Alejandro M. Maeda-Martínez

Effect of aerobic Gram-positive heterotrophic bacteria associated with Artemia franciscana cysts on the survival and development of its larvae

Abstract The study of bacterial interaction with crustaceans used in aquaculture, such as the brine shrimp Artemia , is gaining importance. It is presumed that some bacteria provide nutritional elements, and/or have the capacity to function as probiotics. In this work, aerobic Gram-positive heterotrophic bacteria associated with commercial Artemia cysts were isolated. According to molecular analyses, these bacteria corresponded to the genera Microbacterium and Exiguobacterium . No previous record of these bacteria in association with Artemia cysts exists, nor are there studies of their effect on Artemia culture. In this study, nauplii of Artemia franciscana Kellogg, 1906 were challenged in 6-day-monoxenic cultures with three bacteria strains: Microbacterium sp. A, Microbacterium sp. B, and Exiguobacterium sp. Also, a putative pathogenic strain of Vibrio parahaemolyticus was tested for comparative purposes. Our objective was to evaluate the effect of these bacteria on the survival, growth, and development of Artemia larvae. Microbacterium sp. B and V. parahaemolyticus negatively affected Artemia larvae (survival Microbacterium sp. A and Exiguobacterium sp. were harmless, having no impact on survival, growth, and development of the larvae when compared with the control treatment (survival >80%). However, the mixture of the harmless bacteria in a dixenic culture had a significant positive effect on the growth and development of Artemia larvae. On the basis of these results, it is suggested that Microbacterium sp. A and Exiguobacterium sp. are potential candidates as probiotic bacteria for the culture of Artemia larvae. The results of the challenge tests demonstrated that the protocol to obtain and culture bacteria-free Artemia larvae, using autoclaved bakers yeast as food, was a useful standardized tool to evaluate the effect of bacteria strains on the survival and development of this crustacean. The method was an in vivo, small-scale (monoxenic or dixenic) test, which was in line with the rationale for the search for probiotics in aquaculture.

Historical biogeography and morphological differentiation of Streptocephalus torvicornis (Waga) since the Würm III-glaciation

We argue that the Wurm III glaciation eradicated possible European populations ofS. torvicornis, and that today, a reconquest of Europe takes place on two fronts.

FRESHWATER SHRIMP OF THE GENUS MACROBRACHIUM (DECAPODA: PALAEMONIDAE) FROM THE BAJA CALIFORNIA PENINSULA, MÉXICO

Abstract Freshwater decapods like the palaemonid river shrimp have received little attention in the Baja California Peninsula, México. From the first formal report in 1878 to now, only three Macrobrachium species have been reported (M. americanum, M. digueti, and M. tenellum) from the peninsula in only three basins. We made a taxonomic study of freshwater shrimp, which included an extensive field survey at 81 sites distributed on both the Pacific and the Gulf of California slopes and a revision of material from the area that had been deposited in scientific collections. We report six species of Macrobrachium by adding M. hobbsi, M. michoacanus, and M. olfersii. We also discuss some aspects of the diversity and conservation of these species in the peninsula and provide an identification key for the Macrobrachium shrimp of northwestern México.

Mixture of parthenogenetic and zygogenetic brine shrimp Artemia (Branchiopoda: Anostraca) in commercial cyst lots from Great Salt Lake, UT, USA

The brine shrimp Artemia is one of the most studied animals in the world. A large part of the knowledge of this crustacean is based on cysts harvested from two main sources; the Great Salt Lake, UT (GSL), and the San Francisco Bay salterns, CA (SFB), USA. Artemia populations from these habitats are recognized to belong to a single zygogenetic species, Artemia franciscana Kellogg, 1906. However, the GSL Artemia has been in doubt for more than a century about the existence of parthenogenetic reproduction. By using morphological, reproductive, and molecular analyses, we report that commercial GSL cyst lots contained two different brine shrimp species; a parthenogenetic (60%) and a zygogenetic (A. franciscana) (40%). From this finding, at least three hypotheses can be drawn. The parthenogenetic Artemia is native of GSL, or it was introduced to GSL, or foreign parthenogenetic cysts were mixed with A. franciscana cysts and canned for commercial distribution. Researchers using brine shrimp cysts from GSL should therefore pay careful attention to the correct identity of the species under study. The potential of an easy and unnoticed introduction of parthenogenetic Artemia into America is discussed.

New records of large branchiopods (Branchiopoda: Anostraca, Notostraca, and Spinicaudata) in Mexico

This paper reports new distribution records of large branchiopods for Mexico following a three year survey of the Baja California peninsula. The occurance of the anostracans Thamnocephalus mexicanus (Linder, 1941) and T. platyurus (Packard, 1877), the notostracan Lepidurus lemmoni (Holmes, 1894), and the spinicaudatans Eulimnadia cylindrova (Belk, 1989) and E. texana (Packard,1871), all represent the first records for the peninsula. An undescribed species of the anostracan genus Streptocephalus is recorded from the state of Baja California (Norte). The occurrence of the notostracan genus Triops and four other anostracan species on the peninsula is also confirmed. The conchostracan Cyclestheria hislopi (Baird, 1859) is recorded from the state of Quintana Roo. The collections of Lepidurus and Cyclestheria are the first records for México. These records increase the number of species of large branchiopods reported fromMéxico to 36: 20 Anostraca, 3 Notostraca, 11 Spinicaudata, and 2Laevicaudata.

Branchinecta oterosanvicentei n. sp. (Branchiopoda: Anostraca), a new fairy shrimp from the Chihuahuan desert, with a proposal for the conservation of the Branchinectidae of Mexico

Branchinecta oterosanvicentei, new species, a fairy shrimp endemic to the south of Coahuila, Mexico is described and figured. Differential features between the new species and the related B. lindahli are discussed on the basis of a SEM micrographs. The main diagnostic characters of Branchinecta oterosanvicentei are: (1) a pulvinus covered by scales localized on the middle of the median side of the proximal article of antenna, and (2) a network of prominent cortical crests on the cyst surface. Of seven Branchinecta species occurring in Mexico, four (B. belki, B. mexicana, B. oterosanvicentei, and B. sandiegonensis) have a restricted geographic range. Because, in addition, extreme fluctuations in the number of mature individuals per population occur, the survival of all of these species is threatened, and measures should be taken to protect them. Branchinecta mackini has a wide distribution in North America, but even this form is rare in Mexico.

Unfertilized Oocytes in Streptocephalids: Resorbed or Released?

ABSTRACT Short interval monitoring of isolated females of Streptocephalus dichotomus Baird, S. proboscideus(Frauenfeld), and S. torvicornis (Waga) revealed no resorption of unfertilized oocytes in the lateral pouches of the oviducts or in the ovisac. Oocytes expelled by the female disintegrate in the medium. This finding is in disagreement with earlier studies on S. dichotomus and S. proboscideus, but corroborates findings on S. vitreus (Brauer) and S. rubricaudatus (Klunzinger). Light and electron microscopic studies of unfertilized and fertilized oocytes show polar-body extrusion, vitelline-membrane formation, and egg-shell deposition in fertilized oocytes only. The streptocephalids studied here differ, in this respect, from two other anostracans, Tanymastix and Artemia, where unfertilized oocytes develop a vitelline membrane, and sometimes an egg shell.

Co-occurrence of two tadpole shrimp, Triops cf. australiensis (Branchiopoda : Notostraca), lineages in middle Paroo, north-western New South Wales, with the first record of Triops hermaphrodites for the Australian continent

The only species of the genus Triops in Australia, T. australiensis, is found to reproduce by gonochorism. Morphological and reproductive data and molecular analyses of fragments of mitochondrial genes 12S rRNA (12S) and cytochrome oxidase I (COI) indicate that a Triops population from the middle Paroo in north-western New South Wales is composed of two different entities, Triops cf. australiensis lineage A, and T. cf. australiensis lineage B. Gonad histology in individuals with ovisacs of lineage A revealed no evidence of testicular tissue; however, large testicular lobes were found in individuals with ovisacs of lineage B, indicating that they were anatomically hermaphrodites. This is the first record of Australian hermaphroditic Triops. For each lineage, a single haplotype of each gene was obtained. Molecular genetic distance and phylogenetic analyses confirmed the closer relationship and monophyly of the two lineages with T. australiensis (GenBank) when compared with Triops species from other continents. COI haplotypes of lineage A and lineage B differed by 7.7% from each other and differed by 10.2% and 9.6% from a published T. australiensis sequence, respectively. The 12S haplotypes of lineage A and lineage B differed by 3.3% from each other and differed by 2% and 2.5% from a published T. australiensis sequence, respectively. Our results suggest that the two co-occurring Triops lineages probably represent two species that are distinct from T. australiensis.

FATTY ACID COMPOSITION OF ARTEMIA (BRANCHIOPODA: ANOSTRACA) CYSTS FROM TROPICAL SALTERNS OF SOUTHERN MÉXICO AND CUBA

Abstract The growing demands and high costs of commercial Artemia cysts and the establishment of new shrimp hatcheries and farms have caused people to search for local sources of Artemia, putting special attention on their nutritional characteristics. As an essential step to determine the biochemical composition of Artemia, the fatty acid profiles of decapsulated cysts from six tropical salterns of southern México [Campeche (1), Oaxaca (1), and Yucatán (4)], two of Cuba (Camagüey and Guantánamo), and from a temperate site (San Francisco Bay, USA) (SFB) were analysed using direct transesterification and gas chromatography-mass spectrometry. Of 51 fatty acids identified, C16:0 (hexadecanoic), C16:1 n5 (hexadecenoic), C18:1 n9 (octadecenoic), C18:1 n7 (octadecenoic), and C18:2 n6 (octadecadienoic) were the major compounds found. The SFB strain from a temperate area showed significant differences from the rest of the samples of tropical origin, having a greater concentration in the fatty acids 18:2 n5 (10, 13-octadecadienoic), 18:3 n3 (octadecatrienoic), and 18:4 n3 (6, 9, 12, 15-octadecatetraenoic). The SFB strain showed the lowest proportion of mono-unsaturated fatty acids. Based on the fatty acid composition, the Artemia strains studied can be assessed as “freshwater” type, except for the one from Oaxaca that had a “marine” type profile characterized by 3% to 4% of the fatty acid C20:5 n3 (eicosapentaenoic).

REPRODUCTIVE CYCLE AND GENITALIA OF THE FAIRY SHRIMP BRANCHINELLA THAILANDENSIS (BRANCHIOPODA: ANOSTRACA)

ABSTRACT Adults of three fairy shrimp species are present in Thailand from February through June in ephemeral waters (ponds, roadside canals, and rice field ditches) filled mostly by the rain. Branchinella thailandensis is of interest in aquaculture because it reproduces rapidly and has high nutritional value. However, no detailed studies on its reproductive biology are available. Anatomical analyses of male and female genitalia were studied with light microscopy and SEM. Shrimp were reared in the laboratory at 28 ± 1 °C in aerated, potable water using the alga Chlorella sp. as food. One female and two males were placed in each of ten 1-L observation containers and the female reproductive stages were monitored every hour over six days. Branchinella thailandensis exhibits zygogenetic reproduction and oviparity, where fertilization is direct and internal; the brood pouch shows an undifferentiated amplexial groove. Males and females reach maturity on days 7 and 8 after hatching, with a mean standard length of 10.3 and 12.2 mm, respectively. Males have unique spines on the gonopods, with a tip on a socket-like base; accessory glands were not evident in histological sections. Females have biramous ovaries; the shell glands are organized in two paired, bilateral clusters, in which the glandular unit is formed by two gland-cells and a single duct. After six complete reproductive cycles, the mean total duration of the reproductive cycle was ∼24.0 h (N = 60). The total duration of the reproductive cycle and egg production increased with age (subsequent reproductive cycles). No oösorption in unmated females was observed, and the oöcytes passed to the ovisac independent of copulation. Our results confirmed that Stage 3 is the longest reproductive stage in anostracan females. Branchinella thailandensis produces typical freshwater anostracan sculptured eggs, and belongs to the fairy shrimp group without a sub-cortical space beneath the egg shell.