Pterosagitta Research Articles

Seasonal variation in chaetognath and parasite species assemblages along the northeastern coast of the Yucatan Peninsula.

Chaetognaths are abundant carnivores with broad distributions that are intermediate hosts of trophically transmitted parasites. Monthly variations in chaetognath and parasite species distributions, abundance, prevalence, and intensity related to seasonal environmental changes were recorded in 2004 and 2005 in Laguna Nichupté, a coral reef, and the adjoining continental shelf of Quintana Roo, Mexico. Of 12 chaetognath species plus Sagitta spp., only 5 (Ferosagitta hispida, Flaccisagitta enflata, Sagitta spp., Serratosagitta serratodentata, and Pterosagitta draco) were parasitized. These species were parasitized with 33 types of flatworms and unidentified cysts (likely protozoan ciliates), having an overall mean prevalence of 6%. Digenean metacercaria larvae numerically dominated the parasite assemblages. Cluster analysis defined 2 chaetognath species assemblages. One included 7 species inside Laguna Nichupté, where F. hispida was numerically dominant (98.9%); the other contained 13 chaetognath species in the continental shelf-coral reef region, where F. enflata was abundant (53%). Canonical correspondence analysis showed that Laguna Nichupté had highly variable and hostile conditions (relatively low salinity and high temperature) for chaetognath species except for F. hispida. The higher density of F. hispida promoted greater parasite diversity (23 types), dominated by Brachyphallus sp. metacercariae. F. enflata prevailed in the continental shelf-coral reef area, which had stable high salinity and relatively low temperature. Monilicaecum and unidentified digenean 'type g' infected 5 chaetognath species on the continental shelf. Distinct primary hosts (mollusks and copepods) and contrasting environmental conditions (salinity, dissolved oxygen concentration, and temperature) between Laguna Nichupté and the continental shelf promoted distinct chaetognath species assemblages, resulting in distinct parasite diversity and prevalence patterns.

The mitochondrial genome of the pelagic chaetognath, Pterosagitta draco

Pterosagitta draco is an important predator in many food webs, and so maintaining the diversity study of Pterosagitta draco in marine ecosystem is essential. In this paper, the complete mitochondrial genome sequence of Pterosagitta draco was determined. Its complete mtDNA sequence is 10,426 bp in length, which contains 11 protein-coding genes (PCGs), 6 transfer RNA genes and 2 ribosomal RNA genes. The composition of A, T, G, C in mtDNA is 27.63%, 23.61%, 23.53% and 25.23%, respectively. The percentage of A + T is 51.24%. The complete mitochondrial genome sequence would be useful for further phylogenetic analysis in Pterosagitta draco.

Relationship between spatial distribution of chaetognaths and hydrographic conditions around seamounts and islands of the tropical southwestern Atlantic.

Relationship between spatial distribution of chaetognaths and hydrographic conditions around seamounts and islands off Northeastern Brazil were analyzed from 133 oceanographic stations during the months of January - April of 1997 and April - July of 1998. Oblique zooplankton tows, using 50 cm diameter Bongo nets with 500µm mesh with a flowmeter to determine the filtered volume, were carried out to a maximum of 200m depth. The Superficial Equatorial Water, which had a salinity > 36 PSU and temperature > 20°C, occupied the top 80 to 200m depth. Below this water mass was the South Atlantic Central Water with salinity ranging from 34.5 to 36 PSU and temperature from 6 to 20°C. The community of chaetognaths showed six species: Pterosagitta draco, Flaccisagitta enflata, Flaccisagitta hexaptera, Pseudosagitta lyra, Serratosagitta serratodentata, and Sagitta helenae. Of these species, F. enflata was the most abundant (32.05% in 1997 and 42.18% in 1998) and the most frequent (87.88% in 1997 and 95% in 1998) during both periods. A mesopelagic specie was identified (P. lyra). This specie was more abundant in 1997 (3.42%), when the upwelling was more intense. P. lyra occurred in 22% of the samples during 1997. The abundance of F. enflata, an epiplanktonic species, increased, associated with greater water-column stability.

Horizontal and vertical distribution of Chaetognatha in the upper 1000 m of the western Sargasso Sea and the Central and South-east Atlantic

The chaetognath abundance, species richness and bathymetric distribution in the upper 1000 m in two regions of the Atlantic Ocean is discussed based on samples collected on two cruises, one to the Sargasso Sea (Northwest Atlantic) on board the R/V R.H. Brown in April 2006, the other along the eastern boundary of the Atlantic (Canary Islands to South Africa) on board the FS Polarstern in November 2007. During both cruises the MOCNESS-1 was used for the sampling. Seventeen species were found in the Sargasso Sea (Ron Brown Cruise) and twenty along the eastern boundary of the Atlantic (the Polarstern Cruise). Sagitta hispida and Krohnitta mutabbii were restricted to the Sargasso Sea, and Sagitta tasmanica, S. gazellae, Eukrohnia macroneura and Krohnitta pacifica to the East Atlantic. In the East Atlantic the most abundant species were Pterosagitta draco, Sagitta enflata, S. serratodentata and Krohnitta subtilis, and in the Sargasso Sea, the most abundant species in Stations 1 and 2 was Sagitta minima. In the other stations S. serratodentata, S. enflata, Pterosagitta draco and Krohnitta subtilis were most abundant. Sagitta zetesios, S. planctonis, S. decipiens, S. sibogae and Eukrohnia fowleri were present at all stations but always in low numbers.

Biodiversity of chaetognaths of the Andaman Sea, Indian Ocean

Andaman Sea is a prominent biodiversity hotspot in the Indian Ocean. Stratified zooplankton collections were taken at 33 locations during 2003-2006. Average density of chaetognaths was 8.5/m 3 in open ocean and 41.6/m 3 in coastal waters. Twenty species of chaetognaths, including two recently described species occur in the area. In the oceanic sector Sagitta enflata dominated the layer above thermocline followed by S. neglecta, S. bipunctata , S. pacifica , Pterosagitta draco, and S. regularis. In the depths from thermocline to 500 m, S. decipiens dominated followed by Eukrohnia fowleri. Aggregations of S. decipiens, a mesopelagic species, were occasionally found in the mixed layer (up to 9.9/m 3) during Northeast monsoon associated with the upward movement of species. In the coastal waters either S. enflata or S. neglecta dominated. Recently described Krohnitta balagopali and Sagitta meenakshiae are endemic to the area. Maximum species diversity was observed at the thermocline. Invariably two clusters were found along each stratum at the 60 to 70% similarity level or higher. Latitudinally, species diversity increased towards south. Variability in the chaetognath community is influenced by unique physical features of the area.

Fine structure of the ventral nerve centre and interspecific identification of individual neurons in the enigmatic Chaetognatha

The enigmatic arrow worms (Chaetognatha) are marine carnivores and among the most abundant planktonic organisms. Their phylogenetic position has been heavily debated for a long time. Most recent molecular studies still provide a diverging picture and suggest arrow worms to be some kind of basal protostomes. In an effort to understand the organization of the nervous system in this clade for a broad comparison with other Metazoa we analysed the ultrastructure of the ventral nerve centre in Spadella cephaloptera by transmission electron microscopy. We were able to identify six different types of neurons in the bilateral somata clusters by means of the cytoplasmic composition (regarding the structure of the neurite and soma including the shape and eu-/heterochromatin ratio within the nucleus) as well as the size and position of these neurons. Furthermore, our study provides new insights into the neuropil composition of the ventral nerve centre and several other fine structural features. Our second goal was to examine if individually identifiable neurons are present in the ventral nerve centres of four chaetognath species, Sagitta setosa, Sagitta enflata, Pterosagitta draco, and Spadella cephaloptera. For that purpose, we processed whole mount specimens of these species for immunolocalization of RFamide-related neuropeptides and analysed them with confocal laser-scanning microscopy. Our experiments provide evidence for the interspecific homology of individual neurons in the ventral nerve centres of these four chaetognath species suggesting that the potential to generate serially arranged neurons with individual identities is part of their ground pattern.

Marine biogeochemical response to a rapid warming in the main stream of the Kuroshio in the western North Pacific

AbstractImpact of climate change on marine biogeochemical parameters and ecosystem is one of the important issues of our environment. Direct evidence of marine pelagic ecosystem changes is found with warming of sea water and sea‐level rise in the main stream of the Kuroshio in the East China Sea and the western North Pacific during these three decades based on the analysis of long‐term comprehensive hydrographic observations. In terms of annual mean, the warming rate of surface air temperature and sea surface temperature ranged from 0.15 to 0.21°C per decade in and around the main stream of the Kuroshio in the East China Sea, which exceed the global mean warming rate of 0.128 ± 0.026°C per decade during the period from 1956 to 2005 reported in IPCC 2007. One of the features in this rapid warming region is an increase of number of Pterosagitta draco, a cosmopolitan warm‐water zooplankton. Biogeochemical parameters, such as wet weight of zooplankton, plant pigment and nutrients concentration in the upper 200 m have been decreasing while dissolved oxygen content and seawater temperature have been increasing in the upper 200 m in the main stream of the Kuroshio in the East China Sea. These observed linear trends of the biogeochemical parameters would be foresights for temperate oceans in the future.

Species composition and seasonal abundance of Chaetognatha in the subtropical coastal waters of Hong Kong

Species composition, species diversity and seasonal abundance of chaetognaths were studied in Tolo Harbour and the coastal waters of eastern Hong Kong. Tolo Harbour is a semi-enclosed and poorly flushed bay with a long history of eutrophication. It opens into the eastern coast of Hong Kong which is fully exposed to water currents from the South China Sea. Zooplankton samples were collected monthly from July 2003 to July 2005 at six stations. Twenty species of chaetognaths were identified. They included six species of the genus Aidanosagitta ( Aidanosagitta neglecta, Aidanosagitta delicata, Aidanosagitta johorensis, Aidanosagitta regularis, Aidanosagitta bedfordii and Aidanosagitta crassa), four species of the genus Zonosagitta ( Zonosagitta nagae, Zonosagitta bedoti, Zonosagitta bruuni and Zonosagitta pulchra), three species of the genus Ferosagitta ( Ferosagitta ferox, Ferosagitta tokiokai and Ferosagitta robusta) and one species each from the genera Serratosagitta ( Serratosagitta pacifica), Decipisagitta ( Decipisagitta decipiens), Flaccisagitta ( Flaccisagitta enflata), Krohnitta ( Krohnitta pacifica), Mesosagitta ( Mesosagitta minima), Pterosagitta ( Pterosagitta draco) and Sagitta ( Sagitta bipunctata). The most abundant species were Flaccisagitta enflata, A. neglecta and A. delicata. Averaged over the entire study period, the densities of Flaccisagitta enflata, A. neglecta and A. delicata were 9.3, 6.6 and 5.2 ind. m −3, respectively. Overall, these species constituted 39.7%, 28.2% and 22.0% of all chaetognaths collected in the study. Averaged over the entire study, the density of most of the low abundance species was <0.6 ind. m −3. Flaccisagitta enflata occurred throughout the year at all sampling stations. Aidanosagitta neglecta occurred at all sampling stations, but was most common in summer. Aidanosagitta delicata was most common in Tolo Harbour during summer. Tolo Harbour supported larger populations, but fewer species of chaetognaths than the surrounding open waters. These observations suggest that some species of chaetognaths were carried into the coastal waters of Hong Kong by water currents from the South China Sea and established large populations in the productive and poorly flushed waters of Tolo Harbour.

Distribuição das espécies de chaetognatha na plataforma continental de Sergipe e Alagoas

The present study investigated the Chaetognatha species distribution in the continental shelf off Sergipe and Alagoas States and its relation to the abiotic variables. Samples were collected at eighteen stations along six transects, perpendicular to the coast line in December (2001 and 2002) and June (2002 and 2003), corresponding to the dry and rainy seasons, respectively. Oblique hauls were done with plankton net, mesh size 200 µm. Temperature, salinity, pH, dissolved oxygen and nutrients were measured in three levels of the water column. Subsamples were taken using a Stempel pippette. Correlations analysis between Chaetognatha distribution and environmental parameters were studied using canonical correspondence analysis. Sagitta tenuis and S. enflata were the most adundant species, following by S. hispida, Sagitta spp., Krohnitta pacifica, Pterosagitta draco and S. bipunctata. Density values ranged between 9 ind.m-3 , in December 2002, and 4,473 ind.m-3 in June 2002, when Sagitta tenuis and S. enflata were more abundant. Density average values decreased from stations located at 10 meters to that located at 30 meters depth. Temperature, phosphate, salinity and water transparence were correlated (p<0,05) to the Chaetognatha species distribution.

Chaetognatha of the Brazil-Malvinas (Falkland) confluence: distribution and associations

The planktonic chaetognaths from the Brazil-Malvinas (Falkland) confluence, extending between 36º 30' - 50º 5' S and 60º 33' - 41º 7' W, were studied. Ten species were found: Eukrohnia hamata (Möbius, 1875) (Eukrohniidae), Pterosagitta draco (Krohn, 1853) (Pterosagittidae), Sagitta enflata Grassi, 1881, Sagitta gazellae Ritter-Zahony, 1909, Sagitta hexaptera d´Orbigny, 1834, Sagitta lyra Krohn, 1853, Sagitta minima Grassi, 1881, Sagitta planctonis Steinhaus, 1896, Sagitta serratodentata Krohn, 1853, and Sagitta tasmanica Thomson, 1947 (Sagittidae). Sagitta gazellae was the most abundant species followed by E. hamata, S. tasmanica and S. serratodentata. The association analysis among the different species, salinity and temperature revealed two groups of species, one related to higher salinities and warmer waters (P. draco, S. hexaptera and S. serratodentata) and the other to lower salinities and colder waters (E. hamata, S. gazellae and S. tasmanica). The fact that P. draco and S. hexaptera, formerly defined as warm-water species, appeared further south than previously reported might be related to the existence of warm core eddies up to 46º S in September and October 1988.

The Chaetognatha of the Southwestern Gulf of Mexico During April-May, 1986

An analysis of the distribution and abundance of Chaetognatha species from the Gulf of Mexico during April–May 1986 is presented. Zooplankton samples were collected at 43 stations from the southwestern and eastern regions of Mexico’s Exclusive Economic Zone in the Gulf of Mexico. Species richness and abundance were higher in the southwestern stations located at the platform slope. The rank of Importance Value (IV) shows 3 groups of species; the first group included Flaccisagitta enflata, Mesosagitta minima, Serratosagitta serratodentata, Krohnitta subtilis, Pterosagitta draco, Sagitta bipunctata, and Krohnitta pacifica which were the most widely distributed species during this period. Density data were classified and analyzed by Morisita’s similarity index, depicting 2 large groups of sampling stations along with a third group made up of 5 stations. Two stations were distinct from the others because of the low species richness and because only 2 species with high densities were present. Simpson’s dominance index showed low values throughout the study area. Densities of chaetognath species did not differ significantly between day and night samples. Gulf and Caribbean Research Vol. 13, 51–57, 2001 Manuscript received July 14, 2000; accepted February 9, 2001

Notes on Some Chaetognaths from Pine Cay, Turks and Caicos Islands (British West Indies)

Seven species of planktonic Chaetognatha - Ferosagitta hispida, Flaccisagitta enflata, F. hexaptera, Krohnitta pacifica, Sagitta bipunctata, Serratosagitta serratodentata, and Pterosagitta draco - were present in plankton samples collected in waters north of Pine Cay, Turks and Caicos Islands, British West Indies. In addition, the epibenthic species Spadella cephaloptera, Paraspadella nana, and P. schizoptera were present, the latter two species associated mainly with shallow clumps of the coralline alga, Neogoniolithon sp., and with sponge-algal communities. One specimen of S. cephaloptera was collected at 35 m from a sand bottom north of the fringing reef adjacent to Pine Cay. Meristic data for F. hispida and for the three epibenthic species are provided.

Records of Deep-Water Chaetognaths from the Northern Gulf of Mexico

Fourteen s p i e s of deep-water Chaetognatha were present in plankton samples collected between 200 and 677 m at five stations along the continental slope of the northem Gulf of Mexico. Samples were taken in conjunction with the MARFWl Geryon cruises of 1987 and 1988. New Gulf of Mexico records resulting from this study were Eukrohnia calliops, Eukrohnia proboscidea, Mesosagitta sibogae, and Sagitta megalophthalma. Other deepwater species present were Eukrohnia fowleri, E. bathypelagica, E . bathyantarctica, Caecosagitta macrocephala. Mesosagitta decipiens, M . minima, Solidosagitta planctonis, Krohnitta subtilis, Flaccisagitta hexaptera, and F . lyra. In addition, the normally epiplanktonic taxa, Pterosagitta draco, Serratosagitta serratadentata, and Sagitta bipunctata occurred in some of the samples.

Spatial and temporal abundance patterns of oceanic chaetognaths in the western North Atlantic—I. Hydrographic and seasonal abundance patterns

Chaetognath abundance was measured from 38 MOCNESS tows collected in the western North Atlantic from August 1975 to November 1977. Twenty-one species were identified from 18 slope water (SW), 18 northern Sargasso Sea (NSS) and two Gulf Stream (GS) tows. Sagitta elegans, S. hispida and S. megalophthalma were collected in only one or two tows. Eukrohnia bathypelagica, E. fowleri, E. hamata, Sagitta helenae, S. macrocephala, S. maxima and S. tasmanica are significantly more abundant in the SW than in the NSS. Krohnitta subtilis, Pterosagitta draco, Sagitta bipunctata, S. decipiens, S. hexaptera, S. lyra, S. minima, S. planctonis and S. serratodentata are significantly more abundant in the NSS. Krohnitta pacifica and Sagitta enflata show no significant abundance differences between the SW and NSS. Most species show at least an order of magnitude abundance difference between the SW and NSS, with intermediate GS abundances. A simple mixing model and previous reports of chaetognath distributions in the North Atlantic indicate that most species have expatriate populations in either the SW or NSS or in both regions. Increased temperature and food abundance probably limit SW species from the NSS, while decreased temperature and increased predator abundance probably limit NSS species from the SW. Spring abundance peaks were observed for many species in the NSS, but no seasonal peaks were detected for species in the SW. The spring abundance peaks in the NSS are probably due to increased food abundance, although temperature could not be ruled out as an important factor.

Spatial and temporal abundance patterns of oceanic chaetognaths in the western North Atlantic—II. Vertical distributions and migrations

Vertically stratified zooplankton tows were collected with the MOCNESS in the upper 1000 m of the western North Atlantic during the period from August 1975 to November 1977. Vertical distributions of 18 abundant chaetognath species were studied from 18 slope water (SW), 18 northern Sargasso Sea (NSS) and two Gulf Stream (GS) tows. Krohnitta pacifica, Pterosagitta draco, Sagitta bipunctata, S. enflata, S. helenae, S. hexaptera, S. minima, S. serratodentata and S. tasmanica were classified as epipelagic species, Eukrohnia hamata, Krohnitta subtilis, Sagitta decipiens, S. lyra, S. maxima and S. planctonis were classified as mesopelagic species, and Eukrohnia bathypelagica, E. fowleri and Sagitta macrocephala were classified as bathypelagic species. Nine species were significantly shallower in the SW relative to the NSS, while K. subtilis and S. lyra were significantly shallower in the NSS. Few seasonal differences were detected in either the SW or NSS for any of these species, and vertical distributions in the two GS tows are similar to those found in the SW and NSS. No diel vertical migrations were detected for any of these species, but ontogenetic vertical migrations were detected for several of the meso- and bathypelagic chaetognaths. That many species occur at shallower depths in the SW is consistent with the hypothesis that they follow isotherms in selecting the depths at which they live. E. hamata is the only species living at approximately the same temperature in the SW and NSS, however; the remaining species live at higher temperatures in the NSS. Other factors, such as pressure and light, may be important in determining the species' vertical distributions. S. lyra occupies greater depths in the SW relative to the NSS because its SW population consists mostly of larger, deep-living individuals, while its NSS population is dominated by younger, shallow-living individuals. It is possible that many of the regional differences in vertical distribution exhibited by the other species are due also to regional differences in population stage structure coupled with ontogenetic migrations.

Observations on Chaetognath Distributions in the Northeastern Gulf of Mexico During the Summer of 1974

The chaetognath population was studied from zooplankton samples collected at twelve stations in the northeastern Gulf of Mexico in June 1974. Quantitative analysis of six stations revealed a large inshore population composed largely of juveniles and neritic species in the upper strata, and a progressively smaller and more evenly dispersed assemblage composed largely of oceanic, stenohaline species at stations further offshore. The high percentage of juveniles in surface samples evidenced an early-summer spawning peak for the population as a whole. Overlying low salinity water throughout the study area was characterized by the presence of two neritic species, Sagitta tenuis and S. friderici, in surface samples, while an underlying high salinity intrusion over the continental shelf was denoted by the submerged occurrence of stenohaline species. Fourteen species were grouped into three ecological categories denoting degrees of tolerance to environmental change: (1) neritic - Sagitta friderici, S. tenuis, S. helenae, S. hispida, (2) mixed water - S. enflata, S. minima, S. serratodentata, Pterosagitta draco, Krohnitta pacifica, and (3) oceanic - S. hexaptera, S. bipunctata, K. subtilis, S. decipiens, S. lyra.

Distributional patterns of chaetognaths in the Bay of Fundy

Nine species of chaetognaths were found in the Bay of Fundy: Sagitta elegans, S. tasmanica, Eukrohnia hamata, S. maxima, S. lyra, S. enflata, S. hexaptera, S. serratodentata, and Pterosagitta draco. Sagitta elegans was the dominant and only native species and maintained a centre of very high abundance in the study area. It is suggested that surface circulation carries young out of the Bay of Fundy and that the centre of abundance is maintained principally by immigration from outside the Bay and by interaction of adult specimens with the hydrographic conditions. Sagitta tasmanica was the second most abundant species and an immigrant carried into the Bay of Fundy by surface circulation. The distribution and abundance of E. hamata indicated a regular but variable inflow of slope water. The occurrence of S. maxima and S. lyra, and S. enflata, S. hexaptera, S. serratodentata, and P. draco indicated periodic inflow of oceanic boreal and (or) Gulf Stream waters.

Some biometrical, ecological, morphological and distributional aspects of Chaetognata

The study of the Chaetognatha picked out from 21 plankton samples taken along the Argentinian, Uruguayan and Brazilian coasts, revealed the presence of the following species: Krohnitta pacifica, K. subtilis, Pterosagitta draco, Sagitta bipunctata, S. enflata, S. friderici, S. hexaptera, S. hispida, S. lyra, S. maxima, S. minima, S. planctonis, S. serratodentata, S. tenuis and S. sp. A. All specimens were measured and a complete biometrical table is included. Based on the Chaetognatha and the Thecosomata fauna analyzed by means of the Sorensen's index of similarity between samples, the area is divided into four zones with different hydrological characteristics. There is a distinct relationship between the total length of fully mature specimens and latitude. Based on diagrams, an inter-specific competition between S. enflata and S. t tenuis is suggested. The geographic distribution of K. subtilis and S. planctonis is enlarged.

Vertical distribution of epiplanktonic Chaetognaths in the upper 100 m of the Hilutangan Channel, Cebu, The Philippines

A study was made on the vertical distribution of Chaetognatha in the Hilutangan Channel, based on analyses of 48 plankton samples. Thirty-min horizontal plankton tows were performed at depths of 1, 20, 50, 70 and 100 m in January 1972. Thirteen species of 3 genera of maturing and mature chaetognaths were identified and counted. Sagitta inflata was the most common and abundant species (63.0%), folloed by S. neglecta (9.7%), S. robusta (8.6%), S. regularis (5.4%), S. serratodentata (4.2%), Krohnitta pacifica (2.9%), S. bedoti (2.3%) and S. decipiens (2.0%). S. pulchra (0.7%), S. ferox (0.5%), K. subtilis (0.3%), Pterosagitta draco (0.2%) and S. hexaptera (0.2%) were represented by less than 1% each. Of these 13 species in the upper 100 m, 12 were epiplanktonic while one species, S. decipiens, is generally considered to be mesoplanktonic. Three species were classified as neritic, 3 as neritic-oceanic, and 6 as oceanic, indicating the dominant influence and strong influx of oceanic water into the Hilutangan Channel. Temperature, salinity and dissolved oxygen content did not seem to influence the vertical distribution. Examination of gut contents showed that copepods, followed by arrow worms, were most common in the guts of the chaetognaths studied.

Distribution and annual occurrence of Chaetognatha off Cananeia and Santos coast (São Paulo, Brazil)

Plankton samples were fortnightly taken at three fixed stations off Cananéia (1958, 1959, 1960) and off Santos (1960, 1961) by vertical hauling. They contained the following species: Sagitta enflata, S. friderici, S. hispida, S. minima, S. serratodentata, Krohnitta pacifica and Pterosagitta draco. S. frideriei is a typical coastal water species. S. enflata is a typical shelf water species. S. hispida and K. pacifica were present more frequently in shelf water but they were sometimes very abundant in coastal water. S. serratodentata, S. minima and P. draco occurred sparingly in tropical water, however, very few samples were taken in this water mass. Three different maturity stages were established (juvenile, intermediate and adult) in order to study the annual variation of the Chaetognatha. A special breeding period throughout the year was not observed as great swarms of juveniles and intermediates were found in spite of the very small number of adults. Two series of samples taken off Santos at a fixed station (Pt. III) during a period of 24 hours in three different levels were also counted to study the vertical distribution of the Chaetognatha in this area. The three most abundant species were: S. enflata, S. hispida and K. pacifica. S. enflata was more frequent at mid-water. S. hispida and K. pacifica seemed to prefer the surface layer. The thermocline did not affect their vertical migration except for S. hispida. There is indication that S. serratodentata performs vertical movements. S. minima seems to live below 25 m depth. K. subtilis occurred exceptionally in this vertical series of samples.