While most of the larvae out there are from crustaceans and insects, larvae come from a wide variety of taxonometric groups including several groups of Chordates. Today’s animal is one of my favorite larvae of all from Belize – the Spotted Trunkfish (Lactophrys bicaudalis (Linnaeus, 1758)). My idea of a perfect day out would be to dive on the reef at Carrie Bow Cay in the early morning and then spend the rest of the day snorkeling in the mangroves nearby, looking for and at the larval forms of fish and the invertebrates. So, on to the trunkfish…

Juvenile Spotted Trunkfish (Lactophrys bicaudalis)

While fish don’t go through complete metamorphosis, many species do go through radical changes from birth through “settlement”. In Belize many of the larval, and post larval juvenile, forms of reef fish can be found in the mangroves including the boxfishes (Ostraciidae), a family of teleost fish which includes fish often named cowfishes and trunkfishes. On my trip to Belize I was thrilled to find some juvenile spotted trunkfish, like the one above, among the mangroves myself. The above picture however is from the Smithsonian Institution’s Larval Fish Group. The Larval Fish Group is one of several excellent resources for larval fish.

Eventually this small (~1.0cm) larvae will grow to become an up to 40cm long (~16″) adult feeding on algae and small benthic (bottom) invertebrates such as mollusks, crustaceans, tunicates, sessile tunicates, and echinoderms (sea stars, sea cucumbers and urchins). They spawn at dusk releasing large eggs (~2mm) into the pelagic ocean. After hatching the larvae will remain in the nekton. The plates that form their armor begin to develop as lumps in the early preflexion larval stages. In Gulf of Mexico sampling they were rarely found and at the pre-settlement stages there were no uniquely distinguishing characteristics to allow identification of pelagic larvae to the genus or species levels. According to William’s wonderful Early Stages of Atlantic Fishes (Marine Biology), Ostraciidae spend a short amount of time as pelagic ichthyoplankton, settling rapidly to seagrass beds and mangroves. Eventually they do recruit back to the reefs to settle and develop a fiercely guarded territory on the reef.

Here then is the adult form:

mature Spotted Trunkfish

Two interesting bits about Spotted Trunkfish:

• They hunt by blowing jets of water into the sediments around the reef to uncover and dislodge the small inverts.
• Some boxfishes (Ostraciidae), including the Spotted Trunkfish (L. bicaudalis) have another form of defense beside their armor. They release a compound called ostracitoxin when stressed which can kill other fish, making members of the boxfish a poor choice for aquaria.

Classification

Kingdom

Animalia

Phylum

Chordata

Class

Actinopterygii (Ray-finned fishes)

Order

Tetraodontiformes (Puffers and filefish)

Family

Ostraciidae (Boxfishes, Cowfishes and Trunkfishes)

Genus

Lactophrys

Species

Lactophrys bicaudalis

References

Böhlke, J.E. and C.C.G. Chaplin, (1993) Fishes of the Bahamas and adjacent tropical waters. 2nd edition. University of Texas Press, Austin.

Richards, W.J.(ed.). (2006) Early Stages of Atlantic Fishes: An Identification Guide for the Western Central North Atlantic. Taylor and Francis, Boca Raton, FL pp. 2640.

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Blowfly Larvae Photo by Leon Higley, UNL Entomology

Yummm… necrophagous larvae, or maggots, of the Blue Blow-Fly,Cynomyopsis cadaverina (Robineau-Desvoidy). The larvae of many species of fly feed on dead tissue. This is highly useful as an ecosystem service as they very effectively clean up any carrion that is missed or left over from any larger scavengers.

Some species maggots feed only on necrotic tissue leaving surrounding healthy tissue completely alone. These maggots clean out the dead tissue of large wounds in the wild and have been reintroduced to modern western medicine recently in a procedure called maggot debridement therapy. The therapy wass reintroduced by a Dr. R. Sherman from the Long Beach Veterans Hospital. He set up breeding of the Green Bottle Fly (Phaenicia sericata). These “Medical Maggots” are disinfected and introduced into wounds with non-healing necrotic tissues. The larvae dissolve and eat only the necrotic tissue, at the same time cleaning the wound of bacterial infection and the combined action of the necrotic tissue removal and secretions released in feeding significantly stimulate new healing of the wound.

C. cadaverina is also an important maggot, but it is used more in forensics. Different flies lay their eggs (oviposit) on carrion at different times and have different larval growth rates. By examining the maggots and eggs on a body and measuring the length and developmental stages of the maggots, forensic entomologists can determine roughly when death occurred. C. cadaverina oviposit 1.5 days after death according to Byrd & Castner’s Forensic Entomology. Of course th question can arise, how we know that a maggot arose from an egg laid on the body in question and whether it has actually fed upon the body. One way to find out ould be to examine the contents of the maggots gut. Of course the contents of the maggot’s gut aren’t like looking at the contents of a fish gut.

Jeffrey Wells and his colleagues needed just such a way of confirming that the maggots actually developed on the body for forensic investigations. They had three cases that come up in forensic investigations they wanted to be able to address:

• Investigators discover maggots but no body of any type, suspect possible foul play.
• Maggots are discovered, but not directly on a corpse, and alternative food sources are near.
• Maggots are found on a corpse, but may have come from somewhere else.

In the first case, if there are necrophagous maggots present there must have been a carcass nearby recently. If it was human then there may need to be an investigation. In the second case, because larva can crawl they may leave a corpse if disturbed or if the soft tissue is gone before they have grown enough to enter the pupal stage. If there are other food sources nearby the issue is to determine which food source the maggots originated on. Similarly in the third case it may be that the maggots found on a corpse may not have originated on that corpse as the maggots can crawl several meters and with the presence of other food sources may have crawled from a different source. If so those particular maggots should not be used to calculate the time of death.

Wells et al. raised eggs to the third instar maggots on human liver from a liver transplant patient. Since the eggs were collected from the wild, they allowed some maggots to pupate and were positively identified as C. cadaverina. They dissected the crops out of the maggots and adult flies and then extracted the DNA from the crops and their contents. The team performed two PCR reactions for each DNA extract. One PCR reaction used primers for fly cytochrome oxidase subunit one (COI), the other used primers for a region of human mtDNA. All the maggot and fly samples successfully amplified the fly COI fragment, and the human blood did not. The adult fly’s crops did not show human mtDNA as expected. They were able to successfully extract human mtDNA from the maggot crops that had fed on the donated liver as well as the blood sample donated by the liver transplant patient. The sequence from the maggot crops differed slightly (two position) from the blood sample. So they were able to conclusively identify maggots which had fed on human tissue, advancing the ability to use maggots in forensic investigations.

Classification

Kingdom

Animalia

Phylum

Arthropoda

SubPhylum

Hexapoda

Class

Insecta

Order

Diptera (Flies)

Family

Calliphoridae (Blow-flies)

Genus

Cynomyopsis

Species

Cynomyopsis cadaverina

References

J.H. Byrd and J.L. Castner, Editors, Forensic Entomology: The Utility of Arthropods in Legal Investigations, CRC Press, Boca Raton (2001)

J Wells, F Introna, G Di Vella, C Campobasso (2001). Human and Insect Mitochondrial DNA Analysis from Maggots Journal of Forensic Sciences, 46 (3)

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Monarch (Danaus plexippus) Chrysalis Day 9, originally uploaded by eclectic echoes.

25 days after hatching from an egg, 9 days after becoming a chrysalis, this was at 6am, by 8pm the female monarch was out and ready to go free.

Free, originally uploaded by eclectic echoes.

Classification

Kingdom

Animalia

Phylum

Arthropoda

SubPhylum

Hexapoda

Class

Insecta

Order

Lepidoptera (Butterflies and Moths)

Family

Danaidae (Milkweed Butterflies

Genus

Danaus

Species

Danaus plexippus

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Nom, originally uploaded by eclectic echoes.

At this point (5th instar) the caterpillar eats like crazy! Of course it actually increased in size 33% to 100% day over day every day except the two days that it spent all day resting getting ready for molting.

Length (mm) of Monarch (D. plexippus) larva each day post-hatch. Two days (day 8 and day 12) no length measurement was recorded as the larva remained essentially motionless on the side of it

Classification

Kingdom

Animalia

Phylum

Arthropoda

SubPhylum

Hexapoda

Class

Insecta

Order

Lepidoptera (Butterflies and Moths)

Family

Danaidae (Milkweed Butterflies)

Genus

Danaus

Species

Danaus plexippus

Life Photo Meme

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1st Instar – Detail, originally uploaded by eclectic echoes.

Last night someone emerged from it’s egg while we slept. Now 1.5mm long. This is the 1:1 pixel crop.

We’ll be tracking how much it eats and it’s daily growth as a project for my son, as things develop I’ll post updated pictures along with the measurements.

Gender in the monarch larvae

Adult monarch gender is very easy to discriminate using the pouches (spots) in the hind-wings, but for the larvae it’s another story. In the pupal stage there is a small visible difference with females having a line dissecting the 8th abdominal sternite. You may need magnifying glass to find it though. With the larval stages (i.e. caterpillar) there is no external difference at all. If dissected, the male testes can be found as red or pink sac(s) dorsal to the gut in the 6th abdominal segment of late instars.

Classification

Kingdom

Animalia

Phylum

Arthropoda

SubPhylum

Hexapoda

Class

Insecta

Order

Lepidoptera (Butterflies and Moths)

Family

Danaidae (Milkweed Butterflies)

Genus

Danaus

Species

Danaus plexippus

References

Hughes, P.R., Radke, C.D., Renwick, A.A. (1993). A Simple, Low-Input Method for Continuous Laboratory Rearing of the Monarch Butterfly (Lepidoptera: Danaidae) for Research.. American Entomologist, 39:109-111.

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