Form, performance and trade-offs in swimming and stability of armed larvae

Diverse larval forms swim and feed with ciliary bands on arms or analogous structures. Armed morphologies are varied: numbers, lengths, and orientations of arms differ among species, change through development, and can be plastic in response to physiological or environmental conditions. A hydromechanical model of idealized equal-armed larvae was used to examine functional consequences of these varied arm arrangements for larval swimming performance. With effects of overall size, ciliary tip speed, and viscosity factored out, the model suggested trade-offs between morphological traits conferring high swimming speed and weight-carrying ability in still water (generally few arms and low arm elevations), and morphologies conferring high stability to external disturbances such as shear flows (generally many arms and high arm elevations). In vertical shear, larvae that were passively stabilized by a center of buoyancy anterior to the center of gravity tilted toward and consequently swam into downwelling flows. Thus, paradoxically, upward swimming by passively stable swimmers in vertical shear resulted in enhanced downward transport. This shear-dependent vertical transport could affect diverse passively stable swimmers, not just armed larvae. Published descriptions of larvae and metamorphosis of 13 ophiuroids suggest that most ophioplutei fall into two groups: those approximating modeled forms with two arms at low elevations, predicted to enhance speed and weight capacity, and those approximating modeled forms with more numerous arms of equal length at high elevations, predicted to enhance stability in shear

When is dispersal for dispersal? Unifying marine and terrestrial perspectives

Recent syntheses on the evolutionary causes of dispersal have focused on dispersal as a direct adaptation, but many traits that influence dispersal have other functions, raising the question: when is dispersal 'for' dispersal? We review and critically evaluate the ecological causes of selection on traits that give rise to dispersal in marine and terrestrial organisms. In the sea, passive dispersal is relatively easy and specific morphological, behavioural, and physiological adaptations for dispersal are rare. Instead, there may often be selection to limit dispersal. On land, dispersal is relatively difficult without specific adaptations, which are relatively common. Although selection for dispersal is expected in both systems and traits leading to dispersal are often linked to fitness, systems may differ in the extent to which dispersal in nature arises from direct selection for dispersal or as a by-product of selection on traits with other functions. Our analysis highlights incompleteness of theories that assume a simple and direct relationship between dispersal and fitness, not just insofar as they ignore a vast array of taxa in the marine realm, but also because they may be missing critically important effects of traits influencing dispersal in all realms

A Vermetid Gastropod with Complex Intracapsular Cannibalism of Nurse Eggs and Sibling Larvae and a High Potential for Invasion.

v. ill. 23 cm.QuarterlyA vermetid gastropod, previously unreported from the Pacific Ocean, was found at O‘ahu, Hawai‘i, in aquariums at the Kewalo Marine Laboratory, in fouling communities on docks, and on intertidal and shallow subtidal coral rubble. It also occurs on coral rubble in Florida. Eggs, or nurse eggs, and early embryos are about 100 mm in diameter. Young are brooded in 1–13 stalked capsules attached inside the tubular shell. Intracapsular development involves an unusual complex adelphophagy (sibling cannibalism). Most eggs are nondeveloping nurse eggs. Ten to 20 eggs develop into apparently normal small veligers. Of these most arrest as small veligers, but a few grow to hatch as large pediveligers or juveniles. The species has a high potential for invasion and establishment following maritime transport or natural rafting. Protected intracapsular development ends with the release of crawling hatchlings that also produce mucous threads on which they can drift. Juveniles settle readily on hard substrata. An apparent rarity or absence of males suggests long-term sperm storage, hermaphroditism, or parthenogenesis, any of which could aid colonization. Adults and juveniles occur in fouling communities and can survive extended periods in still seawater and at low food levels. The species’ global distribution and history of invasions are unknown. We predict widespread distribution and invasions in warm waters

Multiple origins of feeding head larvae by the Early Cambrian

In many animals the head develops early, most of the body axis later. A larva composed mostly of the developing front end therefore can attain mobility and feeding earlier in development. Fossils, functional morphology, and inferred homologies indicate that feeding head larvae existed by the Early Cambrian in members of three major clades of animals: ecdysozoans, lophotrochozoans, and deuterostomes. Some of these early larval feeding mechanisms were also those of juveniles and adults (the lophophore of brachiopod larvae and possibly the ciliary band of the dipleurula of hemichordates and echinoderms); some were derived from structures that previously had other functions (appendages of the nauplius). Trochophores that swim with a preoral band of cilia, the prototroch, originated before divergence of annelids and molluscs, but evidence of larval growth and thus a prototrochal role in feeding is lacking for molluscs until the Ordovician. Feeding larvae that definitely originated much later, as in insects, teleost fish, and amphibians, develop all or nearly all of what will become the adult body axis before they begin feeding. On present evidence, head larvae, including feeding head larvae, evolved multiple times early in the evolution of bilaterian animals and never since.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The behavior of planktotrophic echinoderm larvae;: mechanisms, regulation, and rates of suspension feeding

Thesis (Ph. D.)--University of Washington

Heterochronic Developmental Plasticity in Larval Sea Urchins and Its Implications for Evolution of Nonfeeding Larvae

Preexisting developmental plasticity in feeding larvae may contribute to the evolutionary transition from development with a feeding larva to nonfeeding larval development. Differences in timing of development of larval and juvenile structures (heterochronic shifts) and differences in the size of the larval body (shifts in allocation) were produced in sea urchin larvae exposed to different amounts of food in the laboratory and in the field. The changes in larval form in response to food appear to be adaptive, with increased allocation of growth to the larval apparatus for catching food when food is scarce and earlier allocation to juvenile structures when food is abundant. This phenotypic plasticity among full siblings is similar in direction to the heterochronic evolutionary changes in species that have greater nutrient reserves within the ova and do not depend on particulate planktonic food. This similarity suggests that developmental plasticity that is adaptive for feeding larvae also contributes to correlated and adaptive evolutionary changes in the transition to nonfeeding larval development. If endogenous food supplies have the same effect on morphogenesis as exogenous food supplies, then changes in genes that act during oogenesis to affect nutrient stores may be sufficient to produce correlated adaptive changes in larval development

Henricia pumila Eernisse, Strathmann & Strathmann, 2010, n. sp.

<i>Henricia pumila</i>, n. sp. <p>Figs. 1 B, 3B–D, 4B–C, 5B, 5D, 5F–G</p> <p> <b>Type Material:</b> Holotype USNM 1116585; paratypes USNM 1116586; CASIZ 180559 and 180560; LACM 1987- 519.001 and 2005-065.001; MFS 109</p> <p> <b>Type Locality:</b> Mar Vista Resort, San Juan Island, Washington, USA (48°28.595ʹN 123°04.015ʹW), rocky intertidal under rock in tidepool</p> <p> ? <i>Cribrella laeviuscula</i> var. <i>crassa</i> H.L. Clark 1901:328</p> <p> <i>Henricia leviuscula</i> variety F, in part, Fisher 1911 (see also Feder, 1980; Lambert, 1981; Mah, 2007) <i>Henricia leviuscula</i> (<i>non</i> Stimpson, 1857); in part, Hopkins, 1967: 19 –23, 65–68</p> <p> <b>Other material examined:</b> More than 100 specimens in our collections from the San Juan Archipelago, San Juan Co., Washington, plus other specimens from southern Vancouver Island, British Columbia, Canada, intertidal; Bodega Head, Sonoma Co., California, intertidal; Franklin Pt., San Mateo Co., California, intertidal; Monterey Breakwater, Monterey Co., California, approx. 12–15 m, including one brooding female; Shelter Cove, between Shell Beach and Pismo Beach, San Luis Obispo Co., California, intertidal; Arbolitos, south of Punta Banda, Baja California, Mexico, intertidal. Museum specimens identified included: USNM 1083883 (3 in lot), Carmel, Monterey Co., California; USNM E3831 (2 in lot), Monterey Bay, California; USNM E3832 (2 in lot), Strait of Juan de Fuca, Washington; USNM E21533, San Nicolas Id., California; USNM 1083885 (3 in lot), Puget Sound, Washington; CASIZ 0 0 8558 Crescent City, California (1 specimen in alcohol, likely “variety F” voucher for Fisher, 1911:285); LACM 1959-281.12 (1 specimen), Monterey Co., California, intertidal, 36°32’N 121°56’W; LACM 1928-3.1, Pacific Grove, California, intertidal. We have additionally examined images of seastars from the vicinity of Sitka, Alaska (Fig. 3 C) and from Cape Arago, Oregon (Fig. 3 D) that appear to be the same species.</p> <p> <b>Diagnosis.</b> Small in size; rays stout and short (R/r less than 5), aboral pseudopaxillae well-spaced, bearing up to 50 short spines with fenestrated, crystalline, smooth-sided shafts tipped by up to 10 heavy sharp points that do not noticeably splay. Aboral color in life usually a mottled pattern of ochre, brown, gray, rust-red, or yellow; oral color yellow to cream. Gonopores orally-directed, eggs non-buoyant, development benthic and brooded.</p> <p> <b>Description.</b> Holotype (Figs. 3 B, 4B, 5D, 5F), collected by RRS and MFS on March 30, 2005, is a medium-sized specimen, in life R = 19.7 mm, r = 6.4 mm. Madreporal ray 6.8 mm wide at base. Living aboral colors are ochre mottled with red-brown spots on every ray, orange-red around the anus extending toward one interradius, and orange at the ray tips (Figs. 3 B). Madreporite cream yellow. Oral color orange yellow. A large aboral pseudopaxilla with 25 spines (Fig. 4B, 5 D, 5F).</p> <p>Most specimens have 5 rays; 4- or 6-rayed individuals are rare. The rays taper rather evenly from base to tip but are short and stout. Among 34 specimens from the San Juan Archipelago (the largest having R = 29.4 mm and r = 6.3 mm and the smallest having R = 4.1 mm and r = 1.4 mm), R/r varied from 1.8 to 4.7, average 3.0. Aboral color usually mottled, the mix may include yellow, ochre, brown, rust-red and gray, all colors not always present on each individual (southern specimens show a greater range of mottling); oral color cream to orange yellow. Madreporite distinct; madreporal spines grouped at the periphery and in single rows across the center and the same size as the aboral pseudopaxillar spines. Aboral pseudopaxillae well-spaced and separated by recessed tissue and papular areas containing 1 to 4 papulae, the maximum number increasing with body size. Aboral pseudopaxillae oval or irregularly oblong on the disc and oval to crescentic on the rays consisting of tissue-covered spines in groups of 2 to 50, usually 12 to 45, the number increasing with body size.</p> <p>Aboral spines are short and stout and terminate in multiple short sharp points that do not markedly splay and so are directed more or less distally (Figs. 5B, 5 D, 5F), which can be obscured by tissue in living or airdried (Fig. 5 G) specimens. On the rays, two marginal and one ventrolateral series of pseudopaxillae form regular and obvious rows flanking the ambulacral plates that edge the ambulacral furrow. Near the ray base, a small triangle of interradial pseudopaxillae is enclosed between the superomarginal series, as it descends from the aboral disc to lie along the ray side, and the inferomarginal series. Both the supero- and inferomarginal pseudopaxillae are slightly larger than the aboral pseudopaxillae and extend to the ray tip in 1:1 correspondence with the ambulacral plates. The ventrolateral pseudopaxillae are small and this series extends half to three-fourths of the length of the ray (Fig. 1 B, 4C). Among specimens with R ranging from 9.0 to 29.4 mm, the ratio of ventrolateral to adambulacral pseudopaxillae (V/A, counted from mouth to ray tip) ranged from 0.34 to 0.79, averaging 0.62 (N = 53; holotype V/A = 0.74).</p> <p>A regular series of single papulae occurs between the inferomarginal and ventrolateral pseudopaxillae and single papulae between some ventrolateral and adambulacral pseudopaxillae.</p> <p>Near the base of the ray, superomarginal pseudopaxillae have 12–37 spines each; inferomarginals, 10–32; and ventrolaterals, 5–20. Number of spines per pseudopaxilla generally increases with body size. Each adambulacral plate bears one thin, curved deep-furrow spine and 6–14, usually no more than 10, large, slightly curved, columnar spines in one row that becomes double then triple farthest from the ambulacral furrow. The large spines nearest the furrow are blunt-ended with finely spinous surfaces, the tips sometimes slightly flattened but not spatulate; those farther from the furrow are smaller and more coarsely spinous with sharp terminal points but not radiating thorns. On the holotype, the largest adambulacral spine is about 500 µm long and the points at the tip span 160–200 µm.</p> <p> <b>Distribution.</b> <i>H. pumila</i> is the only small, brooding species of this genus presently known in Puget Sound and the San Juan Archipelago, Washington. It seems to be a widespread Pacific Coast shallow-water coastal species. In the north, it occurs in southern British Columbia, Canada and probably ranges further north to Sitka, Alaska, USA. The southern-most record is from areas of cold-water upwelling at Arbolitos, south of Punta Banda, Baja California, Mexico, but the species appears to skip over southern California, with the nextmost southern record near Pismo Beach, California, north of Pt. Conception. Despite the lack of records from southern California, it might be present in the Channel Islands or in unexplored subtidal areas.</p> <p> <b>Reproduction.</b> We have assumed sexes are separate but have not dissected gonads to thoroughly search for evidence of hermaphroditic tissues, as is known for some small brooding marine invertebrates (e.g., Strathmann <i>et al.</i>, 1984; Eernisse, 1988; Colgan <i>et al.</i>, 2005; Keever and Hart, 2008). Eggs are shed through gonopores on the oral side of the disc edge between rays (Chia, 1966; Hopkins, 1967), in contrast to their aboral position in <i>H. leviuscula</i> and other free-spawning species. Eggs about 1144 µm diameter (Strathmann <i>et al.</i>, 2002) are neither buoyant nor sticky when shed and are held beneath the maternal body with the rays spiraled, pinwheel fashion, around a slightly elevated disc (R. Strathmann, unpubl. observ.). Embyos are brooded under the disc and emerge as crawl-away juveniles. Brooding in rocky low intertidal areas of the San Juan Archipelago and central California has been seen in January to April. The Atlantic deep-water congener, <i>Henricia lisa</i>, has recently been shown to be a facultative brooder (Mercier and Hamel, 2008) and, although the mode of brooding differs, the same possibility exists for <i>H. pumila</i> and other asteroid species known to brood.</p> <p> <b>Etymology.</b> From the Latin for dwarf, the term used by Fisher (1911) for the small adult body size of this species.</p> <p> <b>Remarks.</b> It is possible that this species is the same as Hubert Lyman Clark’s (1901) stout-rayed variety <i>Cribrella</i> (= <i>Henricia</i>) <i>laeviuscula</i> [sic] variety <i>crassa</i> from Puget Sound. Clark was an affiliate of Olivet College, Olivet, MI, about the time he described this variety by only its body size and ray shape. The museum at Olivet College was unfortunately destroyed by fire in 1968, and most of the records were lost (Marie Davis to Robert Woollacott, pers. comm.). We have not found types for Clark’s nominal variety in museums where it seemed plausible that he might have deposited material, including the Museum of Comparative Zoology at Harvard University (where Clark was later curator of echinoderms from 1910 to 1946) or the American Museum of Natural History (Clark reported that the specimens were collected in Puget Sound by a group from Columbia University, and Columbia’s museum later became part of the AMNH collections). A partially dissected dried specimen was found at Harvard’s MCZ; its only label is clearly not the original because it reads “ <i>Henricia laeviuscula crassa</i> (Clark) Locality: Puget Sound, Washington” (MCZ 1046). The morphology of this specimen corresponds to <i>H. pumila</i> but the entries for it in the accession catalogue and a 1930s list of specimens do not give collection information or an accession date. Given the brevity of the description and the lack of verifiable type material, we consider Clark’s varietal name, <i>crassa</i>, to be a <i>nomen dubium</i>, as similarly concluded by Fisher (1911, 1930) and Verrill (1914).</p> <p> Fisher’s (1911) specimens of the small form that he called <i>H. leviuscula</i> variety F were collected from the vicinities of Monterey, San Francisco, and Crescent City in California and the Straits of [Juan de] Fuca and Puget Sound in Washington. Although Fisher knew some of these to be brooders, and described the brooding posture as arched, his specimens (see also Kozloff, 1996; Mah, 2007) may have included more than the one species we describe here as <i>H. pumila</i>.</p> <p> There is at least one other at least partly co-occurring, and probably undescribed, small-bodied species from British Columbia south to northern Baja California. Yet another species is usually small and is so far known from the subtidal of central and southern California (D. J. Eernisse and M. Strathmann, in prep.). Both of these species have finer and more numerous spines per plate. Nothing is yet known of their life history traits so the possibility remains that one or both might be brooders. Other <i>Henricia</i> species are known to be brooders but differ in their distribution and morphology. <i>H. tumida</i> Verrill 1909 grows larger and has broader, thicker arms and is reported from the Aleutians Islands, Alaska, and the Bering Sea. It was discussed as <i>H. sanguinolenta eschrichtii</i> or <i>H. tumida</i> by Fisher (1911, 1930), and as <i>H. tumida</i> or <i>H. tumida borealis</i>, or possibly as <i>H. arctica,</i> by Verrill (1909, 1914). Djakonov (1950: 85–86) later described and illustrated specimens of <i>H. tumida, H. tumida borealis,</i> and a similar smaller species, <i>H. arctica</i>, from the Sea of Okhotsk and the Bering Sea. He reported that <i>H. arctica</i> is also found in the Litke Strait and off Cape Lisburne, Alaska. It is not known if <i>H. arctica</i> is a brooding species. Small brooding species have been reported from Japan, and the development of one, <i>H. nipponica</i>, has been described (Komatsu & Tayayama 1980). We have not studied <i>H. nipponica</i> but believe it unlikely to be the same as <i>H. pumila</i> because nothing resembling <i>H. pumila</i> is yet known from the intervening Aleutian Islands. We have seen little genetic evidence of marine species with such a disjunct eastern and western Pacific distribution. Thus, we speculate that any brooding <i>Henricia</i> in the northwestern Pacific might be closely related to, but not conspecific with, <i>H. pumila</i>. An extension of the study of small brooding species of <i>Henricia</i> to the far northern and northwestern Pacific is still needed.</p>Published as part of <i>Eernisse, Douglas J., Strathmann, Megumi F. & Strathmann, Richard R., 2010, Henricia pumila sp. nov.: A brooding seastar (Asteroidea) from the coastal northeastern Pacific, pp. 22-36 in Zootaxa 2329</i> on pages 30-34, DOI: <a href="http://zenodo.org/record/275445">10.5281/zenodo.275445</a&gt

Henricia Gray 1840

Henricia Gray 1840 (type species Asterias oculata Pennant 1777 by monotypy)Published as part of Eernisse, Douglas J., Strathmann, Megumi F. & Strathmann, Richard R., 2010, Henricia pumila sp. nov.: A brooding seastar (Asteroidea) from the coastal northeastern Pacific, pp. 22-36 in Zootaxa 2329 on page 25, DOI: 10.5281/zenodo.27544