Rostral Spine Research Articles

Presence of the extinct sawfish, Onchosaurus (Neoselachii, Sclerorhynchiformes) in the Late Cretaceous of Peru with a review of the genus

Abstract In this paper we report the first Peruvian record of the extinct giant sclerorhynchiform sawfish, Onchosaurus pharao . The single specimen consists of a characteristic rostral spine, which was recovered from nodular limestone in the West-Peruvian Trough of the central Andean Basin, close to the city of Cajamarca. The fossil-bearing strata belong to the lower part of the Celendin Formation, which is of middle–late Coniacian age. This specimen is the first Coniacian record of Onchosaurus pharao and constitutes the third known record of this sclerorhynchiform taxon in South America filling previous gaps in the stratigraphic and geographic distribution of this species. A review of the distribution patterns of both species assigned to Onchosaurus reveals that the genus originated in circum-Equatorial, tropical waters and subsequently dispersed along different pathways south- and northwards. Based on its palaeogeographic distribution and the size of the rostral spines, both Onchosaurus spp. are considered large, bottom-dwelling sclerorhynchiforms primarily inhabiting shallow marine, near-coastal environments. The palaeogeographic distribution nevertheless indicates that they were powerful swimmers and able to cross wide, open marine distances. The reason for the disappearance of Onchosaurus in the Campanian remains unknown. In the early Maastrichtian, Dalpiazia seemingly replaced Onchosaurus ecologically. However, we hypothesize that the different histologies of rostral spines of Onchosaurus and Dalpiazia are of minor taxonomic importance. Dalpiazia thus might represent a derived onchosaur rather than a distinct taxon.

A new species of Oxypleurodon Miers, 1886 (Crustacea, Brachyura, Majoidea) from the Bismarck Sea, Papua New Guinea

Recently collected specimens from the deep sea off Papua New Guinea revealed the presence of a new species of Oxy-pleurodon Miers, 1886 (Majoidea). The new species is a member of the O. auritum group but its flattened rostral spines and the triangular shape of the carapace easily distinguishes it from congeners.

Seasonal Variability in Morphology of Blue Crab, Callinectes sapidus, Megalopae and Early Juvenile Stage Crabs, and Distinguishing Characteristics Among Co-Occurring Portunidae

Abstract Declines in abundance of the commercially important blue crab Callinectes sapidus have led fishery managers to search for new management strategies. Assessing year-class strength at megalopal or early juvenile stages may contribute to this effort, but separation from co-occurring species is difficult in many areas because morphological characteristics vary with season and published descriptions do not adequately distinguish C. sapidus from C. similis and other related species. Callinectes sapidus and C. similis megalopae were collected monthly and cultured in the laboratory to a size at which positive identification could be made. Measurements on intact megalopae and early crab exuviae of both species revealed seasonal differences, with spring megalopae having larger carapaces, longer rostral spines and antennae and more setae on some mouth parts than fall megalopae. This seasonal pattern of morphological variability was verified through examination of samples collected from MS (1976–1979) and NC...

Freshwater Prawns of the Genus Macrobrachium (decapoda, Palaemonidae) with Abbreviated Development from the Papaloapan River Basin, Veracruz, Mexico: Distribution and New Species

Abstract In the Papaloapan River two freshwater prawns with abbreviated development have been recorded: Macrobrachium villalobosi (a stygobitic species) and Macrobrachium totonacum (an epigeal species). In this paper we describe four new species from this genus, and the distribution of these six species along the river basin. M. oaxacae nov. sp. occurs in the River La Junta, and together with M. cosolapaense nov. sp. is geographically close to the stygobitic species and M. totonacum, but differs from these in the following aspects: pigmentation, the number of rostral spines, and the relative proportions of the articles of the second pereiopod, of appendix masculina and appendix interna, and the number of spines on the appendix masculina. Macrobrachium mazatecum nov. sp. lives in two streams in Veracruz: the first close to Tierra Blanca Veracruz and the second on the Zapotal Veracruz near Mpio. Lerdo de Tejada. This species was also recorded in two springs near Valle Nacional Oaxaca, and differs from M. oaxacae nov. sp. and M. cosolapaense nov. sp. in the number of rostral spines, and the relative proportions on the articles of second pereiopod, of appendix masculina and appendix interna, and of the spines on the appendix masculina. Finally, Macrobrachium jacatepecense nov. sp. occurs only in a spring near Jacatepec, Oaxaca. This species differs from the other species in the relative proportions of the articles of the second pereiopod: however, it is very close to Macrobrachium oaxacae nov. sp. in the number of rostral spines, but based on the geographical distribution of both species and other features, it is clearly a different species. In this Papaloapan River basin, the distribution of this complex of species is very limited, because the various populations live in very restricted areas associated with springs or small streams, and without direct interconnections. All these new species are comparable with the epigeal Macrobrachium species in the southeast of Mexico that have abbreviated larval development.

Larval development of Scyra acutifrons (Crustacea: Decapoda: Epialtidae) with a key from the northern Pacific

The larvae of Scyra acutifrons are described and illustrated for the first time. The larval stage consists of two zoeal and a megalopal stages. The zoea of S. acutifrons is compared with those of other known species of the Epialtidae from the northern Pacific. The zoea of Scyra acutifrons can be easily distinguished from that of S. compressipes by having a longer rostral carapace spine and an endopod of maxillule with three setae. It is found that the genus Scyra (Pisinae) shows a great similarity to Pisoides bidentatus (Pisinae) and the genus Pugettia (Epialtinae) in the family Epialtidae; especially, S. acutidens coincides well with two Pugettia species (Pugettia incisa and P. gracilis) in the characteristics of the zoeal mouthpart appendages. To facilitate the study of plankton-collected material, a provisional key to the known zoeae of the Epialtidae from the northern Pacific is provided.

Morphology and growth of the larval stages of Geograpsus lividus (Crustacea, Brachyura), with the descriptions of new larval characters for the Grapsidae and an undescribed setation pattern in extended developments

Cuesta, J.A., Guerao, G., Schubart, C.D. and Anger, K. 2011. Morphology and growth of the larval stages of Geograpsus lividus (Crustacea, Brachyura), with the descriptions of new larval characters for the Grapsidae and an undescribed setation pattern in extended developments. —Acta Zoologica (Stockholm) 92: 225–240. Among the eight currently recognized genera and 40 species belonging to the brachyuran crab family Grapsidae (Thoracotremata), the complete larval development is only known for three species of Metopograpsus. In this study, we investigated the larval development of Geograpsus lividus originating from Jamaica and reared under controlled conditions in the laboratory. It consists of eight zoeal stages and the megalopa, representing the longest recorded developmental pathway for any brachyuran. Although long developments had been suggested for some species, based on specimens collected from the plankton, these were never confirmed by laboratory culture. In this study, zoeal growth (measured as increase in body size, dry mass, and contents of carbon, nitrogen, and hydrogen) is quantified, and morphological and meristic characters of the larval stages of G. lividus are described and illustrated. The development from hatching to the end of the zoeal phase took 2 months. During this time span, larval size (cephalothorax length) increased 4.4-fold, while the various measures of biomass increased by factors of 57–72. Morphologically, the larvae present most characters previously established for the family Grapsidae. However, the two last zoeal stages show new features that differ from the typical setation pattern known from grapsid species with only five zoeal stages. These were found in the number of natatory setae on the exopods of the maxillipeds and in the setation of the basis of the first maxilliped. Other characters, which had previously only been described for zoeae of Pachygrapsus and plankton-collected ones attributed to Planes, were observed also in G. lividus and could be confirmed as common features for the Grapsidae. Moreover, the larvae of G. lividus present a spinulation on the lateral and rostral spines of the cephalothorax. This character is recorded for the first time in grapsid crabs. A comparison of these observations is made with those based on terminal zoeal stages of species belonging to other brachyuran families, where similar characters have been documented.

Crinoid-associated shrimps of the genus Laomenes A.H. Clark, 1919 (Caridea: Palaemonidae: Pontoniinae): new species and probable diversity

Three new species of the genus Laomenes A.H. Clark are described as symbionts of feather stars (Crinoidea: Comatulida) from shallow waters of Nhatrang Bay, Vietnam. Including these new species, the genus comprises 8 species and can be arranged into 3 suggested groups of species. The “L. amboinensis” species group with 4 species, L. amboinensis (De Man, 1888), L. cornutus (Borradaile, 1915), L. clarki sp. nov. and L. pardus sp. nov., characterized by the presence of ventral rostral teeth, distoventral spines on propodus of pereiopod III and a fixed tooth on distolateral margin of uropodal exopod. The “L. jackhintoni” species group includes 2 species, L. jackhintoni (Bruce, 2006) and Laomenes tigris sp. nov., characterized by the absence of ventral rostral teeth, extremely elongated apical papilla on cornea of eyes, the presence of fixed tooth on exopod of uropod, the absence of distoventral spines on propodus and the presence of large accessory tooth on dactylus of pereiopod III. The “L. ceratophthalmus” species group includes 2 species, L. ceratophthalmus (Borradaile, 1915) and L. nudirostris (Bruce, 1968), characterized by the absence of ventral rostral teeth and distoventral spines on propodus of pereiopod III, the presence of small accessory tooth on dactylus of pereiopod III, tiny marginal dorsal spines on telson and the absence of a fixed distolateral tooth on exopod of uropod. Remarks and a key for all species of the genus as well as a discussion of the undescribed diversity of the genus are given.

Larval development of the grooved tanner crab, chionoecetes tanneri rathbun, 1893 (decapoda: Brachyura: Majidae) described from the laboratory‐reared specimens

This paper documents the defining morphological characteristics of the larval stages of Chionoecetes tanneri Rathbun, 1893, the grooved Tanner crab, from specimens reared in the laboratory. Chionoecetes tanneri larval stages include two zoeae and one megalopa. The first zoea is characterized by: six setae on the posterior margin of the carapace; postero‐lateral spines on abdominal somites 3 and 4, extending beyond the posterior margin of adjacent somites and bearing 9–10 spinnules; 12 plumose setae and one stout distal plumose seta present on the margin of the scaphognathite of the maxilla; and one fused lateral spine and one articulated dorso‐medial spine on each fork of the telson. The second zoea is characterized by: 9 setae on the postero‐lateral margin of the carapace; a serrated mandible molar; a mandibular palp bud; 25–26 plumose setae on the margin of the scaphognathite of the maxilla; pereiopods with well‐developed gills and buds; and four pairs of stout setae on the posterior margin of the telson. For the megalopal stage, the distinguishing characteristics include: a rostral spine equal in length to the supraorbital spine; six setae on the exopod of the uropod; and a single spine on the ischium of the second pereiopod. This study allows C. tanneri larvae to be distinguished from the larvae of known sympatric congeners. This information provides a basic taxonomic tool for researchers in fisheries management and zooplankton ecology who are addressing issues related to trophic interactions, metapopulation dynamics and ecosystem impacts in the evolving marine resource management strategies in the North Pacific, and those related to Chionoecetes species in particular.

Macrobrachium sbordonii (Decapoda: Palaemonidae), a new stygobitic species of freshwater prawn from Chiapas Mexico

The fourth stygobitic species of the genus Macrobrachium from caves in America is described. Macrobrachium sbordonii, a new species inhabiting a cave of Chiapas Mexico, is similar to M. villalobosi, M. acheronthium and M. catonium in exhibiting reduced eyes, unpigmentated body and enlargement of ambulatory appendages. It differs from these in length of the first pereiopod and relative proportions of the articles of the second pereiopod, pigmentation degrees on eyes, number of rostral spines, proportions of the scaphocerite, and relative proportions of the carpus and propodus of the first pereiopod. Macrobrachium sbordonii occurs in the inner lake of the Sistema de La Lucha, a cave located near the Chiapas-Oaxaca border, in the Tehuantepec Itsmus Region.

Description of Zoeae and Habitat of Elamenopsis ariakensis (Brachyura: Hymenosomatidae) Living within the Burrows of the Sea Cucumber Protankyra bidentata

The morphological characteristics of the zoeas and crabs of the false spider crab Elamenopsis ariakensis are described and their habitats are documented, with an emphasis on their symbiosis with the burrowing sea cucumber Protankyra bidentata. The 16 zoeas and 91 crabs were collected from the Ariake Sea and adjacent Yatsushiro Sea, Japan. Zoeas have no lateral spine, whereas the rostral and dorsal spines are extremely long. In all zoeal stages, the pleon consists of six segments, including the telson. Adult crabs have fused pleons, with five segments in males and three segments in females, including the telson, but six segments are found in young male crabs. All crabs were collected from P. bidentata burrows. In addition to E. ariakensis, seven commensal species were collected from P. bidentata burrows: two crabs, four bivalves, and one scale worm. The microhabitats in the burrow of P. bidentata were divided somewhat among species.

Abnormal Rostrum in Polycheles Typhlops Heller, 1862 (Decapoda: Polychelidae) from the Central Western Mediterranean

Abstract Anomalies of the number of rostral spines have been recorded in blind lobsters, Polycheles typhlops, caught in Sardinian waters (Central Western Mediterranean). The abnormal specimens, 66 out a total of 789 individuals analysed, showed all the morphometric characteristics of P. typhlops except for the unusual presence of two rostral spines instead of the canonical one. The analysis of partial nucleotide sequences of the mitochondrial cytochrome oxidase subunit I gene (COI) showed that the individuals with two spines were not genetically different from the normal specimens of P. typhlops, while both were quite dissimilar from the other Mediterranean species, P. sculptus. Our results suggest the need of an update of the morphological classification guides for this family combined with a wider genetic study.

Barbouria yanezi sp. nov., a new species of cave shrimp (Decapoda, Barbouriidae) from Cozumel Island, Mexico

A new species of the genus Barbouria from Cozumel Island, Mexico, is described. The new species, Barbouria yanezi is similar to Barbouria cubensis in exhibiting a cornea narrower than the eyestalk, and in its telson ornamentation, but differs from the latter species in the number of rostral spines, the proportions of the scaphocerite, the relative proportions of the carpus and propodus of the first and second pereiopods, the relationship between the appendices masculina and interna, and in size: it is larger than B. cubensis. The geographical relationship between the species is discussed.

A new species of Calaxius Sakai & de Saint Laurent, 1989, from West Africa (Crustacea: Decapoda: Axiidae) and synonymy of Manaxius Kensley, 2003

ABSTRACT Calaxius kensleyi, new species (Axiidae), is described from three specimens collected on the continental shelf off Gabon, West Africa, in the course of an environmental impact survey. The new species is characterized by having cornea level with the subterminal rostral spines; a bidentate median carina on the carapace, 4–5 denticles on the submedian carina; larger chela with moveable finger as long as palm, smaller chela with moveable finger twice as long as palm; and abdominal pleura 3–5 ventrally rounded. It is the first member of Calaxius recorded from the eastern Atlantic Ocean. The monospecific genus Manaxius Kensley 2003, is synonymized with Calaxius Sakai & de Saint Laurent 1989.

Changes in zoeae of the snow crab, Chionoecetes opilio, with variation in incubation temperature

The purpose of this study was to evaluate the effect of embryonic incubation temperature on the morphology, energetic content, and individual weights of C. opilio zoeae. Ovigerous female C. opilio were collected by trawl from the eastern Bering Sea in the summer of 2002 and were held in the laboratory at five temperature treatments (− 1, 0, 1, 3, and 6 °C) from embryo stage five to hatching. The mean duration of incubation ranged from 240 d at 6 °C to 353 d at − 1 °C. No relationship between larval weight and caloric content with incubation temperature was detected, indicating that increased development time at cooler temperatures may not have an energetic cost. However, several morphological features varied with temperature. Most larval characters including rostro-dorsal length, rostral spine length, lateral spine length, and carapace width were smaller at the warmest incubation temperature. Protopodite length did not differ with temperature. The length of the 3rd abdominal somite consistently increased with increased temperature and may serve as a suitable indicator that could be used in field populations to infer temperature of incubation. Variation in morphology with temperature could confound identification of C. opilio zoeae from those of a congener, Chionoecetes bairdi because identification of C. bairdi is based on the length of the 3rd abdominal somite.

The complete larval development of the crab Pilumnus spinifer (Brachyura: Xanthoidea: Pilumnidae) reared in the laboratory

The complete larval development of the crab Pilumnus spinifer from the western Mediterranean was obtained in the laboratory. All four zoeal stages and the megalopa are described and illustrated. The morphological characters of the larvae of Pilumnus spinifer are compared with those of other known larvae of the genus. The zoeae of P. spinifer show the rostral spine longer than the antennule (excluding aesthetascs); short lateral spines present on the carapace, and the mediolateral processes are present only in abdominal somites 2 and 3. The megalopa is similar to that of other Pilumnidae species. The morphology of the larval stages shows very similar characteristics to that of those of P. hirtellus and P. dasypodus, among the described stages of the family.

Batch fecundity of the swimming crab Portunus trituberculatus (Brachyura: Portunidae)

We assessed batch fecundity of the swimming cab Portunus trituberculatus for the purpose of seed production. Oocyte number and number and body size of first zoeas were examined for females collected from natural habitats in the Seto Inland Sea of Japan. The relationships between carapace width (CW) of females and batch fecundity were analyzed using a power function. Oocyte number was examined for the overwintering females. Size and number of first zoeas were determined for ovigerous females collected from May to August. Oocyte number increased with increasing female body size and predicted estimates ranged between 0.8 and 4.5 million for CW of 130–240 mm. Size of first zoeas (distance between tips of dorsal and rostral spines of the carapace) ranged between 1.22 and 1.62 mm and tended to linearly decrease with advancing hatching date, i.e., increasing hatching temperatures. Number of first zoeas increased with female body size and showed no fluctuation throughout the breeding season in females of the same size. Predicted numbers of first zoeas ranged between 0.7 and 3.8 million for CW of 130–240 mm. Number of first zoeas being less than the oocyte number for females of the same size, it is suggested that egg loss occurred from oviposition to hatching.

La temperatura como factor de variabilidad en el desarrollo y morfología de larvas zoeas de Acanthocyclus hassleri Rathbun (Decapoda, Brachyura, Atelecyclidae) cultivadas en laboratorio

Zoeae larvae of A. hassleri were reared at 10, 17 and 20oC, evaluating their survival, duration of larval life, larval size, sizes of different larval structures and morphometric proportions among structures with respect to larval size. Larval development of A. hassleri included four zoeal stages (ZI-ZIV) and one megalopa. The highest mean zoeal survival rate was 95.2% at 20oC in ZIV, decreasing to 13.2% in megalopae. Time of zoeal developmment fluctuated between 80.2 ± 3.2 d at 10oC and 28.2 ± 0.9 d at 20oC. The largest larval sizes were reached by ZI at 20oC, and ZII-IV at 17oC. Growth in size of the rostral spine, cephalothorax, abdomen and telson were directly proportional to culture temperature; growth of the dorsal spine, antenna, and both maxillipeds were inversely proportional to culture temperature. Morphometric proportion values between the rostral spine and abdomen remained constant; for cephalothorax and telson, the proportion disminished in stages ZIII and ZIV; those of the rostral spine, dorsal spine, antenna and both maxillipeds were significately higher at 10oC than at 17 and 20°C from the ZII stage onward. Results suggest a high capacity for thermal resistence in the zoeae of A. hassleri but not in its' megalopae. This capacity of the zoeae represents a high level of morpho-adaptive plasticity to temperature, suggesting a model of morphological plasticity associated with the culture temperature.

Nuevo registro de Paralomis otsuae Wilson, 1990 (Decapoda, Anomura, Lithodidae) en la costa centro-sur de Chile

A report is made on the capture of five male specimens of Paralomis otsuae Wilson on the continental slope off the coast of Corral, Chile (39o50'S). This finding significatively extends the southern latitudinal geographic range of the species. The specimens measured between 89 and 115 mm in cephalotoracic length excluding the rostral spine, and between 94 and 118 mm in cephalothoracic width excluding the lateral spines. Some morphological characteristics and morphometric dimensions were noteworthy. Discussion is presented on the significance of the characteristics of this species and its' geographic distribution.

Additions to the Eocene selachian fauna of Antarctica with comments on Antarctic selachian diversity

ABSTRACT Antarctic Eocene selachians were reported from the La Meseta Formation of Seymour Island and from glacial erratics of Mount Discovery, Antarctica. Seymour Island has produced the most diverse Palaeogene selachian fauna of the Southern Hemisphere so far. Up to now, 23 selachian taxa (20 sharks, 2 rays) have been described from the Eocene of Antarctica. Recent geological and palaeontological investigations on Seymour Island yielded new selachian remains from Lutetian (middle Eocene) deposits. An upper tooth is referred to the requiem shark Carcharhinus and a rostral spine to the sawfish Pristis. These occurrences represent the first Eocene records of both groups in the Southern Hemisphere and extend their geographic distribution. In addition, a fragmentary stinging ray attributed to Myliobatoidea is presented for the first time from Antarctica. The diversity of Eocene La Meseta fishes is reflected.

Engyprosopon vanuatuensis, a new species of bothid flounder (Pleuronectiformes: Bothidae) from off Vanuatu, South West Pacific

A new bothid flounder, Engyprosopon vanuatuensis, is described on the basis of 15 specimens (9 males and 6 females, 41.1–55.8 mm in standard length) collected from deep waters (163–165 m) off Vanuatu Island in 1994 during the French exploratory cruise “MUSORSTOM 8.” The new species clearly differs from its congeners in having a short body, big eyes, large scales, and many gill rakers without serrations. Remarkable sexual dimorphism appears in interorbital width, anterior curve of head profile, rostral and orbital spines, length of ocular-side pectoral fin, small dots on eyes, and pigmentation of blind-side body.