varieties, especially in their colors.
Hawaiian Megalagrion damselflies can be blue, green, yellow, orange, or red. The Megalagrion xanthomelas is special because the males are red and the females are brown. This is why it's called the orangeblack Hawaiian damselfly. When males and females of a species look different, it's called being sexually dimorphic.
There's one interesting exception to this color difference. If these damselflies live at a very high elevation, both the males and females can be red. This is a type of natural selection. The red color helps protect them from harmful ultraviolet (UV) rays from the sun.
Why Their Numbers Are Dropping
In the early 1900s, the Megalagrion xanthomelas was very common on the Hawaiian Islands. But after World War II, their numbers dropped very quickly. By the 1990s, many Hawaiian Islands no longer had any of these damselflies.
Because of this fast decline, the Megalagrion xanthomelas was put on the List of Endangered and Threatened Wildlife in 1994. This means it is protected under the Endangered Species Act of 1973. In 1996, it was listed as a vulnerable species. The last time it was checked, on January 18, 2019, it was officially listed as an endangered species.
Where They Live
Favorite Places
The Megalagrion xanthomelas often lives near the coastal wetlands of the Hawaiian Islands. You can also find them in wetlands that are fed by underground springs. They live at different heights above sea level, usually between 60 and 610 meters. Some groups have even been seen as high as 1000 meters up.
These damselflies love habitats with tall Guinea grass around the water. Female damselflies use the long leaves of this grass to lay their eggs. Males perch on the leaves, watching for other males to chase away.
The inlet of Pearl Harbor used to be a common home for the Megalagrion xanthomelas. But after World War II, their numbers there went down. Now, they are no longer found in Pearl Harbor. This happened because of airport traffic and new buildings for military bases in the area.
Anchialine Ponds
Anchialine ponds are the most common home for the Megalagrion xanthomelas. These ponds are found in low-lying areas of the Hawaiian Islands. An anchialine pond forms when a water source mixes with groundwater and has no direct connection to a larger body of water, like an ocean.
These ponds are known for their changing salinity (saltiness) levels. This happens because groundwater mixes with the original water. Anchialine ponds also have changing temperatures. This is because cold freshwater often mixes with warm saltwater. Both temperature and saltiness are very important for how well a group of damselflies will survive and grow.
How Salty Water Affects Them
The saltiness of the water is the most important factor. Things like precipitation (rain) and evaporation can make the salt levels go up and down. The average rainfall in the Hawaiian Islands is about 300 centimeters each year. This can really affect the saltiness in anchialine ponds.
On the east coast, anchialine ponds usually have a saltiness of about 3.5 parts per thousand (ppt). On the west coast, they are saltier, around 7.0 ppt. Because salt levels can change, different groups of Megalagrion xanthomelas have learned to live in different levels of saltiness.
.jpg)
New Species Moving In
The Megalagrion xanthomelas shares its home with other dragonflies and damselflies that are already there. It also shares its home with new species that have been brought to the Hawaiian Islands. Other damselfly and dragonfly species that live with the orangeblack Hawaiian damselfly include Ischnura posita, Tramea abdominalis, and Paniala flavescens. These species do not harm the orangeblack Hawaiian damselfly.
However, over the last 100 years, different types of fish have been put into the damselfly's water sources. These new fish have caused the damselfly's numbers to drop in these Hawaiian Island habitats.
Life Cycle
.jpg)
The entire life cycle of the Megalagrion xanthomelas happens in water that has a saltiness level lower than 8 ppt. Damselflies, like the Megalagrion xanthomelas, go through incomplete metamorphosis in their lives. This means they don't have a pupa stage like butterflies.
Their life cycle has four stages:
- The first stage is the egg, which takes about 21 days to hatch.
- Next is the pre-larva stage, which lasts between 11 and 17 days.
- The third stage is the naiad (or nymph), which can take from 103 to 111 days to develop.
- The last stage is the adult, which is the only stage that does not need water.
When female damselflies lay their eggs, they place them completely underwater on aquatic plants. The eggs are covered by an outer shell called a chorion. This shell helps the baby damselfly inside get oxygen. It also stops salt from getting in and harming the developing organism. After the life cycle is complete, the adult Megalagrion xanthomelas can either look for a new place to reproduce or stay near the water source where it grew up.
Environmental Challenges
City Growth
The Megalagrion xanthomelas is very sensitive to any changes or damage to its habitat. Habitat damage can happen because of urbanization, which is when cities and towns grow. This forces the damselflies into smaller living areas.
In the 1800s, the Megalagrion xanthomelas was so common that fields and shallow water areas were full of them. But in the 20th century, urbanization started to take over their natural homes in the Hawaiian Islands. Water sources were changed, filled in, or turned into mangroves. This made the water quality much worse for many species, including the damselfly.
One big event that led to their decline was the attack on Pearl Harbor. The inlet of Pearl Harbor used to be shallow and home to many species. But after World War II, it became a busy airport and military base. Later, more damage happened when the Pearl Harbor Memorial was built. All this construction wiped out any remaining damselfly groups there. It also made the water in the inlet much saltier.
Invasive Species
.jpg)
New invasive species have been a major threat to most aquatic habitats in the Hawaiian Islands. They are the main reason why the numbers of Megalagrion xanthomelas have dropped. Invasive fish species brought to the Hawaiian Island habitats have made many damselfly species, including the Megalagrion xanthomelas, more vulnerable.
Some of these invasive fish include Xiphophorus helleri, Poecilia mexicana, Poecilia reticulata, and Gambusia. There are more Megalagrion xanthomelas in areas where these invasive fish are not present. However, the damselflies can survive with some invasive species like carp and apple snails.
The introduction of invasive species doesn't just bring new predators. It also brings new diseases and parasites. Native species, like the Megalagrion xanthomelas, often cannot survive these new threats.
Weather Changes
The Megalagrion xanthomelas is very sensitive to higher salt levels and any big changes in saltiness. This can cause their numbers to drop. Anchialine ponds, which are their most common home, are easily affected by too much groundwater being taken out. This leads to an increase in saltiness.
When saltiness increases, it makes it harder for the damselflies to control their body fluids. This is especially true for the naiad (nymph) stage. Naiads do not have the protective outer shell (chorion) that eggs have, and they cannot control their body fluids as well as adults. If the naiads cannot survive, then entire groups of damselflies could be wiped out before the adults have a chance to reproduce again.
How We Can Help
More Research Needed
Not many studies, research, or experiments have been done on the Megalagrion xanthomelas. This means we don't have enough information about the orangeblack Hawaiian damselfly. It's hard to learn how they behave, how they live in their habitat, and how to best protect this endangered species from becoming extinct.
To help protect them, we need to do more basic research. This way, conservation biologists and others who want to help will have the right information. We should compare how younger and older damselflies react to different salt levels in the water. This can help us figure out what information is needed to help them survive better. It's especially important to focus on the naiad stage. This stage lives in the water and cannot protect itself from high salt levels.
Protecting Their Homes
The homes of Megalagrion xanthomelas, especially anchialine ponds, are very easily affected by pollution, damage, changes, and new invasive species. Their habitat can get dirty from pollutants and sediment (dirt) washed into the water from construction sites and roads. Pollution and sediment make the water quality poor, which is bad for the damselflies to live and reproduce in.
We need strong conservation efforts to protect the water quality and amount in anchialine ponds. This will make sure their habitat is good enough for them to reproduce and create more damselfly groups. Damage to the orangeblack Hawaiian damselfly's home is also caused by urbanization. This includes building new developments or roads into their habitats. Urbanization changes their habitat by making it smaller. This forces the damselflies into tiny areas that are not good for their species or their numbers. Being in a smaller area makes them more likely to be caught by predators and affected by invasive species.
If there are too many different types of invasive species in the damselfly's original home, the best way to help is to move the damselfly groups. This is because invasive species are very hard to control and get rid of once they are settled. If the orangeblack Hawaiian damselfly is moved to another natural anchialine pond or even one made by humans, the species can grow and restart without the problems of invasive species.
