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Fulltext Twins! Microsatellite analysis of two embryos within one egg case in oviparous elasmobranchs

Hook SA, Musa SM, Ripley DM, Hibbitt JD, Grunow B, Moritz T, et al.

PLoS One, 2019;14(12):e0224397.
PMID: 31790403 DOI: 10.1371/journal.pone.0224397

Elasmobranchs display various reproductive modes, which have been key to their evolutionary success. In recent decades there has been a rise in the number of reported cases of foetal abnormalities including fertilised, double-embryos held within one egg capsule, hereafter referred to as twins. Previously, the occurrences of twin egg cases have been reported in two batoid and one shark species. We report the first cases of twins in three species of oviparous elasmobranchs: the undulate ray (Raja undulata), the nursehound (Scyliorhinus stellaris), and the small-spotted catshark (Scyliorhinus canicula). We investigated the genetic relationships between the twins in S. stellaris, and S. canicula using microsatellite markers. Whilst the S. stellaris twins displayed the same genotypes, we found that the S. canicula twin individuals arose through heteropaternal superfecundation. This is the first reported incidence of such a paternity in elasmobranchs. The relationship between environmental change and reproductive strategy in elasmobranchs is unclear and further research is needed to determine its effect on the prevalence and mechanisms of formation of elasmobranch twins.

Matched MeSH terms: Elasmobranchii/embryology*; Elasmobranchii/genetics; Elasmobranchii/physiology
A revision of the Rhoptrobothriidae (Cestoda: Tetraphyllidea)

Jensen K, Pen IAM, Caira JN

Zootaxa, 2021 Jul 12;4999(3):201-218.
PMID: 34810491 DOI: 10.11646/zootaxa.4999.3.1

The Rhoptrobothriidae are one of the more enigmatic families of cestodes of elasmobranchs. Opinions on the taxonomic status of the familys three original genera (i.e., Myzophyllobothrium, Rhoptrobothrium, and Myzocephalus) have varied over the 115 years since they were erected. Some authors have considered all three valid, others have considered Rhoptrobothrium to be a synonym of Myzopyllobothrium or a genus inquirendum, yet others have considered Myzocephalus to be a synonym of the phyllobothriid genus Thysanocephalum. All three genera were established for specimens collected from eagle rays off Sri Lanka. The erection of Mixophyllobothrium for two specimens from a cowtail stingray off India three decades ago added additional confusion to the situation, with some authors considering it valid and others a synonym of Myzocephalus. These disagreements stem largely from differences in interpretation of the complex morphology of the scolex of members of these genera. Furthermore, with the exception of Rhoptrobothrium comprising four species, each genus is monotypic. All but Rhoptrobothrium has not been considered in detail for nearly a century, largely because of a lack of available material. The taxonomic status of these genera is assessed here based on light and scanning electron microscopy, and molecular data generated from new material collected from eagle rays off Indonesian and Malaysian Borneo, Japan, Sri Lanka, and Viet Nam. Morphological work indicates that the genera differ largely only in the degree of folding of the four remi that extend from the cephalic peduncle. A molecular phylogeny based on sequence data for the D1D3 region of the 28S rRNA gene, which include new data for eight specimens of four species, indicates that Myzophyllobothrium, Myzocephalus, and Rhoptrobothrium are not mutually monophyletic. The latter two genera and Mixophyllobothrium are considered synonyms of Myzophyllobothrium and five species are transferred to that genus. Myzophyllobothrium okamuri n. comb. is considered a species inquirendum. Myzophyllobothrium nagasawai n. sp. is described from Aetobatus narutobiei off Japan. Myzophyllobothrium narinari n. comb. is re-described based on newly collected cestodes from the type host and locality (i.e., Aetobatus ocellatus off Sri Lanka). Despite consisting of only a single genus, the family status of the group is retained in recognition of the unusual configuration of the scolex, which bears four biloculate bothridia and four remi extending from the cephalic peduncle. The ordinal placement of the family remains uncertain, but affinities with the Phyllobothriidea, rather than Tetraphyllidea are considered.

Matched MeSH terms: Elasmobranchii*
Fulltext Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park

Germanov ES, Pierce SJ, Marshall AD, Hendrawan IG, Kefi A, Bejder L, et al.

PeerJ, 2022;10:e13302.
PMID: 35602898 DOI: 10.7717/peerj.13302

BACKGROUND: The reef manta ray (Mobula alfredi) is a globally threatened species and an iconic tourist attraction for visitors to Indonesia's Komodo National Park (NP). In 2013, manta ray fishing was banned in Komodo NP and its surroundings, preceding the nationwide manta ray protection in 2014. Over a decade ago, a previous acoustic telemetry study demonstrated that reef manta rays had high fidelity to sites within the park, while more recent photo-identification data indicated that some individuals move up to 450 km elsewhere. Characterization of manta ray demographics, behavior, and a focused assessment on site use of popular tourism locations within the park is vital to assist the Komodo NP Management Authority formulate appropriate manta ray conservation and management policies.
METHODS: This study uses a long-term library (MantaMatcher.org) of photo-identification data collected by researchers and citizen scientists to investigate manta ray demographics and habitat use within the park at four sites frequented by tour operators: Cauldron, Karang Makassar, Mawan, and Manta Alley. Residency and movements of manta rays were investigated with maximum likelihood analyses and Markov movement models.
RESULTS: A total of 1,085 individual manta rays were identified from photographs dating from 2013 to 2018. In general, individual manta rays displayed a higher affinity to specific sites than others. The highest re-sighting probabilities came from the remote southern site, Manta Alley. Karang Makassar and Mawan are only ~5 km apart; however, manta rays displayed distinct site affinities. Exchange of individuals between Manta Alley and the two central sites (~35.5 km apart) occurred, particularly seasonally. More manta rays were recorded traveling from the south to the central area than vice versa. Female manta rays were more mobile than males. Similar demographic groups used Karang Makassar, Mawan, and Manta Alley for foraging, cleaning, cruising, or courtship activities. Conversely, a higher proportion of immature manta rays used the northern site, Cauldron, where foraging was commonly observed. Fishing gear-related injuries were noted on 56 individuals (~5%), and predatory injuries were present on 32 individuals (~3%). Tourism within the park increased from 2014 to 2017, with 34% more dive boats per survey at Karang Makassar and Mawan.
DISCUSSION: The Komodo NP contains several distinct critical habitats for manta rays that encompass all demographics and accommodate seasonal manta ray movements. While the present study has not examined population trends, it does provide foundational data for such work. Continued research into manta ray abundance, long-range movements, and identifying and protecting other critical aggregation areas within the region is integral to securing the species' recovery. We provide management recommendations to limit undue pressure on manta rays and their critical habitats from tourism.

Matched MeSH terms: Elasmobranchii*
Reproductive biology, length-weight relationship and diet of co-occurring butterfly rays, Gymnura poecilura and Gymnura zonura, in Malaysian waters

Leung AJ, Then AY, Loh KH

J Fish Biol, 2023 Mar;102(3):564-574.
PMID: 36504128 DOI: 10.1111/jfb.15288

Recent IUCN assessments had resulted in up listing of the status of butterfly rays due to concerns of overfishing, but inadequate biological understanding of these rays prevents meaningful conservation and management measures. Therefore, this study was undertaken to address knowledge gaps in the reproductive biology and diet of longtail butterfly ray (Gymnura poecilura) and zone tail butterfly ray (Gymnura zonura) in Malaysian waters. From surveys of landing sites and fish markets from years 2017 to 2022, size (disc width, DW), weight and maturity were recorded, and stomachs were collected from 94 G. poecilura (N = 39 females and 55 males) and 20 G. zonura (N = 10 females and 10 males) specimens. The length-weight relationships were significantly different between sexes for G. poecilura. The size at maturity (DW50) was estimated to be 476.0 mm (females), 385.0 mm (males) for G. poecilura and 442.0 mm (combined) for G. zonura. The number of embryos ranged from 1 to 6, and the embryo size was between 73.90 to 130.44 mm DW. Dietary analysis of stomach contents revealed that fish prey was dominant in both G. poecilura [94.4% Index of Relative Importance (IRI)] and G. zonura (100% IRI). Ontogenetic shift was seen in G. poecilura that fed on more variety of prey items, including shrimps, squids and crabs with an increase in body size. Both species co-occur all along coastal Malaysia although G. zonura is rarely encountered from fisheries surveys along the Strait of Malacca. Given similar habitat associations and dietary habits, G. poecilura may be able to outcompete G. zonura across their shared habitat range. The validity of G. japonica and G. micrura records in Malaysia remains questionable and requires future investigation.

Matched MeSH terms: Elasmobranchii*
The complete mitogenome of the cow tail ray Pastinachus atrus (Macleay, 1883) (Elasmobranchii; Myliobatiformes; Dasyatidae)

Austin CM, Tan MH, Lee YP, Croft LJ, Meekan MG, Gan HM

Mitochondrial DNA A DNA Mapp Seq Anal, 2016;27(2):1372-3.
PMID: 25103432 DOI: 10.3109/19401736.2014.947586

The complete mitogenome of the ray Pastinachus atrus was recovered from a partial genome scan using the HiSeq sequencing system. The P. atrus mitogenome has 18,162 base pairs (61% A + T content) made up of 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs, and a 2516 bp non-coding AT-rich region. This mitogenome sequence is the first for a ray from Australian waters, the first for the Genus Pastinachus, and the 6th for the family Dasyatidae.

Matched MeSH terms: Elasmobranchii/genetics*
Assessment of metallic trace elements in the muscles and fins of four landed elasmobranchs from Kuala Terengganu Waters, Malaysia

Ong MC, Gan SL

Mar Pollut Bull, 2017 Nov 30;124(2):1001-1005.
PMID: 28807418 DOI: 10.1016/j.marpolbul.2017.08.019

A study had been carried out to determine Cu, Zn, Cd, Hg and Pb concentrations in the muscle and fins of four elasmobranchs species namely spot-tail sharks, milk sharks, whitespotted bamboo sharks and whitespotted guitarfish from Pulau Kambing LKIM Fishery Complex, Kuala Terengganu, Malaysia. Zinc level was found to have the highest concentration whereas Cd had the lowest concentration in both organs. By comparing both organs, metals concentrations in fins of all elasmobranchs species were higher than muscle. Result obtained was compared with the guidelines set by Malaysian Food Regulation and the provisional tolerable weekly intake was also determined. Current study recommends that the muscle of whitespotted bamboo shark from Kuala Terengganu Waters is likely not to be consumed due to it exceeded the allowable consumption guideline. Finding of this paper is very useful as it provides the baseline data on the pollution status of elasmobranchs in Kuala Terengganu Waters.

Matched MeSH terms: Elasmobranchii*
Dollfusiella Campbell & Beveridge, 1994 (Trypanorhyncha: Eutetrarhynchidae) from elasmobranchs off Borneo, including descriptions of five new species

Schaeffner BC, Beveridge I

Syst Parasitol, 2013 Sep;86(1):1-31.
PMID: 23949646 DOI: 10.1007/s11230-013-9435-6

Sampling of a large number of elasmobranchs from coastal waters off Borneo revealed the presence of five new species of Dollfusiella Campbell & Beveridge, 1994 (Trypanorhyncha: Eutetrarhynchidae), namely D. angustiformis n. sp., D. hemispinosa n. sp., D. spinosa n. sp., D. imparispinis n. sp. and D. parva n. sp. Dollfusiella angustiformis n. sp. is described from the spiral intestines of four species of the dasyatid stingray genus Himantura Müller & Henle from both the Indonesian and Malaysian parts of Borneo. All the other species were obtained from Malaysian Borneo. Dollfusiella hemispinosa n. sp. is described from the spiral intestines of three species of Himantura, whereas D. spinosa n. sp. was obtained from several specimens of Pastinachus solocirostris Last, Manjaji & Yearsley (Dasyatidae) as well as from Taeniura lymma 1 (sensu Naylor et al., 2012) (Dasyatidae), Neotrygon kuhlii 2 (sensu Naylor et al., 2012) (Dasyatidae), and Glaucostegus cf. typus (sensu Naylor et al., 2012) (Rhinobatidae). Dollfusiella imparispinis n. sp. is described from the spiral intestine of a single specimen of Chiloscyllium punctatum Müller & Henle (Hemiscyllidae) from the South China Sea off Sarawak, whereas D. parva n. sp. was obtained from several species of Himantura. Specimens of the five novel taxa possess scoleces covered with enlarged microtriches, a morphological characteristic exhibited by several other congeners. However, the new species differ from all congeners by possessing unique patterns of oncotaxy as well as combinations of additional morphological features. The number of valid species within Dollfusiella is increased to 26. For this reason, a key for the species of Dollfusiella is provided. Furthermore, novel information on hosts and geographic distribution is provided for two previously described species of Dollfusiella, D. michiae (Southwell, 1929) and D. spinulifera (Beveridge & Jones, 2000). The latter species differs slightly from the original description and shows a much higher variability with regard to the lengths of the scolex and muscular bulbs and the number of testes. These variable characters subdivided specimens of D. spinulifera into relatively distinct groups. However, the specimens did not differ in their oncotaxy and are considered to represent a single variable species.

Matched MeSH terms: Elasmobranchii/parasitology*
Three new species of Merizocotyle Cerfontaine, 1894 (Monogenea: Monocotylidae) from the nasal tissues of dasyatid rays collected off Malaysian and Indonesian Borneo

Chisholm LA, Whittington ID

Syst Parasitol, 2012 Jun;82(2):167-76.
PMID: 22581252 DOI: 10.1007/s11230-012-9358-7

Three new species of Merizocotyle Cerfontaine, 1894 (Monogenea: Monocotylidae) are described from the nasal tissues of stingrays collected off Borneo. Merizocotyle macrostrobus n. sp. is described from the dwarf whipray Himantura walga (Müller & Henle) collected in shallow waters off Sematan, Sarawak, Malaysia. This species can be distinguished from the other members of the genus by the morphology of the sclerotised male copulatory organ, which is long with many twists and loops. The vaginae of this species are also long and looped. Merizocotyle papillae n. sp. is described from the roughnose stingray Pastinachus solocirostris Last, Manjaji & Yearsley collected off Sematan and Mukah, Sarawak, Malaysia. It is distinguished from the other species of Merizocotyle by the morphology of the male copulatory organ, which is a sclerotised tube that expands slightly and then tapers at the distal end, and by the presence of papillae on the dorsal edge of the haptor. Merizocotyle rhadinopeos n. sp. is described from the whitenose whip ray Himantura uarnacoides (Bleeker) collected off Manggar, East Kalimantan, Indonesia. It can be differentiated by the male copulatory organ, which is a short, narrow, curved, sclerotised tube tapering distally, and the path of the ovary, which runs anteriorly to the base of the oötype. We also provide details of new host and/or locality records for M. australensis (Beverley-Burton & Williams, 1989) Chisholm, Wheeler & Beverley-Burton, 1995, M. icopae Beverley-Burton & Williams, 1989 and M. pseudodasybatis (Hargis, 1955) Chisholm, Wheeler & Beverley-Burton, 1995.

Matched MeSH terms: Elasmobranchii/parasitology*
Redescriptions of species of Tetrarhynchobothrium Diesing, 1850 and Didymorhynchus Beveridge & Campbell, 1988 (Cestoda: Trypanorhyncha), with the description of Zygorhynchus borneensis n. sp

Beveridge I

Syst Parasitol, 2008 Feb;69(2):75-88.
PMID: 18038196

Tetrarhynchobothrium tenuicolle Diesing, 1850 is redescribed from the type-specimens collected from Raja clavata Linnaeus in the Adriatic Sea. T. striatum (Wagener, 1854) is redescribed from voucher specimens from the type host, Myliobatis aquila Linnaeus, from the type-locality, off Naples, Italy. The two species are very similar in tentacular armature, but are provisionally maintained as independent species, since the armature of T. tenuicolle cannot be fully described and because all available specimens of T. striatum are immature, limiting comparisons of potential differences in segment anatomy. T. setiense Dollfus, 1969 is treated as a synonym of T. striatum. Zygorhynchus borneensis n. sp. is described from Himantura uarnacoides (Bleeker) and H. pastinacoides (Bleeker) off Sabah, Malaysia. The new species is distinguished from its congeners by the very small hooks present in the basal region and by the presence of a uterine pore. The metabasal tentacular armature of Didymorhynchus southwelli Beveridge & Campbell, 1988, described for the first time, is homeoacanthous and homeomorphous in form. However, it has a basal swelling with hook rows originating on the bothrial surface and terminating on the antibothrial surface of the tentacle.

Matched MeSH terms: Elasmobranchii/parasitology*