Soldier behaviour and division of labour in the aphid genus Pemphigus (Hemiptera, Aphididae)

Summary. We devised a test for quantitatively measuring the defensive behaviour of individual aphids of the gall generations of the genus Pemphigus. Five species (P. spyrothecae, P. gairi, P. bursarius, P. phenax, and P. protospirae) were shown to have soldiers, but the early instars of Pemphigus populi showed no aggressive behaviour. A higher proportion of the first instars of P. spyrothecae showed aggressive behaviour, compared with the other four soldier-producing species. Although the first instars were always the most likely to be aggressive, later instars also showed significant levels of aggression in all the soldier-producing species. Soldier behaviour was elicited by a range of stimuli. A live, restrained, predator was the most effective stimulus tested, but physical stimulation (with a paintbrush) enhanced the attack rate. The aphids could distinguish between lures soaked in water and those soaked in aphid haemolymph, which elicited a higher level of response. First instars of the early and late gall generations of P. spyrothecae were equally likely to attack predators. Although the species with the most specialized soldiers (P. spyrothecae) also had the most prolonged gall phase, this is clearly not the only factor that is important in the evolution of soldiers in this genus.     

A new species of the spider genus Baalzebub (Araneae,Theridiosomatidae) from Brazilian caves

A new species of the spider genus Baalzebub Coddington from Brazil, B. acutum sp. nov., is described and illustrated based on 95 specimens collected from caves around the Iron Quadrangle in the state of Minas Gerais. This species is recognized by male palpal bulb with strong and large conductor covering almost entire embolus, and epigyne of females with long and tapered scape, which extends towards the spinners. Baalzebub acutum sp. nov. is the second species recorded from Brazil, the first for Brazilian caves, bringing the total number of species in the genus to seven in the world.     

Comparative study of the defensive behavior and morphology of the gland opening area among harvestmen (Arachnida, Opiliones, Gonyleptidae) under a phylogenetic perspective

The arachnids of the order Opiliones (harvestmen) have a pair of scent glands opening at the sides of the body, the substances of which are used in defense. Several types of behavioral, morphological and chemical defensive mechanisms have been assigned to the order as a whole, although some of these tactics were restricted to particular groups. Only around 25 species have been studied from this perspective so far. In the present paper, we analyzed 33 species (mostly from the largest harvestmen family, the Gonyleptidae) aiming at recognizing the usefulness of the defensive characters in taxonomy and evolutionary biology. We observed the morphology of the gland opening (ozopore) area and the defensive behavior, and their relationship, and mapped these traits on an available phylogenetic hypothesis of relationship within Gonyleptidae. As outgroups, we analyzed Cosmetidae and Stygnidae. Combining the observed behavioral characters of the emission of defensive secretion (near the ozopore, with liquid displacement through an integumentary groove, or in form of a jet) with the morphological types of the gland opening (direction of the integumentary dome that surrounds the gland opening, presence of two openings and the relationship between their sizes, and presence of a V-shaped cut at the anterior opening), we recognized eight patterns. In addition, we could examine the evolution of such traits within Gonyleptidae.     

Male work and sex ratio in social crab spiders

Summary: Biased sex ratios may alter the contribution that individuals of either sex make to group living. Such a possibility has not been examined in social spiders, in part as adult male spider anatomy and behaviour are focussed on mating. Subadult male behaviour was examined in two congener social crab spiders that have similar ecological niches, Diaea ergandros with an equal sex ratio and D. socialis with a female-biased sex ratio. A laboratory experiment that varied sex ratios of groups of subadults of the two species found that nest construction in D. ergandros did not vary with sex ratio, but that of D. socialis did as males did not contribute to nest construction. This may suggest that among social species, biased sex ratios might influence the appearance of drone-like behaviour.     

Interspecific,ontogenetic, and sexual variation in ozopore morphology among cosmetid harvestmen (Arachnida,Opiliones, Laniatores)

The ozopores of cosmetid harvestmen rest upon lateral projections of the carapace, have simple or highly reduced channels, and are partially obscured by enlarged dorsal processes associated with coxae I and II. Rather than use scent gland secretions to form a chemical shield on the dorsum, the cosmetid harvestman exhibits a unique defensive behavior known as “leg dabbing” in which the distal tip of tarsus I or II is dipped into fluid that accumulate at the base of coxa II and the droplet on the tarsus is pointed toward the predator. Relatively little is known about interspecific variation in ozopore morphology among cosmetid harvestmen. In this study, we used scanning electron microscopy to examine the ozopores of males and females of nine species as well as those of antepenultimate nymphs for two species. Among adults, we found differences between species in the shapes of the ozopores (round or subtriangular), the morphology of the dorsal and lateral channels (if present), and the relative size, shape and armature of the dorsal posterior process (dpp) of coxa I and the dorsal anterior process (dap) of coxa II. Our observations suggest that the morphology of dpp I and dap II could be sources for systematic characters in future phylogenetic studies of the Cosmetidae. We observed ontogenetic differences but relatively little intersexual variation in the morphology of the ozopore. The ozopores of nymphs are generally more oval than those of adults and the opening of the ozopore of the nymph is less obstructed, if at all, by the dorsal coxal processes of legs I–II. These morphological differences suggest that nymphs may use scent gland secretions in a manner different from that of adults.     

The type of leg lost affects habitat use but not survival in a non‐regenerating arthropod

Finding shelter and surviving encounters with predators are pervasive challenges for animals. These challenges may be exacerbated after individuals experience bodily damage. Certain forms of damage arise voluntarily in animals; for instance, some taxa release appendages (tails, legs, or other body parts) as a defensive strategy (“autotomy”). This behavior, however, may pose long‐term negative consequences for habitat use and survival. Additionally, these putative consequences are expected to vary according to the function of the lost body part. We tested the effects of losing different functional leg types (locomotor or sensory) on future habitat use and survival in a Neotropical species of Prionostemma harvestmen (Arachnida: Opiliones) that undergo frequent autotomy but do not regrow limbs. Daytime surveys revealed that both eight‐legged harvestmen and harvestmen missing legs roosted in similar frequencies across habitats (tree bark, mossy tree, or fern), and perched at similar heights. Mark–recapture data showed that harvestmen that lost sensory legs roosted in tree bark less frequently, but on mossy trees more frequently. On the contrary, we did not observe changes in habitat use for eight‐legged animals or animals that lost locomotor legs. This change might be related to sensory exploration and navigation. Lastly, we found that recapture rates across substrates were not affected by the type of legs lost, suggesting that leg loss does not impact survival. This potential lack of effect might play a role in why a defensive strategy like autotomy is so prevalent in harvestmen despite the lack of regeneration.     

Gregariousness does not vary with geography,developmental stage,or group relatedness in feeding redheaded pine sawfly larvae

Aggregations are widespread across the animal kingdom, yet the underlying proximate and ultimate causes are still largely unknown. An ideal system to investigate this simple, social behavior is the pine sawfly genus Neodiprion, which is experimentally tractable and exhibits interspecific variation in larval gregariousness. To assess intraspecific variation in this trait, we characterized aggregative tendency within a single widespread species, the redheaded pine sawfly (N. lecontei). To do so, we developed a quantitative assay in which we measured interindividual distances over a 90‐min video. This assay revealed minimal behavioral differences: (1) between early‐feeding and late‐feeding larval instars, (2) among larvae derived from different latitudes, and (3) between groups composed of kin and those composed of nonkin. Together, these results suggest that, during the larval feeding period, the benefits individuals derive from aggregating outweigh the costs and that this cost‐to‐benefit ratio does not vary dramatically across space (geography) or ontogeny (developmental stage). In contrast to the feeding larvae, our assay revealed a striking reduction in gregariousness following the final larval molt in N. lecontei. We also found some intriguing interspecific variation: While N. lecontei and N. maurus feeding larvae exhibit significant aggregative tendencies, feeding N. compar larvae do not aggregate at all. These results set the stage for future work investigating the proximate and ultimate mechanisms underlying developmental and interspecific variation in larval gregariousness across Neodiprion.     

Colonization under threat of predation: avoidance of fish by an aquatic beetle, Tropisternus lateralis (Coleoptera: Hydrophilidae)

Documenting the role of past interactions in the assembly of present communities has proven problematic. Colonization is a key process in community assembly that is both potentially driven by past interactions and amenable to experimental approaches. Colonization and oviposition by an aquatic beetle (Tropisternus lateralis) was assayed in the presence and absence of both 'harmless' and tactilely/visually isolated predatory fish (Lepomis gibbosus and L. macrochirus). Beetles avoided each treatment with fish when compared to fish-free experimental pools. Activity levels after colonization also differed significantly between adults in fish and fish-free tanks. Predator effects on species composition are typically ascribed to contemporary predation events; the presence of a strong avoidance response demonstrates that past species interactions affect present distributions and may play an important role in the ongoing assembly of contemporary communities. Documentation of such avoidance behavior in a growing number of species fundamentally alters our view of the processes affecting species distributions and the process of community assembly.     

Effects of familiarity and nestmate number on social interactions in two communal bees, Andrena scotica and Panurgus calcaratus (Hymenoptera, Andrenidae)

Summary: Communality is considered a widespread form of social organization in bees and wasps, one in which two or more females of the same generation share a common nest and amongst whom there is no reproductive division of labor. The evolution and maintenance of egalitarian communal societies poses theoretical difficulties where 'cheating' amongst nestmates is practised. Yet there is little knowledge of the intranidal social interactions among communal conspecifics that allow an understanding of the degree of cooperation versus exploitation amongst nestmates in such societies. Using a circle-tube arena, we staged interactions in the laboratory among pairs of female conspecifics using two communal andrenid species, Andrena scotica and Panurgus calcaratus, to score their cooperative and aggressive behaviors. For both species, females did not discriminate between familiar (nestmate) and unfamiliar (non-nestmate) conspecifics in their cooperative and aggressive behaviors, suggesting that there is universal acceptance of conspecifics. Levels of cooperation and aggression did not vary with the number of nestmates in the nest of origin for either species. In addition, frequencies of social interactions did not vary with body size, wing wear or ovarian development in P. calcaratus. Interspecific comparisons were made with published data on social interactions of other bee species at varying levels of social organization (solitary to eusocial) derived from analogous circle-tube experiments. Panurgus calcaratus displayed highly cooperative behavior, similar to that of a previously studied communal bee, Lasioglossum hemichalceum (Kukuk, 1992a). Andrena scotica displayed lower levels of cooperation, and was in this sense more similar to solitary species and to interactions amongst non-nestmate individuals of eusocial species. Both A. scotica and P. calcaratus displayed very low levels of aggressive behavior, again similar to L. hemichalceum. As a working hypothesis, we suggest the existence of a communal behavioral syndrome comprising high levels of intranidal cooperation and low aggression, both directed indiscriminately at conspecifics.     

A new species of Cuacuba (Araneae,Theridiosomatidae) from Brazilian caves

ABSTRACT

A new species of the spider genus Cuacuba from Brazil, C. ribeira sp. nov. is described and illustrated based on eighty-six specimens collected from caves in the Vale do Ribeira region, in the states of São Paulo and Paraná. This species is recognized by the hook-shaped median apophysis on the male palp, and females by having invaginations on the sides of the median posterior edge of the epigynal plate. Cuacuba ribeira sp. nov. is the third species recorded for the genus, and like the other two, also comes from Brazilian caves.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:44036D6B-CA3F-4C15-BBA3-3E5FE81FB299     

Taxonomic studies of the Antarctic icefish genus Cryodraco Dollo, 1900 (Notothenioidei: Channichthyidae)

Based on a meristic and morphometric study of 101 specimens, we recognise 2 valid species in the Antarctic channichthyid genus Cryodraco: Cryodraco antarcticus Dollo, 1900 and C. atkinsoni Regan, 1914. Although the species overlap in most meristic and morphometric characters, we have distinguished several reliable characters for diagnosis and identification. Multidimensional scaling, a nonparametric multivariate technique, clearly separates the two species on the basis of pelvic fin length, head length, number of second dorsal fin rays and origin of the lower lateral line relative to the anal fin rays. We provide a revised identification key to the species of Cryodraco. From a zoogeographical point of view, C. antarcticus has a circum-Antarctic distribution whereas C. atkinsoni is largely confined to the East Antarctic Zoogeographic Province.     

Two New Species of the Enigmatic Leptokoenenia (Eukoeneniidae: Palpigradi) from Brazil: First Record of the Genus Outside Intertidal Environments

Two new species of Leptokoenenia Condé 1965 (Eukoeneniidae: Palpigradi), Leptokoenenia pelada sp. nov. and Leptokoenenia thalassophobica sp. nov., are described based on both male and female specimens collected in iron ore caves from the Brazilian Amazon. This is the first record of the genus for the Americas. Furthermore, a new combination is stated for Eukoenenia gallii based on its morphology.     

Change in habitat of the sympagic copepod <Emphasis Type="Italic">Paralabidocera</Emphasis><Emphasis Type="Italic">antarctica</Emphasis> from fast ice to seawater

The occurrence and age structure of an Antarctic ice-associated copepod, Paralabidocera antarctica, were investigated using a light trap under fast ice near Syowa Station. Sampling was carried out between May and November 1984. P. antarctica were found in high numbers in the traps on 1-2 and 23-24 November. No copepods were found in any trap between May and October. The timing of the absence and occurrence of P. antarctica in the light traps coincided with their ice-dwelling and pelagic life-phases. More than 99% of the total catch was taken in the traps set in the water immediately below the ice in both sampling periods on 1-2 and 23-24 November. The age structure of the P. antarctica populations consisted of copepodite stage III (CIII) to adult and IV (CIV) to adult, respectively. The earlier population was dominated by CIV and CV and the later one by adults. The behavior pattern of P. antarctica is suggested to be controlled by phototactic and thigmotactic traits, and their habitat change from sea ice to seawater may occur by trade-off between two behavioral traits with the acquisition of swimming ability.     

Prevalence of the parasite Strepsiptera in <Emphasis Type="Italic">Polistes</Emphasis> as detected by dissection of immatures

Summary. hough the paper wasp genus, Polistes, is well studied, we know little of the incidence of parasitism in this group. Here we present details of 45 nest dissections for 4 species: P. dominulus (Christ), P. gallicus (L.), P. stabilinus Richards and P. carnifex (F.) to detail levels of parasitism of colony members by the obligate parasitic group of insects, the Strepsiptera. All 4 species showed evidence of parasitism among immature members. For 3 species, more than 50% of inspected nests were parasitized and the levels of parasitism among brood (larvae and pupae) was very high and did not differ significantly between parasitized nests. One species, P. stabilinus, suffered very low levels of parasitism, which may be related to its habitat choice. The number of parasites per host was positively related to the proportion of infected brood (parasite prevalence) and in some cases reached phenomenally high levels, which casts doubt on previ ously assumed mechanisms of infection for nest-making Hymenoptera, i.e. phoresy. We also document cases of egg parasitism and encapsulation in Polistes nests. Our data show that parasitism levels greatly varied among areas. Finally, the recent debate on the competitive advantage of P. dominulus in its introduced range, USA, has credited an absence of strepsipteran parasites of this species in facilitating its spread. For the first time, we document levels of parasitism for this species in its nature P range and this would appear to corroborate previous claims. We place our work in the context of other studies of parasitism of social insects and posit that the genus Polistes may have much to offer to this field.     

Resources and the flexible allocation of work in the desert ant, Aphaenogaster cockerelli

Summary: Social insect colonies can respond to changes in resource availability by altering their foraging behavior. Colonies of the desert ant, Aphaenogaster cockerelli, responded to experimental changes in the distribution and type of available resources by adjusting the numbers of ants engaged in foraging and other tasks outside the nest, and by adjusting the temporal patterns of these activities. Colonies foraged more intensely for protein resources than for seed resources, and for high-density resources more than for low-density resources. This flexible allocation and resource use may promote coexistence with interspecific competitors such as ants in the genus Myrmecocystus.     

Analysis of genetic diversity and sectional relationships in Musa using AFLP markers

The AFLP technique was used to assess the genetic diversity and sectional relationships in 39 accessions representing the four main sections of the genus Musa. Eight AFLP + 3 primer pairs produced 260 polymorphic bands that were used in cluster and PCO analysis. A wide range of variability was observed among the species within the sections of the genus Musa. AFLP data was useful in separating the different sections of the genus as well as differentiating the different genomic groups of section Eumusa. Section Rhodochlamys (x = 11) appeared as a distinct entity and clustered closely with the Musa acuminata Colla complex of section Eumusa that has the same basic chromosome number. This relationship is congruent with previous studies. However, unlike previous proposals that questioned the identity of Rhodochlamys as a separate taxonomic unit, PCO analysis of the AFLP data showed that it is a distinct entity. Musa laterita Cheesman (Rhodochlamys) and Musa schizocarpa Simmonds clustered with the M. acuminata complex suggesting that they may be sources of useful genes for the improvement of the cultivated bananas. Callimusa formed a distinct unit and was closer to Australimusa than to the other sections. Although both sections share the same basic chromosome number of x = 10 these sections are genetically distinct     

Phylogenetic position of the cryopelagic codfish genus Arctogadus Drjagin, 1932 based on partial mitochondrial cytochrome b sequences

In order to elucidate the phylogenetic position of the cryopelagic cod genus Arctogadus, gadine phylogenetic relationships were examined using the mitochondrial DNA cytochrome b gene. A segment of 401 base pairs was sequenced from 6 gadine species [Arctogadus borisovi Drjagin, A. glacialis (Peters), Gadiculus argenteus Guichenot, Micromesistius poutassou (Risso), Pollachius pollachius (L.), Pollachius virens (L.)] and from 4 gadiform outgroup species. With additional data from GenBank, a dataset of all 12 gadine genera (19 species) was analysed using parsimony and neighbour-joining. Arctogadus appeared in a terminal clade as sistergenus to Boreogadus and closely related to Gadus and Theragra. The relatively small genetic difference between these four genera indicates a need for taxonomic revision, and possibly that Arctogadus should be synonymised with Boreogadus or Gadus. A difference of only 0-2 base pairs between specimens of A. borisovi and A. glacialis indicates that they are conspecific, with A. borisovi as the junior synonym.     

Genetic variation within <Emphasis Type="Italic">Symbiodinium</Emphasis> clade B from the coral genus <Emphasis Type="Italic">Madracis</Emphasis> in the Caribbean (Netherlands Antilles)

The internal transcribed spacer (ITS) region was sequenced in symbiotic dinoflagellates (zooxanthellae) from five morphospecies in the genus Madracis. The phylogeny of the symbionts is congruent with a companion phylogeny of the coral host. Comparison with known clade B symbiont ITS types reveals that M. mirabilis contains the B13 symbiont and that the other morphospecies contain the B7 symbiont. Madracis formosa also contains a previously undescribed type. The B7 and B13 symbionts appear to be highly specific to morphospecies in the genus Madracis. The host specificity between the B13 symbionts and its coral host may be the result of co-evolution of the coral-symbiont association and suggests that the brooding species, M. mirabilis, is reproductively isolated. Microhabitat differentiation associated with light utilization independent of depth is discussed.