Gopal Murugan

First record of the family Thamnocephalidae (Crustacea: Anostraca) from Southeast Asia and description of a new species of Branchinella

During a two-year investigation of freshwater microcrustaceans in Thailand, an undescribed species of fairy shrimp of the genus Branchinella Sayce, 1903 in the family Thamnocephalidae, was discovered. This is the first record of the genus and the family from Southeast Asia and the second anostracan reported from Thailand. The new species, Branchinella thailandensis n. sp. appears to be morphologically intermediate between B. kugenumaensis (Ishikawa, 1895) from Japan and east China, and B. madurai Raj, 1951 from India and Pakistan. B. thailandensis n. sp. was collected from several temporary ponds in 11 provinces of the northeast and the central Thailand, often co-occurring with Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers & Dumont, 2000.

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.

Molecular characterization of the tadpole shrimp Triops (Branchiopoda: Notostraca) from the Baja California Peninsula, México: New insights on species diversity and phylogeny of the genus

Using sequence analyses of fragments of the small and large subunits of mitochondrial genes 12S and 16S rRNA, we studied the molecular identity of five Triops populations from the Baja California Peninsula, México. Additionally, we explored the phylogeny of the genus by comparing with sequence data from gonochoric T. longicaudatus (Zacatecas, México), commercial Triops kit (U.S.A.), T. `granarius (Japan), T. cancriformis (Austria), T. australiensis (Australia) and Lepidurus lemmoni (U.S.A.). The 16S fragment was not useful to discriminate the American Triops forms because their sequences were more than 99% similar. Molecular and phylogenetic analyses using the 12S gene fragments, in agreement with previous allozyme studies, indicate that the nominal (morphological) species T. longicaudatus is a mixture of several species such that, of the seven Triops American populations studied, six phylogenetic species can be identified and two morphologically and reproductively highly divergent forms can be grouped into a single monophyletic clade. The molecular data, rather than supporting our previous proposal that the phylogenetic relationships of Triops species could be deduced by similarities in the number of total and legless rings, suggest that T. cancriformis may represent an independent group from the rest of the species in that genus. In spite of detectable differences among American populations, our analyses indicate these represent a single monophyletic group when compared to Triops from outside of the New World.

Are Prorocentrum hoffmannianum and Prorocentrum belizeanum (DINOPHYCEAE, PROROCENTRALES), the same species? An integration of morphological and molecular data.

The taxonomic assignment of Prorocentrum species is based on morphological characteristics; however, morphological variability has been found for several taxa isolated from different geographical regions. In this study, we evaluated species boundaries of Prorocentrum hoffmannianum and Prorocentrum belizeanum based on morphological and molecular data. A detailed morphological analysis was done, concentrating on the periflagellar architecture. Molecular analyses were performed on partial Small Sub‐Unit (SSU) rDNA, partial Large Sub‐Unit (LSU) rDNA, complete Internal Transcribed Spacer Regions (ITS1‐5.8S‐ITS2), and partial cytochrome b (cob) sequences. We concatenated the SSU‐ITS‐LSU fragments and constructed a phylogenetic tree using Bayesian Inference (BI) and maximum likelihood (ML) methods. Morphological analyses indicated that the main characters, such as cell size and number of depressions per valve, normally used to distinguish P. hoffmannianum from P. belizeanum, overlapped. No clear differences were found in the periflagellar area architecture. Prorocentrum hoffmannianum and P. belizeanum were a highly supported monophyletic clade separated into three subclades, which broadly corresponded to the sample collection regions. Subtle morphological overlaps found in cell shape, size, and ornamentation lead us to conclude that P. hoffmanianum and P. belizeanum might be considered conspecific. The molecular data analyses did not separate P. hoffmannianum and P. belizeanum into two morphospecies, and thus, we considered them to be the P. hoffmannianum species complex because their clades are separated by their geographic origin. These geographic and genetically distinct clades could be referred to as ribotypes: (A) Belize, (B) Florida‐Cuba, (C1) India, and (C2) Australia.

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).

Reproduction, molting, and growth of two Mexican uniparental forms of the tadpole shrimp Triops (Branchiopoda: Notostraca) under a recirculating culture system

Two forms (here called short and long) of the tadpole shrimp Triops from the Baja California peninsula (Mexico) exhibit interesting features for aquacultural purposes; rapid growth, early maturation (six days) and uniparental reproduction via cysts (i.e. drought-resistant dormant eggs). The use of Triops for aquaculture depends on the standard production of viable cysts. Basic information on the reproductive potential of Triops is scarce. Using a recirculating system, we studied, through two culture tests, the cyst production, frequency of molting, and growth rate of the two Mexican forms. For each form, individual data were obtained from five specimens in Test 1 over 15 days, and from 10 specimens in Test 2 over 20 days. Hatching response of cysts produced in Test 1 was also studied. The short-form showed a high fecundity depositing groups of cysts from the ovisacs several times a day. The mean cyst production per day was 156–306 (Test 1 & 2), and the mean total cyst production was 2028 (range 728–3193) (Test 1), and 5821 (range 4136–7554) (Test 2). The maximum number of cysts deposited by one short-form individual in a day was 1231 (Test 2). The reproductive performance of the long-form was poor. The mean cyst production per day was only 4.2–7.9 (Test 1 & 2). The short-form molted every 2.5–2.8 days and the long-form molted every 2.8–3.7 days. The mean growth rate calculated from the standard length (mm d−1) of the short-form was 0.43–0.84 (Test 1 & 2), and in the long-form the values were 0.84–1.25 (Test 1 & 2). The poor cyst production of the long-form may be explained by inadequate food resources that did not fulfill the nutritional requirements for reproduction. Given its prolific uniparental reproduction (vs. biparental reproduction), the short-form Triops appears as a good potential candidate for aquaculture.

Clarifying the taxonomic status of Merluccius spp. in the northeastern Pacific: a combined morphological and molecular approach

The taxonomic status of hake (Merluccius spp.) in the northeastern Pacific is unclear. Hakes in this region are Merluccius productus, M. angustimanus, M. hernandezi, and a morphotype known as dwarf hake. Of these, only the first two species are currently valid. Descriptions in previous studies have been limited by overlapping morphological characteristic, lack of biological material, and limited numbers of sampling localities. To clarify their taxonomy, 461 hake were obtained from eight localities along the North American coast for morphological and mitochondrial DNA sequence analyses (cytochrome b, cytochrome c oxidase subunit I, and 16S ribosomal rDNA). Morphological and molecular analyses suggest that hake in this region represent a continuum of a single species with some levels of morphological and genetic intra-specific variation. In light of these results, we propose that M. productus is the only species of hake present along the North American and northern Central American coast.

FIRST REPORT OF GYNANDROMORPHY IN PARTHENOGENETIC ARTEMIA (BRANCHIOPODA: ANOSTRACA)

Abstract We describe three diploid gynandromorphs in Artemia. Two belong to A. parthenogenetica and represent the first report of gynandromorphy for the species. One specimen was a female with a globular brood-pouch and gynandromorphic second antennae, whilst the other was a female with a closed malformed brood-pouch filled with live nauplii, and a long, mobile, penis-like structure projecting from the left side of the genital segments. Offspring from the latter parthenogenetic gynandromorph developed as normal all-female parthenogenetic Artemia. The third gynandromorph belongs to the zygogenetic species A. franciscana, being a female with claspers as previously reported in the same taxon. The occurrence of parthenogenetic gynandromorphs is best explained in light of sex determination mechanisms supporting the view that gynandromorphy might be triggered by a mitotic chromosomal mutation during early embryonic development.