Population biology of Gnathophausia longispina (mysidacea: Lophogastrida) from a central north pacific seamount

Large numbers of the lophogastrid mysid Gnathophausia longispina were discovered in 1984 over Southeast Hancock Seamount on the northern Hawaiian Ridge. Additional specimens were collected from the same area during subsequent surveys in 1985, 1987, and 1988 to obtain new information on the life history of this species. Estimates of growth suggest that G. longispina reaches sexual maturity by its second year. Young are brooded by the female for nearly a year and released in late winter-early spring. It is doubtful if G. longispina live longer than 2 yr or produce more than one brood. Most G. longispina are found within 100m above the seamount summit. The modal progression of size classes over time indicates that this species is dependent on local processes rather than recruitment from other areas to maintain its populations at the seamount.     

Larval development in the Tasmanian mysids Anisomysis mixta australis, Tenagomysis tasmaniae and Paramesopodopsis rufa (Crustacea: Mysidacea)

We describe the brood duration and marsupial development of three temperate coastal mysid species, Anisomysis mixta australis (Zimmer), Tenagomysis tasmaniae Fenton and Paramesopodopsis rufa Fenton, found commonly in Tasmanian waters. Larvae cultured in vitro had brood durations at 13 °C (17 °C) of 22 (15), 23 (15), and 28 (20) d, respectively. Development through seven larval stages, and brood durations for these three species are similar to those reported for coastal mysids from other temperate areas throughout the world. Received: 10 June 1997 / Accepted: 1 July 1997     

Resident mysids: community structure,abundance and small-scale distributions in a coral reef lagoon

Seasonal and diel variations in community structure and abundance of coral-reef lagoon mysids were examined at Davies Reef in the central region of the Great Barrier Reef (GBR) between June 1980 and May 1981. Twenty-five mysid species belonging to three subfamilies of the family Mysidae were captured during the study, with six new records for the GBR. The epibenthic mysid community differed from that in the overlying water, was faunistically uniform, but formed characteristic seasonal and diel groupings. The dominant epibenthic species were Erythrops sp., Anisomysis pelewensis, Doxomysis littoralis, A. laticauda, Prionomysis stenolepis, A. lamellicauda, and A. australis, five of which formed schools. Total mysid abundances ranged between 110 and 790 m^-3 with peak abundance in October. Schooling species occurred at local densities of up to 500 000 m^-3. Mysids were absent from shallow and midwater depths during the day, but were distributed throughout all depths at night with peak abundances in mid-water and deep layers. The dominant species in the water column at night were Pseudanchialina inermis, A. laticauda and Gastrosaccus indicus, in descending order of abundance. Lagoonal mysids contribute little to the food of sessile reef planktivores, as all but three species remain concentrated near or on the lagoon floor both day and night. The contribution of resident lagoon mysids to reef trophodynamics is probably through remineralization of lagoon detritus. Given the vast reef areas comprised of sandy lagoons, the large populations and relatively large size of lagoon mysids, this trophodynamic role may be of considerable importance.A.I.M.S. Contribution No. 477     

Winter food utilisation by sympatric mysids in the Baltic Sea,studied by combined gut content and stable isotope analyses

We studied the winter dietary characteristics of two sympatric mysid species, Mysis mixta and M. relicta, which exploit both benthic and pelagic habitats during diel vertical migrations. Samples collected before and after the ice-covered period in the northern Baltic Sea were investigated using both stomach content analyses and stable isotope analyses of carbon and nitrogen. Both of the mysid species were omnivorous during winter and utilised both benthic and pelagic food sources. The main food source before the ice period was calanoid copepods (40 and 36% for M. mixta and M. relicta, respectively), and after ice-out calanoid copepods (23%) and zooplankton resting eggs (23%) for M. mixta and diatoms (44%) and calanoids (25%) for M. relicta. Their patterns of food utilisation broadly followed seasonal fluctuations in the abundance of the main prey groups. Although pelagic food availability is low in winter both mysid species utilised pelagic prey widely. We also show that when combining these different diet analysis methods it is important to take into account the time lag in isotopic signatures, otherwise the obtained results do not correspond but instead show the feeding history at different times.     

Brood sex ratio adjustment in collared flycatchers (<Emphasis Type="Italic">Ficedula albicollis</Emphasis>): results differ between populations

Recently, a number of studies have found adaptive brood sex ratio (BSR) manipulation in birds. The reason for such manipulations is thought to be the different reproductive value of male and female nestlings. Several studies have found that parental quality and food supply can affect BSR, however results are sometimes inconsistent between species and populations. We investigated BSR patterns in a Hungarian population of Collared Flycatchers (Ficedula albicollis) and compared the results with those obtained in a previous study of the same species in Sweden. We found two significant differences. First, the male forehead patch size, a heritable, sexually selected trait, affected the brood sex ratio in the Swedish population, but not in our Hungarian study population. This difference might be a consequence of the different information content of the forehead patch size in the two populations. Second, a seasonal shift in BSR (more sons late in the season) was observed in the Hungarian, but not in the Swedish population.Communicated by J. Graves     

The effects of size-dependent predation risk on the interaction between behavioral and life history traits in a stream-dwelling isopod

In field surveys, laboratory observations and field-based assays of behavior, I examined the effects of size-dependent predation risk on the interaction between size at reproductive maturity and maternal care behavior in the stream-dwelling isopod, Lirceus fontinalis. L. fontinalis exhibit population-specific sizes at reproductive maturity which result in population differences in predation risk during the adult phase. Females from streams containing salamander larvae (that prefer small prey) mature at large sizes and then become relatively safe from predation. Females from streams containing fish (that consume all size classes of prey equally) mature at small sizes and remain at risk. I tested whether these differences in expected survival were reflected in the behavior of females during the maternal phase (i.e., the period during which females exhibit maternal care). Female L. fontinalis carry developing juveniles inside a brood pouch. I simulated predatory attacks on gravid female L. fontinalis from the different population types and found that female behavior correlated with population differences in risk. When “attacked”, females from streams with predatory fish (that experience high risk to adult females) released juveniles from the brood pouch, whereas females from populations with predatory salamander larvae (that pose relatively little risk to adult females) did not release juveniles. I discuss the results with reference to the joint evolution of behavioral and life history traits. Received: 6 March 1996 /Accepted after revision: 12 August 1996     

Population characteristics of the deep-sea lobsters Polycheles typhlops and Stereomastis sculpta (Decapoda: Polychelidae) in a bathyal mud community of the Mediterranean Sea

Distribution and abundance as a function of depth, and population parameters such as sex and size structure of the population and aspects of reproductive biology have been studied in the deep-sea polychelid lobsters Polycheles typhlops and Stereomastis sculpta. Samples were taken by otter trawl in the Balearic Sea, a deepsea basin in the northwestern Mediterranean Sea from 1985 to 1989. In both species the largest size classes were dominated by females. In S. sculpta, male and female sizes were very similar. In P. typhlops, ovigerous females and those with external spermatophores were 23 and 25 mm in carapace length (CL), respectively; males with external spermatophores were 17 mm in CL. In S. sculpta, ovigerous females and those with external spermatophores were 24 and 19 mm CL, respectively, and males with external spermatophores 19 mm CL. Highest densities of P. typhlops occurred along the middle slope at depths between 500 and 1000 m. Only small-sized individuals were found at the deepest depths sampled; some recruitment must therefore occur in waters much deeper than those usually inhabited by the adult population. The sex-ratio was 1:1 in most samples, but in some of the shallowest samples females predominated. The depth distribution range of S. sculpta was 981 to 2253 m: densities clearly increased with increasing depth. There were no apparent variations in size distribution as a function of depth. Since very few adult males and females were captured, the population in the survey area would seem to be comprised mainly of juveniles. As a function of depth, females were numerically dominant only in some of the shallowest samples taken in the distribution range of this species. There is strict habitat partitioning between the two species. In both species, the variation in the sex-ratio as a function of depth suggests differential migration between the sexes, probably related to egg incubation and hatching.     

Growth rate of the bathypelagic crustacean Gnathophausia ingens (Mysidacea: Lophogastridae)

The content of water, ash, carbohydrate, lipid, protein, chitin, carbon, hydrogen, nitrogen and energy was measured for all life stages of the bathypelagic mysid Gnathophausia ingens collected in San Clemente Basin off Southern California, USA between January 1969 and February 1982. These data are used to examine the life history, growth rates, growth pattern and partitioning of material and energy over the life of this species. Females reproduce only once and brood their young for about 1.5 yr, during which time the females do not feed. This species has a very high reproductive effort: of the energy accumulated over its life, 61.3% is used in egg production, 13.4% in parental care of young, 5.6% in cast exoskeletons and only 19.6% remains in the females after brooding. The relative rate of growth (percentage of energy d^?1) is about 1% immediately after leaving the mother and declines to about 0.2% as maturity is approached. Such growth rates appear to be typical for an animal of this size living at low temperatures. The evolutionary context of this mysid's life history is discussed.     

Feeding by larvae of intertidal invertebrates: assessing their position in pelagic food webs

One of the leading determinants of the structure and dynamics of marine populations is the rate of arrival of new individuals to local sites. While physical transport processes play major roles in delivering larvae to the shore, these processes become most important after larvae have survived the perils of life in the plankton, where they usually suffer great mortality. The lack of information regarding larval feeding makes it difficult to assess the effects of food supply on larval survival, or the role larvae may play in nearshore food webs. Here, we examine the spectrum of food sizes and food types consumed by the larvae of two intertidal barnacle species and of the predatory gastropod Concholepas concholepas. We conducted replicated experiments in which larvae were exposed to the food size spectrum (phytoplankton, microprotozoan and autotrophic picoplankton) found in nearshore waters in central Chile. Results show that barnacle nauplii and gastropod veligers are omnivorous grazers, incorporating significant fractions of heterotrophs in their diets. In accordance with their feeding mechanisms and body size, barnacle nauplii were able to feed on autotrophic picoplankton (<5 microm) and did not consume the largest phytoplankton cells, which made the bulk of phytoplankton biomass in spring-summer blooms. Balanoid nauplii exhibited higher ingestion rates than the smaller-bodied chthamaloid larvae. Newly hatched C. concholepas larvae also consumed picoplankton cells, while competent larvae of this species ingested mostly the largest phytoplankton cells and heterotrophic protozoans. Results suggest that persistent changes in the structure of pelagic food webs can have important effects on the species-specific food availability for invertebrate larvae, which can result in large-scale differences in recruitment rates of a given species, and in the relative recruitment success of the different species that make up benthic communities.     

Mating opportunities,paternity, and sexual conflict: paternal care in northern and southern temperate house wrens

Males are generally predicted to care less for their young when they have more additional mating opportunities, lower paternity, or when their mates care more. We tested these predictions using male provisioning as a proxy for paternal care in two temperate populations of house wrens (Troglodytes aedon) with divergent life histories. Males in the migratory, occasionally socially polygynous New York, USA (northern) population provisioned less when more local females were fertile. A similar relationship was only weakly supported in the resident, socially monogamous Buenos Aires Province, Argentina (southern) population, possibly due to the higher density of house wrens there. A relationship between male provisioning and level of paternity within the brood was supported in both populations, but in opposite directions: while males in the southern population provisioned less at broods containing more extra-pair young, males in the northern population provisioned such broods more, contradicting predictions. Males provisioned less when their mates provisioned more in both populations, in agreement with sexual conflict theory. Additionally, the populations both exhibited a positive relationship between male provisioning and nestling age, but differed in the direction of the relationships of male provisioning with date and brood size. Our results suggest that even within a species, life history differences may be accompanied by differences in the determinants of behavior such as paternal care.     

Distribution,life history,and production of three species of <Emphasis Type="Italic">Neomysis</Emphasis> in Akkeshi-ko estuary,northern Japan

Spatial and seasonal distribution pattern, life history and production of three species of Neomysis (Mysidacea) which commonly occur in northwestern subarctic Pacific coastal waters, were investigated throughout the year in the Akkeshi-ko estuary, northern Japan. The most abundant species Neomysis awatschensis (annual mean density: 179.8 inds. m⁻², biomass: 108.8 mg DW m⁻²) occurred at the inner part of the estuary including low salinity areas with no clear preference for the seagrass bed. The second most abundant Neomysis mirabilis (mean density: 95.8 inds. m⁻², biomass: 90.1 mg DW m⁻²) occurred at relatively saline seagrass site throughout the year. Occurrence of Neomysis czerniawskii in the estuary was limited to the seagrass bed during summer when their population mainly consisted of juveniles, suggesting that this species is a seasonal migrant between the estuary and the marine environment. Both N. awatschensis and N. mirabilis populations were composed of two generation types, a larger sized overwintering and smaller sized spring/summer generations; however, each species had a different reproductive strategy. N. awatschensis was characterized by fast growth to maturity at a smaller size than N. mirabilis with a relatively high fecundity during warm season, suggesting that this species is an r-strategist which can utilize opportunistically a wide variety of habitats. In contrast, the seagrass bed resident N. mirabilis was a K-strategist which matures at a larger size producing fewer but larger offspring. The annual production of N. awatschensis (0.57–0.70 g DW m⁻², mean of the whole estuary) and N. mirabilis (0.58–0.68 g DW m⁻², mean of the seagrass bed) at their respective habitats was comparable. Consequently, species-specific life history and distribution pattern are concluded to allow Neomysis spp. to coexist in the estuary and the high carrying capacity of seagrass bed is suggested to contribute to maintain their high biomass level.     

Reproductive patterns of three intertidal salt-marsh gammaridean amphipods

Among three sympatric species of epibenthic amphipods found at different tide marks at Jamaica Bay, New York (USA), the length of time juveniles spend with the mother increases and the number of juveniles per brood decreases as tidal height increases. Each brood has two developmental periods: (1) the embryonic period, from ovulation to hatching; (2) the juvenile period, from hatching to emergence from the marsupium. Gammarus palustris, found at the high-tide mark, has a mean juvenile period of 1.7 days and a mean brood size of 12.4 offspring; G. mucronatus, found at mean-tide mark, has a mean juvenile period of 0.8 days and a mean brood size of 27.4 offspring; Melita nitida, found at low-tide mark, has a mean juvenile period of 0.5 days and a mean brood size of 30.0 offspring. Further, the range of days that a juvenile may emerge is widest for G. palustris (0 to 8 days after hatching) and narrowest for M. nitida (0 to 2 days).This work was submitted in partial fulfillment of the requirements for the Ph.D. at the City University of New York.     

Food utilisation of pelagic mysids, Mysis mixta and M. relicta, during their growing season in the northern Baltic Sea

The dietary habits of the pelagic mysid Mysismixta were studied during its growing season at an open sea location in the Gulf of Finland, the northern Baltic Sea. Stomach samples were taken twice a month from June to September 1997. The most abundant phytoplankton taxa in the stomachs were diatoms and dinoflagellates, and copepods and cladocerans were the most abundant zooplankton identified. A clear change was found in the diets during the study period. Small mysids (3 to 6 mm) fed on sedimented phytoplankton in the early summer (90% benthic particles in June) but shifted gradually to a more pelagic and carnivorous diet (>40% pelagic particles, consisting of ca. 60% zooplankton in September). Seasonal changes in mysid capture ability as well as food availability were suggested to affect the diet composition of mysids during their growth. The ratio of pelagic and benthic food particles could – irrespective of the season – be explained by mysid size, whereas the zooplankton:phytoplankton ratio was better explained by season. The stomach analysis suggests that the mysids needed to attain a threshold size of 8 to 11 mm to initiate feeding on the more evasive copepods. Mysids also started to grow faster at the same time as the proportion of copepods increased in the diet, which suggests that copepods are an important energy source for M. mixta in late summer. Finally, a comparison was made between the M. mixta diet and that of the less abundant M. relicta. The diets of the two pelagic mysid species overlapped by 75% (Schoener's index). The main difference was due to M. mixta eating more zooplankton and pelagic material than M. relicta. Received: 15 September 1999 / Accepted: 18 January 2000     

Paternal expenditure is related to brood sex ratio in polygynous great reed warblers

In many polygynous animals, parents invest more heavily in individual sons than in daughters. However, it is unclear if these differences in investment are a consequence of sex differences in the demand of offspring related to sexual size dimorphism or a consequence of parental manipulation. Here, we report on parental food delivery frequency in relation to brood size and brood sex ratio in a wild population of polygynous great reed warblers Acrocephalus arundinaceus. We used the polymorphic microsatellite loci on the Z chromosome to sex chicks. We found that paternal feeding frequency (times/h per nest) increased not with brood size, but with the proportion of males in the brood, although the demand per nest was more closely related to brood size than to brood sex ratio. Additionally, the increase in rate of paternal feeding frequency in relation to the brood sex ratio was much higher than the increase in rate of nestling food demands. Maternal feeding frequency was independent of both brood size and brood sex ratio. These results strongly suggest that fathers preferentially invest in their sons. We propose that parents can afford sex-biased parental care in animals in which food provisioning is enough for all offspring to survive. Received: 22 January 1996/Accepted after revision: 30 June 1996     

Cuckoo growth performance in parasitized and unused hosts: not only host size matters

The quality and quantity of food delivered to young are among the major determinants of fitness. A parental provisioning capacity is known to increase with body size. Therefore, brood parasitism provides an opportunity to test the effects of varying provisioning abilities of different-sized hosts on parasitic chick growth and fledging success. Knowledge of growth patterns of common cuckoo, Cuculus canorus, chicks in nests of common hosts is very poor. Moreover, no study to date has focused on any currently unused hosts (i.e., suitable cuckoo host species in which parasitism is currently rare or absent). Here, I compare the growth performance of cuckoo chicks in nests of a common host (the reed warbler, Acrocephalus scirpaceus) and two unparasitized hosts (the song thrush, Turdus philomelos, and the blackbird, Turdus merula). Parasitic chicks were sole occupants of the observed nests, thus eliminating the confounding effect of competition with host chicks. Experiments revealed striking differences in parasitic chick growth in the two closely related Turdus hosts. Cuckoo chicks cross-fostered to song thrush nests grew much quicker and attained much higher mass at fledging than those in nests of their common reed warbler host. Alternatively, parasitic chicks in blackbird nests grew poorly and did not survive until fledging. I discuss these observations with respect to host selection by parasitic cuckoos.     

Comparisons of genetic population structures in four intertidal brachyuran species of contrasting habitat characteristics

Genetic population structures along the Japanese coast, analyzed by sequence data from the mitochondrial DNA COI region, were determined for four intertidal brachyuran species in the superfamily Thoracotremata (Ocypode ceratophthalma, Gaetice depressus, Chiromantes dehaani and Deiratonotus japonicus), which were characterized by different habitat requirements. O. ceratophthalma (seashore; supratidal sand) and C. dehaani (estuarine; supratidal marsh) showed no significant genetic differentiation among Japanese populations. The Japanese populations of O. ceratophthalma, however, were found to genetically differentiated from the Philippine population. G. depressus (seashore; intertidal cobbles) exhibited significant genetic differentiation between the Amami-Ohshima population and other local populations. D. japonicus (estuarine; intertidal cobbles) showed significant genetic differentiation among many local populations separated by about 30–1,200 km. The different patterns of genetic population structure recorded for the four species, thus, do not simply correspond to habitat type. An erratum to this article can be found at     

Feeding habits and food requirements of some amphipods in the Black Sea

Food composition and food requirements of four amphipod species of the Black Sea — Dexamine spinosa (Mont.), Amphithoe vaillanti Lucas, Gammarellus carinatus (Rathke), Gammarus locusta L. — were studied and an attempt made to assess the quantitative composition of the food, daily rhythms of feeding, and daily food rations. The composition of the food of the above-named amphipods is similar and consists primarily of seaweeds. Daily feeding intensity is characterized by a distinct increase during the dark period (D. spinosa, A. vaillanti); however, in G. locusta feeding intensity increases in the morning. The daily food rations of amphipods vary greatly (from 1.7 to 360% of the specimens' body weight), depending upon factors such as the kind of food, age, sex, the physiology of specimens, and the water temperature. The total quantity of food eaten by the populations of these amphipods in the coastal zone of the Black Sea amounts to 4000 g organic matter per square metre within 1 year.     

Body size preferences in the pot-bellied seahorse <Emphasis Type="Italic">Hippocampus abdominalis:</Emphasis> choosy males and indiscriminate females

Male seahorses (genus Hippocampus) provide all post-fertilization parental care, yet despite high levels of paternal investment, these species have long been thought to have conventional sex roles, with female mate choice and male–male competition. Recent studies of the pot-bellied seahorse (Hippocampus abdominalis) have shown that sex-role reversal occurs in high-density female-biased populations, indicating that male mating preferences may lead to sexual selection on females in this species. Egg size, egg number, and offspring size all correlate positively with female body size in Hippocampus, and by choosing large mating partners, male seahorses may increase their reproductive success. While male brood size is also positively correlated with body size, small H. abdominalis males can carry exceptionally large broods, suggesting that the fecundity benefits of female preference for large partners may be limited. We investigated the importance of body size in reproductive decisions of H. abdominalis, presenting focal individuals of both sexes with potential mating partners of different sizes. Mating preferences were quantified in terms of time spent courting each potential partner. Male seahorses were highly active throughout the mate-choice trials and showed a clear behavioral preference for large partners, while females showed significantly lower levels of activity and equivocal mating preferences. The strong male preferences for large females demonstrated here suggest that sexual selection may act strongly on female body size in wild populations of H. abdominalis, consistent with predictions on the importance of female body size for reproductive output in this species. An erratum to this article can be found at     

Brooding of the sub-Antarctic heart urchin, <Emphasis Type="Italic">Abatus cavernosus</Emphasis> (Spatangoida: Schizasteridae), in southern Patagonia

The reproductive cycle of the sub-Antarctic spatangoid sea urchin, Abatus cavernosus, was examined during a 2-year period in southern Patagonia, Argentina. The population studied is the northernmost known coastal population in the austral oceans, and is influenced by a greater annual range of seawater temperature than other Abatus species. The sex ratio of the overall A. cavernosus population did not differ significantly from 1:1, but was not homogeneous across size classes. A clearly defined annual reproductive cycle was found. Spawning occurred from May to July and was synchronous between sexes. Females were observed to be brooding within a 9-month period, from May to February. Juveniles were released during the austral summer, from January to February. The length at which 50% of the females were brooding occurred at a test length of 25.9 mm. A. cavernosus had a large egg size (mean diameter = 1.4 mm) and low fecundity (maximum = 57 eggs per female) compared to closely related species. The number of eggs within each brood pouch was highest in larger anterior brood pouch, which is close to two gonopores, as opposed to the other anterior and two smaller posterior pouches. Significant interannual variation was observed in gonad cycles, fecundity, and embryo development such as: brood size decreased during 2001; adjusted gonad dry weight and fecundity were higher during 2003. Hypotheses concerning the gonadal and brooding cycles and fecundity of sub-Antarctic and Antarctic Schizasteridae are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Larval biology of six species of the genus Conus (Gastropoda: Toxoglossa) in Hawaii,USA

Among the Hawaiian species in the genus Conus, larval life histories range from long-term planktotrophy to nonpelagic lecithotrophy. Prehatching developmental time, hatching size, pelagic period and total prejuvenile developmental time are all significantly correlated with egg size, while settling size is correlated with none of these larval characteristics. Therefore, larval life history patterns in the genus Conus appear to be determined by 2 sets of selective forces: the first influencing egg size, and the second stipulating settling size. As egg sizes become larger, hatching sizes and prehatching developmental time increase while pelagic periods and total prejuvenile developmental times decrease. Settling size appears to be related to water depth, but food requirements of newly metamorphosed juveniles may also be important.