Tardigrades and Their Emergence as Model Organisms

Experimentally tractable organisms like C. elegans, Drosophila, zebrafish, and mouse are popular models for addressing diverse questions in biology. In 1997, two of the most valuable invertebrate model organisms to date – C. elegans and Drosophila – were found to be much more closely related to each other than expected. C. elegans and Drosophila belong to the nematodes and arthropods respectively, and these two phyla and six other phyla make up a clade of molting animals referred to as the Ecdysozoa. The other ecdysozoan phyla could be valuable models for comparative biology, taking advantage of the rich and continual sources of research findings as well as tools from both C. elegans and Drosophila. But when the Ecdysozoa was first recognized, few tools were available for laboratory studies in any of these six other ecdysozoan phyla. In 1999 I began an effort to develop tools for studying one such phylum, the tardigrades. Here, I describe how the tardigrade species Hypsibius exemplaris and tardigrades more generally have emerged over the past two decades as valuable new models for answering diverse questions. To date, these questions have included how animal body plans evolve and how biological materials can survive some remarkably extreme conditions.

Selective Drivers of Simple Multicellularity

In order to understand the evolution of multicellularity, we must understand how and why selection favors the first steps in this process: the evolution of simple multicellular groups. Multicellularity has evolved many times in independent lineages with fundamentally different ecologies, yet no work has yet systematically examined these diverse selective drivers. Here we review recent developments in systematics, comparative biology, paleontology, synthetic biology, theory, and experimental evolution, highlighting ten selective drivers of simple multicellularity. Our survey highlights the many ecological opportunities available for simple multicellularity, and stresses the need for additional work examining how these first steps impact the subsequent evolution of complex multicellularity.

Lifespan Extension in Long-Lived Vertebrates Rooted in Ecological Adaptation

Contemporary studies on aging and longevity have largely overlooked the role that adaptation plays in lifespan variation across species. Emerging evidence indicates that the genetic signals of extended lifespan may be maintained by natural selection, suggesting that longevity could be a product of organismal adaptation. The mechanisms of adaptation in long-lived animals are believed to account for the modification of physiological function. Here, we first review recent progress in comparative biology of long-lived animals, together with the emergence of adaptive genetic factors that control longevity and disease resistance. We then propose that hitchhiking of adaptive genetic changes is the basis for lifespan changes and suggest ways to test this evolutionary model. As individual adaptive or adaptation-linked mutations/substitutions generate specific forms of longevity effects, the cumulative beneficial effect is largely nonrandom and is indirectly favored by natural selection. We consider this concept in light of other proposed theories of aging and integrate these disparate ideas into an adaptive evolutionary model, highlighting strategies in decoding genetic factors of lifespan control.

COMPARATIVE BIOLOGY AND PREDATORY POTENTIAL OF Cryptolaemus montrouzieri ON MEALYBUGS

Comparative biology of Cryptolaemus montrouzieri on Maconellicoccus hirsutus and Pseudococcus citri revealed that it had completed its life cycle successfully on both species. The mean total developmental period (egg to pupa) was 18.1 days, when reared on P. citri and it was 20.9 days in M. hirsutus. The adults developed on P. citri had high fecundity 284.2 eggs / female and longevity 47.0 days than those developed on M. hirsutus. Analysis on the growth indices of C. montrouzieri showed more preference on P. citri with high suitability index of 2.51 than M. hirsutus (1.78). Among two life stages, adults of C. montrouzieri was more voracious and each adult consumed an average 258.7, 352.1 and 217.3 numbers on M. hirsutus while, it was 323.8, 715.6 and 328.6 number of eggs, nymphs and adults for P. citri, respectively. The grubs required 221.1, 55.1 and 36.6 numbers of M. hirsutus and 1079.0, 341.3 and 41.0 number of eggs, nymphs and adults of P. citri, respectively to complete life stages. Out of different instars of C. montrouzieri, third and fourth instars required around 92.1, 78.5 and 85.9 per cent and 88.9, 93.5 and 79.0 per cent of total eggs, nymphs and adults of P. citri and M. hirsutus consumed, respectively.

Postnatal development in a marsupial model, the fat-tailed dunnart (Sminthopsis crassicaudata; Dasyuromorphia: Dasyuridae)

Marsupials exhibit unique biological features that provide fascinating insights into many aspects of mammalian development. These include their distinctive mode of reproduction, altricial stage at birth, and the associated heterochrony that is required for their crawl to the pouch and teat attachment. Marsupials are also an invaluable resource for mammalian comparative biology, forming a distinct lineage from the extant placental and egg-laying monotreme mammals. Despite their unique biology, marsupial resources are lagging behind those available for placentals. The fat-tailed dunnart (Sminthopsis crassicaudata) is a laboratory based marsupial model, with simple and robust husbandry requirements and a short reproductive cycle making it amenable to experimental manipulations. Here we present a detailed staging series for the fat-tailed dunnart, focusing on their accelerated development of the forelimbs and jaws. This study provides the first skeletal developmental series on S. crassicaudata and provides a fundamental resource for future studies exploring mammalian diversification, development and evolution.

Comparative Biology of Coconut Leaf Beetle (Clb) Brontispa longissimi (Gestro) (Coleoptera: Chrysomelidae) on Selected Coconut Varieties

Comparative biology and development study of B. longissima Gestro was conducted using different coconut varieties namely: Baybay tall (BAYT) green, Baybay tall (BAYT) brown, Malayan Red dwarf (MRD), Malayan Yellow dwarf (MYD), Albuera dwarf (ALD), and Tacunan dwarf (TACD) varieties was investigated in the laboratory. The duration of the developmental period of B. longissimi was influenced by the different coconut varieties used as host plant. Duration from egg laying to hatching of eggs of B. longissima on tall varieties ranged from 3 to 5 days, while on dwarf varieties it took 4 to 5 days. In all varieties, Brontispa beetles underwent 5–6 instars. In addition, it was observed that the fifth and sixth instars took a longer time period compared to other instars. The total mean developmental period of Brontispa on BAYT (green and brown) was shorter in days compared to all dwarf varieties except to ALD. The results generally showed that BAYT (green and brown) seemed to be a preferred variety. There was considerably higher larvae mortality in dwarf variety like MRD (40%) than those reared in the BAYT green and brown (22.21%, 19.12%), respectively. Beetles reared on BAYT (brown) also had the highest fecundity which was statistically different from the rest of the varieties. In addition, results showed that adults reared in both BAYT (green and brown) had the highest longevity observed compared to other varieties

Comparative biology of four Rhodanthidium species (Hymenoptera, Megachilidae) that nest in snail shells

Some species of two tribes (Anthidiini and Osmiini) of the bee family Megachilidae utilize empty gastropod shells as nesting cavities. While snail-nesting Osmiini have been more frequently studied and the nesting biology of several species is well-known, much less is known about the habits of snail-nesting Anthidiini. We collected nests of four species of the genus Rhodanthidium (R. septemdentatum, R. sticticum, R. siculum and R. infuscatum) in the Czech Republic, Slovakia, Catalonia (Spain) and Sicily (Italy). We dissected these nests in the laboratory and documented their structure, pollen sources and nest associates. The four species usually choose large snail shells. All four species close their nests with a plug made of resin, sand and fragments of snail shells. However, nests of the four species can be distinguished based on the presence (R. septemdentatum, R. sticticum) or absence (R. siculum, R. infuscatum) of mineral and plant debris in the vestibular space, and the presence (R. septemdentatum, R. infuscatum) or absence (R. sticticum, R. siculum) of a resin partition between the vestibular space and the brood cell. Rhodanthidium septemdentatum, R. sticticum and R. siculum usually build a single brood cell per nest, but all R. infuscatum nests studied contained two or more cells. For three of the species (R. siculum, R. septemdentatum and R. sticticum) we confirmed overwintering in the adult stage. Contrary to R. siculum, R. septemdentatum and R. sticticum do not hide their nest shells and usually use shells under the stones or hidden in crevices within stone walls. Nest associates were very infrequent. We only found two R. sticticum nests parasitized by the chrysidid wasp Chrysura refulgens and seven nests infested with pollen mites Chaetodactylus cf. anthidii. Our pollen analyses confirm that Rhodanthidium are polylectic but show a preference for Fabaceae by R. sticticum.

Comparative Computational Modeling of the Bat and Human Immune Response to Viral Infection with the Comparative Biology Immune Agent Based Model

Given the impact of pandemics due to viruses of bat origin, there is increasing interest in comparative investigation into the differences between bat and human immune responses. The practice of comparative biology can be enhanced by computational methods used for dynamic knowledge representation to visualize and interrogate the putative differences between the two systems. We present an agent based model that encompasses and bridges differences between bat and human responses to viral infection: the comparative biology immune agent based model, or CBIABM. The CBIABM examines differences in innate immune mechanisms between bats and humans, specifically regarding inflammasome activity and type 1 interferon dynamics, in terms of tolerance to viral infection. Simulation experiments with the CBIABM demonstrate the efficacy of bat-related features in conferring viral tolerance and also suggest a crucial role for endothelial inflammasome activity as a mechanism for bat systemic viral tolerance and affecting the severity of disease in human viral infections. We hope that this initial study will inspire additional comparative modeling projects to link, compare, and contrast immunological functions shared across different species, and in so doing, provide insight and aid in preparation for future viral pandemics of zoonotic origin.