February 2023 – Discover-Nature

Aquatic Insects

Rivers and streams meander, fall, swirl, pool and flow through landscapes based on how their channel has been shaped and filled. Moving water, referred to as a current, goes in different directions and speeds as it flows. Currents are slower on the water’s surface, sides, and bottom due to friction with air, soil and rock. The fastest current is just below the surface where nothing impedes its progress, and the slowest is where the water pushes in all directions due to obstacles in its path.

^{Woodland stream by John Holmes, Getty Images}

Aquatic insects living in these turbulent waters employ a variety of methods to anchor themselves in place to breathe and eat. Most aquatic insect species are in their larval stage and will leave their aquatic environment when they become adults. Some are benthic species living attached to the bottom; some are swimmers commonly found in slower moving water; some live in the swift-moving current.

^{Water Penny by Cliff White; Stonefly larva by Jim Rathert, Riffle beetle by Cliff White, all images courtesy of Missouri Department of Conservation}

Most insects must be able to securely anchor themselves to breathe and eat. The water penny, a flow-adapted insect, uses its whole body, a flattened oval disc, to adhere itself to a rock using suction. With its smooth back and with no protrusions, water easily flows over and around this species. Where the current flows around rocks on the bottom, an area of quiet water forms just behind each rock. The caddisfly builds a case around itself from rocks, sticks, and mud and remains in this quieter area. Stoneflies and riffle beetles use sharp hooks at the ends of their legs to hang onto the bottom substrate even while walking about in the flowing water. Where water pools and currents slow after a sandbar, mayflies, crane flies, and midges live in burrows in the silty bottom.

^{Pseudiron mayfly by Dave Ostendorf, courtesy Missouri Department of Conservation}

Mosquito larva courtesy Missouri Department of Conservation

^{Damselfly nymph by Cliff White, courtesy Missouri Department of Conservation}

For animals with lungs, muscles expand the lungs pulling in air where oxygen can be absorbed into the blood stream and transported to cells in the body. Insects do not have lungs but use air tubes attached to spiracles, openings on the outside of their bodies that can be opened or closed. A fine network of air tubes allow oxygen to be absorbed directly by each cell. Damselfly, mayfly, and stonefly use gills to extract oxygen from flowing water and pump it into their air tubes. Mosquitos and water scorpions use snorkeling, where a breathing tube connected to a spiracle breaks the water’s surface. Water beetle adults trap a bubble of air under their wing covers when they dive. It is held in place by hairs on their bodies and covers the spiracles located along the sides of the abdomen.

^{Caddisfly larva with pebble case by Jim Rathert, courtesy Missouri Department of Conservation}

^{Caddisfly larva with plant fiber case by Jim Rathert, courtesy Missouri Department of Conservation}

In addition to oxygen, water currents bring a steady supply of food downriver and carry away waste. In forested streams, vegetation and decaying animals falling into the water provide a variety of food. Midges are able to collect tiny particles of plants and animals found in slow-moving water. Some species of stonefly and caddisfly are shredders, feeding on vegetation moving past them by chewing it into small bits. Filter feeders, including black fly and riffle beetles, use nets and fans to trap particles from faster-moving currents.

^{Midge fly larva by Cliff White, courtesy Missouri Department of Conservation}

^{Crane fly larva by Jim Rathert, courtesy Missouri Department of Conservation}

In areas exposed to lots of sunlight, algae and aquatic insects are the main food sources. Mayfly, caddisfly, and water pennys scrape algae from rocky surfaces. Other species of stonefly and riffle beetles are predators and use their hooked feet to position themselves in steady currents where they are able to snag other species being swept along. Another predator, the alderfly, burrows its bottom into the streambed to catch prey swimming nearby. Damselfly larva may anchor themselves to the bottom or fill a bladder at their rear end with water and expel it with enough force to propel themselves through the current to snag prey.

^{Alderfly larva courtesy Missouri Department of Conservation}

Whether the current is fast or slow, flowing through clear areas or obstacles, streams provide insects with numerous places to live. On you next walk along a waterway, consider all that is happening just below the surface.

Sei Whale

The sei (SAY) whale, Balaenoptera borealis, is the third largest rorqual, a group of large baleen whales that feed by straining food from the water. They live 50 to 70 years and grow up to 60 feet in length, weighing 100,000 pounds. They have bluish-gray backs, creamy bellies, a tall, hooked dorsal fin, and a large mouth with 200-400 baleen plates made of keratin. Their skin is often marked with a series of curvy healed scars made by “cookie-cutter” sharks which attach themselves to large species with suction-cup lips hiding sharp teeth that cut out a section of flesh about two inches in diameter to eat.

There are two types of whales, toothed whales and baleen whales which are considerably larger, but have no teeth. Toothed whales and other cetaceans including dolphins and porpoises, have one blowhole leading to the left nasal passage. Baleen whales have both nasal passages open as two blowholes to accommodate their huge size, allowing a much greater air exchange when surfacing. In all cetaceans, muscles are contracted to open a nasal plug in the blowhole allowing them to breathe. When underwater, the muscles are relaxed, blocking the blowhole and preventing the animal from breathing in water. Air sacs immediately below the blowholes allow for creation of long, loud, low-frequency calls within the hearing range of humans. Most calls last less than one second and sound levels are equivalent to standing next to a jack hammer, carrying long distances underwater.

Sei whales are found in temperate oceans around the world, but not in polar or tropical waters. The southern sub-species population is slightly larger than the northern one, and there is no evidence of interbreeding. Current population estimates place a total of 80,000 individuals world-wide, but sei whales prefer deep ocean waters and rarely come near land making placement of tracking devices and accurate estimates difficult. Tagging has been moderately successful, with many lost signals. It is known that they migrate annually, following the available prey and using prevailing currents to move quickly, but exact migration routes and breeding areas are not yet known.

Sei whale feeding by Allison Henry, NOAA

Sei whales generally travel alone or in small groups of up to six individuals. They are one of the fastest swimmers of all ocean species, attaining speeds up to 35mph for short distances. When feeding, they swim on their sides near the surface with one side of their huge mouths open taking in large amounts of water and straining out prey. Their favorite food is copepods, a tiny planktonic crustacean, but they will also consume krill, squid, and small schooling fish such as anchovies, sardines, and mackerel. They may make shallow dives to pursue schools of fish, quietly sinking below the surface; they can stay underwater for five to twenty minutes. Each whale consumes about 1,000 pounds of food daily.

Sei whale mother & calf, by Christin Khan, NOAA, Jun 2014

Sei whales reach sexual maturity between six and twelve years old, and a young adult is about 45 feet in length. Females are slightly larger than males. Gestation is 11 to 13 months, and each female mates once every two to three years. One calf is born in winter. A newborn is about fifteen feet in length and weighs 1500 pounds at birth. Calves remain with their mother for six to nine months before being weaned off its mother’s milk. Males are polygynous where one male has mating rights with several females.

Sei whales were overhunted in the mid-1960s for meat and oil after blue whale and fin whale populations were decimated in earlier years. They were added to the IUCN Red List as endangered in 1970. Their only natural predator is a pack of orcas. Massive die-offs have been recorded in the last fifty years, and evidence suggests the cause is red tides, a harmful algal bloom that severely depletes oxygen levels in large areas and may last for several weeks or months.

Other threats include entanglement in fishing gear, leading to whales dragging the gear for long distances, ultimately tiring them to a point where feeding and breeding are impossible. Climate change affecting ocean water temperatures and currents is altering prey distribution and availability resulting in less successful foraging. Opening more shipping lanes in polar regions along the edges of sei whale territory, another result of climate change, contributes to more vessel strikes. Shipping also increases ocean noise, making long-range communications for all species more difficult; however, the impacts from this on the sei whale population is not well understood.

The sei whale remains a species with more mystery than knowledge. You can learn more about cetaceans in general from your local natural history museum or come to the Jurica-Suchy Nature Museum at Benedictine University to see a full skeleton of a sei whale on display.

Flamingos

The greater flamingo, Phoenicopterus roseus, with its long neck and legs, hooked downward bill, and bright pink plumage can be found on five of the seven continents, not including Australia or Antarctica. Only one of the six species is native to the continental U.S., the American greater flamingo, Phoenicopterus ruber, and its native range encompasses only the far southern portions of Florida. Three additional species are found in the Caribbean and northeastern and southwestern portions of South America, plus two species are native to coastal areas of Europe, Africa , and Asia.

Flamingos are found in all types of shallow water habitats. They forage in both saltwater lakes and coastal lagoons, in addition to freshwater wetlands, ponds, and mudflats. They are able to eat prey found in very alkaline waters that most other avian species cannot tolerate. Feral birds, ones that have escaped captivity and are now breeding in the wild, from the other three species found in North and South America have formed several colonies along the southeastern coast of the U.S.

The name flamingo comes from a Spanish word meaning flame, bright and red in color. Immature birds are gray or brown. They absorb carotene, a reddish-yellow pigment, from their food, which slowly changes their plumage to light pink, deepening to darker shades including reds and oranges. It takes about three years until a bird attains the bright pink adult plumage everywhere except their flight feathers which are jet black and can be seen only when their wings are extended.

^{Greater Flamingo chick in water by JHVEPhoto, Getty Images}

Flamingos have the longest neck and legs of any native bird in the U.S. Wingspans on full-grown adults may reach five feet. Flying in a V-formation, flocks move quickly, with necks extended, taking short, strong wingbeats. Flamingos call is a strong honking, sometimes hard to distinguish from geese, to maintain the group’s cohesion in flight. Webbed feet provide stability on soft sand, mudflats, and in shallow waters along lake bottoms. Flamingos are excellent swimmers, and they use their webbed feet to stabilize their bodies in the water when reaching downward for food growing in deeper lakes and ponds.

^{Flamingo head, by XavierMarchant, Getty Images}

A flamingo’s bill is sharply angled downward in the middle. On most birds, the upper bill is part of the bones of the head, heavier and immovable. On flamingos, this is reversed and the upper bill can be used as a flap against a heavy lower bill. When feeding, the bird lowers its head, turning the bill upside down, sweeping it from side to side through the water. A central groove in the lower bill contains space for a fat tongue, used to push and pull higher volumes of water through the bill. The edges of the bill are lined with rows of horny plates called lamellae that strain out crustaceans, mollusks, and small insects. Flamingos are typically night feeders, resting during the day.

Flamingos roost in single species colonies. They will only breed if they are part of a large group, and breeding occurs for all at the same time. Nest mounds are volcano-shaped, arranged close by one another on a mudflat. Each breeding pair of birds lays only one egg on top of its mound. Parents take turns incubating the egg while the other is foraging. Chicks stay with the parents for four to six weeks after hatching, until they are able to feed themselves. Still unable to forage and in need of protection, all of the chicks in larger colonies may form one group called a creche. The group can be guarded by only a few adults, giving the rest of the colony the opportunity to forage for themselves and bring back food for the creche.

^{Nesting Rose Flamingo with egg in nest, by Artush, Getty Images}

^{Chick and mother, by tane-mahuta, Getty Images}

Toward the end of the 1800s, feather collecting for the millinery markets adversely impacted many bird populations. However, this did not include flamingos because their feathers quickly lose the pink color once they are removed from the bird. Today, flamingo populations around the world are shrinking due to habitat loss. Much of their native habitat is wetland coastal areas being developed. In addition, flamingos do not have the capacity to switch diets, and as more wetlands are drained or polluted, food sources are continually disappearing.

Look for these magnificent birds at your local zoo, or consider a trip to see them in many of the nature areas in southern Florida.

At The Waterhole

Last week, we discovered adaptations that allow elephants to deal with gravity and heat. Asian elephants live mostly in tropical forests that are warm from plenty of sunlight, although very little light reaches through the canopy to the forest floor. Rainfall may be intermittent, and shade-tolerant vegetation changes with a lack or an abundance of water. African savannas have lots of grasslands with a few trees and shrubs. They have distinct wet and dry periods, but grasses grow deep root systems that sustain them throughout the year. African woodlands are more open than Asian forests allowing a variety of trees and shrubs that grow well in full sunlight.

Elephants live in large groups, called herds, led by the strongest adult female. The herd members include all the females plus any males who not yet teenagers. The matriarch knows where to find food and water. She is aggressive when it comes to protecting the rest of the herd and is always the first to confront any threat. Males grow into bulls and will start to fight other males in their teen years. Once this aggression starts, the matriarch will kick the young bull out of the family. Bulls travel alone or together with other bulls, but it is a dangerous time for them because they do not have the support and knowledge of the matriarch for finding food and water.

_{^{The Herd by WLDavies, Getty Images Signature}}

Elephants are old enough to mate in their mid-teens. Pregnancy lasts 18-22 months, and each cow has a baby once every five years until they are in their forties. The herd is very social and several females take care of each calf. Water holes are places where the herd engages in many social activities. Elephants use water to drink, to swim and play in, and to bathe. However, bathing for an elephant means getting dirty, not clean. Elephants stir up the edges of a water hole to create mud to wallow in. Or they will cover themselves with water followed by dirt sprayed on their bodies with their trunks. Dried mud provides cooling from the sun and keeps biting insects away from tender skin. Elephants love water and bathe often, helping to keep skin moisturized.

Lovely mud by bucky_za, Getty Images Signature

Food eaten daily includes about 300 pounds of grass, tree bark, fruit, and other green vegetation. Elephants also need salt to supplement their diet. Their tongues are too short to lick anything not in their mouth, so they use their tusks to dig furrows in the ground and pile up soil and stones. Large stones can be placed into their mouth to lick salt from, and small stones are ground up by their huge molars. Food eaten daily includes about 300 pounds of grass, tree bark, fruit, and other green vegetation.

African elephants are larger than Asian elephants and males are larger than females in all species. Asian elephants average life span is about 80 years in the wild, while African elephants live only 60 years. They are excellent swimmers, often submerging their whole body underwater except for their trunks, which are used as snorkels to breathe. On land, they are slow moving, but can run short distances at better than 20 mph. They use many vocalizations to communicate such as grunts, rumbles, trumpets, screams, and purrs, and they can use their trunks to modulate sounds.

A thousand years ago, ivory was a hot commodity, and hunters exterminated elephants in North Africa. In the last century, after remaining populations were severely depleted by the late 1800s, many countries banned the trade of ivory. Elephants are recovering today, but poaching continues to be a serious threat. As more humans have moved into their native ranges, existing populations have to live in smaller areas. At their rate of food consumption, vegetation does not have enough time to grow back, and herds today are experiencing food shortages. Several conservation organizations are working to provide land for the establishment of wider ranges, care for orphaned elephants, and combat poaching.

You can see and learn more about these wondrous animals at your local zoo or natural history museum.

^{Clockwise above: African bush elephants by designerpoint, Pixabay; Masai Mara elephants by tankbmb, Getty Images; African elephant by Donvanstaden, Getty Images; Friends by cocoparisienne, Pixabay; Asian elephant by miharing, Getty Images}