Evolution of Larval Forms
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Aquatic Critters Aquatic Critters (Pictures Not to Scale) (Pictures Not to Scale)
Aquatic Critters Aquatic Critters (pictures not to scale) (pictures not to scale) dragonfly naiad↑ ↑ mayfly adult dragonfly adult↓ whirligig beetle larva (fairly common look ↑ water scavenger for beetle larvae) ↑ predaceous diving beetle mayfly naiad No apparent gills ↑ whirligig beetle adult beetle - short, clubbed antenna - 3 “tails” (breathes thru butt) - looks like it has 4 - thread-like antennae - surface head first - abdominal gills Lower jaw to grab prey eyes! (see above) longer than the head - swim by moving hind - surface for air with legs alternately tip of abdomen first water penny -row bklback legs (fbll(type of beetle larva together found under rocks damselfly naiad ↑ in streams - 3 leaf’-like posterior gills - lower jaw to grab prey damselfly adult↓ ←larva ↑adult backswimmer (& head) ↑ giant water bug↑ (toe dobsonfly - swims on back biter) female glues eggs water boatman↑(&head) - pointy, longer beak to back of male - swims on front -predator - rounded, smaller beak stonefly ↑naiad & adult ↑ -herbivore - 2 “tails” - thoracic gills ↑mosquito larva (wiggler) water - find in streams strider ↑mosquito pupa mosquito adult caddisfly adult ↑ & ↑midge larva (males with feather antennae) larva (bloodworm) ↑ hydra ↓ 4 small crustaceans ↓ crane fly ←larva phantom midge larva ↑ adult→ - translucent with silvery bflbuoyancy floats ↑ daphnia ↑ ostracod ↑ scud (amphipod) (water flea) ↑ copepod (seed shrimp) References: Aquatic Entomology by W. Patrick McCafferty ↑ rotifer prepared by Gwen Heistand for ACR Education midge adult ↑ Guide to Microlife by Kenneth G. Rainis and Bruce J. Russel 28 How do Aquatic Critters Get Their Air? Creeks are a lotic (flowing) systems as opposed to lentic (standing, i.e, pond) system. Look for … BREATHING IN AN AQUATIC ENVIRONMENT 1. -
Visceral and Cutaneous Larva Migrans PAUL C
Visceral and Cutaneous Larva Migrans PAUL C. BEAVER, Ph.D. AMONG ANIMALS in general there is a In the development of our concepts of larva II. wide variety of parasitic infections in migrans there have been four major steps. The which larval stages migrate through and some¬ first, of course, was the discovery by Kirby- times later reside in the tissues of the host with¬ Smith and his associates some 30 years ago of out developing into fully mature adults. When nematode larvae in the skin of patients with such parasites are found in human hosts, the creeping eruption in Jacksonville, Fla. (6). infection may be referred to as larva migrans This was followed immediately by experi¬ although definition of this term is becoming mental proof by numerous workers that the increasingly difficult. The organisms impli¬ larvae of A. braziliense readily penetrate the cated in infections of this type include certain human skin and produce severe, typical creep¬ species of arthropods, flatworms, and nema¬ ing eruption. todes, but more especially the nematodes. From a practical point of view these demon¬ As generally used, the term larva migrans strations were perhaps too conclusive in that refers particularly to the migration of dog and they encouraged the impression that A. brazil¬ cat hookworm larvae in the human skin (cu¬ iense was the only cause of creeping eruption, taneous larva migrans or creeping eruption) and detracted from equally conclusive demon¬ and the migration of dog and cat ascarids in strations that other species of nematode larvae the viscera (visceral larva migrans). In a still have the ability to produce similarly the pro¬ more restricted sense, the terms cutaneous larva gressive linear lesions characteristic of creep¬ migrans and visceral larva migrans are some¬ ing eruption. -
Evolution of Direct-Developing Larvae: Selection Vs Loss Margaret Snoke Smith,1 Kirk S
Hypotheses Evolution of direct-developing larvae: selection vs loss Margaret Snoke Smith,1 Kirk S. Zigler,2 and Rudolf A. Raff1,3* Summary echinoderms, sea urchins, reveal that a majority of sea urchin Observations of a sea urchin larvae show that most species exhibit one of two life history strategies (Fig. 1).(10) species adopt one of two life history strategies. One strategy is to make numerous small eggs, which develop One strategy is to make many small eggs that develop into a into a larva with a required feeding period in the water larva that must feed and grow for weeks or months in the water column before metamorphosis. In contrast, the second column before metamorphosis. In the water column, these strategy is to make fewer large eggs with a larva that does larvae are dependent on plankton abundance for food and are not feed, which reduces the time to metamorphosis and subject to high levels of predation.(11) The other strategy thus the time spent in the water column. The larvae associated with each strategy have distinct morpholo- involves increasing egg size and maternal provisioning, which gies and developmental processes that reflect their decreases the reliance on planktonic food sources and the feeding requirements, so that those that feed exhibit time to metamorphosis, thus minimizing larval mortality. indirect development with a complex larva, and those that However, assuming finite resources for egg production, do not feed form a morphologically simplified larva and increasing egg size also reduces the total number of eggs exhibit direct development. Phylogenetic studies show that, in sea urchins, a feeding larva, the pluteus, is the produced. -
Hookworm-Related Cutaneous Larva Migrans
326 Hookworm-Related Cutaneous Larva Migrans Patrick Hochedez , MD , and Eric Caumes , MD Département des Maladies Infectieuses et Tropicales, Hôpital Pitié-Salpêtrière, Paris, France DOI: 10.1111/j.1708-8305.2007.00148.x Downloaded from https://academic.oup.com/jtm/article/14/5/326/1808671 by guest on 27 September 2021 utaneous larva migrans (CLM) is the most fre- Risk factors for developing HrCLM have specifi - Cquent travel-associated skin disease of tropical cally been investigated in one outbreak in Canadian origin. 1,2 This dermatosis fi rst described as CLM by tourists: less frequent use of protective footwear Lee in 1874 was later attributed to the subcutane- while walking on the beach was signifi cantly associ- ous migration of Ancylostoma larvae by White and ated with a higher risk of developing the disease, Dove in 1929. 3,4 Since then, this skin disease has also with a risk ratio of 4. Moreover, affected patients been called creeping eruption, creeping verminous were somewhat younger than unaffected travelers dermatitis, sand worm eruption, or plumber ’ s itch, (36.9 vs 41.2 yr, p = 0.014). There was no correla- which adds to the confusion. It has been suggested tion between the reported amount of time spent on to name this disease hookworm-related cutaneous the beach and the risk of developing CLM. Consid- larva migrans (HrCLM).5 ering animals in the neighborhood, 90% of the Although frequent, this tropical dermatosis is travelers in that study reported seeing cats on the not suffi ciently well known by Western physicians, beach and around the hotel area, and only 1.5% and this can delay diagnosis and effective treatment. -
Evolutionary Developmental Biology 573
EVOC20 29/08/2003 11:15 AM Page 572 Evolutionary 20 Developmental Biology volutionary developmental biology, now often known Eas “evo-devo,” is the study of the relation between evolution and development. The relation between evolution and development has been the subject of research for many years, and the chapter begins by looking at some classic ideas. However, the subject has been transformed in recent years as the genes that control development have begun to be identified. This chapter looks at how changes in these developmental genes, such as changes in their spatial or temporal expression in the embryo, are associated with changes in adult morphology. The origin of a set of genes controlling development may have opened up new and more flexible ways in which evolution could occur: life may have become more “evolvable.” EVOC20 29/08/2003 11:15 AM Page 573 CHAPTER 20 / Evolutionary Developmental Biology 573 20.1 Changes in development, and the genes controlling development, underlie morphological evolution Morphological structures, such as heads, legs, and tails, are produced in each individual organism by development. The organism begins life as a single cell. The organism grows by cell division, and the various cell types (bone cells, skin cells, and so on) are produced by differentiation within dividing cell lines. When one species evolves into Morphological evolution is driven another, with a changed morphological form, the developmental process must have by developmental evolution changed too. If the descendant species has longer legs, it is because the developmental process that produces legs has been accelerated, or extended over time. -