Distribution of Trypetesa lampas (Cirripedia,Acrothoracica) in various gastropod shells

The distribution of Trypetesa lampas (Hanoock) and its rates of infection of different species of gastropod shells in the waters of Anglesey were studied. T. lampas was found in depths from 3 to at least 25 fathoms (5 to 46 m). It infected dead shells, mainly of Buccinum undatum L., Colus gracilis (da Costa), Neptunea antiqua (L.) and Natica alderi (Forbes); it was absent from shells occupied by hermit crabs in the intertidal zone. Significantly more B. undatum shells were infected than shells of N. antiqua and Natica alderi, and more of both C. gracilis and N. antiqua than of Natica alderi. Larger shells of B. undatum were more likely to be infected than were the smaller ones. The number of females per shell varied with the shell length raised to the power 2.39 instead of as expected with the square of the length.     

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

A consistent diploid number of 2n = 36 was determined for the sea urchinParacentrotus lividus from the Gulf of Palermo by analysis of mitotic chromosomes of both early developing embryos and male gonads. The haploid numbern = 18 was determined by counts of spermatocyte bivalents at diakinesis. A heteromorphic chromosome sex mechanism of the XY type is likely present in this species. This is indicated by the occurrence of a chromosomal pair, pair No. 2, which is heteromorphic in both morphology and size in about 50% of the mitotic figures (metaphases and anaphases) of einbryos. In addition, heteromorphism of the same pair of chromosomes occurred during spermatogonial metaphases in the five male specimens investigated here. The detection of a low chromosome number (2n = 36) compared to other echinoids (2n = 42 to 44), a heteromorphic chromosome sex system and the involvement of three chromosome pairs in nucleolar organization (NORs) provide evidence of the specialization of theP. lividus karyotype.     

A stereoscan electron microscope study of male reproductive characters in the Jaera albifrons group of species (Crustacea: Isopoda)

The male secondary sex characters of Jaera albifrons Leach, Jaera ischiosetosa Forsman, Jaera praehirsuta Forsman and Jaera forsmani Bocquet are described with the Stereoscan electron microscope (S.E.M.). These characters, which are present on the peraeopods, are the only means of identification for these Jaera species which together form the Jaera albifrons group (Isopoda, Asellota). The male praeoperculum (modified, fused, first pair of pleopods) and appendix masculinae (modified endites of the second pair of pleopods) have also been studied with the S.E.M. and possible functions of the various sex characters are discussed. Both the male operculum and appendix masculinae are similar for each species, suggesting that copulation with females of a different species is anatomically possible. The fact that hybrids are rarely collected in ecological investigations is discussed with reference to the present known information. Two methods of copulation for the members of this group have been proposed and these are discussed. A method of sperm transfer along the male operculum is outlined.     

Inbreeding and local mate competition in the ant Cardiocondyla batesii

The ant species Cardiocondyla batesii is unique in that, in contrast to all other ant species, both sexes are flightless. Female sexuals and wingless, ergatoid males mate in the nest in autumn and young queens disperse on foot to found their own colonies in spring. The close genetic relatedness between queens and their mates (r_qm=0.76±SE 0.12) and the high inbreeding coefficient (F=0.55; 95%CI 0.45–0.65) suggest that 83% of all matings are between brothers and sisters. As expected from local mate competition theory, sex ratios were extremely female biased, with more than 85% of all sexuals produced being young queens. Despite the common occurrence of inbreeding, we could not detect any adult diploid males. Though the probability of not detecting multiple mating was relatively high, at least one-third of all queens in our sample had mated more than once. Multiple mating to some extent counteracts the effects of inbreeding on worker relatedness (r_ww=0.68±SE 0.05) and would also be beneficial through decreasing diploid male load, if sex was determined by a single locus complementary system.Communicated by L. Sundström     

Secondary sex ratios do not support maternal manipulation: extensive data from laboratory colonies of spiny mice (Muridae: Acomys)

Spiny mice of the genus Acomys (Muridae) represent a very suitable mammalian model for studying factors influencing the secondary sex ratio (SSR). The maternal effort in these rodents is extremely biased in favour of the prenatal period and, therefore, maternal manipulation of the SSR is potentially more advantageous. We studied the SSR in four populations/species of spiny mice kept in family groups consisting of two closely related females, one non-relative male and their descendants. The groups were established from founding animals aged about 3 months (maturing age) and were allowed to breed freely for several months. Each litter was sexed after birth, and relevant data were thoroughly recorded. Altogether, data were collected on 1684 litters: 189 of Acomys sp. from Iran, 203 of A. cilicicus, 875 of A. cahirinus, and 417 of A. dimidiatus. We recorded the sex of 4048 newborns of which 1995 were males and 2053 were females. The overall sex ratio was close to 1:1 (49.2%). Generalized linear mixed models and/or generalized linear models were constructed to evaluate the effect of four life history and eight social variables on the sex ratio. No consistent effects of these variables on the sex ratio were found and, interestingly, none of the variables associated with maternal life history had any effect on the sex ratio. Three factors associated with group composition (i.e. the number of immature males, the number of immature females and the number of breeding females) did have significant effects on the sex ratio, but these effects were not consistent across the studied species. In conclusion, our evaluation of this large dataset revealed that the sex ratio in spiny mice is surprisingly stable.     

Cytogenetic studies in green mussel, Perna viridis (Mytiloida: Pteriomorphia), from West Coast of India

Chromosomes of Perna viridis were characterized by karyotype analysis, C-banding and nucleolus organizer regions (NORs). The diploid chromosome number was confirmed as 30 and the karyotype is composed of ten metacentric and five submetacentric chromosome pairs. Constitutive heterochromatin blocks were found on all chromosomal pairs except chromosomal pair 15, which showed uniform staining throughout the entire chromosomes. Silver staining revealed nucleolus organizer regions on telomeric region of four chromosomal pairs, viz. 1, 3, 7 and 11. This is the first comprehensive study undertaken on chromosomes of Perna viridis.     

The ecophysiological complex of Bathyporeia pilosa and B. pelagica (Crustacea: Amphipoda). II. Effects of exposure

The resistance to high and low temperatures, starvation and desiccation effects in the sand dwelling amphipods Bathyporeia pilosa Lindström and B. pelagica (Bate) have been tested. B. pilosa was the more tolerant species in all experiments. Gravid females showed a greater resistance to high temperatures than adult males in both species, and starvation tolerance was in the order gravid females>juvenile males> adult males. Time-temperature relationships, however, would seem to be of greater ecological significance than upper or lower lethal temperatures, and desiccation effects become obvious well within any limits set by starvation. Exposure would appear to be an important concept limiting the intertidal distribution of sand dwelling animals, particularly those confined to the surface layers of sediment. The amplitude, rate and degree of environmental change and its effect on feeding and reproduction offer severe limitations to the distribution of the two Bathyporeia species studied.     

Multiple sex-chromosome system and other karyological characterizations of Pterotrachea hippocampus (Mollusca: Mesogastropoda)

Two modal diploid numbers of chromosomes were found for Pterotraches hippocampus Philippi (Mollusca: Mesogastropoda) collected from the Gulf of Palermo in 1990: 2n=31 and 32 for males and females, respectively. This, along with other karyological characteristics such as the occurrence of a trivalent configuration at diakinesis and two types of metaphase-II spreads in spermatocytes, supports the notion that a X₁X₂Y/X₁X₁X₂X₂ sex mechanism operates in the species investigated here. Silver nitrate procedure revealed an intraindividual variation in the Ag-staining pattern occurring in this species. The majority of the chromosome pair displayed terminal and/or interstitial heterochromatic blocks after C-banding.     

Karyotype differentiation between two species of carangid fishes,genusTrachurus (Perciformes: Carangidae)

A karyological study ofTrachurus trachurus andT. mediterraneus (Perciformes: Carangidae) was conducted by standard, fluorochrome staining (CMA₃, mithramycin, quinacrine mustard, DAPI), C-, Ag-NOR, and Alu-I banding methods. The karyotypes of both species consisted of 2n = 48 chromosomes, but of different FN:T. trachurus possessed a chromosome complement of 2 metacentric and 46 acrocentric elements, fundamental number (FN) = 50 andT. mediterraneus, a chromosome complement of 4 metacentric, 4 submetacentric, 14 subtelocentric and 26 acrocentric chromosomes, FN = 70. In neither of the two taxa investigated were heteromorphic sex chromosomes observed. The nucleolar organizer region was interstitially located on the long arm of the Ist pair of chromosomes in both species, intermediate inT. mediterraneus and subterminal inT. trachurus. Constitutive heterochromatin was found in nearly all centromeric and telomeric regions inT. trachurus; inT. mediterraneus it formed less intense telomeric and centromeric bands and thin interstitial bands on eight chromosome pairs. In addition, the C-positive material reacted differently to the digestion with endonuclease Alu-l in the two species. The results are discussed and compared with karyological data known for other species of Carangidae.     

d-Pinitol as a key oviposition stimulant for sulfur butterfly, Colias erate: chemical basis for female acceptance of host- and non-host plants

The sulfur butterfly, Colias erate, utilizes various legumes as host plants. We examined the chemical constituents of its primary host plant, Trifolium repens (white clover), to identify phytochemicals inducing oviposition by C. erate females. Since one of the four aqueous subfractions prepared from a methanolic extract of the plant has previously been shown to be the most responsible for the oviposition-stimulatory activity exerted by the plant, chemical analyses were conducted of the fraction concerned. Activity-directed fractionation of the subfraction by ion-exchange chromatography revealed that the key substance(s) resided in the neutral fraction. Preparative TLC of the neutral fraction and subsequent spectral analyses identified d-(+)-pinitol, glycerin, methyl β-d-glucoside, and myo-inositol as characteristic components together with ubiquitous sugars (e.g., sucrose and glucose). Of these, only pinitol singly evoked significant oviposition responses at concentrations over 0.05%. In dual-choice bioassays, however, females laid significantly more eggs on pinitol solutions admixed with glycerin or methyl β-d-glucoside than on pinitol alone. Two cyanoglucosides, linamarin, and lotaustralin, occurring in the other aqueous subfractions, also synergistically increased the oviposition response in combination with pinitol. The results clearly indicated that pinitol is a crucial oviposition stimulant involved in host recognition, while glycerin, methyl β-d-glucoside, linamarin, and lotaustralin function as synergists. We further examined the oviposition responses of C. erate females to aqueous fractions, along with their chemical compositions, that had been prepared from five other host plants and a non-host plant, Aristolochia debilis (Aristolochiaceae), on which oviposition occasionally took place in an outdoor cage during the experiments. The plant species accepted by ovipositing females were all found to contain pinitol in amounts enough to induce egg laying by the butterfly, thus leading to the conclusion that pinitol serves as the essential mediator in recognizing and accepting potential host plants.     

The mouthparts of the members of the Jaera albifrons group of species (Crustacea: Isopoda)

The mouthparts of Jaera albifrons Leach, Jaera ischiosetosa Forsman, Jaera praehirsuta Forsman and Jaera forsmani Bocquet were examined with the light microscope and the Stereoscan electron microscope, and were found to be identical in all species. The structure of the mouthparts indicate that all four species feed by scouring and abrading algal or bacterial films from rocks or Fucus. Food, therefore, does not seem to be an isolating factor involved in the microdistribution of the four species on a shore.     

Morphologie,Entwicklung und Ökologie digener Trematoden-Larven der StrandschneckeLittorina littorea

More than 6000 individuals of the snailLittorina littorea L., from 6 different localities on the coast of the German Bay (North Sea), were examined for larval trematodes by crushing their shells, an additional 6000 by isolation in small quantities of sea water. Six species of larval trematodes were found inL. littorea and described: Notocotylid larva —Cercaria lebouri Stunkard, 1932; Cercaria ofHimasthla elongata (Mehlis, 1831); Cercaria ofPodocotyle atomon (Rudolphi, 1802); Cercaria ofRenicola roscovita (Stunkard, 1932) n. comb.; Metacercaria ofMicrophallus pygmaeus (Levinsen, 1881); Cercaria ofCryptocotyle lingua (Creplin, 1825). Considering the large number of investigated snails, the trematode fauna ofL. littorea in this area is assumed to be completely known. The life cycles ofHimasthla elongata andRenicola roscovita are described. Larvae of the different trematode species show differential preferences for distinct size groups of snail hosts. Juvenile snails are not infected. No correlation exists between infection rates and sex of the hosts. Quantitative aspects of multiple infections are calculated and discussed. The incidence of larval trematodes in the investigated localities differs. Information is presented on seasonal variations of infestations and their possible causes.     

Replication,C and Ag-NOR chromosome-banding in two anguilliform fish species

The chromosomes of the Conger conger and Echelus myrus (Anguilliformes: Teleostei), were analysed by conventional (C and Ag-NOR) and by replication-banding techniques. Both species had a diploid number of 38 and one chromosome pair with C-positive nucleolar organizer regions (NOR). These cytogenetic traits are mainly consistent with those recorded for anguilliform species in general. The replication-banding pattern allowed us to identify individual chromosome pairs, to detect different classes of chromatin, and to suggest chromosome evolutive mechanisms in these two species. The results confirm the superiority of replication patterns in resolving longitudinal differentiation of fish chromosomes, that is not generally possible from structural bands.     

Karyotype, nucleolus organiser regions and constitutive heterochromatin in Ostrea angasi (Molluscae: Bivalvia): evidence of taxonomic relationships within the Ostreidae

Chromosome preparations from gill tissue of the Australian flat oyster Ostrea angasi Sowerby were studied with conventional Giemsa staining, C-banding and silver staining techniques. A diploid complement of 2n = 20 was observed, consisting of five metacentric, three submetacentric and two subtelocentric pairs. Constitutive heterochromatin was distributed as large centromeric blocks in Chromosome Pairs 3, 6, 8, 9 and 10. The nucleolus organizer regions (NORs) were located terminally on long arms of Chromosome Pairs 9 and 10. This allowed the identification of homologous chromosomes in submetacentric and subtelocentric pairs. Intraspecific variability in NOR pattern as revealed by differences in the number of silver-stained NORs (Ag-NORs) per cell was found to be very common. Comparison of the patterns of karyotype, C-band and Ag-NORs between species of the larviparous oysters for which data have been published demonstrate that the chromosomal structure of the endemic Australian and New Zealand species O. angasi shows little similarity to the Southern Hemisphere oysters O. (Eostrea)puelchana Orbigny and Tiostrea chilensis (Philippi) and the Indo-West Pacific oyster O. denselamellosa, but very high resemblance to the European species O. edulis. Received: 12 August 1996 / Accepted: 16 September 1996     

Effects of dieldrin in seawater on the development of two species of crab larvae,Leptodius floridanus and Panopeus herbstii

Some of the effets of dieldrin on the development of two species of crabs, Leptodius floridanus (Rathbun) and Panopeus herbstii (Milne-Edwards), were studied. It was found that the larvae of neither species were able to complete their development at 10 ppb dieldrin or higher in seawater. Groups of L. floridanus larvae reared in 1 ppb dieldrin in seawater had a 15 to 27% higher mortality during development to the postlarval stage than controls. The highest mortality occurred during the first zoeal stage. The time of development to the megalopal stage was as much as 11.4% longer among larvae reared in 1 ppb than among controls. The survival of L. floridanus larvae was not affected by 0.5 ppb dieldrin in seawater. The survival of P. herbstii larvae to the first crab stage was not affected by 1 ppb dieldrin in seawater at 28.5 °C, 30%.S. It was concluded that a comprehensive study of the toxicity of a given pesticide to all stages in the life cycle of a species is necessary to give even an incomplete idea of how the pesticide might affect the animal in its natural environment.     

Chromosomal complements of two forms of Neanthes japonica (Polychaeta,Nereididae) with evidence of male-heterogametic sex chromosomes

Karyotypes of the brackish-water polychaeteNeanthes japonica (Izuka) collected from five rivers in Japan from 1984 to 1988 were examined with air-drying and flame-drying methods using materials consisting of regenerating tails, clumps of spermatogonia and youngN. japonica specimens (embryos, larvae or juveniles). A diploid number of 28 was determined in well-spread metaphase chromosomes of mitotic cells. The presence of an XX-XY (male heterogametic) sex chromosome system was established for the first time in polychaetes. The Y chromosome was larger than the X chromosome. Slight differences in karyotype were found between two forms (the small- and large-egg forms), which are very similar in adult morphology but can be distinguished by reproductive and developmental characteristics.     

Electrophoretic studies of serum proteins of four Tilapia species (Pisces)

The blood serum of 4 Tilapia species were analyzed electrophoretically for protein components, and the percentage of proteins in each fraction was determined. Sera from Tilapia nilotica Linnaeus, T. zillii Gervais, T. galilaea Artedi, and T. aurea (Steindachner) were studied. Characteristic protein fractions for each species were obtained. The species differed in the number of protein fractions and in the final mobilities; T. nilotica sera migrate 120 mm, T. zillii sera 95 mm, T. galilaea sera 90 mm, and T. aurea sera 118 mm. The mobilities for fractions 1 and 2 were similar for the 4 species' sera. Inter-specific differences in the amount of protein occurred. Diet may be a major contributing factor to the variations observed in the amount of total protein.     

Breeding Periodicity for Male Sea Turtles,Operational Sex Ratios,and Implications in the Face of Climate Change

Abstract: Species that have temperature‐dependent sex determination (TSD) often produce highly skewed offspring sex ratios contrary to long‐standing theoretical predictions. This ecological enigma has provoked concern that climate change may induce the production of single‐sex generations and hence lead to population extirpation. All species of sea turtles exhibit TSD, many are already endangered, and most already produce sex ratios skewed to the sex produced at warmer temperatures (females). We tracked male loggerhead turtles (Caretta caretta) from Zakynthos, Greece, throughout the entire interval between successive breeding seasons and identified individuals on their breeding grounds, using photoidentification, to determine breeding periodicity and operational sex ratios. Males returned to breed at least twice as frequently as females. We estimated that the hatchling sex ratio of 70:30 female to male for this rookery will translate into an overall operational sex ratio (OSR) (i.e., ratio of total number of males vs females breeding each year) of close to 50:50 female to male. We followed three male turtles for between 10 and 12 months during which time they all traveled back to the breeding grounds. Flipper tagging revealed the proportion of females returning to nest after intervals of 1, 2, 3, and 4 years were 0.21, 0.38, 0.29, and 0.12, respectively (mean interval 2.3 years). A further nine male turtles were tracked for short periods to determine their departure date from the breeding grounds. These departure dates were combined with a photoidentification data set of 165 individuals identified on in‐water transect surveys at the start of the breeding season to develop a statistical model of the population dynamics. This model produced a maximum likelihood estimate that males visit the breeding site 2.6 times more often than females (95%CI 2.1, 3.1), which was consistent with the data from satellite tracking and flipper tagging. Increased frequency of male breeding will help ameliorate female‐biased hatchling sex ratios. Combined with the ability of males to fertilize the eggs of many females and for females to store sperm to fertilize many clutches, our results imply that effects of climate change on the viability of sea turtle populations are likely to be less acute than previously suspected.     

Harpacticoid copepod respiration: Enhydrosoma propinquum and Longipedia helgolandica

Oxygen consumption rates of 2 harpacticoid copepods, one benthic, Enhydrosoma propinquum (Brady) and one benthopelagic, Longipedia helgolandica (Klie), were determined and compared with those of the pelagic harpacticoid Euterpina acutifrons. The respiratory rates of the 3 species differed significantly and could be correlated with activity patterns and habitat preferences. E. propinquum consumed the least oxygen, E. acutifrons an intermediate amount, and L. helgolandica the most per unit dry weight. Gravid L. helgolandica had a lower metabolic rate than the non-gravid females. The lower values for the gravid females most likely reflected the metabolic activity of the developing egg mass. Harpacticoids may be important contributors to total meiobenthic metabolism, since they respire more per unit weight than do nematodes.Supported by NSF Grant GB-8189 to Duke University Cooperative Program in Biological Oceanography (BCC) and NSF Grant 7435 (WBV).     

Do protandric pandalid shrimp have environmental sex determination?

Based on demographic analysis of four different temporally enclosed demes of Pandalus borealis in Gullmarsfjorden on the Swedish west coast and published information, I discuss the notion of environmental sex determination in protandric pandalid shrimps as suggested by sex allocation theory. Demographic results showed that age structure and mortality rates varied substantially between four studied periods without noticeable effects on the age of sex change in the fjord populations. The majority of shrimps changed sex at an approximate age of 3 years and became females at an age of 3 to 4 years, however, low proportions (4 to 7%) of 2nd year females (transitional at ca. 1 year) and 3rd year females (5 to 12%) (transitional at ca. 2 years) were present each year. Low proportions of primary females were also found in two of the temporally enclosed demes, in 1985 (9%) and in 1987 (5%). These results do not indicate that yearly variations in age structure, mortality, or frequency of older breeders in the breeding population affect the age of sex change in temporally enclosed fjord demes of this protandric species. An alternative to assuming that the protandric mode of reproduction in pandalid shrimp is combined with environmental sex determination is suggested. Received: 24 September 1996 / Accepted: 6 November 1996