Abundance,size, and feeding success of larval shortnose suckers and Lost River suckers from different habitats of the littoral zone of Upper Klamath Lake

We examined near-shore habitat use by larval shortnose and Lost River suckers in the lower Williamson River and Upper Klamath Lake of south-central Oregon. Emergent macrophytes Scirpus, Sparganium and Polygonum supported significantly more, larger, and better-fed larvae than submergent macrophytes, woody vegetation, or open water. Abundance, size, and gut fullness were similar for sucker larvae collected from different emergent macropytes. During the larval period, there was no evidence of density dependant effects or habitat shifts. Ranked catch per unit effort data indicated potential predators also were more likely to use emergent macrophytes, but ordination indicated larvae and potential predators were differentially distributed along a vegetation structure-water depth gradient with larvae in shallow vegetated areas. Between-habitat differences appeared to be due to larval sucker selection for, or better survival in, emergent macrophytes, rather than differential access or exclusion from other habitats. The importance of emergent macrophytes appears to be related to increased foraging success and reduced predation. Because larvae in emergent macrophytes have a size and gut fullness advantage, the amount of emergent habitat could affect early survival. However, interannual differences in recruitment to the adult population may or may not be dependent on larval dynamics. Our results suggest larval sucker access to emergent macrophytes may be necessary, but perhaps not sufficient, for promoting good year class formation.     

Apoptosis in the digestive tract of herbivorous Rana pipiens larvae and carnivorous Ceratophrys ornata larvae: An immunohistochemical study

The lifespan of herbivorous Rana pipiens larvae is ～3 months, while that of carnivorous Ceratophrys ornata larvae is only about 2 weeks. During metamorphic climax, the larval gut shortens dramatically, especially in R. pipiens, and its luminal epithelium is replaced by adult‐type epithelium. To determine when programmed cell death occurs during the metamorphic restructuring of the gut, we prepared cross‐sections of the stomach, small intestine, and large intestine from representative larval stages and from juvenile frogs of both species. The sections were incubated with monoclonal antibody against active caspase‐3, one of the key enzymes in the apoptotic cascade. We observed apoptosis in some luminal epithelial cells in each of the three regions of the larval gastrointestinal tract of both species. However, apoptotic cells appeared earlier in larval stages of R. pipiens than C. ornata and few were seen in juvenile frogs of either species. The results demonstrate the occurrence of apoptosis in the metamorphic remodeling of the gut of both R. pipiens larvae and C. ornata larvae. J. Morphol., 2011. © 2011 Wiley Periodicals, Inc.     

Do differences in life‐history traits and the timing of peak mating activity between host‐associated populations of Chilo suppressalis have a genetic basis?

The development of host races, genetically distinct populations of the same species with different hosts, is considered to be the initial stage of ecological speciation. Ecological and biological differences consistent with host race formation have been reported between water‐oat and rice‐associated populations of Chilo suppressalis. In order to confirm whether these differences have a genetic basis, we conducted experiments to determine the extent to which various life‐history traits and the time of peak mating activity of these populations were influenced by the species of host plant larvae were raised on. Individuals from each population were reared for three consecutive generations on either water‐oat fruit pulp or rice seedlings. Descendants of both populations had higher larval survival rates, shorter larval developmental periods, higher pupal weight, and longer adult forewings, when reared on water‐oats than when reared on rice. The time of peak of mating activity differed between the descendants of each population, irrespective of whether they were raised on water‐oats or rice. These results indicate that although some life‐history traits of host‐associated populations of C. suppressalis are influenced by the host plant larvae are raised on, time of peak mating activity is not. Because it is a stable, objective, phenotypic trait, further research on difference in the time of peak mating activity between host‐associated populations of C. suppressalis should be conducted to clarify the mechanism responsible for host race formation in this species.     

Tail regression induced by elevated retinoic acid signaling in amphioxus larvae occurs by tissue remodeling,not cell death

The vitamin A derived morphogen retinoic acid (RA) is known to function in the regulation of tissue proliferation and differentiation. Here, we show that exogenous RA applied to late larvae of the invertebrate chordate amphioxus can reverse some differentiated states. Although treatment with the RA antagonist BMS009 has no obvious effect on late larvae of amphioxus, administration of excess RA alters the morphology of the posterior end of the body. The anus closes over, and gut contents accumulate in the hindgut. In addition, the larval tail fin regresses, although little apoptosis takes place. This fin normally consists of columnar epidermal cells, each characterized by a ciliary rootlet running all the way from an apical centriole to the base of the cell and likely contributing substantial cytoskeletal support. After a few days of RA treatment, the rootlet becomes disrupted, and the cell shape changes from columnar to cuboidal. Transmission electron microscopy (TEM) shows fragments of the rootlet in the basal cytoplasm of the cuboidal cell. A major component of the ciliary rootlet in amphioxus is the protein Rootletin, which is encoded by a single AmphiRootletin gene. This gene is highly expressed in the tail epithelial cells of control larvae, but becomes downregulated after about a day of RA treatment, and the breakup of the ciliary rootlet soon follows. The effect of excess RA on these epidermal cells of the larval tail in amphioxus is unlike posterior regression in developing zebrafish, where elevated RA signaling alters connective tissues of mesodermal origin. In contrast, however, the RA‐induced closure of the amphioxus anus has parallels in the RA‐induced caudal regression syndrome of mammals.     

Life history and host range of Sauris nr. purpurotincta,an unsuitable biological control agent for Chinese tallowtree

Foreign surveys in China discovered a defoliating insect species feeding on the leaves of Chinese tallowtree (Triadica sebifera), an invasive weed of the southeastern U.S.A. The life history of this species, Sauris nr. purpurotincta (Lepidoptera: Geometridae), was examined and larval no-choice and adult multiple-choice host range tests were conducted in quarantine to evaluate their suitability for biological control of Chinese tallowtree. The results indicated that the larvae have five instars and require approximately 22 days to complete development to the adult stage. Host range tests indicated that the larvae could not feed and complete development on most species tested. However, 40% of the larvae survived when fed leaves of Hippomane mancinella, a state-listed endangered species in Florida, and all larvae survived when fed Morella cerifera, a common native species of the southeastern U.S.A. Multiple-choice oviposition tests indicated eggs were laid on leaves of both a south Florida native plant Gymnanthes lucida and Chinese tallowtree. Considering this broad host range, this species will not be considered further for biological control of Chinese tallowtree in the U.S.A.     

Characterization and expression of p23 gene in the amphioxus Branchiostoma belcheri

The cDNA AmphiP23, encoding an amphioxus p23, was identified from the gut cDNA library of amphioxus Branchiostoma belcheri. It contains a 513 bp open reading frame corresponding to a deduced protein of 170 amino acids. Phylogenetic analysis shows that vertebrate and invertebrate p23/p23-like proteins are each grouped together, with AmphiP23 falling at the base of vertebrate p23/p23-like clade, suggesting that the divergence of vertebrate and invertebrate p23 genes probably occurs prior to the split of invertebrate/vertebrate from a common ancestor around 550 million years ago. Northern blotting reveals a ubiquitous expression pattern of AmphiP23 in all adult tissues examined, while whole mount in situ hybridization demonstrates a tissue- and stage-specific expression pattern of AmphiP23 in developing embryos and larvae. Presumably, the ubiquitous expression pattern of AmphiP23 in adult amphioxus represents the ancestral type of p23 gene prior to its split to human paralogs p23 and tsp23, while the tissue- and stage-specific expression pattern during early embryonic development implicates a role of AmphiP23 in anterior/posterior patterning.     

<Emphasis Type="Italic">Prodajus curviabdominalis</Emphasis> n. sp. (Isopoda: Epicaridea: Dajidae), an ectoparasite of mysids,with notes on morphological changes,behaviour and life-cycle

Adults and larvae of a new ectoparasitic isopod, Prodajus curviabdominalis n. sp., are described from the mysid Siriella okadai Ii collected from the Seto Inland Sea, western Japan. The adult female is found within the host marsupium with the cephalon directed posteriorly, whereas the dwarf adult male attaches to the ventral surface of the female pleon. The cryptoniscid larva usually attaches to the second or third abdominal somite of the host, using an oral sucker. Mature adults of the new species are distinguished from all other congeners by: pleon of ovigerous female strongly curved dorsally, with large swellings on ventral side; pereon of ovigerous female narrow; exopods on male uropods present; male pleon short and thick. This is the third record of a member of the Dajidae from Japan. The behaviour of the cryptoniscid larvae of the new species on the host mysid was also observed using a video camera. Larvae moved from the first attachment site, usually the second or third abdominal somite of the host mysid, into the marsupium. When host oostegites were not fully developed, larvae entered beneath the host carapace until her marsupium was fully formed. The host infected by a female P. curviabdominalis moved the oostegites rhythmically, an action which may aid the respiration of the parasite.     

Host location by the fruit fly parasitoid Diachasmimorpha krausii: role of fruit fly species,life stage and host plant

• 1 Diachasmimorpha krausii is a braconid parasitoid of larval tephritid fruit flies, which feed cryptically within host fruit. At the ovipositor probing stage, the wasp cannot discriminate between hosts that are physiologically suitable or unsuitable for offspring development and must use other cues to locate suitable hosts.
• 2 To identify the cues used by the parasitoid to find suitable hosts, we offered, to free flying wasps, different combinations of three fruit fly species (Bactrocera tryoni, Bactrocera cacuminata, Bactrocera cucumis), different life stages of those flies (adults and larvae) and different host plants (Solanum lycopersicon, Solanum mauritianum, Cucurbita pepo). In the laboratory, the wasp will readily oviposit into larvae of all three flies but successfully develops only in B. tryoni. Bactrocera tryoni commonly infests S. lycopersicon (tomato), rarely S. mauritianum (wild tobacco) but never C. pepo (zucchini). The latter two plant species are common hosts for B. cacuminata and B. cucumis, respectively.
• 3 The parasitoid showed little or no response to uninfested plants of any of the test species. The presence of adult B. tryoni, however, increased parasitoid residency time on uninfested tomato.
• 4 When the three fruit types were all infested with larvae, parasitoid response was strongest to tomato, regardless of whether the larvae were physiologically suitable or unsuitable for offspring development. By contrast, zucchini was rarely visited by the wasp, even when infested with B. tryoni larvae.
• 5 Wild tobacco was infrequently visited when infested with B. cacuminata larvae but was more frequently visited, with greater parasitoid residency time and probing, when adult flies (either B. cacuminata or B. tryoni) were also present.
• 6 We conclude that herbivore‐induced, nonspecific host fruit wound volatiles were the major cue used by foraging D. krausii. Although positive orientation to infested host plants is well known from previous studies on opiine braconids, the failure of the wasp to orientate to some plants even when infested with physiologically suitable larvae, and the secondary role played by adult fruit flies in wasp host searching, are newly‐identified mechanisms that may aid parasitoid host location in environments where both physiologically suitable and unsuitable hosts occur.

     

Demography of an endangered,long-lived fish: Informing management options in the face of cyclic and stochastic climate variation

June sucker (Chasmistes liorus) is a long-lived, endangered fish endemic to Utah Lake, Utah. For several decades June sucker have failed to recruit sufficient numbers to the adult size classes such that the current wild population consists of a small number of old adults and it continues to decline. Vital rates of June sucker are influenced by climate-driven variation in lake level and inflow from the Provo River. We used population projection matrix modeling to assess effects of cyclic and stochastic environmental variation on population growth trajectories of June sucker in Utah Lake. The stable stage distribution is dominated by stage 1 individuals (93% of the total population) in contrast to the current situation where old age classes are the most abundant. Total population size is highly influenced by the stochastic component of climate variation; whereas, the adult population of June sucker closely tracks the systematic drought cycle. If changes in survival of larvae and juveniles can be coordinated such that positive changes in both parameters can occur somewhat simultaneously, then each parameter would only have to be increased by a factor of about 8.8 to achieve sustainable population growth (compared to a 77-fold increase for each parameter separately). Stochastic climatic variation has relatively little long-term effect on population growth. However, the multidecadal cyclic pattern of lake level and river discharge imposes a similar pattern on population growth rates of the June sucker, such that during some periods, populations decline even when the long-term trend is positive.     

Description and ecology of larvae and juveniles of three native cypriniforms of coastal southern California

Larval series of the Santa Ana sucker, Catostomus santaanae (Federally Threatened), arroyo chub, Gila orcutti (California Species of Special Concern), and Santa Ana speckled dace, Rhinichthys osculus (California Species of Special Concern) are described from wild-caught specimens from the Los Angeles and Santa Ana river drainages. Santa Ana sucker larvae are elongate, having 41–46 myomeres and a distinctive paired-triangle patch of melanophores over the midbrain. Melanophores present on the snout, dorsal body, lateral midline, dorsal gut, postanal ventral body, and caudal fin. Preanal length 74–79% in body length (BL), typical of catostomids. Arroyo chub larvae relatively deep-bodied, 36–39 myomeres, and a heart-shaped patch of melanophores over the midbrain with a line of melanophores trailing posteriorly. Heavy pigment present on the snout, lower jaw, dorsal body, lateral midline, gill arches, dorsal gut, postanal ventral body, and caudal fin; short preanal length of 65–72% BL, typical of native North American cyprinids. Santa Ana speckled dace are similar to arroyo chub except for having less pigment on the ventral gut, large distinct melanophores on the ventrolateral caudal peduncle, a wedge-shaped patch of midbrain melanophores with no distinct line trailing posteriorly, and lateral midline melanophores that do not extend anteriorly. These three species often occur together and with nonnative cyprinids. Characters distinguishing them from other local larvae, including southern fathead minnow, Pimephales promelas confertus and red shiner, Cyprinella lutrensis, are discussed with their habitat preferences.     

Calcitonin-immunoreactive cells of the digestive tract of the amphioxus are distributed concentrically in a restricted region of the mid-gut

In amphioxus (Branchiostoma belcheri), calcitonin‐immunoreactive cells of the digestive tract were distributed concentrically in a 1‐mm region of the latter half of the mid‐gut. In the mid‐gut caecum these cells were also present, but were dispersed throughout the length. The total number of cells in both parts ranged from 280 to 1157, varying from individual to individual, although the number in the mid‐gut caecum was only 100–200. These cells were morphologically typical gut endocrine cells. Considering their morphology and the characteristics of their distribution pattern, these cells may be related to some phenomena of digestive processes.     

Diversity of form and behaviour among nemertean pilidium larvae

A selection of pilidium larvae are described from plankton collected from Bamfield Inlet in British Columbia, Canada, the Florida Gulf Coast and the Great Barrier Reef of Australia. Among the Bamfield larvae are examples attributable to Cerebratulus and Lineus, the former being among the largest pilidia known, up to 1.45 mm in height, and two previously undescribed types. Pilidium brachiatum from Florida is re‐described to highlight differences from Hubrechtella larvae, which are superficially similar, and an assortment of tropical forms is included to illustrate the predominance of the compressed gyrans‐type larva in this location. Pilidium larvae have typically been categorized by their shape as seen in lateral view. This account emphasizes the importance of three‐dimensional shape, pigmentation, overall architecture and behaviour in distinguishing between the larvae of different species.     

Host range testing and life history of the defoliator Hymenomima nr. memor: an unsuitable biological control agent for Schinus terebinthifolia in the U.S.A.

Host range of larvae of Hymenomima nr. memor (Lepidoptera: Geometridae) was examined in quarantine to evaluate its suitability as a biological control of Brazilian peppertree, Schinus terebinthifolia. Brazilian peppertree, S. terebinthifolia is an environmental and agricultural weed from South America that had invaded many subtropical and tropical areas of the world including Florida and Hawaii, USA. Laboratory life history and quarantine host range studies of H. memor were conducted with no-choice feeding tests. These tests included eight species of the Anacardiaceae and one species of Sapindaceae. Larvae of H. memor had five to six instars with each head capsule width increasing by 1.68-X. Development time from neonate to adult was 46.7?±?2.2 days. In host range tests, neonates completed development to the adult stage on all non-target species, except Toxicodendron radicans. Moreover, developmental times were delayed and pupal weights were reduced for larvae fed Spondias purpurea leaves. Due to the broad host range exhibited by H. memor larvae, this species will not be considered as a biological control agent of S. terebinthifolia in the continental U.S.A.     

Influence of the larval environment on performance and adult body size of the wood-boring beetle Phoracantha semipunctata

Large body size confers a reproductive advantage to adults of the wood‐boring beetle Phoracantha semipunctata (F.) (Cerambycidae: Cerambycinae: Phoracanthini). Larvae of this species feed subcortically in stressed and dying eucalypt trees and logs. We evaluated the influence of the larval environment on larval performance and adult body size by manipulating the post‐felling age of host logs (from freshly cut to 2‐weeks‐old) and the density of colonizing neonates (low density with minimal competition for resources vs. high density with intense competition). Adult beetles emerged in greater numbers from logs that had been subjected to the aging treatment which reduced bark moisture content and favored colonization by neonates. Survival was greatest in larger logs having lower densities of neonates, but was greatly diminished in all treatments by mortality during pupation. Development time varied from 2 months to more than a year and was shortest in smaller logs having high densities of larvae. The size of adult beetles emerging from a log was not influenced by larval density, but was positively correlated with the age of logs when the neonates colonized, and log size. These findings suggest that the optimal developmental conditions for P. semipunctata larvae, in terms of larval performance and adult body size, are available in large, aged host logs having low densities of larvae. Manipulation of the larval environment in this study resulted in a considerable variation in adult body size, but large individuals were relatively more common in the wild population that was the source of neonates for the experiment. Potential body size may have been constrained by our use of only one host species and a narrow range of log dimensions.     

The relationship between larval size and fitness in the tapeworm Schistocephalus solidus: bigger is better?

In organisms with complex life cycles, fitness often increases with body size at the transition from larva to adult. The translation of larval size into fitness, however, can depend on the source of size variation, with size, per se, not always increasing adult success. In parasitic worms, many factors influence larval growth, but little is known about the consequences of this growth variation. We examined how the size of the tapeworm Schistocephalus solidus in its copepod first intermediate host affects infection success and growth in the stickleback second host. Moreover, we assessed whether the conspicuous growth variation caused by copepod size is fitness‐relevant. Using larvae of the same age, we found that larger worms had a substantially higher infection probability and they tended to still be slightly larger after several months of growth in fish. However, big larvae from bigger copepods did not have higher fitness, suggesting that being large relative to the host, but not necessarily large in general, is important. These findings clarify some aspects of the life history strategy of S. solidus (e.g. why there is a flat ontogenetic reaction norm across copepod stages), but also raise questions (e.g. why growth costs have been hard to document). More generally, our results indicate that larval size can correlate with fitness in helminths, but that not all size variation is predictive of success in the next host.     

The effect of host plant on larval survivorship of the Alaskan swallowtail butterfly (Papilio machaon aliaska)

The Alaskan swallowtail butterfly, Papilio machaon aliaska (Lepidoptera: Papilionidae), uses three plant species as host plants. Cnidium cnidiifolium (Turcz.) Schischk. belongs to the family Apiaceae, the ancestral host‐plant family of the P. machaon group. Artemisia arctica Less. and Petasites frigidus (L.) Franch, in contrast, belong to the distantly related Asteraceae family and were colonized relatively recently by this group of butterflies. Previous work has shown that larval survival is highest on the novel host plants when natural enemies are present in the field. Here I examine whether P. m. aliaska fitness varied when individuals were reared on the three host plants in a common environment, free of environmental and ecological complications such as predation. I collected 12 P. m. aliaska females and measured their reproductive success when their progeny were reared on each of the three host plants. I assessed larval fitness on each of the hosts by recording the percentage pupation and percentage emergence as well as by measuring pupal mass. I found that larvae reared on the ancestral host plant, C. cnidiifolium, had higher fitness than did larvae reared on either of the novel host plants, A. arctica or P. frigidus. Larvae reared on C. cnidiifolium were more likely to pupate, achieved a greater pupal mass, and had higher emergence rates than larvae reared on the novel hosts. I interpret these results to mean that, in the absence of predation, the ancestral host plant is a better host for P. m. aliaska larvae than either novel host and I contend that this result does not appear to support the hypothesis that P. m. aliaska populations in central Alaska are divided into host races.     

Impact of the parasitoid Lathrolestes ensator (Hym., Ichneumonidae, Ctenopelmatinae) as antagonist of apple sawfly Hoplocampa testudinea (Hym., Tenthredinidae)

Abstract: Lathrolestes ensator (Brauns) was the only parasitoid species reared from larvae of apple sawfly Hoplocampa testudinea (Klug) collected in Dutch orchards. The life history parameters of apple sawfly and its parasitoid L. ensator were investigated in field and semi‐field experiments. Usually, the adult parasitoids emerge in synchrony with the preferred host stage, the second instar sawfly larvae. Parasitoid females carried 120–175 eggs, but never laid more than half this number. The mortality of sawfly eggs and larvae varied from 75 and 99%. The eggs and mining larvae are most vulnerable, as the older larvae survive for 90% on average. Three factors at least determine how many of the descending larvae become adult sawfly or parasitoid next spring. The failure of descending larvae to construct a cocoon varied from 7 to 31% and was highest in clay soil. Probably a similar mechanical hindrance prohibited more emerging adults, of both sawfly and L. ensator, from attaining the surface in heavier soils next spring. Relatively more sawfly prepupae than parasitoids died in the cocoon stage, from fungus disease or other causes, but more parasitoids than hosts stayed in prolonged diapause. Mainly due to this last factor, the overall result was a decrease of the parasitoid : host ratio during the first season underground. A life table based on survival rates during various life stages yields a net reproductive rate of up to 2.4 daughters per female sawfly. It indicates that 60% of the sawfly larvae need to be parasitized to stop population growth, or correspondingly less when more than 75% of the host eggs and young larvae are killed by predators or other causes.     

Competitive Growth Strategies in Intermediate Hosts: Experimental Tests of a Parasite life-History Model Using the Cestode, Schistocephalus solidus

In parasites with a complex life cycle, the fitness of an individual depends on its probability of reaching the final host and on its fecundity. Because larval growth in intermediate hosts may affect both transmission and adult size, selection should optimize growth patterns that are conditional on the presence and number of conspecific competitors. A recent model predicts that the total parasite volume per host should increase with intensity if larvae are able to vary growth depending on the number of conspecifics in the host (Life History Strategy hypothesis, i.e. LHS). Further, we would here expect growth rates to increase with intensity. By contrast, under the simplest alternative hypothesis of Resource Constraints (i.e. RC), the total parasite volume should remain constant. We experimentally infected copepods Macrocyclops albidus with the cestode Schistocephalus solidus to achieve 1, 2 or 3 parasites per host taking care that hosts had similar quality status at each infection level, and compared larval growth trajectories at the three intensity levels. The asymptotic total parasite volume was larger in double and triple infections than in single infections. Furthermore, the asymptotic total parasite volume was significantly larger in triple than in double infections but only in larger copepods that were less constrained by a host-size ceiling effect. These results, together with the fact that growth rates increased with intensity, support the LHS hypothesis: procercoids of a tapeworm may “count” their conspecific competitors in their first intermediate host to harvest its resources strategically until the next step in their complex life cycle. Co-ordinating editor: A. Biere