The morphology and behavior of dimorphic males in Perdita portalis (Hymenoptera : Andrenidae)

Summary In Perdita portalis, a ground nesting, communal bee, males are clearly dimorphic. The two male morphs are easily distinguished based on head size and shape into (1) a flight-capable, small-headed (SH) morph that resembles the males of other closely related species and (2) a flightless, large-headed (LH) morph that possesses numerous derived traits, such as reduced compound eyes, enlarged facial foveae and fully atrophied indirect flight muscles. The SH morph occurs exclusively on flowers while the LH morph is found only in nests with females. While on flowers, SH males are aggressive, fighting with conspecific males and heterospecific male and female bees, and they mate frequently with foraging females. Using artificial observation nests placed in the field, I observed the behavior of females and LH males within their subterranean nests. LH males are aggressive fighters; males attacked each other with mandibles agape, and male-male fights always ended in the death of one male. LH males are highly attentive to the reproductive behavior of females; they spend increasing amounts of time near open cells during cell provisioning, and mating only takes place immediately prior to oviposition when females are forming the accumulated pollen and nectar into a ball. Based on larvae reared to adulthood in the laboratory, the two male morphs occur in equal proportions. The behavior of males in closely related species, especially P. texana, and the origin and maintenance of male dimorphism are discussed.     

Factors affecting production of dimorphic males of Euterpina acutifrons

This paper attempts to explain the various factors affecting production of dimorphic males in Euterpina acutifrons. Experiments conducted by crossing different males with virgin females under laboratory conditions have shown that both environmental and genetical factors contribute to the production of dimorphic males in nature.     

Larval development of Euphausia nana (Crustacea: Euphausiacea)

The larvae of Euphausia nana Brinton in Sagami Bay and Suruga Bay, Central Japan, are described and illustrated. The furcilia stage is separated into six stages on the basis of the form of the pleopods and the number of terminal telson spines. Furcilia I, no pleopod or non-setose pleopods and seven terminal telson spines. Furcilia II, nonsetose and setose pleopods and seven terminal telson spines. Furcilia III, five pairs of setose pleopods and seven terminal telson spines. Furcilia IV, five pairs of setose pleopods and five terminal telson spines. Furcilia V, five pairs of setose pleopods and three terminal telson spines. Furcilia VI, five pairs of setose pleopods and one terminal telson spine. Segmentation of the antennal endopod and mandible palp occurred at the furcilia V stage. The dominant forms of early furcilia larvae of E. nana differed during different seasons of the year. The total lengths of calyptopis III and furcilia I to VI larvae also showed seasonal changes; they were largest in May and smallest from September to December.     

Growth and production of Euphausiacea (Crustacea) in the Rockall Trough

The euphausiid fauna of the Rockall Trough has been sampled in time series at approximately two-monthly intervals between 1973 and 1976 between surface and depths greater than 2000 m. Length/frequency histograms have modes that are coherent for periods of at least 4 to 6 mo, indicating that populations are being sampled. Rates of growth were determined for six species. Epipelagic species have winter checks to the growth rates, but such checks are absent in the growth of Thysanopoda acutifrons, Nematobranchion boöpis and Stylocheiron maximum. Ratios of annual production: biomass were determined and are all within the previously determined range of values for epipelagic and coastal populations. Lack of a winter check to the growth rate in deep-living species enables these potentially to have overall rates of growth comparable to those of temperate, epipelagic, shelf and coastal species.     

Diagnostic value of the thelycum in euphausiids. II. Oceanic species,genus Nematoscelis

The thelycum morphology of 7 species of the genus Nematoscelis, based upon observations with the scanning electron microscope, is described. The thelycum of N. megalops and N. difficilis did not differ either with respect to general morphology of the thelycum, or in spermatophore insertion. In the other 5 species, N. tenella, N. gracilis, N. atlantica, N. lobata, N. microps, the main thelycum structure consists of a central lobe of various forms, to which a filamentous spermatic mass is attached. Preliminary observations on the position of the genital pores of two species are reported briefly.     

Labial gland marking secretion in males of two Scandinavian cuckoo bumblebee species (genusPsithyrus)

Summary Chemical components of the cephalic labial gland secretion, which most likely is used as a precopulatory attracting signal, were identified in males of the cuckoo bumblebeesPsithyrus vestalis (Geoffroy) andP. bohemicus (Seidl.) by gas chromatography-mass spectrometry (GC-MS). The former species has geranylcitronellyl acetate as main component, plus in decreasing amounts geranylcitronellol, an eicosadienal, an eicosenol, and an eicosenal. Another 17 fatty acid derivatives are present in minor amounts. The labial secretion ofP. vestalis differs distinctly in its chemistry from that of all of the 8 other ScandinavianPsithyrus species. In the taxonomically closely related (same subgenus)P. bohemicus, the labial gland secretion contains 16 fatty acid derivatives, of which 12 (75%) are present also in the secretion ofP. vestalis. Thus, both the labial gland secretions, and morphological traits lend support to the hypothesis that the two species share a common ancestor. The reproductive isolation between them is, at least in part, supported by the inclusion of a second biosynthetical pathway (the mevalonic acid pathway producing terpenoids) inP. vestalis, in addition to the pathway common to both species (the polyketide pathway producing fatty acid derivatives).     

Mating behavior in three species of Pseudodiaptomus (Copepoda: Calanoida)

Quantitative studies of mating behavior between conspecific and heterospecific pairs of three closely related species in the genus Pseudodiaptomus reveal differences in the timing of life-history events, species-specific attraction of mates, distinctive tactile cues, multiple spermatophore attachments, and gametic incomptibility or hybrid inviability. These differences may function as reproductive isolating mechanisms among calanoid copepods. Differences in breeding behaviors and associated morphological features are greater between sympatric than between allopatric species, indicating that selection reinforces both behavioral and morphological divergences.     

Genetic divergence among three sympatric species of Mediterranean Patella (Archaeogastropoda)

Patella caerulea L., P. aspera Lam. (=P. ulyssiponensis Gmelin). P. rustica L. (=P. lusitanica Gmelin) are coexisting Mediterranean species of the genus Patella. P. caerulea and P. rustica have a haploid complement of n=9 with seven metacentric and two telocentric chromosomes, while P. aspera has a haploid complement of n=8 without telocentric chromosomes. To better define the phylogenetic relationships among these three species, an electrophoretic analysis of 12 enzyme coding loci was performed on samples of the three species collected from Laigueglia (Liguria, Italy) in 1989. On the whole, genotypic frequencies were in agreement with Hardy-Weinberg expectations and no significant differences were observed among the populations of the three species as far as their genetic structure is concerned. Nearly 50% of the sampled loci were diagnostic. Nei's genetic distance was 0.82 between P. caerulea and P. aspera, 0.97 between P. aspera and P. rustica and 0.94 between P. caerulea and P. rustica. By greatly separating P. rustica from the other two species, results of the electrophoretic analysis are consistent with the traditional view, which regards P. aspera and P. caerulea as more closely related than P. rustica on the basis of radular teeth morphology. Using genetic distances and the assumptions of the molecular clock, lineages leading to P. aspera and to P. caerulea may have diverged from the stem common to P. rustica ca. 18 million years ago.     

Nestmate recognition in three species of stenogastrine wasps (Hymenoptera,Vespidae)

The capacity to recognise a conspecific intruder was investigated in Parischnogaster jacobsoni, Liostenogaster flavolineata and L. vechti, three species of primitively social wasps of the subfamily Stenogastrinae. Results of behavioural experiments carried out in the field showed that females of all three species react pacifically if presented with female nestmates, but aggressively reject an intruder from a conspecific colony. As L. flavolineata and L. vechti both build large clusters of nests, often very close to each other, the recognition capacity among females from different nests, but in the same conspecific cluster, was also investigated. Females of both species were more aggressive towards females from a different colony in the same cluster than towards their female nestmates. Additional experiments on L. flavolineata showed that there was no difference in reaction towards females from colonies nearer or further from the tested colony but within the same cluster, nor towards females from a different cluster. The capacity to recognise an alien conspecific nest containing immature brood was investigated in P. jacobsoni. Adult females of this species, invited to land on an alien nest which had experimentally been exchanged for their own, accepted the new nest and partially destroyed the immature brood. The behaviour of the females when they land on an alien nest, however, suggests that they do recognise the nest as foreign. Acceptance of foreign nests coupled with low immature brood destruction is probably due to the high energetic costs of egg-deposition and larval rearing in stenogastrine wasps. These results suggest that nestmate recognition in these wasps is very efficient, even though they belong to the most primitive subfamily of social wasps. Received: 16 April 1996/Accepted after revision: 9 August 1996     

Eine isolierte population von Pseudeuphausia latifrons (Crustacea: Euphausiacea) im Persischen Golf

During the expedition of RV “Meteor” in 1964/1965 a population of Pseudeuphausia latifrons (G. O. Sars, 1883) was found in the Persian Gulf; this population is isolated and morphologically different from a population of the same species in the Arabian Sea. The adults of the Persian Gulf population are between 7 and 16 mm long which means that they are considerably larger than those found elsewhere. Morphological differences of the copulatory appendages of the male specimens from the Persian Gulf can only partly be regarded as allometric, which may be due to the abnormal length of these specimens. It is possible that isolation and the particular ecological conditions in the Persian Gulf have led to genetic changes in this population so that it can be regarded as a distinct geographical variation. Comparative analysis has shown that Pseudeuphausia colosii Torelli, 1934, described from the Red Sea, is synonymous with Pseudeuphausia latifrons (G. O. Sars, 1883).     

Breeding of Euterpina acutifrons,a harpacticid copepod,with special reference to dimorphic males

The breeding of Euterpina acutifrons, a marine harpacticid copepod, was studied both in the laboratory and in the natural population round Anglesey, England, with special reference to dimorphic males. As a result of successful rearing of the species under laboratory conditions, rates of development at different temperatures, and survival and maturation of all types of adults were studied. The dimorphic males developed faster than the females, and the small males had a shorter development time than the larger individuals. Laboratory observations clearly indicated that the males differ markedly in sexual behaviour, the small male being more potent, readily copulating with females, and always very active in breeding. In natural populations, temperature was found to have a limiting influence on the breeding period. Breeding began when the temperature reached 15° to 16°C, and ceased when it fell to 8°C. The most significant feature was the production of small males in nature; they increased in number with the onset of breeding, and always formed a high proportion of the actively breeding population. Both laboratory and field investigations have shown that the small male is a breeding form, and is apparently an adaptation of the species for carrying out successful breeding in the colder areas of its distribution.     

Molecular systematics of six Calanus and three Metridia species (Calanoida: Copepoda)

The discrimination of species of the copepod genus, Calanus (Copepoda; Calanoida), is problematical-especially in regions of sympatry. Although the species of Calanus exhibit exceptional morphological similarity, they are quite distinct in genetic character. The DNA base sequences of the mitochondrial large subunit (16S) ribosomal RNA (rRNA) gene unambiguously discriminated C. finmarchicus (Gunnerus 1765), C. glacialis (Jaschnov 1955), C. marshallae (Frost 1974), C. helgolandicus (Claus 1863), C. pacificus (Brodsky 1948), C. sinicus (Brodsky 1965), and C. hyperboreus (Kroyer 1838). Sequence differences among Calanus species for this gene portion range from 7.3% (between C. glacialis and C. marshallae) to 23.9% (between C. glacialis and C. sinicus). Differences among conspecific individuals were approximately 1 to 2%. [These sequence data were determined between April and November 1993; the sequenced domain is similar to that published previously in Bucklin et al. (1992) but are derived from analysis of additional individuals.] Statistical analysis of the sequence data using a variety of tree-building algorithms separated the taxa into one group of species corresponding to the C. finmarchicus group (C. finmarchicus, C. marshallae, and C. glacialis) and another ungrouped set of species corresponding to the C. helgolandicus group (C. helgolandicus, C. pacificus, and C. sinicus). The C. helgolandicus group may be older than the C. finmarchicus group, making the tree topology less reliable in this area. Calanus hyperboreus was an outlier; Nannocalanus minor (Claus 1863) was the outgroup. Similar analysis of Metridia species confirmed that M. lucens (Boeck 1864) and M. pacifica (Brodsky 1948) are distinct species; M. longa (Lubbock 1854) was still more divergent. These sequence data will allow the design of simple, molecular tools for taxonomic identifications. Diagnostic characters, assayed by rapid molecular protocols, will enable biological oceanographers to answer important questions about the distribution and abundance of all life stages (as well as patterns of reproduction) of morphologically similar species, such as those of Calanus.     

Contribution of moulting and eggs to secondary production in Nyctiphanes australis (Crustacea: Euphausiacea)

This study was designed to assess the contribution of moulting and eggs to production of the euphausiid Nyctiphanes australis G. O. Sars. For this purpose, live specimens were collected from Storm Bay, south-eastern Tasmania, between August and December 1981, while preserved samples, collected between February 1980 and February 1981, were also examined. The intermoult period of N. australis increased exponentially with increase in body length and weight. Larvae moulted approximately every 2.5 to 3 d and adults every 4 to 5 d at 15°C. A decrease in temperature from 15° to 10°C resulted in the intermoult period almost doubling. The mean weight of exuviae produced represented nearly 6% of the body dry weight of the individual. Continuous maturation of ova was observed, with an individual female capable of releasing a total of 1 100 eggs in a lifetime. These are deposited as a series of batches into a pair of external ovisacs every 30 d. The size of the batch of eggs was dependent on the size of the female. Moulting of euphausiids forms a significant contribution of organic matter to detrital food webs. A value of 42.01 mg m^-3 yr^-1 was obtained for the production of exuviae. Egg production was calculated to be between 1.41 and 4.22 mg m^-3 yr^-1. Production and mean annual biomass of N. australis was previously calculated as 78.29 mg m^-3 yr^-1 and 5.39 mg m^-3, respectively. Thus, the total production integrated for the whole of Storm Bay was 125 mg m^-3 yr^-1 or 2 309 tonnes dry wt yr^-1, representing an overall P:B ratio of 23.1.     

Spirorbinae (Serpulidae: Polychaeta) from South Africa,including three new species

Five Antarctic or south-temperate species of Spirorbiaae are centred in south-west Africa, whilst 6 tropical species extend round the south-east and another 4 are recorded from Mozambique. Of the three new species, Pileolaria (Pileolaria) annectans sp. n. has a rudimentary opercular plate surmounting a sort-walled sac of embryos, which somewhat resembles a thoracic brood pouch. Pileolaria (Pileolaria) dayi sp. n. has a helmet-like brood chamber, but this opens distally, like the brood cups found in the subgenus Duplicaria. Janua Pil-natalensis sp. n. has the dorsal collar folds usually separate, but partially fused in some juveniles.     

Genetic differentiation in three Sepia species (Mollusca: Cephalopoda) from Galician waters (north-west Iberian Peninsula)

The systematics of the genus Sepia is not yet clear. Morphological evidence has led to S. officinalis Linnaeus, 1758 being considered as belonging to the subgenus Sepia sensu stricto, and S. orbignyana Férussac, 1826 and S. elegans Blainville, 1827 as belonging to the subgenus Rhombosepion. Samples of 30 individuals of S. officinalis and S. orbignyana from both sides of an oceanographic boundary off the north-west Iberian Peninsula, and a sample of S. elegans from the northern side, were collected in 1993–1994. Allozyme electrophoresis for 32 presumptive loci revealed low levels of genetic variability for the three Sepia species (mean expected heterozygosity estimates were <0.052). No significant differences in allozyme frequencies were detected among populations of either S. officinalis or S. orbignyana. The genetic identities (I) of S. officinalis and S. orbignyana (I=0.12) and of S. elegans (I=0.13) were significantly different from that of S. orbignyana and S. elegans (I=0.49). The former are typical of values for confamilial genera, and a new generic status is proposed for the latter two species, which become Rhombosepion orbignyana (Férussac, 1826) and R. elegans (Blainville, 1827).     

Scanning electron microscope study of the modified spine characteristic for males of some Tisbe (Copepoda: Harpacticoida) species

The scanning electron microscope proved to be an ideal instrument for examining the species-specific spine (on the endopodite basal segment of male P2) in the group of sibling species Tisbe holothuriae, T. pontina and T. battagliai. Three other species: T. gracilis, T. cucumariae and T. biminiensis belonging to the gracilis group are included in the present study. A possible functional significance of the spine is discussed.     

Larval distribution and reproductive ecology of Thysanoessa macrura (Crustacea: Euphausiacea) in the Scotia Sea

In the Scotia Sea, the larvae of Thysanoessa macrura G.O. Sars, 1885 were scarce in spring (September 27 to October 6, 1971) and mainly present at the Calyptopis I stage, while in summer (December 17, 1974 to January 3, 1975) they were much more abundant and much further developed (up to Furcilia VI). The spawning season commences as early as September and, as indicated by the presence of numerous nauplii and metanauplii in summer, is rather long. T. macrura begins to spawn much earlier in West-Wind-Drift waters than in waters of the Weddell Sea. It starts to spawn simultaneously with Euphausia frigida and E. triacantha, but significantly earlier than E. superba. These timings of the breeding process are related to differential biogeographical characteristics of these species. Plankton collections made at depths of 500 or 1000 m have, for T. macrura, revealed a developmental ascent analogous to that of E. superba. Ontogenetical deep-water migrations are, consequently, characteristic not only for E. superba, but also for other Antarctic euphausiids (in particular E. frigida, but possibly not for inshore E. crystallorophias) and, as correctly postulated by several other investigators, for all oceanic euphausiid species.     

Estimating annual survival in sexually dimorphic species from proportions of first-year birds

We estimated the annual adult survival (S) of several species of temperate and tropical sexually dimorphic tanagers and manakins from the proportions of first-year and older individuals in museum collections. In the case of the sexually dimorphic species included here, young males through their first year resemble females and can be distinguished from older males. We assumed that the sex ratio among first-year birds is even and estimated the number of immature females (IF) in a sample as equal to the number of immature males (IM), using sex information on museum labels. The number of adult females (AF) is the total number of females (F) minus IF, and survival can be estimated by S = AF/F. We used a Monte Carlo resampling approach to estimate standard errors and 1% and 99% confidence limits on S for samples of size N, based on 1000 sets of N randomly drawn individuals and observed proportions of the F, IM, and AM classes. Estimates of annual survival (S) were 0.60-0.73 in four North American species of Piranga tanagers and 0.50 and 0.62 in two montane Central American species. Values of S in lowland species of Habia and Ramphocelus tanagers ranged between 0.68 and 0.82. Annual survival in Pipra manakins was 0.53-0.68, and values for two Manacus species were 0.69 and 0.70. Where estimates of apparent survival (phi) from capture-recapture studies were available, the two methods produced correlated results with a tendency for phi < S. Among tanagers, only Ramphocelus dimidiatus (0.82) and Piranga bidentata (0.50) stood out from the other species, for which S averaged 0.66 +/- 0.05 (SD). Annual survival rates of temperate and tropical species overlapped broadly in this analysis, reinforcing the conclusion that distinctive life-history traits of temperate vs. tropical species cannot be explained completely by the adjustment of reproductive investment in relation to adult survival and the expectation of future life.     

Rythmes nutritionnels et organisation trophique d'une population de crustacés pélagiques (Euphausiacea)

The nature of the food (animal, plant or mixed) and the fullness of the stomachs at different times of the day have been studied through dissection of 18620 specimens representative of almost all the euphausiid species of the Central and Western Tropical Pacific Ocean. Animal food predominates in 22 of the 28 species studied, while 12 can be considered as omnivorous; only 4 are mainly phytophagous. The trophic level of a given species is more or less the same in different zones, but scarcity of phytoplankton in oligotrophic tropical regions results in an increase of the trophic level of herbivorous and omnivorous species. There is no correlation between trophic level and vertical distribution of a species. Each species follows a clearly defined feeding rhythm, usually characteristic for each genus: nutrition most active by night in Euphausia, continuous in Thysanopoda, restricted to light hours in Stylocheiron, mainly from noon to midnight in Nematoscelis and Nematobrachion. As a rule, it is obvious that the smaller the daily vertical migration, the more pronounced the feeding rhythm: the range of fluctuations in fullness of stomachs over 24 h is weak or non-existent in migrating species, maximum in non-migrating ones. Nevertheless, daily vertical migration does not appear to be “advantageous” from the point of view of trophic efficiency: assuming that the stomachal transit is the same for all species (a speculative proposition), it is shown that the ratio “total biomass of species: food consumed during 24 h”, i.e., “biomass permanently available for the upper link: biomass eaten daily at the expense of the lower link” is 4 times higher in non-migrating than in migrating species. It is thus considered that daily vertical migration is an expensive manner to transfer energy from link to link, and therefore fulfills other functions, amongst which diffusion throughout the whole water column of the biomass produced in the upper levels is probably one of the most important.