Ecology of the red-tide dinoflagellate Ceratium furca: distribution, mixotrophy, and grazing impact on ciliate populations of Chesapeake Bay

Ceratium furca is a primarily photosynthetic dinoflagellate also capable of ingesting other protists. During 1995 and 1996, we documented the abundance of C. furca in Chesapeake Bay and determined grazing rates on prey labeled with fluorescent microspheres. Abundance usually remained below 20 cells ml(-1), although the species was capable of localized late-summer blooms (< or = 478 cells ml(-1)) in the more saline lower to mid-Bay region. Feeding rates ranged from 0 to 0.11 prey dinoflagellate(-1) h(-1) or from 0 to 37 pg C dinoflagellate(-1) h(-1) and were highest at lower salinities. Clearance rates averaged 2.5 +/- 0.35 microl dinoflagellate(-1) h(-1). Impact of C. furca feeding on prey populations was higher in the lower Bay, averaging 67% of Strobilidium spp. removed d(-1). Ingestion rates were positively correlated with prey abundance and dissolved inorganic nitrogen, but negatively with salinity, depth, dissolved inorganic phosphorus, and inorganic P:N ratio. Daily consumption of prey biomass by C. furca averaged 4.6% of body carbon, 6.5% of body nitrogen, and 4.0% of body phosphorus. with maximal values of 36, 51, and 32%, respectively. Thus, the ability to exploit an organic nutrient source when inorganic nutrients are limiting may give C. furca a competitive advantage over purely photosynthetic species.     

Mixotrophy in the phototrophic dinoflagellate Takayama helix (family Kareniaceae): Predator of diverse toxic and harmful dinoflagellates

Takayama spp. are phototrophic dinoflagellates belonging to the family Kareniaceae and have caused fish kills in several countries. Understanding their trophic mode and interactions with co-occurring phytoplankton species are critical steps in comprehending their ecological roles in marine ecosystems, bloom dynamics, and dinoflagellate evolution. To investigate the trophic mode and interactions of Takayama spp., the ability of Takayama helix to feed on diverse algal species was examined, and the mechanisms of prey ingestion were determined. Furthermore, growth and ingestion rates of T. helix feeding on the dinoflagellates Alexandrium lusitanicum and Alexandrium tamarense, which are two optimal prey items, were determined as a function of prey concentration. T. helix ingested large dinoflagellates ≥15 μm in size, except for the dinoflagellates Karenia mikimotoi, Akashiwo sanguinea, and Prorocentrum micans (i.e., it fed on Alexandrium minutum, A. lusitanicum, A. tamarense, A. pacificum, A. insuetum, Cochlodinium polykrikoides, Coolia canariensis, Coolia malayensis, Gambierdiscus caribaeus, Gymnodinium aureolum, Gymnodinium catenatum, Gymnodinium instriatum, Heterocapsa triquetra, Lingulodinium polyedrum, and Scrippsiella trochoidea). All these edible prey items are dinoflagellates that have diverse eco-physiology such as toxic and non-toxic, single and chain forming, and planktonic and benthic forms. However, T. helix did not feed on small flagellates and dinoflagellates <13 μm in size (i.e., the prymnesiophyte Isochrysis galbana; the cryptophytes Teleaulax sp., Storeatula major, and Rhodomonas salina; the raphidophyte Heterosigma akashiwo; the dinoflagellates Heterocapsa rotundata, Amphidinium carterae, Prorocentrum minimum; or the small diatom Skeletonema costatum). T. helix ingested Heterocapsa triquetra by direct engulfment, but sucked materials from the rest of the edible prey species through the intercingular region of the sulcus. With increasing mean prey concentration, the specific growth rates of T. helix on A. lusitanicum and A. tamarense increased continuously before saturating at prey concentrations of 336–620 ng C mL⁻¹. The maximum specific growth rates (mixotrophic growth) of T. helix on A. lusitanicum and A. tamarense were 0.272 and 0.268 d⁻¹, respectively, at 20 °C under a 14:10 h light/dark cycle of 20 μE m⁻² s⁻¹ illumination, while its growth rates (phototrophic growth) under the same light conditions without added prey were 0.152 and 0.094 d⁻¹, respectively. The maximum ingestion rates of T. helix on A. lusitanicum and A. tamarense were 1.23 and 0.48 ng C predator⁻¹d⁻¹, respectively. The results of the present study suggest that T. helix is a mixotrophic dinoflagellate that is able to feed on a diverse range of toxic species and, thus, its mixotrophic ability should be considered when studying red tide dynamics, food webs, and dinoflagellate evolution.     

Description of the new phototrophic dinoflagellate Alexandrium pohangense sp. nov. from Korean coastal waters

The planktonic phototrophic dinoflagellate Alexandrium pohangense sp. nov. isolated from the coastal waters off Korea is described from living and fixed cells by light and scanning electron microscopy (SEM). DNA sequence data were collected from the small subunit (SSU), the large subunit (LSU), internal transcribed spacer regions (ITS1 and ITS2), and 5.8S of the ribosomal DNA (rDNA). The SSU and LSU rDNA sequences of the new dinoflagellate were 4–7% and 14–17%, respectively, different from those of Alexandrium minutum, Alexandrium ostenfeldii, Alexandrium tamutum, Alexandrium margalefii, and Alexandrium pseudogonyaulax, the most closely related species. In addition, the 5.8S rDNA sequence of the new dinoflagellate was also 12% different from those of A. minutum, A. ostenfeldii, A. tamutum, and Alexandrium peruvianum. In a phylogenetic tree based on LSU rDNA sequences, A. pohangense formed a clade with A. margalefii, and this clade was clearly distinct from the clade of A. minutum, Alexandrium diversaporum, A. tamutum, Alexandrium leei, A. ostenfeldii, and Alexandirum andersoni. Moreover, in a phylogenetic tree based on SSU rDNA sequences, A. pohangense was positioned at the base of the clade containing A. leei and A. diversaporum. Morphological analysis showed that A. pohangense has a Kofoidian plate formula of Po, 4′, 6′′, 6c, 8s, 5′′′, and 2′′′′, which confirmed its assignment to the genus Alexandrium. This dinoflagellate has a wide rectangular 1′ plate, the upper left side of which is slightly bent, protruding, and touching the 2′ plate, unlike A. margalefii, which has a wide rectangular 1′ plate that does not touch the 2′ plate, or A. pseudogonyaulax and Alexandrium camurascutulum, which have a narrower elongated pentagonal 1′ plate that touches the 2′ plate. Furthermore, the 1′ plate of A. pohangense meets the 1′′ plate as a straight vertical line, whereas that of A. camurascutulum meets the 1′′ plate as an inclined line because it is lifted by the intrusion of the 1′′ plate. In addition, A. pohangense had a relatively small ventral pore whose majority was located on the 4′ plate, unlike A. margalefii or A. pseudogonyaulax, which have a relatively large ventral pore whose majority is located on the 1′ plate. Furthermore, A. pohangense had pores of two different sizes on the cell surface, unlike A. margalefii and A. pseudogonyaulax, which have similar pores of only one size. On the basis of morphological and phylogenetic criteria, it is proposed that this is a new species of the genus Alexandrium.     

深圳海域近20年赤潮发生的特征分析

本文根据深圳海域1981-2002年发生的93起赤潮记录,综合分析了赤潮发生的特征,可归纳为5点：①深圳海域的赤潮多发区位于大鹏湾、大亚湾和深圳圳湾,其中大鹏湾的盐田水域、大亚湾两部的东山和坝光水域、深圳湾的后海与东角头水域为赤潮多发地段;②赤潮发生的频率增高,赤潮持续时间延长;③全年中有两个赤潮多发季节,主要集中在3～5月,其次为9～11月;④赤潮引发种类丰富,约有39种,其中甲藻最多,其次为硅藻,具有一定的区域分布特征;⑤赤潮引发种类具有明显的演替规律,不断有新的种类引发赤潮。     

我国近海赤潮多发区域及其生态学特征

根据有关的研究资料,分析我国近海赤潮多发区分布、主要赤潮生物种类、环境状况及赤潮发生生态学特点.结果表明,我国辽东湾、渤海湾、莱州湾、大连湾、长江口、舟山海域、杭州湾、厦门湾、柘林湾、大鹏湾、珠江口等为赤潮多发区.引发赤潮的因素较多,它与气象、水动力、营养盐及生物环境的变化密切相关,人类活动(如海水养殖、陆源污水排放等)影响加剧近海富营养化是引发赤潮的重要因素;但富营养化并非发生赤潮的唯一条件,低营养海区也可能发生赤潮.目前对诱发赤潮的关键因子及赤潮发生机理,应加强定点长期监测和开展深入研究.     

Grazing impact of heterotrophic dinoflagellates and ciliates on common red-tide euglenophyte Eutreptiella gymnastica in Masan Bay, Korea

The euglenophyte Eutreptiella gymnastica is a common red tide causative species. However, there have been no studies on the grazing impact of heterotrophic protists on this species. To investigate the grazing impact of heterotrophic protists on E. gymnastica, we measured daily the abundances of E. gymnastica and co-occurring potential heterotrophic protistan grazers in Masan Bay, Korea, in August 2004 when an E. gymnastica red tide occurred. In addition, we tested whether the common heterotrophic dinoflagellates Gyrodinium dominans, Oxyrrhis marina, Pfiesteria piscicida, Polykrikos kofoidii, Protoperidinium bipes, and Stoeckeria algicida and the naked ciliates Strobilidium sp. (30–40 μm in cell length) and Strombidinopsis sp. (70–100 μm in cell length) were able to feed on E. gymnastica. We also measured their growth and ingestion rates on E. gymnastica as a function of prey concentration. Finally, we calculated the grazing coefficients by combining field data on the abundance of the heterotrophic dinoflagellate and ciliate grazers and co-occurring E. gymnastica with laboratory data on ingestion rates obtained in this study. The maximum abundance of E. gymnastica in Masan Bay in August, 2004 was 7575 cells ml⁻¹, while those of Gyrodinium spp., P. kofoidii, P. bipes, the naked ciliates (≤50 μm in cell length), and naked ciliates (>50 μm in cell length) were 50, 9, 58, 32, and 3 cells ml⁻¹, respectively. The maximum growth rate of G. dominans on E. gymnastica (1.13 d⁻¹) was higher than that of O. marina (0.81 d⁻¹) or P. bipes (0.77 d⁻¹). However, E. gymnastica did not support positive growth of P. kofoidii, Strobilidium sp., and Strombidinopsis sp. (−0.04 ∼ −2.8 d⁻¹). The maximum ingestion rates of G. dominans, P. kofoidii, P. bipes, O. marina, and Strobilidium sp. on E. gymnastica (2.1–2.7 ng C predator⁻¹ d⁻¹) were similar, but they were much lower than that of Strombidinopsis sp. (156 ng C predator⁻¹ d⁻¹). The calculated grazing coefficients for P. bipes, small heterotrophic Gyrodinium spp. (25–35 μm in cell length), naked ciliates (≤50 μm in cell length), P. kofoidii, and naked ciliates (>50 μm in cell length) on E. gymnastica were up to 0.77, 0.61, 0.22, 0.07 and 0.03 d⁻¹, respectively (i.e., up to 54%, 46%, 20%, 7%, and 3% of E. gymnastica populations were removed by the population of each of these heterotrophic protistan grazers in 1 d, respectively). The results of the present study suggest that P. bipes, small heterotrophic Gyrodinium spp., and naked ciliates (≤50 μm in cell length) sometimes have considerable potential grazing impact on the populations of E. gymnastica.     

Growth and ingestion rates of larval fish populations in the coastal waters of Israel

Clupeoid larvae were collected on eight cruises between February1984 and February 1985 in the coastal waters of Israel. Fromanalysis of daily growth increments of otoliths, growth ratesof the abundant clupeoids, Engraulis encrasicolus, Sardina pilchardusand Sardinella aurita were found to be 0.55 mm day^–1,0.67 mm day^–1 and 0.60 mm day^–1, respectively, duringthe first month after hatching. Ingestion rates were estimatedusing an equation from the literature relating ingestion andgrowth of larval fish. Ingestion calculated for populationsof fish larvae in pelagic waters ranged from 0 to >23 mgC m^–2 day^–1 with maximum rates observed in April.Annual ingestion by larval fish at a pelagic station near Haifawas calculated to be 2.2 g C m^–2 year^–1, 10–20%of annual primary production estimated from ¹⁴C uptake.     

Mixotrophy in the phototrophic harmful alga Cochlodinium polykrikoides (Dinophycean): prey species, the effects of prey concentration, and grazing impact

We first reported here that the harmful alga Cochlodinium polykrikoides, which had been previously known as an autotrophic dinoflagellate, was a mixotrophic species. We investigated the kinds of prey species and the effects of the prey concentration on the growth and ingestion rates of C. polykrikoides when feeding on an unidentified cryptophyte species (Equivalent Spherical Diameter, ESD = 5.6 microm). We also calculated grazing coefficients by combining field data on abundances of C. polykrikoides and co-occurring cryptophytes with laboratory data on ingestion rates obtained in the present study. Cocholdinium polykrikoides fed on prey cells by engulfing the prey through the sulcus. Among the phytoplankton prey offered, C. polykrikoides ingested small phytoplankton species that had ESD's < or = 11 microm (e.g. the prymnesiophyte Isochrysis galbana, an unidentified cryptophyte, the cryptophyte Rhodomonas salina, the raphidophyte Heterosigma akashiwo, and the dinoflagellate Amphidinium carterae). It did not feed on larger phytoplankton species that had ESD's > or = 12 microm (e.g. the dinoflagellates Heterocapsa triquetra, Prorocentrum minimum, Scrippsiella sp., Alexandrium tamarense, Prorocentrum micans, Gymnodinium catenatum, Akashiwo sanguinea, and Lingulodinium polyedrum). Specific growth rates of C. polykrikoides on a cryptophyte increased with increasing mean prey concentration, with saturation at a mean prey concentration of approximately 270 ng C ml(-1) (i.e. 15,900 cells ml(-1)). The maximum specific growth rate (mixotrophic growth) of C. polykrikoides on a cryptophyte was 0.324 d(-1), under a 14:10 h light-dark cycle of 50 microE m(-2) s(-1), while its growth rate (phototrophic growth) under the same light conditions without added prey was 0.166 d(-1). Maximum ingestion and clearance rates of C. polykrikoides on a cryptophyte were 0.16 ng C grazer(-1)d(-1) (9.4 cells grazer(-1)d(-1)) and 0.33 microl grazer(-1)h(-1), respectively. Calculated grazing coefficients by C. polykrikoides on cryptophytes were 0.001-0.745 h(-1) (i.e. 0.1-53% of cryptophyte populations were removed by a C. polykrikoides population in 1 h). The results of the present study suggest that C. polykrikoides sometimes has a considerable grazing impact on populations of cryptophytes.     

Copepod grazing during an iron-induced diatom bloom in the Antarctic Circumpolar Current (EisenEx): I. Feeding patterns and grazing impact on prey populations

Feeding activity, selective grazing and the potential grazing impact of two dominant grazers of the Polar Frontal Zone, Calanus simillimus and Rhincalanus gigas, and of copepods < 2 mm were investigated with incubation experiments in the course of an iron fertilized diatom bloom in November 2000. All grazers were already actively feeding in the low chlorophyll waters prior to the onset of the bloom. C. simillimus maintained constant clearance rates and fed predominantly on diatoms. R. gigas and the small copepods strongly increased clearance and ingestion of diatoms in response to their enhanced availability. All grazers preyed on microzooplankton, most steadily on ciliates, confirming the view that pure herbivory appears to be the exception rather than the rule in copepod feeding. The grazers exhibited differences in feeding behavior based on selectivity indices. C. simillimus and R. gigas showed prey switching from dinoflagellates to diatoms in response to the phytoplankton bloom. All grazers most efficiently grazed on large diatoms leading to differences in daily losses for large and small species, e.g. Corethron sp. or Thalassionema nitzschioides. Species-specific diatom mortality rates due to grazing suggest that the high feeding activity of C. simillimus prior to and during the bloom played a role in shaping diatom population dynamics.     

Resistance to copper ions and antibiotics in marine heterotrophic bacteria in the coastal waters of Vietnam

Copper and antibiotic resistance was experimentally studied for the first time in marine heterotrophic bacteria that were isolated from microfoulings of copper and copper-alloy test plates in coastal waters of Vietnam. Resistance to copper ions and to at least one of the antibiotics tested was detected in 78.7% of the isolates. A total of 28 models of antibiotic resistance were found in the bacteria. All strains isolated from the foulings of the copper plates were resistant to seven or more antimicrobials. The microfouling communities of copper and copper-alloy plates were dominated by Bacillus spp. and Staphylococcus spp. Copper and antibiotic resistance was statistically independent of the taxon of the tested bacteria.     

放牧、刈割及摘顶对亚热带人工草地牧草种群的影响

通过比较放牧、刈割及摘顶3种干扰发现,适度放牧、刈割提高了亚热带高山人工草地鸭茅、黑麦草种群的适应性,部分原因在于2种干扰均对牧草进行了摘顶．摘顶解除了牧草的顶端优势及生殖生长。放牧、刈割对牧草产生的生态影响在某种程度上可通过摘顶而实现。从而提高种群密度、热值及能量积累．单因子的人工摘顶试验表明,牧草顶端优势的维持降低了牧草种群密度,抑制了能量积累。从抑制了种间竞争．持续摘顶解除了牧草的顶端优势。促进了牧草密度及能量的增长,从而提高了牧草种群的竞争力．     

Natural ingestion rates and grazing impact of the marine cladoceran Penilia avirostris Dana in Tolo Harbour, Hong Kong

The gut fluorescence method was used to study algal grazingby Penilia avirostris in a semiestuarine embayment. Grazingimpact estimated from ingestion rate and animal abundance revealedthat only {small tilde}1% of the algal biomass was grazed perday by the cladocerans.     

Starvation survival of the fish pathogenic bacteria Vibrio anguillarum and Vibrio salmonicida in marine environments

Abstract The possible fate in sea water of the two fish pathogenic bacteria Vibrio anguillarum and Vibrio salmonicida is discussed on the basis of microcosm experiments with these and other copiotrophic bacteria. Recent articles dealing with the survival of fish pathogens are reviewed, and the reported survival capacities are discussed in relation to ecological mechanisms, such as death, and predation, leading to the removal of bacteria from the water column.     

Resolving the intra-specific succession within Cochlodinium polykrikoides populations in southern Korean coastal waters via use of quantitative PCR assays

While the toxic dinoflagellate Cochlodinium polykrikoides is known to form blooms that are maintained for extended periods, the genetic differentiation of these blooms are currently unknown. To assess this, we developed a real-time PCR assay to quantify C. polykrikoides at the intra-specific level, and applied this assay to field samples collected in Korean coastal waters from summer through fall. Assays were successfully developed to target the large-subunit ribosomal RNA region of the three major ribotypes of C. polykrikoides: Philippines, East Asian, and American/Malaysian. Significant linear relationships (r² ≥ 0.995) were established between C_t and the log of the copy number for each ribotype qPCR assay. Using these assays, C. polykrikoides blooms in Korean coastal waters were found to be comprised of Philippines and East Asian ribotypes but not the American/Malaysian ribotype. The Philippines ribotype was found to be highly abundant during summer bloom initiation and peak, whereas the East Asian ribotype became the dominant ribotype in the fall. As such, this newly developed qPCR assay can be used to quantify the cryptic ecological succession of sub-populations of C. polykrikoides during blooms that light microscopy and previously developed qPCR assays cannot resolve.     

不同pH和盐度下海洋细菌对赤潮藻生长和产毒的影响

研究了在可控生态条件下。一株分离自厦门西海域沉积物的海洋细菌S10在不同pH和盐度条件下对赤潮原因种塔玛亚历山大藻(Alexandrium tamarense)生长和产毒的影响．结果表明。实验用藻株适宜生长pH为6～8,适宜盐度为20～34;该藻株在不同pH及不同盐度条件下,藻细胞毒力差异显著,且随着pH升高而下降。随着盐度增加而加大,到盐度为30时达到最高值。然后逐渐下降;菌株Sl0(1．02×10^l0cells·ml^-1)在pH7～9和盐度15～34下均能有效抑藻生长和产毒。且在pH7、盐度34时其抑藻生长作用最强;在pH7时抑藻产毒效果较好,且其抑藻产毒作用强度不随盐度变化而异．     

Survival of natural sewage populations of enteric bacteria in diffusion and batch chambers in the marine environment

The survival of natural populations of Escherichia coli and enterococci in sewage was measured in large-volume diffusion chambers in an estuary and a salt marsh. The 5-liter chambers, with polycarbonate membrane sidewalls, were found to be suitable for up to week-long experiments. Decay rates, measured monthly from February to August 1978, ranged from 0.042 to 0.088 h(-1) (time for 90% of the population to die = 25 to 55 h) for E. coli and 0.019 to 0.083 h(-1) (time for 90% of the population to die = 29 to 122 h) for enterococci and were significantly correlated with temperature. In contrast to the diffusion culture experiments, the decay of E. coli in batch culture did not correlate with temperature. Enterococci survived longer than E. coli in the Narragansett Bay (estuary) experiments, but survived less well in the more eutrophic salt marsh. The effect of light on survival was examined with light/dark experiments and sampling at frequent intervals over the diel cycle. Diel changes in survival were not evident in the Narragansett Bay experiments. E. coli, however, exhibited a diel pattern of growth during the day and death at night in the salt marsh. There was no significant difference in decay rates between light and dark diffusion chambers, nor were decay rates correlated with light intensity. In concurrent batch experiments, survival was significantly greater in the dark for both organisms. These results suggest that the effect of light is complex and that conditions in batch culture may modify the survival of enteric bacteria. Observations made in diffusion chambers may more closely follow the in situ survival of enteric microorganisms.     

黄渤海海水养殖自身污染的评估

探讨了投饵和非投饵两种养殖方式自身污染对海洋环境的影响.结果表明,海水养殖产量与营养盐类、COD和赤潮发生次数均呈正相关关系,其中无机氮含量和赤潮发生次数与虾养殖产量有显著正相关关系,说明海水养殖自身污染对邻近海域富营养化及赤潮发生有一定影响.通过黄渤海海水养殖向海洋排泄氮、磷、COD等污染物估算,分别占相应陆源污染物排海量的2.8%、5.3%、1.8%.虽然与人类其他活动向海洋排污量相比,水产养殖的排污量所占比重还不算大,对于某些局部水域,特别是海水养殖密集区,将对海洋环境的影响产生叠加作用,很可能成为刺激近海富营养化和赤潮发生的一个重要因素,应引起足够的重视.     

In situ feeding rates and grazing impact of Mesopodopsis africana O. Tattersall in the St Lucia Estuary, South Africa

Mesopodopsis africana is an important mysid in southern African coastal zooplankton and a key species in the St Lucia estuarine lake, which is currently undergoing severe desiccation owing to freshwater deprivation. M. africana populations through much of the system are consequently under severe environmental stress. This study investigates the grazing dynamics of this mysid species, in relation to autotrophic food availability and other environmental constraints in two contrasting areas of the St Lucia Estuary, Charters Creek, heavily affected by the desiccation process and the Mouth, virtually under unchanged conditions. Gut evacuation experiments were conducted once each during the day and the night. Evacuation rates were consistently higher during the night, ranging from 0.27 to 0.33 h^-1 at Charters Creek and from 1.13 to 1.24 h^-1 at the Mouth. Ingestion rates were, therefore, higher at the Mouth resulting in population grazing impacts of 2.5% of the total microalgal biomass, while the grazing impact at Charters Creek was only 0.5%. The spatial variation in ingestion rates could be attributed to seasonal differences in gut evacuation rates, differences in the mean size of mysids used, or the physicochemical conditions present at the two stations. It is suggested that mysid populations at Charters Creek are predominantly driven by bottom-up forces, initiated by the harsh environmental conditions. Despite the lower ingestion rates exhibited at Charters Creek, results indicate that these mysids are capable of meeting all their energetic requirements from a microalgal diet alone, although they may also utilise a heterotrophic diet.     

Distribution and biology of marine cladocerans in the coastal waters of southern China

Geographical and seasonal distributions of marine cladocerans in the coastal waters of southern China were studied. Penilia avirostris was the most common species, followed by Evadne tergestina and Podon schmackeri. P. avirostris and E. tergestina were most common during summer. P. schmackeri, found only in a small bay northeast of Hong Kong, showed no clear seasonal pattern of occurrence. P. avirostris and E. tergestina were found at temperatures ranging from 16–32°C and salinity ranging from 7.3–37.2. P. schmackeri was restricted to a temperature range of 17–29°C and a salinity range of 31.0–37.2. No significant relationships between marine cladoceran abundance and chlorophyll a concentration were found in samples taken from Tolo Harbour. Parthenogenetic brood size of P. avirostris and E. tergestina ranged from 1 to 14, while P. schmackeri was found to carry up to 19 embryos per brood. No geographical trend in fecundity patterns was observed. No correlation was found between body length and brood size. The occurrence of females with resting eggs was rare.