Biometric and reproductive aspects of the pen shell Atrina seminuda (Bivalvia: Pinnidae) in northeastern Venezuela

The pen shell Atrina seminuda is a target for a small artisanal Caribbean fishery; however, little is known about its biology. The length frequency distribution, biometric relations and reproduction of this species were studied in northeastern Venezuela. Using transects selected from among 360 stations a population was sampled monthly by SCUBA diving. An analysis of 1748 individuals showed a shell height (SH) between 4?cm and 23.6?cm, with an average of 16.7?±?2.5?cm. For both sexes, statistical differences in mean SH were observed (analysis of variance F (1, 1113)?=?69.538; P?SL), total weight (TW) and adductor muscle weight (MW) as a function of SH. In all cases there were statistical differences between males and females, with males presenting positive allometry and females showing isometry. Mean SH at maturity for males (8.24?cm) was lower than for females (11.88?cm), and for sexes combined was estimated at 8.71?cm. Gametogenic activity was observed throughout the year, with two main peaks of spawning (April and August/September 2008). All this information is crucial for demographic modelling and stock assessment for managing this species.     

Abundance,population structure and growth of the Atrina maura (Bivalvia: Pinnidae) in a tropical lagoon of the Mexican Pacific coast

The abundance, population structure, and growth of the Pen-shell Atrina maura in the Corralero-Alotengo tropical lagoon system in Oaxaca, Mexico, were studied from February to September of 1997. An abundance analysis showed significant temporal and spatial differences (Kruskal-Wallis, p < 0.001). Two spatial groups of abundance were found in the area, one from the mouth of the lagoon system to the middle of the Pen-shell bank, and the other between the middle of the Pen-shell bank and the head of the system. Three temporal periods of abundance were found (February-April-May; July-August; March-June-September). The distribution of population size showed that benthic recruitment of A. maura occurred from February to July. Length frequency of A. maura is commonly wide-ranging; nevertheless, in this study Pen-shell organisms with a valve length of 15 cm were frequently found. The growth rate length was 3.7 cm/month during the dry season (February to May), and 3.5 cm/month during the rainy season (June to September). Sex ratio was maintained at 1:1 from February to May, but males were dominant from June to August, and the minimum length for reproduction was registered at 10 cm valve length.     

Annual reproductive cycle and condition index of Mactra corallina (Mollusca: Bivalvia) from the north coast of Tunisia

This work aims to examine the reproductive cycle of the bivalve Mactra corallina inhabiting the Gulf of Tunis (Tunisia). Histological analysis indicated that the reproductive cycle is composed of six stages and was synchronous between sexes. Gonadal development began in January. From April to July, an increase in temperature (from 16 to 28°C) and a rise in chlorophyll a (from 3.25 to 6.35 mg/L) marked the period of sexual maturity in both sexes, which was also confirmed by an elevation in condition index (CI). Partial spawning started in April for males and in May for females, peaking in late summer indicating a prolonged reproductive period. The reproductive cycle of M. corallina finished with an inactive stage during autumn. From the total number of animals used in this study, we identified 104 females (52%) and 96 males (48%) corresponding to a sex ratio 1:0.92 that did not differ significantly from a 1:1 ratio.     

Isolation and characterization of 13 microsatellite loci in the pen shell Atrina pectinata (Bivalvia: Pinnidae)

The pen shell Atrina pectinata is a commercially important and over-exploited bivalve. In this survey, the first set of 13 polymorphic microsatellite loci for the pen shell was developed and characterized. The number of alleles ranged from 6 to 28 per locus with the observed and expected heterozygosities ranging from 0.640 to 1.000 and from 0.731 to 0.970, respectively. These informative microsatellite markers will be useful in studies of population and conservation genetics for this species.     

Isolation and characterization of new microsatellite markers in the pen shell Atrina pectinata (Pinnidae)

The pen shell, Atrina pectinata, is a commercially important bivalve species, widely consumed in the Asian Pacific region. We identified 16 new microsatellite makers for A. pectinata using a modified fast isolation by AFLP of sequences containing repeat protocols; 27 individuals were collected from Xiamen to evaluate the degree of polymorphism. The number of polymorphic alleles per locus ranged from 2 to 11. The observed and expected heterozygosities were 0.050-0.913 and 0.049-0.869, respectively. The loci identified in this study could provide a useful tool for research on genetic diversity and genetic differentiation of A. pectinata populations.     

Spatial variation in the annual reproductive cycle of Turbo (Batillus) cornutus (Gastropoda: Trochidae) at Jeju Island,Korea

The annual reproductive cycle of the top shell Turbo cornutus from Jeju Island was investigated in two populations using histology. In the northern population, gametogenesis commenced in January as the surface water temperature reached 14?°C, while in the southern population gametogenesis began a month earlier, as the water temperature remained at 17?°C. Ripe top shells first appeared in June and spawning continued from June to October when water temperatures were between 20 and 24?°C. Histology indicated that the spawning period of the southern population was a month earlier and lasted longer (June–October) than in the northern population (July–September). The percentage gonad area of animals in the southern population in March and April was significantly higher than in the northern population (p?相似文献   

Cryptic diversity in the pen shell Atrina pectinata (Bivalvia: Pinnidae): high divergence and hybridization revealed by molecular and morphological data

Cryptic species have been increasingly revealed in the marine realm through an analytical approach incorporating multiple lines of evidence (e.g., mtDNA, nuclear genes and morphology). Illustrations of cryptic taxa improve our understanding of species diversity and evolutionary histories within marine animals. The pen shell Atrina pectinata is known to exhibit extensive morphological variations that may harbour cryptic diversity. In this study, we investigated A. pectinata populations along the coast of China and one from Japan to explore possible cryptic diversity and hybridization using a combination of mitochondrial (cytochrome c oxidase subunit I, mtCOI) and nuclear (ribosomal internal transcribed spacer, nrITS) genes as well as morphology. Phylogenetic analyses of mtCOI ‘DNA barcoding gene’ sequences resolved six divergent lineages with intralineage divergences between 0.4% and 0.8%. Interlineage sequence differences ranged from 4.3% to 22.0%, suggesting that six candidate cryptic species are present. The nrITS gene revealed five deep lineages with Kimura 2‐parameter distances of 3.7–30.3%. The five nuclear lineages generally corresponded to mtCOI lineages 1–4 and (5 + 6), suggestive of five distinct evolutionary lineages. Multiple nrITS sequences of significant variance were found within an individual, clearly implying recent hybridization events between/among the evolutionary lineages, which contributed to cytonuclear discordance. Morphologically, five morphotypes matched the five genetic lineages, although the intermediates may well blur the boundaries of different morphotypes. This study demonstrates the importance of combining multiple lines of evidence to explore species cryptic diversity and past evolutionary histories.     

Age,growth, and fishery assessment of spotted sand bass in the Northern Gulf of California,Mexico

Spotted sand bass (Paralabrax maculatofasciatus) is one of the most common inshore reef fishes in the northern Gulf of California (GOC), Mexico, but has rarely been studied. Objectives of this study were to estimate age and growth parameters of this species from two areas in the northern GOC and use an age-structured model to assess fishery yield and Spawning Potential Ratio (SPR) over a wide range of exploitations. Samples yielded fish up to age 8, although most were between age 2 and 5. Growth was extremely rapid, with most of the growth in length achieved in the first year, followed by much slower growth. Conditional rates of natural mortality averaged 0.37. Yield models predicted that spotted sand bass in the GOC were less vulnerable to fishing than those in the Pacific Ocean, likely due to faster growth and higher natural mortality. Growth overfishing and SPR values below 0.20 were only predicted at the lowest natural mortality and high (>0.50) exploitation rates. Results suggested that the species could support a commercial fishery in the GOC that might alleviate some of the conservation issues currently facing biologists in this unique marine ecosystem.     

Annual distribution and abundance of Ceratium dens (Peridinales: Ceratiaceae) in the Gulf of California, Mexico

Ceratium dens distribution in the Gulf of California was studied based on three oceanographic campaigns, monthly abundance (1995-96) and during three red tide events in Mazatlán Bay. 52 phytoplankton samples with a Bongo net and 64 microns mesh light, during the year 120 water samples with a van Dorn bottle were collected in two sampling stations and from three red tide events. All samples were counted by the inverted-microscope method. The results showed that C. dens was present in the upper Gulf of California and surroundings of Cabo San Lucas. Two peaks were observed during spring and autumn in Mazatlán Bay during 1995-1996. The highest densities (20-360 cells.-l-1) were observed in coastal areas, whereas the lowest densities (1-14 cells.-l-1) were recorded in the open sea. During red tide events in 1985, 1989 and 1997, 144,000-256,000 cells.-l-1, 100,000-400,000 cells.-l-1, and 189,000-592,000 cells.ul-l was observed, respectively. During the red tide events C. dens varied, although sometimes was replaced by Skeletonema costatum or Pseudonitzchia spp and Ceratium furca. C. dens, seems to prefer areas with high productivity.     

Annual changes in brain concentration of arginine vasotocin and isotocin correspond with phases of reproductive cycle in round goby,Neogobius melanostomus

Reproductive cycle of seasonally breeding fish is synchronized with changes of photoperiod and temperature in environment. We hypothesize that arginine vasotocin (AVT) and isotocin (IT) are involved in timing and synchronization of seasonal reproductive activity in the round goby (Neogobius melanostomus). To verify this hypothesis, we examined the annual profiles of brain AVT and IT in round goby males and females in relation to their reproductive cycle. Wild round gobies were exposed to annual environmental changes in their natural habitats from where they were sampled monthly over a year. AVT and IT were measured using HPLC with fluorescence detection preceded by solid-phase extraction. This study shows seasonal variations in brain AVT and IT levels. Profiles of changes were similar in males and females: the peak of AVT was observed before spawning in March-April, whereas that of IT during spawning in May–June. Furthermore, the lowest AVT level was noted out of breeding season from November to January, while the level of IT decreased immediately at the end of the spawning. The results show that high AVT levels correlate with pre-spawning period whereas the highest IT levels correspond to spawning. A significant decline in AVT and IT in non-spawning season coincided with the quiescent phase of gametogenesis in both sexes.     

Annual reproductive cycle and sexual dimorphism in the dragonet,repomucenus valenciennei, in tokyo bay, japan

The annual reproductive cycle of the dragonet,Repomucenus valenciennei, from Tokyo Bay, Japan, was studied by analysis of seasonal trends in gonadosomatic indices and histological observations of gonads. Sexual dimorphism in the growth of several body parts relative to standard length (SL) and changes in color pattern of the first dorsal fin with growth were also investigated. The spawning season lasted from spring (April [1991] or February [1992]) to autumn (October) with two spawning peaks, in spring and autumn. In spring, only one-year-old (age 1+) fish spawned, age 0+ females not spawning until autumn, at which time they had reached age 1+. Likewise, histological observations of males indicated that testes had reached full maturity by 80 mm SL (age 1+). The minimum mature size of females was estimated as 60 mm SL. In males 45–80 mm SL, the first spine of the first dorsal fin, last ray of the second dorsal fin, last ray of the anal fin, and caudal fin ray showed strongly positive allometry, indicating rapid growth of these structures relative to SL. Subsequently, their growth returned to an isometric pattern in males>80 mm SL. In females, on the other hand, the same body parts showed slightly positive allometry throughout their growth. The color pattern on the first dorsal fin also changed in males 45–80 mm SL.     

Histomorphological and endocrine assessment of female Arabian carpetshark,Chiloscyllium arabicum (Elasmobranchii: Hemiscylliidae) from the Persian Gulf during annual reproductive cycle

The present study aimed at assessing the annual reproductive cycle of female Arabian carpetshark, Chiloscyllium arabicum from the Persian Gulf by a macroscopic and microscopic evaluation of the reproductive tract. The annual cycle of gonadal steroids [17β-estradiol (E2), progesterone (P4) and testosterone (T)] was also assessed in this shark. In total, 130 female C. arabicum were collected from the Bahrakan Creek (located northwest of the Persian Gulf) between January 2018 and March 2019. Females were oviparous with an external-type ovary and only one functional ovary. Five sexual maturity stages were recognized based on macroscopic and microscopic evaluation: Immature I (August–October), Immature II (November–January), Mature (February–March), Pregnant (April–May) and Spent (June–July). The structural changes in the oviducts, oviducal glands and uterus throughout the annual reproductive cycle were consistent with their roles in the egg movement, the egg capsule production and sperm storage. The plasma levels of the gonadal steroids were associated with morphological changes in the reproductive tract. E2 showed two detectable peaks during March (close to ovulation) and June (just before mating). P4 and T displayed a peak just before ovulation.     

Role of brain hormone in oogenesis of the Indian freshwater leech,Poecilobdella viridis (Blanchard) during the annual reproductive cycle

The possible role of a brain hormone in oogenesis of Poecilobdella viridis has been investigated by brain extirpation and brain extract injections during non-reproductive (November to January) and reproductive (March to May) periods. Brain extirpation during the non-reproductive period ceased maturation of the ovary. It is inferred that brain secretion bears possibly a gonadotropic principle which governs and regulates the oogenesis during the annual reproductive cycle.     

Biochemical and energy dynamics throughout the reproductive cycle of the striped venus Chamelea gallina (Mollusca,Bivalvia)

The striped venus Chamelea gallina is an important commercial bivalve species in Europe. However, large inter-annual fluctuations in stock abundance and periodic recruitment failure threaten the biological and economic sustainability of this fishery. This study aimed to improve the knowledge of the reproductive cycle and reproductive strategies of this species from the Algarve coast (southern Portugal) in order to contribute to the establishment of management measures and to assess its potential for aquaculture. The reproductive cycle of C. gallina followed a seasonal cycle, significantly influenced by sea surface temperature and food availability. Gametogenesis took place in winter, coinciding with the phytoplankton bloom. Spawning occurred during summer, followed by a short period of sexual inactivity in autumn. Condition index did not reflect the reproductive cycle of C. gallina and generally, followed the same trend of chlorophyll a. Glycogen was positively correlated with gonadal index and chlorophyll a. High total lipid values were recorded throughout gonad ripeness and spawning, but decreased at the end of the spawning and in the rest period. The extended spawning period of C. gallina will allow larvae to be obtained for much of the year by artificial spawning of wild broodstock.     

Blooms of Cochlodinium polykrikoides (Gymnodiniaceae) in the Gulf of California, Mexico

Cochlodinium polykrikoides was the species responsible for the discoloration that occurred between September 15th and 27th, 2000 in a shallow coastal lagoon located in the southern part of the Bahia de La Paz, on the west side of the Gulf of California. Blooms of C. polykrikoides were observed four days after two rainy days with a seawater temperature of 29 to 31 degrees C. Nutrient concentration ranges during the bloom were 0.165-0.897 microM NO2+NO3, 0.16-3.25 microM PO4, and 1.0-35.36 microM SiO4. Abundance of C. polykrikoides ranged from 360 x 10(3) to 7.05 x 10(6)/cells l(-1). Biomass expressed in terms of chlorophyll a was high, ranging from 2.7 to 56.8 mg/m3. A typical dinoflagellate pigment profile (chlorophyll a and c, peridinin, diadinoxantin, and beta-carotene) was recorded. In this study, the red tide occurred in front of several fish and shrimp-culture ponds. No PST toxins were found in the samples. However, 180 fish were found dead in the infected fish-pond; the gills were the most affected part. C. polykrikoides is a cyst-forming species that recurs in this area. New blooms were observed in November 2000 and September-November 2001 in the same area. Anthropogenic activities, such as eutrophication caused by water discharge in this shallow lagoon, and nutrient enrichment in the culture ponds, as well as effects from precipitation and wind stress, could have favored the outbreak of this dinoflagellate.     

Temporal and latitudinal comparisons of reproductive parameters in a heavily exploited shark,the bonnethead,Sphyrna tiburo (L. 1758), in the southern Gulf of Mexico

In the southern Gulf of Mexico, the bonnethead shark, Sphyrna tiburo, is one of the most frequently captured species in landings of small-scale fisheries. Based on the analysis of two fishery-dependent sampling periods (1993–1994 and 2007–2014), this study aimed to determine reproductive parameters and identify temporal differences between the two time periods. In the first sampling period, 776 males and 352 females with a size range of 28.0–120.0 cm total stretched length (L_T) were analysed, and in the second sampling period, 387 males and 432 females with a size range of 28.0–122.0 cm L_T were analysed. The size at 50% maturity in the second sampling period was significantly different between sexes, 82.6 cm L_T for females and 73.8 cm L_T for males (no estimation was possible for the first sampling period). The size at 50% maternity was not different between sampling periods, 97.3 cm L_T for the first sampling period and 99.0 cm L_T for the second sampling period. Litter size varied from 3 to 19 embryos and the average was not statistically different in both periods, 10.1 (S.D. = 3.8) for the first sampling period and 11.3 (S.D. = 3.5) for the second sampling period. The female reproductive cycle is asynchronous, and it seems to be annual, with a gestation period of 5–6 months, and a consecutive ovarian cycle and gestation period. Temporal (between sampling periods) and latitudinal (southern Gulf versus northern regions) variations occur in the synchronicity of the reproductive cycle, temporal variation in the relationship between maternal length and litter size, and latitudinal variation in average size of mature sharks.     

Reproductive biology of the brown smoothhound shark Mustelus henlei,in the northern Gulf of California,México

Female brown smoothhound sharks Mustelus henlei were found to reproduce annually. A mature female carried both developing oocytes in the ovary and developing embryos in the uteri concurrently for c. 1 year. A great variability in the size of embryos was recorded each month, and the maximum embryo sizes were found from late January to mid‐March. The largest oocytes in mature females were observed in mid‐March. Gestation lasted c. 10 months. A linear relationship between maternal total length (L_T) and the number of pups per litter (litter size one to 21) was estimated. Birth L_T was reached in c. 280 mm. Females and males matured at 570–660 and 550–560 mm L_T, respectively. Difference in the litter size among Californian coast (one to 10) and northern Gulf of California (one to 21) populations existed for this smoothhound shark.     

Characterization,expression, and functional analysis of testis-specific serine/threonine kinase 1 (Tssk1) in the pen shell Atrina pectinata

Abstract

Testis-specific serine/threonine kinase 1 (Tssk1) was named since its function was determined in mouse spermiogenesis. In our research, we cloned a homolog of the pen shell Atrina pectinata Tssk1, ApTssk1, and determined its expression characteristics at mRNA. The full length of ApTssk1 cDNA was 1517 bp, with an open reading frame of 1089 bp (58–1146), which encodes a peptide including 362 amino acids. The homologous analysis indicated that the deduced amino acid sequences of ApTssk1 shared a close identity with other reported Tssk1. In addition, the highly conserved fragment containing a serine/threonine protein kinase catalytic (S-TKc) domain was predicted to exist in ApTssk1. Results from the RT-qPCR display that ApTssk1 was only transcribed in the male gonad of A. pectinata, and was highest in the mature testis. Therefore, this study indicated that ApTssk1 might play a functional role during spermatogenesis in A. pectinata.     

Age-specific birth rates of California sea lions (Zalophus californianus) in the Gulf of California, Mexico

Estimates of demographic parameters are essential for assessing the status of populations and assigning conservation priority. In light of the difficulties associated with obtaining such estimates, vital rates are rarely available even for well-studied species. We present the first estimates of age-specific birth rates for female California sea lions ( Zalophus californianus ) >10 yr of age. These rates were estimated from the reproductive histories of five cohorts of animals branded as pups between 1980 and 1984 at Los Islotes colony in the Gulf of California, Mexico. Age-specific birth rates varied among age classes and ranged between 0.06 and 0.80. The highest birth rates were observed for females between 10 and 15 yr of age, with decreased birth rates among older females. The effect of age, year, and resighting effort were explored using logistic regression analysis. Based on Akaike Information Criteria, birth rates were best explained by female age, while year and resighting effort did not have a significant effect. The odds ratio of producing a pup decreased with age but did not change significantly for middle-aged females. Our estimates of age-specific birth rates are consistent with general patterns observed for other large vertebrates.