Invertebrate Biology

Cover image for Vol. 133 Issue 3

Edited By: Bruno Pernet

Impact Factor: 1.061

ISI Journal Citation Reports © Ranking: 2013: 65/102 (Marine & Freshwater Biology); 72/152 (Zoology)

Online ISSN: 1744-7410

Cover Gallery


Volume 133, Issue 1
Volume 133, Issue 2
Ctenophores are gelatinous marine animals that use cilia for an unusually wide range of purposes, including locomotion, feeding, escape, and sensory responses, coordinated in part via epithelial and mesogleal nerve nets. In this issue (pp. 1–46), Tamm reviews a large body of work on the form, function, control, and development of ciliary structures in ctenophores. These data are particularly useful given the recent release of the whole genome of the ctenophore Mnemiopsis leidyi, along with phylogenomic analyses suggesting that ctenophores are the earliest living animals, a finding important for our understanding of the evolution of mesoderm and nervous systems. In addition to providing a timely review of the role of cilia in the life of ctenophores, Tamm also provided our cover illustration, a cut paper collage showing a lobate ctenophore like Mnemiopsis leidyi dining on copepods (printed and distributed by Local Colors Gallery, Woods Hole, Massachusetts at Invertebrate biologists have long been making observations of the fine structure of invertebrate sperm, with the aims of using these data to evaluate phylogenetic hypotheses and to understand how the functional requirements of sperm transfer and fertilization have shaped the evolution of sperm form. In this issue (pp. 146–157), Eckelbarger & Hodgson describe the formation and ultrastructure of the sperm of the spionid annelid Spio setosa. These cells have several unusual features, including a highly coiled nucleus. This is clearly seen in the cover illustration, a transmission electron micrograph of numerous sperm packed together in the spermatheca of a female of S. setosa (the largest nuclei visible in this section are about 10 μm in length along the axis of coiling). In addition, mature sperm in the male contain numerous membrane-bounded inclusions; these are absent from sperm stored in the female spermatheca, suggesting a function during transfer or storage. Additional comparative studies are required to fully understand the phylogenetic significance of these observations, and functional studies are needed to understand how sperm form is related to sperm function in this species. (Micrograph by Kevin Eckelbarger and Alan Hodgson.)


Volume 132, Issue 1
Volume 132, Issue 2
Effective monitoring and conservation of animal populations requires knowledge of their dynamics, but these long time-series data are relatively rare in the literature, especially for threatened invertebrates. In this issue (pp. 46–51), Lawrence, Samways, Kelly, and Henwood describe a long time-series study of the population dynamics of the Seychelles Giant Millipede, Sechelleptus seychellarum, a large (the specimens pictured on the cover are ~20 cm in length) millipede endemic to granitic islands of the Seychelles. For 11 years, they monitored populations of this species on Cousine Island, the only Seychelles granitic island that is free of potentially predatory invasive mammals. Millipedes were most abundant and active during high rainfall months, leading the authors to suggest that any population manipulations (e.g., translocations, augmentations) should be done during this season. In addition, they suggest that control efforts for the invasive African big-headed ant, which involve the use of a pesticide that may affect millipedes, should be confined to low rainfall months, when millipede activity is at its lowest. (Image by James Lawrence.) Most living cephalopods can alter the color of their skin on fine spatial scales and rapid time scales, producing stunning visual displays that are important in prey capture, predator avoidance, mating, and communication. These color changes are driven in large part by the expansion or retraction of many thousands of pigmented chromatophore organs. In cephalopod chromatophore organs, pigment cell expansion is controlled by the contraction of radially arranged muscle cells. A number of chromatophore pigment cells surrounded by their radial muscles are shown in the cover image; the largest, most central pigment cell is roughly 400 μm in diameter. How radial muscles adhere to the flexible, elastic skin is an important, but previously undescribed, anatomical feature that enables chromatophore function. In this issue (pp. 120–132), Bell et al. use confocal and electron microscopy to show that the distal ends of the chromatophore radial muscle fibers of the squid Doryteuthis pealeii branch extensively, and that these branches are connected to the underlying basal lamina by costamere-like projections. These detailed observations of the form and function of cephalopod chromatophores may be useful as a source of “bio-inspiration” for the design of soft, flexible, adaptive displays. (Confocal micrograph by George Bell and Trevor Wardill.)

Volume 132, Issue 3
Volume 132, Issue 4
Methods to mark individuals are extremely useful in studies of the growth or dispersal of individuals. Animals that build calcitic skeletons can often be marked using fluorescent compounds – e.g., calcein or tetracycline – that are incorporated into their growing skeletons, and can later be viewed under appropriate illumination. In this issue (pp. 251–269), Johnson et al. report on a careful analysis of mark persistence and allometries of growth in the green sea urchin, Strongylocentrotus droebachiensis, after marking with four different fluorochromes. Marks were externally visible (thus allowing non-lethal examination) for nearly a year, and visible on internal structures (such as the 1.3 mm long jaw demipyramid labeled with calcein shown on the cover) for at least two years. Their results will aid in the design and interpretation of both laboratory and field studies of the growth, ecology, and evolution of sea urchins. (Fluorescence micrograph by Jonathan Allen and Amy Johnson.) Siboglinid annelids have long interested biologists because of their lack of a functional gut, their obligate nutritional symbioses with bacteria, and the unusual marine habitats (e.g., cold seeps and hydrothermal vents) they inhabit. Members of the siboglinid genus Osedax, first discovered in 2002, occupy yet another unusual habitat – burrows in the bones of dead vertebrates on the seafloor (hence their common name of “boneworms”). The macroscopic boneworms that were first discovered were females; males are microscopic, and live in harems in the gelatinous tubes formed by females. For several years it has been known that females spawn fertilized primary oocytes, as shown in the cover image of a female of an undescribed species of Osedax, O. ‘orange collar’ (the female’s trunk is ~0.4 mm in diameter). This suggests that fertilization is internal, but the mechanism of sperm transfer and location of fertilization have not been identified. In this issue (pp. 368–385), Katz and Rouse address those questions using a detailed analysis of the morphology of the female reproductive system in four species of Osedax. Their results show that males transfer unpackaged sperm to females, where it is stored in ovarian tissue before being used to fertilize oocytes. In addition to enhancing our understanding of the reproductive biology of boneworms, their data are useful in assessing homologies in the reproductive systems of siboglinids more broadly. (Macro photograph by Greg Rouse.)