Salamanders (Urodela) – LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED

October 31, 2023October 31, 2023

If You’re Out Collecting Sweets, It Pays to Look Scary

Only fools mess around with bees, wasps, and hornets as they collect nectar and go about their business while visiting flowering plants. Relentlessly curious predators and other trouble makers quickly learn that patterns of white, yellow, or orange contrasting with black are a warning that the pain and anguish of being zapped with a venomous sting awaits those who throw caution to the wind. Through the process of natural selection, many venomous and poisonous animals have developed conspicuously bright or contrasting color schemes to deter would-be predators and molesters from making such a big mistake.

"Red Eft" — The brilliant colors of the “Red Eft”, the terrestrial sub-adult stage of the aquatic Eastern Newt (Notophthalmus viridescens), provide protection not as a form of camouflage, but as a warning to potential predators that “I am inedible” due to the presence of tetrodotoxin, a strong neurotoxin. Over the generations, natural selection has better enabled the brightest of the individual “Red Efts” to survive to adulthood and reproduce. Meanwhile, those efts that provided a less obvious visual clue to their toxicity frequently allowed their pursuer to learn of their defense mechanism by the taste-test method. As one might expect, far fewer of these latter individuals survived to breed and pass along their more cryptic color variation.

Visual warnings enhance the effectiveness of the defensive measures possessed by venomous, poisonous, and distasteful creatures. Aggressors learn to associate the presence of these color patterns with the experience of pain and discomfort. Thereafter, they keep their distance to avoid any trouble. In return, the potential victims of this unsolicited aggression escape injury and retain their defenses for use against yet-to-be-enlightened pursuers. Thanks to their threatening appearance, the chances of survival are increased for these would-be victims without the need to risk death or injury while deploying their venomous stingers, poisonous compounds, or other defensive measures.

**Armed and Dangerous** The yellow-and-black color pattern on this European Paper Wasp signals a potential aggressor that they have come upon a social insect and could be struck with a venomous sting. The warning colors alone may be all the defenses necessary for this wasp to survive an otherwise fatal encounter.

One shouldn’t be surprised to learn that over time, as these aforementioned venomous, poisonous, and foul-tasting critters developed their patterns of warning colors, there were numerous harmless animals living within close association with these species that, through the process of natural selection, acquired nearly identical color patterns for their own protection from predators. This form of defensive impersonation is known as Batesian mimicry.

Let’s take a look at some examples of Batesian mimicry right here in the Lower Susquehanna River Watershed.

Suppose for a moment that you were a fly. As you might expect, you would have plenty to fear while you spend your day visiting flowers in search of energy-rich nectar—hundreds of hungry birds and other animals want to eat you.

You might not hurt a fly, but plenty of other creatures will. This Greenbottle Fly relies upon speed and maneuverability to quickly flee predators.

Like the Greenbottle Fly, the Common Flesh Fly (Sarcophaga species) needs to be constantly vigilant and survives by being quick to the wing.

If you were a fly and you were headed out and about to call upon numerous nectar-producing flowers so you could round up some sweet treats, wouldn’t you feel a whole lot safer if you looked like those venomous bees, wasps, and hornets in your neighborhood? Wouldn’t it be a whole lot more fun to look scary—so scary that would-be aggressors fear that you might sting them if they gave you any trouble?

Suppose Mother Nature and Father Time dressed you up to look like a bee or a wasp instead of a helpless fly? Then maybe you could go out and collect sweets without always worrying about the bullies and the brutes, just like these flies of the lower Susquehanna do…

FLOWER FLIES/HOVER FLIES

The Common Drone Fly (Eristalis Tenax) is a Honey Bee mimic — The Common Drone Fly (Eristalis tenax) is an unarmed Honey Bee mimic. This one is gathering nectar on goldenrod flowers.

The Transverse Flower Fly (Eristalis transversa) is another bee mimic. Members of the genus Eristalis scavenge carcasses in aquatic habitats. Their larvae are known as rat-tailed maggots, a name that references their long siphons used for breathing surface air while submerged in ponds, streams, and wetlands.

Spilomyia species Flower Fly — Flower flies of the genus Spilomyia are convincing mimics of temperamental yellowjacket wasps.

The Yellowjacket Hover Fly (Milesia virginiensis) is usually heard long before it is seen. It will often approach people and persist with a loud buzzing, sounding more like a bee than a bee does. Scary, isn’t it?

The Maize Calligrapher (Toxomerus politus) is a hover fly mimic of wasps. Seen here on Indiangrass, it is believed to associate primarily with Corn (Zea mays).

The Narrow-headed Marsh Fly (Helophilus fasciatus) is a wasp mimic. Like other mimics of hymenopterans, they are important pollinators of flowering plants.

Syrphus species Hoverfly — This hover fly of the genus Syrphus is another wasp mimic.

TACHINID FLIES

The Feather-legged Fly (Trichopoda species) is a wasp mimic. Its larvae are parasitoids of stink bugs and leaf-footed bugs.

BEE FLIES

Bee Fly (Exoprosopa species) — Bee flies of the genus Exoprosopa convincingly resemble bumble bees.

So let’s review. If you’re a poor defenseless fly and you want to get your fair share of sweets without being gobbled up by the beasts, then you’ve got to masquerade like a strongly armed member of a social colony—like a bee, wasp, or hornet. Now look scary and go get your treats. HAPPY HALLOWEEN!

March 25, 2023April 17, 2023

Underwater View of Life in a Vernal Pool

It may look like just a puddle in the woods, but this is a very specialized wetland habitat, a habitat that is quickly disappearing from the Lower Susquehanna River Watershed. It’s a vernal pool—also known as a vernal pond or an ephemeral (lasting a short time) pool or pond.

Viable vernal pools have several traits in common…

- - They contain water in the spring (hence the name vernal).
  - They have no permanent inflow or outflow of water.
  - They typically dry up during part of the year—usually in late summer.
  - They are fish-free.
  - They provide breeding habitat for certain indicator species of forest-dwelling amphibians and other animals.
  - They are surrounded by forest habitat that supports the amphibians and other vernal pool species during the terrestrial portion of their life cycle.

To have a closer look at what is presently living in this “black leaf” vernal pool, we’re calling on the crew of the S. S. Haldeman to go down under and investigate.

Along the surface of the pool we’re seeing clusters of amphibian eggs, a sign that this pond has been visited by breeding adult frogs and/or salamanders during recent weeks.

Amphibian eggs and the white tail filaments of an invertebrate of interest, Springtime Fairy Shrimp (Eubranchipus vernalis), an endemic of vernal ponds.

Let’s take it down for a better look. Dive, all dive!

Algae provides food for the shrimp and other inhabitants of the pool. Leaf litter furnishes hiding places for the pool’s many inhabitants.

These loose clusters of eggs appears to be those of Wood Frogs, a vernal pool indicator species.

Clusters of Wood Frog eggs, the embryos within those in the center of the image less developed than those to the left.

More Wood Frog eggs. Hatching can take anywhere from two weeks to two months, depending on temperature.

Wood Frog eggs with developing larvae (tadpoles) plainly visible. The green color of the eggs is created by a symbiotic algae, Oophila amblystomatis, a species unique to vernal pools. The algae utilizes the waste produced by the developing embryos to fuel its growth and in return releases oxygen into the water during photosynthesis. Upon hatching, the tadpoles rely upon the algae as one of their principle food sources.

A zoomed-in view showing development of the larvae and what appears to be a tiny invertebrate clinging on the white egg in the upper right. White eggs don’t hatch and may be infected by a fungus.

Wood Frog eggs and Springtime Fairy Shrimp.

Springtime Fairy Shrimp swim upside-down. Note the small, bluish clusters of eggs attached to the abdomens of these females. Springtime Fairy Shrimp live their entire lives in the vernal pool. After being deposited in the debris at the bottom of the pool, the eggs will dry out during the summer, then freeze and re-hydrate before hatching during the late winter.

A damselfly larva consuming fairy shrimp. (Visible in the margin between the uppermost lobes of the dark-colored oak leaf to the right.)

Getting in close we see A) the damselfly larva eating a Springtime Fairy Shrimp and B) one of several discarded exoskeletons of consumed shrimp near this predator.

A fishfly larva (Chauliodinae). Mosquito numbers are kept in check by the abundance of predators in these pools.

Springtime Fairy Shrimp and a Marbled Salamander (Ambystoma opacum) larva. The presence of these species confirms this small body of water is a fully-functioning vernal pool.

Springtime Fairy Shrimp and two more larval Marbled Salamanders. The salamanders’ enlarged gills are necessary to extract sufficient oxygen from the still waters of the pool.

The Marbled Salamander is one of three species of mole salamanders found in the Lower Susquehanna River Watershed. All breed in vernal pools and live their air-breathing adult lives under the leaves of the forest in subterranean tunnels where they feed on worms and other invertebrates. Photos of an adult Marbled Salamander and the other two species, Spotted Salamander (Ambystoma maculatum) and Jefferson Salamander (Ambystoma jeffersonianum), can be found by clicking the “Amphibians” tab at the top of this page.

Marbled Salamanders lay their eggs during the fall. If the bed of the pool is dry at breeding time, the adult female will remain to guard the eggs until rain floods the pool. The eggs hatch upon inundation, sometimes during the winter.

Marbled Salamanders, like all amphibians that develop in vernal pools, must complete transformation into their air-breathing terrestrial life stage before the pool dries up in the summer heat.

A larval Marbled Salamander explores the bottom of the pool.

A larval Marbled Salamander, Wood Frog eggs, and Springtime Fairy Shrimp, it’s an abundance of life in what at first glance may appear to be just a mud puddle.

We hope you enjoyed this quick look at life in a vernal pool. While the crew of the S. S. Haldeman decontaminates the vessel (we always scrub and disinfect the ship before moving between bodies of water) and prepares for its next voyage, you can learn more about vernal pools and the forest ecosystems of which they are such a vital component. Be sure to check out…

- - The Pennsylvania Natural Heritage Program page

If you are a landowner or a land manager, you can find materials specifically providing guidance for protecting, restoring, and re-establishing vernal pool habitats at…