Hemimysis anomala Survey & Monitoring Network
Finding Hemimysis
The NOAA National Center for Research on Aquatic Invasive Species
(NCRAIS) is coordinating a rapid research response to define the range, distribution,
and impact of Hemimysis anomala in the Great Lakes.
Determining the basin-wide distribution of H. anomala was
identified as the top priority for immediate action. A three-tiered survey and
monitoring network was outlined, requiring participation by various groups:
A) A public outreach network to engage and involve the general public in the search for Hemimysis. Help is needed to document and prevent the spread of this species! We are asking the public's help in documenting other locations around the Great Lakes basin where this species has spread. Look for swarms in shadowed areas along the shoreline, especially near breakwalls, docks, channel edges, and near boats (see "How to Help" below)
B) A network of basin-wide site-specific technical volunteers with appropriate training and resources who are willing to respond to public reports of Hemimysis sightings in their area by accessing the reported location and attempting to verify their presence, and if possible, collect samples for taxonomic verification and genetic analysis.
C) Multi-institutional technical personnel with appropriate field-sampling capabilities and resources, such as agency and academic scientists, who are willing to conduct surveys for the presence of Hemimysis at various sites around the Great Lakes basin. Development of recommended sampling methodologies and monitoring protocols is a key first step.
All three related networks are under development with the goal to activate them by April 2007.
One of the important needs and uses for a rapid survey and longer-term monitoring program is that as locations with populations are identified, appropriate information can be provided to the shipping industry (domestic and saltwater fleet representatives), the boating public (marinas, sport fishing associations, etc), aquarium hobbyists, and the scientific community (especially with respect to field gear). These organizations can act on information about new species, such as Hemimysis, to avoid aiding in their spread.
The Hemimysis Survey and Monitoring Network will include inland lakes, since there is great potential for Hemimysis to reach inland lakes via recreational boats and bail buckets, especially those close to the Great Lakes and their harbors and embayments.
How to help:
- Determine whether Hemimysis has already been reported in your area. [Check Reports]
- Know where and how to look for Hemimysis swarms [See "Where to Look" below]
- Report possible Hemimysis sightings to the Monitoring Network [Make a Report]
Where to Look
By day: A Hemimysis swarm appears as a
dense, reddish cloud of active animals, with individuals a quarter to half inch
long. A swarm may contain several thousand animals and be less than a foot
to several feet across. Look for Hemimysis swarms. especially in late summer.
Push a docked boat a few inches over and look in the shadows between the boat
and pier. When not swarming, Hemimysis is also
reported to spend daylight hours hiding in rock crevices. Thus they may
be found by turning over rocks in shallow waters, but only a few individuals
are likely to appear if present. Hemimysis are
reported in Europe at depths up to 50m (165 ft) among rocks and shells.
Hemimysis avoids dense submerged plant beds and
soft bottoms, though it may be associated with loose vegetation. It has not been reported in
waters over 50m (165 ft) deep.
By night: Hemimysis disperses at night – swarms break apart into individuals and individuals leave their hiding places to forage throughout the surface waters. On a clear calm night in clear water, a spotlight or flashlight sweeping the surface can reveal these animals actively swimming just below the surface – they appear as reddish flashes as they try to avoid the light.
Capturing Hemimysis
Hemimysis are relatively strong
swimmers and are not easily captured using standard scientific sampling nets or traps.
Individuals may be captured using a fine mesh dip net such as used for minnows –
this is clearly easiest to do when animals are swarming. Live Hemimysis
should not be transported! Scientists need Hemimysis to be
preserved in ethanol (grain alcohol), preferably 90% strength, although 70% ethanol, or
isopropanol (rubbing alcohol) are also acceptable and may be available from local pharmacies.
Drain water from the specimens and place them in a small glass or plastic container
and fill it with the ethanol or isopropanol.
Fish gut contents: several reports have been received of apparent Hemimysis remains being found in the stomach contents of fish, so another way to potentially find Hemimysis is to look at the stomach/gut contents of freshly-caught fish. However, we need to verify that it is Hemimysis and to do so we need a sample of the stomach contents. Place the sample in a small container and refrigerate it, or cover it with alcohol, and contact us. We’ll send you mailing instructions or arrange for someone to collect the sample from you.
Identification
Hemimysis is a small, shrimp-like
animal about one-quarter to one-half inch long. It has stalked eyes, antennae, and
an elongated body. Hemimysis is capable of changing its
body color from reddish to ivory-yellow to almost transparent with a touch of
ivory-yellow color. Preserved specimens become opaque after preservation.
Hemimysis looks very similar to the native
Mysis relicta (identified in some recent scientific literature as
Mysis diluviana) – size and color
ranges of the two animals overlap.
However, the native species prefers cold waters and is rarely found at
depths less than 26 meters (85 ft) in summer and rarely shallower than 6m
(20 ft) even in winter. Scuds such as Diporeia
spp. lack the elongate tail of the mysids.
Identification for Amateur Microscopists
The eyes of mysids are stalked and a carapace covers
the head and most of the thorax. Orange-red chromatophores can expand and contract
to alter the color of the individual. The 8 pairs of thoracic legs are more adapted
for swimming than walking and each has two branches. There is a long abdomen with 6
segments (somites). The final segment of the abdomen (telson) is longer, ending in a
tail fan of two uropods which stabilizes the animal while it is swimming. Female
mysids have a marsupium below the thorax where embryos are kept until they grow into
juveniles.
Close examination of the telson is the key to differentiating the native Great Lakes Mysis relicta from Hemimysis anomala. The native Mysis has a deeply forked telson (B) without terminal spines, whereas Hemimysis (A) has a flat end to its telson with two prominent terminal spines. New reports should be confirmed by an expert as several additional mysid species are invading across Europe with significant potential to invade the Great Lakes.