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Parasites

Sea Lampreys Spawning In Connecticut River

e-eagle with sea lamprey 325Sea Lampreys aren’t a common sight, but an opportunity presented itself after this Bald Eagle “rowed” from the middle of the Connecticut River to the shore with its too-heavy-to-lift prey, ate a portion of it and flew to its nest with a slightly lighter load.  At first glance I thought it had captured a large snake, but closer inspection revealed that a three-to-five pound Sea Lamprey approaching 30 inches in length was clasped in the eagle’s talons!

Lampreys were accidentally introduced into the Great Lakes and Vermont’s Lake Champlain, where they became parasites of other fish due to being landlocked.  However, during the time the native Sea Lampreys are found in the Connecticut River, they are not parasitic. These fish are anadromous – they live as adults in the ocean (where they are parasitic) and return in May and June to spawn in fresh water.

Sea lamprey young spend three or four years as worm-like creatures burrowed in the soft mud of the Connecticut River.  When they reach five or six inches (which can take up to ten years), young lamprey head for the sea. The ocean-dwelling adults uses their round, rasping mouth – filled with concentric circles of teeth – to scrape a hole in the side of a host fish and feed on blood and body fluids before letting go. They weaken, but don’t kill, their hosts. After spending one to two years in salt water, Sea Lamprey head back to the closest freshwater stream or river, migrate upstream, cease feeding and spawn.  They never return to the ocean, as they die after mating and laying eggs.

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Promethea Pupae Parasitized

12-21-15 promethea cocoon 257Although a lack of snow makes tracks difficult to find, there are other, more permanent, animal signs such as bird nests and cocoons that are visible this time of year. Among the more obvious is the cocoon of the Promethea Moth – a giant silk moth. When the time for pupating arrives the Promethea caterpillar selects a leaf and strengthens its attachment to the tree by spinning silk around the petiole of the leaf as well as the branch it grows on (to assure that it doesn’t fall off the tree). With more silk it rolls the leaf up into a tube and then proceeds to spin its cocoon inside the rolled-up leaf, leaving a valve-like structure at the top of the cocoon through which the adult moth exits in the spring.

Unfortunately for silk moths, many are parasitized by flies and wasps (there are nearly 100 natural parasites that affect the 24 species of silk moths east of the Mississippi River). Frequently flies or wasps lay their eggs in silk moth caterpillars and then develop inside them. Eventually the fly or wasp larva secretes a substance that causes the caterpillar to pupate, at which time the fly or wasp also pupates and then exits the moth pupa and cocoon (see exit hole in smaller photo), causing the death of the moth pupa. Silk moth populations are decreasing, in part as a result of these parasitoids. Among others, a non-native parasitic tachinid fly, Compsilura concinnata, is wreaking havoc on silk moths.

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Parasitoids & Parasites

9-10-15 pelecinid wasp with mites 071By definition, a parasitoid is an organism that lives on or in a host organism and ultimately kills the host. The pictured Pelecinid Wasp is a parasitoid. Its host is the grub, or larval stage, of June Bug beetles. The female Pelecinid Wasp uses its long abdomen to probe into the soil until it locates a June Bug grub and then it lays an egg on the grub. When the egg hatches, the wasp larva burrows into and feeds on the grub, eventually causing its death.

A parasite is much like a parasitoid, deriving nutrients from a host, but, unlike a parasitoid, a parasite does not usually kill its host. Often parasites are much smaller than their host, and frequently live in or on their host for an extended period of time. In this photograph, a parasitoid, the Pelecinid Wasp, is host to reddish parasitic mites (located on its thorax).

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Beechdrops Flowering

9-4-14  beechdrops 249Beechdrops (Epifagus virginiana) are parasitic plants which obtain nutrients from the American Beech tree. They insert a root-like structure called a haustorium into a beech root and absorb enough nutrition to sustain themselves and produce flowers between August and October. Beechdrops belong to a family of plants (Broomrape) whose members live as root parasites. Being annuals, Beechdrops don’t live long enough to damage their host trees. Because they lack chlorophyll and obvious leaves (their leaves are scale-like and pressed flat against their stem), Beechdrops are easily overlooked. Keep an eye on the forest floor near American beech trees for these 5 – 18-inch plants which are flowering right now.

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Braconid Wasps Pupating and Emerging

8-29-14 braconid wasps 010Tobacco Hornworms, Manduca sexta (often found feeding on tomato plants and confused with Tomato Hornworms, Manduca quinquemaculata) are often the target of a species of a Braconid wasp (Cotesia congregata) that parasitizes beetle, moth, fly and sawfly larvae. The adult wasp lays her eggs inside the hornworm with her long ovipositor. The eggs hatch and the wasp larvae feed on the caterpillar. Eventually the wasp larvae emerge and spin silk pupa cases (cocoons) on the skin of the dying hornworm caterpillar, inside of which they transform into winged adults within four to eight days. Braconid wasps are extremely good at locating hornworms, even when there are very few to find. Because they parasitize hornworm, cabbage worm, aphid and gypsy moth larvae, Braconid wasps are considered important biological control agents. If you want to discourage Tobacco Hornworms in your tomato patch, allow the wasps to complete their metamorphosis – this accomplishes both the demise of the hornworm, as well as an increased population of Braconid wasps. (Thanks to Emily and Joe Silver for photo op.)

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Pelecinid Wasps Laying Eggs

9-11-13 pelecinid wasp 211The two-inch, skinny, black, shiny wasps with extremely long abdomens (five times the length of their bodies) that have been appearing on lawns lately are not the villains you may think. These female Pelecinid Wasps (males are much smaller and rarely seen) are actually beneficial, in that they greatly decrease the June Bug population. That long abdomen, or ovipositor, cannot sting you – it is strictly a mechanism for laying eggs. Its length is due to the fact that the wasp inserts its ovipositor deep into the ground in order to locate beetle larvae — specifically, June Bug beetle larvae. The wasp then lays one egg on each host beetle larva, and when the egg hatches, the wasp larva burrows into the host as it feeds on it, thereby killing the June Bug beetle larva. Eventually the wasp larva pupates and emerges above ground as an adult wasp the following summer – the phenomenon we are currently witnessing.

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Birds & Ticks

7-18-13  song sparrow with tick 252Several recent studies demonstrate that wild birds are actively transporting ticks and their associated diseases during migration. In addition, a number of bird species are able to contract Borrelia burgdorferi (the bacterial causal agent of Lyme Disease infection) and transmit it to uninfected ticks that parasitize the birds for a blood meal. Since ground-feeding species such as Northern Cardinals, Gray Catbirds, Song Sparrows (pictured) and American Robins spend a significant amount of time foraging for food at the optimal height for ticks, they are excellent hosts and have all demonstrated the ability to infect larval ticks with Borrelia burgdorferi upon their first blood meal. (Look carefully at the Song Sparrow’s neck and you will find a tick.)