Some aspects of the biology of the amphipods <Emphasis Type="Italic">Ischyrocerus anguipes</Emphasis> associated with the red king crab, <Emphasis Type="Italic">Paralithodes camtschaticus,</Emphasis> in the Barents Sea

This paper describes size composition, morphometric, and reproductive parameters of the summer generation of the amphipod Ischyrocerus anguipes (Krǿyer, 1838) associated with the red king crab Paralithodes camtschaticus (Tilesius, 1815) in Dalnezelenetskaya Bay (southern Barents Sea, Russia). In summer 2004–2007, prevalence and mean number of I. anguipes per host were 15.0% and 6.9 ± 1.1 specimens, respectively. The majority of amphipods were found on the host carapace (47.4%) and the limbs (43.9%). High infestation indices and absence of negative impacts for the host indicate that I. anguipes is a facultative commensal of the red king crab. The amphipods sex ratio was significantly biased toward females (F:M = 2:1). Females had a greater size than males. The size at 50% maturity of I. anguipes females was estimated to be 3.37 mm. The number of eggs laid is linearly correlated with the size of a female. Some differences in biological features of symbiotic and free-living amphipods (data obtained in 1940–1950) may be explained by climatic changes in the Barents Sea or advantages of living on the crab.     

Reproductive biology of the guitarfish <Emphasis Type="Italic">Rhinobatos hynnicephalus</Emphasis> (Batoidea: Rhinobatidae) in Ariake Bay,Japan

Size at sexual maturity, reproductive cycle, and fecundity of the guitarfish, Rhinobatos hynnicephalus, were examined in Ariake Bay, Japan. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: males, 431 mm; females, 476 mm]. Monthly gonadosomatic indices of males decreased abruptly from July to August. Histological examinations confirmed the presence of mature spermatozoa in the testes in July, with semen in seminal vesicles in July and August. Preovulatory ova were observed in females with near-term embryos in August. Parturition occurred in August, immediately followed by mating, ovulation, and fertilization. Gestation period is approximately 1 year. Fertilized uterine eggs without embryonic development were present throughout the annual reproductive cycle. Embryonic development began in June and ended in August, indicating that R. hynnicephalus undergoes embryonic diapause (9 months). Fecundity increased with TL and ranged from 1 to 9 (mean, 4.4) embryos per litter.     

Population Biology and Breeding Period of the Sand-Bubbler Crab <Emphasis Type="Italic">Dotilla Fenestrata</Emphasis> (Brachyura: Ocypodidae) from Southern Mozambique

The sand-bubbler crab Dotilla fenestrata (Hilgendorf, 1869) is the most common and abundant brachyuran in the intertidal area of many East African sandy shores. Monthly sampling surveys were performed from March 2001 to February 2002 at Praia do Triunfo, Southern Mozambique. At each sampling survey, 15 stations (0.25 m²) were sampled to a depth sediment of 30 cm. Crabs were identified, sexed, and measured for carapace width (mm). A total of 2456 crabs were collected of which 1247 were males (mean ± sd: 5.36 ± 0.04 mm), 938 non-ovigerous females (5.03 ± 0.03 mm) and 271 ovigerous females (5.15 ± 0.06 mm). The overall size frequency distribution showed a unimodal pattern suggesting a stable population with continuous recruitment. A clear sexual dimorphism was observed, with males being larger than ovigerous females, which in turn, were larger than non-ovigerous females. The overall sex ratio did not differ from 1:1. The annual reproductive cycle of Dotilla fenestrata was continuous and ovigerous females were recorded throughout the year, with peaks of occurrence during the warmer months (February–August). Despite of this continuous cycle, few juveniles were observed during the study period. These observations and the maximum size attained by adults supports the hypothesis that for this burrowing crab, recruitment may occur in different habitat than that occupied by adults. However, the studied area is favourable for growth, since the analysed population attains sexual maturity in smaller sizes than that from close areas.     

Density,distribution and population structure of <Emphasis Type="Italic">Opusia indica</Emphasis> (Ocypodoidae: Camptandriidae) in a coastal mangrove creek in Pakistan

The density, distribution and population structure of Opusia indica were studied through transects method. Two transects were delimited in a mangrove area of Korangi creek (24°79′ N/67°20′ E). On each transect, three 0.25 m² quadrats were sampled at three tidal levels on a monthly basis during low tide. A total of 1919 crabs were obtained, of which 775 were males, 945 were non-ovigerous females and 199 were ovigerous females. Density of crabs varied between 198 m⁻² to 798 m⁻². The density and size distribution showed significant difference from low tide level to high tide level and were positively correlated with the percent moisture, percent organic matter and sediment structure. Based on carapace width (CW) males were significantly larger than the females indicating sexual dimorphism. The monthly size frequency distribution of crabs showed recruitment of juvenile crabs (< than 4 mm) nearly throughout the year except in few months. The monthly sex ratio deviated from 1:1 throughout the year, with female bias (χ ² = 31.633, P = 0.001 and df =11). Breeding was seasonal with peaks in SW monsoon. Size at sexual maturity based on smallest ovigerous female was CW = 4.0 mm. The average number of eggs per female were 2066 ± 479 (n = 25). Positive linear relationship was observed between the size of the female crabs and the egg numbers (r ² = 0.554).     

Sex-ratio,seasonality and long-term variation in maturation and spawning of the brown shrimp <Emphasis Type="Italic">Crangon crangon</Emphasis> (L.) in the German Bight (North Sea)

Aspects of the reproductive and maturation biology of the brown shrimp Crangon crangon (L.) were studied in various subareas of the German Bight (North Sea). The size-specific sex ratio of C. crangon was examined based on length frequency distribution data. The sex ratio for the smallest size groups at which sex was determined was typically around 0.5, indicating an even ratio between males and females. The proportion of females decreased in the 30–45 mm size range. In length classes larger than 50 mm, the proportion of females constantly increases to 100% at around 60 mm total length. We concluded that sex reversal from male to female may not occur in C. crangon. Size at sexual maturity was determined from the proportion of ovigerous females. Size at maturity (L ₅₀) was estimated as 55.4 and 62.0 mm total length for spring and winter data, respectively. The seasonal spawning cycle was studied over the period 1958–2005. Between mid February and late June and for size classes larger than 65 mm ovigerous shrimps exceeded 80% and reached up to 100% of the females in the population. This period can be seen as the core spawning season. From early August to early December the proportion of ovigerous shrimps in the female population is very low. Interannual differences in the seasonal process are obvious with a dramatic decline in C. crangon reproductive success in the late 1980s. Various options are discussed for the reasons of the decline and recovery of the reproductive performance.     

Reproductive biology of the fanray, <Emphasis Type="Italic">Platyrhina sinensis</Emphasis> (Batoidea: Platyrhinidae) in Ariake Bay,Japan

The reproductive biology of the fanray, Platyrhina sinensis, was examined in Ariake Bay, Japan, from May 2002 until December 2006. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: male, 393 mm; female, 421 mm]. The present data support a distinct annual reproductive cycle for P. sinensis. The gonadosomatic index (GSI) for mature males showed a clear seasonal trend, declining from August to November. Histological observations showed that mature sperm in the testes occurred from August to November when monthly GSI declined. Concomitantly, pre-ovulatory ova were observed in females collected from August to November. These data indicate that mating, ovulation and fertilization occurred from August to November. Near-term embryos, neonates and recent post-partum females also occurred from August to November. Additionally, all post-partum females possessed large pre-ovulatory ova. Parturition occurred from August to November followed immediately by mating, ovulation and fertilization. Mature females become pregnant every year, and the gestation period is almost 1 year. Fertilized uterine eggs without macroscopic embryonic development were present throughout the annual reproductive cycle, indicating that P. sinensis utilizes embryonic diapause as its reproductive strategy. Both reproductive tracts of females were functional, and fecundity ranged from 1 to 12 with a mean of 6.0, increasing with TL.     

Spawning season and size at sexual maturity of <Emphasis Type="Italic">Kyphosus bigibbus</Emphasis> (Kyphosidae) from northwest Kyushu,Japan

The reproductive characteristics of Kyphosus bigibbus were examined using individuals collected between June 2004 and February 2009 off Nagasaki Peninsula in northwest Kyushu, Japan. The spawning season and size at sexual maturity of this species were characterized based on a gonad index and histological examination of the gonads. The spawning season extends from June to October. This species is assumed to be an indeterminate, multiple-batch spawner. Females reached sexual maturity at larger size than males (fork length at 50% sexual maturity: males 284 mm, females 360 mm).     

Inter- and intra-specific variation in the facial colours of <Emphasis Type="Italic">Perisesarma eumolpe</Emphasis> and <Emphasis Type="Italic">Perisesarma indiarum</Emphasis> (Crustacea: Brachyura: Sesarmidae)

The colour of the characteristic facial bands in the mangrove crabs Perisesarma eumolpe (De Man) and Perisesarma indiarum (Tweedie) were investigated in relation to species, sex and size. Quantitative red/blue/green (RBG) values extracted from close-up digital photographs of 27 P. indiarum and 48 P. eumolpe specimens revealed significant differences between species and sexes. Males of both species possessed facial bands characterized by a greater intensity of blue, whereas green was more pronounced in female facial bands. It is postulated that these colour differences play a role in intra-specific sexual recognition. There existed a significant positive relationship between size and the intensity of blue in the facial bands of females of both species, suggesting these traits function as an indicator of their maturity (and possibly body condition). In large males, facial band colours contrast strongly against the surrounding mudflat and may play an important role in conspecific signalling during territorial disputes or contests over access to females. Handling editor: K. Martens     

Winter and spring ecology of <Emphasis Type="Italic">Anaphes nitens</Emphasis>, a solitary egg-parasitoid of the <Emphasis Type="Italic">Eucalyptus</Emphasis> snout-beetle <Emphasis Type="Italic">Gonipterus scutellatus</Emphasis>

We investigated the effects of temperature, photoperiod, food and host availability, and body size on the overwintering abilities of the egg parasitoid Anaphes nitens Girault (Hymenoptera, Mymaridae) under natural conditions. Seven groups of eighty females received one of four treatments (n = 20): (i) honey and hosts, (ii) water and hosts, (iii) honey, or (iv) water. Seven groups of forty males received only honey or water (n = 20). To test if short day-length is the main cue for larval dormancy, the experiment was replicated inside a climate chamber at 20°C and under a winter photoperiod. A. nitens overwinters because of quiescence or oligopause inside the hosts and increased adult longevity. Mean pre-emergence mortality was up to 26% indoors and 15.2% outdoors, males being more affected. Development time had a significant and positive effect on body size. Honey-fed females without hosts had the highest longevity (53 days). Mother’s diet and size affected development time, body size, longevity, and fecundity of the progeny. The results confirm the good adaptation of the parasitoid to the environmental conditions of NW Spain and its ability to synchronize its life cycle with the phenology of the host. Handling editor: Drik Babendreier.     

Conservation genetics of the Critically Endangered Saint Croix ground lizard (<Emphasis Type="Italic">Ameiva polops</Emphasis> Cope 1863)

The Saint Croix ground lizard (Ameiva polops) is a Critically Endangered species endemic to Saint Croix, U.S. Virgin Islands. Although it is completely extirpated from Saint Croix Island (last seen in 1968), two small natural satellite populations survive on two islets off St. Croix: one on Protestant Cay (estimated at ~30 individuals in 2002); and one on Green Cay (estimated at ~180 individuals in 2002). Two additional small populations exist that were founded with individuals translocated from the two surviving natural populations. One is on Ruth Island, a man-made islet off St. Croix, founded in 1990 with 10 individuals from Protestant Cay. The other is on Buck Island, ~2.5 km from Saint Croix, founded in 2008 with 57 individuals from Green Cay. All populations are vulnerable to catastrophic events such as hurricanes, sea level rise, introduction of exotic species, and landscape transformation. Herein, we used mitochondrial and nuclear-microsatellite markers to examine levels of genetic diversity within extant populations of A. polops and the degree of genetic differentiation among them. We also conducted analyses to search for signatures of recent bottlenecks in these populations and to estimate their effective population size (N _e ). We found low genetic variability within populations of this lizard, comparable to that observed in other threatened vertebrates. We also found significant genetic differentiation among the three populations examined, as well as signatures of recent bottlenecks and critically low N _e values in all populations. Based on our results, we suggest two different conservation units for A. polops: (1) Green Cay and its replicate population at Buck Island; and (2) Protestant Cay and its replicate population at Ruth Island. We discuss the implications of our findings on the conservation and management of A. polops.     

Biological traits of naturally induced hybrid individuals of two gizzard shads, <Emphasis Type="Italic">Nematalosa come</Emphasis> and <Emphasis Type="Italic">N. japonica</Emphasis>, in coastal waters around Okinawa Island,Ryukyu Archipelago,southwestern Japan

The age, growth, reproductive condition, and occurrence of natural hybrids of two Nematalosa species around Okinawa Island were examined using 128 specimens obtained from April 2003 to June 2004. Standard length (SL) reached approximately 150–210 mm within the first 2 years, and then remained stagnant. The maximum age for both sexes was ca. 5 years old. Maturity sizes and ages were estimated to be at least 173.2 mm SL and 2 years old for females and 192.6 mm SL and 3 years old for males. Spawnable individuals were mainly observed from January to March based on histological observations of gonads. Natural hybrids appeared at all sampling sites except for the Haneji Inlet and were dominant at Makiminato (in south-central Okinawa Island). Their incidence was also quite high (66.9%) in the Makiminato population, when compared with records for other marine fishes around Japan. In Okinawa Island, these shallow areas are rapidly decreasing in size because of recent reclamation and land exploitation. Hybrid production may be caused by not only the reproductive biology and sympatric distributions of the parent species but also recent environmental changes.     

Growth and Development in Wild Owl Monkeys (<Emphasis Type="Italic">Aotus azarai</Emphasis>) of Argentina

Life history predicts that in sexually dimorphic species in which males are the larger sex, males should reach sexual maturity later than females (or vice versa if females are the larger sex). The corresponding prediction that in sexually monomorphic species maturational rates will differ little between the sexes has rarely been tested. We report here sex differences in growth and development to adulthood for 70 female and 69 male wild owl monkeys (Aotus azarai). In addition, using evidence from natal dispersal and first reproduction (mean: 74 mo) for 7 individuals of known age, we assigned ages to categories: infant, 0–6 mo; juvenile, 6.1–24 mo; subadult, 24.1–48 mo; adult >48 mo. We compared von Bertalanffy growth curves and growth rates derived from linear piecewise regressions for juvenile and subadult females and males. Growth rates did not differ between the sexes, although juvenile females were slightly longer than males. Females reached maximum maxillary canine height at ca. 2 yr, about a year earlier than males, and females’ maxillary canines were shorter than males’. Thus apart from canine eruption and possibly crown–rump length, the development of Azara’s owl monkeys conforms to the prediction by life history that in monomorphic species the sexes should develop at similar paces.     

The reproductive cycle,size at maturity and fecundity of garfish (<Emphasis Type="Italic">Belone belone</Emphasis>, L. 1761) in the eastern Adriatic Sea

A recent study concerning the reproductive biology of the garfish (Belone belone, L. 1761) has been carried out in the eastern part of the Adriatic Sea along the Croatian coastline. Specimens of the fish (N = 3,393) were collected over a 6-year period (2003–2008). Their length varied between 20.8 and 75.4 cm (mean ± SD = 38.3 ± 7.94). Female garfish were dominant in larger length groups being most apparent during the resting phase of sexual cycle and in the peak of the spawning period, occurring in April and May. The sexual ratio of all specimens was m/f = 0.98. Males were prevalent in March—at the beginning of the highest spawning activities. Fifty percentage of the garfish population sexually matured at 28.5 cm of total length. Males and females reached their sexual maturity at 28.0 and 31.5 cm of total length, respectively. Spawning began in January peaking during March to May. According to their maturity stages, gonad weight and the gonadosomatic index, males began to spawn one month earlier (April) than females (May). The mean batch fecundity of garfish was 1,242.46 ± 843.64 of matured oocytes per ovary. Matured oocyte diameters ranged from 1.223 to 4.283 mm with the mean value of 2.269 ± 0.332 mm.     

Length-based growth,maturity and natural mortality of the cockfish <Emphasis Type="Italic">Callorhinchus callorhynchus</Emphasis> (Linnaeus, 1758) off Coquimbo,Chile

The growth rate, reproductive aspects, and natural mortality of chimaeras and ratfish are poorly known. In this study, life-history parameters for cockfish Callorhinchus callorhynchus (Holocephali—Callorhinchidae) are estimated, which is an important fish resource exploited in Chile. Specimens were sampled from the artisanal fishery captures, from November 2006 to November 2007. The standard length (SL) of males fluctuated between 20 and 62 cm, and between 21 and 70 cm for females. Von Bertalanffy growth parameters were estimated through length-frequency data analysis using MULTIFAN. The length-weight relationship and von Bertalanffy growth parameters were significantly different for males and females, as well as the length at 50% maturity. For males a model with 5 age-classes was the best, with asymptotic length L _∞ = 52 cm SL, growth coefficient K = 0.473 yr⁻¹, and age at length zero t ₀ = −0.690 yrs. For females the best model was represented by 10 age-classes (L _∞ = 70.3 cm SL, K = 0.193 yr⁻¹, t ₀ = −1.158 yrs) in the length-frequency data sets. Length at 50% maturity of males was estimated in 43.7 cm SL, and in 50.2 cm SL for females. The natural mortality rate fluctuated between 0.42 and 0.82 yr⁻¹ for males and between 0.12 and 0.37 yr⁻¹ for females, depending upon the method used. It is concluded that C. callorhynchus is a species with life-history parameters significantly different between males and females, and such differences should be taken into account in future population dynamics analysis.     

Reproduction and initial development of manybar goatfish <Emphasis Type="Italic">Parupeneus multifasciatus</Emphasis> (Mullidae)

Features of reproductive biology and the stages of early ontogeny are described in the mass tropical species manybar goatfish Parupeneus multifasciatus. In general, in the catches represented by mainly sexually mature fishes, females prevail but males prevail in the largest size classes. The females reach their first sexual maturity by approximately 110 mm fork length, and they are characterized by continuous oogenesis and egg deposition in batches. The fish spawn over the entire year with a trend to lower values of the gonadosomatic index (GSI) of the females from June to October. The features of early ontogeny are compared in manybar goatfish and red mullet Mullus barbatus ponticus from the Black Sea.     

Effects of <Emphasis Type="Italic">Acanthocephalus</Emphasis> sp. (Acanthocephala: Echinorhynchidae) on the body size and reproduction of isopods (<Emphasis Type="Italic">Asellus hilgendorfi</Emphasis>)

 Isopods Asellus hilgendorfi were collected from a small lake in northern Japan and examined to determine whether their body size and reproduction were affected by infection with larval acanthocephalans (Acanthocephalus sp.). Seasonal changes in the breeding ratio of isopods and the prevalence of larval acanthocephalan infection showed a reverse trend. Acanthocephalan larvae occurred mainly in males and immature females and were rarely found in mature females. In late immature females, the body size, as indicated by the width of the pleotelson, of infected isopods was significantly larger than that of uninfected ones. These results suggest that acanthocephalans can prevent female isopods from attaining sexual maturity and increasing their body size. Received: January 9, 2002 / Accepted: December 16, 2002 Acknowledgments We thank Professor Shōichi Saito, Faculty of Education, Hirosaki University, for his encouragement of the present study. Thanks are also due to the Iwasaki Village Office and the Fukaura Forestry Office for giving us permission for the survey. Correspondence to:A. Ohtaka     

Demographic characteristics of the copepod <Emphasis Type="Italic">Acanthocyclops americanus</Emphasis> (Sars, 1863) (Copepoda: Cyclopoida) fed mixed algal (<Emphasis Type="Italic">Scenedesmus acutus</Emphasis>)-rotifer (<Emphasis Type="Italic">Brachionus havanaensis</Emphasis>) diet

The predatory copepod Acanthocyclops americanus is commonly found in shallow ponds and lakes in Mexico. We tested the survivorship and reproduction-related variables of this copepod, isolated from Lake Huetzalin (Xochimilco, Mexico City), on four mixed diets comprising two algal concentrations (0.8 × 10⁶ and 1.6 × 10⁶ cells ml⁻¹ of Scenedesmus acutus) and two rotifer densities (1 and 8 ind. ml⁻¹ of Brachionus havanaensis). Survivorship patterns of naupliar and adult stages of A. americanus were evaluated at 24 ± 1°C. The demography experiments were initiated with five females and five males (1:1 ratio, 5th copepodites) into each of the 16 test [= 4 diet combinations × 4 replicates (cohorts)] jars containing 50 ml medium and with one of the chosen algal-rotifer diets. Data on the survival of naupliar and copepodites (up to V) showed a high death rate (80%) in A. americanus by the time nauplii reached the adult stage. The duration of developmental time for nauplii and the copepodite V (C-V) was about 28 days by which time A. americanus became adults. Food combination had a significant effect on both survival and duration of the naupliar and C-V but not on the development time in C-I, C-II, C-III, and C-IV. Naupliar stages showed highest life expectancy at low food levels (rotifers or alga). Adult male and female copepods showed better survival under higher availability of rotifers in the medium, while higher algal density resulted in steep mortality during the first days. Average adult lifespan and life expectancy of A. americanus varied from 19 to 23 days, depending on the diet combination. Age-specific reproductive output (m _x ) of female A. americanus showed low reproduction (<10 offspring per female on any given day) when raised on low rotifer density, regardless of the algal concentration. On the other hand, enhanced offspring production (average of about 50 nauplii per female) was recorded when the rotifer density was higher (i.e., 8 ind. ml⁻¹). Gross and net reproductive rates varied from 48 to 438 and 27 to 318 offspring per female, respectively. In general, higher availability of rotifers in the medium resulted in higher (8–10 times as compared to those in low rotifer density) gross and net reproductive rates. There was no significant difference in the generation time (13–14 days) in relation to the diet combination. The rate of population increase (r) (range: 0.29–0.69 per day) increased with greater abundance of B. havanaensis in the medium. Thus, our study showed that inclusion of animal protein in the diet is necessary for high population growth rates of A. americanus.     

Seasonality in Reproduction of <Emphasis Type="Italic">Lepilemur edwardsi</Emphasis>

Sportive lemurs are threatened species in the IUCN Red Data Book. However, quantitative information on their reproduction, urgently required for conservation, has been lacking. We collected first data on reproductive activity of Milne-Edwards’ sportive lemurs in a population inhabiting the dry deciduous forest of the Ankarafantsika National Park in northwestern Madagascar during 1998, 2001, and 2003. The species showed a seasonal reproduction. The main mating season extended from May to June, as indicated by the presence of males with high testes volumes and estrus females. In the mating and early postmating season and in the postparturition season, sexes did not differ in body mass. Females had a significantly higher body mass than males in August and November, indicating pregnancy, which together with the presence of small infants in October and November implies that gravidity in females lasted for about 4–5 mo. All litters consisted of singletons. Individuals with body mass at the lower limit of the population either did not develop measurable testes volumes (males) or were not in estrus (females). They were probably juveniles from the previous birth season that achieved sexual maturity not before their second year after birth. The first data on reproduction suggest a low reproduction rate for Lepilemur edwardsi and a request for a higher conservation status than previously attributed and the need for further management strategies.     

Annual reproductive cycle,spawning periodicity and sexual maturity of false scad Caranx rhonchus (Geoffroy Saint‐Hilaire, 1817) (Pisces,Carangidae) from the South‐Eastern Mediterranean (Gulf of Gabès,Tunisia)

The reproductive biology of Caranx rhonchus (Geoffroy Saint‐Hilaire, 1817) (Pisces, Carangidae) was studied in the Gulf of Gabès (Mediterranean Sea) from June 2004 to May 2006. Of 1313 individuals examined, 668 were females (50.9%) and 645 were males (49.1%). The overall sex ratio did not deviate significantly in favour of females (♀ : ♂ = 1.04 : 1). Monthly changes in the Gonado–Somatic Index (GSI) showed a rapid increase from May to June and an extended very high level from June to September (4.43–3.47% for females and 3.35–2.61% for males), before declining sharply in October (down to 2.02% for females and 0.57% for males). The gametogenesis activity began with a pre‐maturation phase from March to May, followed by a ripe‐spawning phase from June to September. From the last days of July to the end of October, the gonads were in the spent and post‐spawning stages. From November to early May, gonads were in the resting stages. The size at which 50% of the population reached sexual maturity was not significantly different between males and females :  males attained sexual maturity at fork length FL₅₀ = 161.20 ± 0.37 mm (n = 262), whereas females attained maturity at FL₅₀ = 160.70 ± 0.23 mm (n = 296). The age of maturity for both sexes occurred at 2.1 years.