Bathymetric Distribution Research Articles

Do larvae from deep-sea hydrothermal vents disperse in surface waters?

Larval dispersal significantly contributes to the geographic distribution, population dynamics, and evolutionary processes of animals endemic to deep-sea hydrothermal vents. Little is known as to the extent that their larvae migrate vertically to shallower waters and experience stronger currents and richer food supplies. Here, we first provide evidence from early life-history traits and population genetics for the surface dispersal of a vent species. Planktotrophic larvae of a red blood limpet, Shinkailepas myojinensis (Gastropoda: Neritimorpha: Phenacolepadidae), were cultured to observe their swimming behavior and to evaluate the effects of temperature on survival and growth. In addition, the population structure was analyzed based on 1.2-kbp mitochondrial DNA sequences from 77 specimens that cover the geographic and bathymetric distributions of the species (northwest Pacific, 442-1,227m in depth). Hatched larvae constantly swam upward at 16.6-44.2mm/min depending on temperature. Vertical migration from hydrothermal vents to the surface, calculated to take ~4-43d, is attainable given their lengthy survival time without feeding. Fed larvae best survived and grew at 25°C (followed by 20°C), which approximates the sea surface temperature in the geographic range of the species. Little or no growth was observed at the temperature of the vent habitat where adult limpets occur (≤15°C). Population genetic analyses showed no differentiation among localities that are <1,350km apart. The larvae of S.myojinensis most likely migrate to the surface water, where high phytoplankton biomass and strong currents enable their growth and long distance dispersal over many months. Sea surface temperature may represent a critical factor in determining the geographic distribution of many vent endemic species with a planktotrophic early development, and in turn the faunal composition of individual vent sites and regions.

Giant embryos and hatchlings of Antarctic nudibranchs (Mollusca: Gastropoda: Heterobranchia)

Bathydoris hodgsoni and Doris kerguelenensis are two of the largest Antarctic nudibranchs. They are both common circumpolar species with broad bathymetric distributions, although B. hodgsoni is restricted to deep waters in the Antarctic high latitude. Egg masses and juveniles of these species were collected over multiple years (1998–2012) in the eastern Weddell Sea and the South Shetland Islands, and here new data are provided about egg mass characteristics and ontogeny using histological techniques. The egg mass of B. hodgsoni has a maximum length of 12.4 cm with one or two egg capsules with a mean diameter of 4.9 cm. The capsules either contained non-developing eggs or ready-to-hatch juveniles up to 2.9 cm long. The egg mass of D. kerguelenensis is a semicircular ribbon-like structure including 1,500–2,400 oval capsules (~1.7 × 1.2 mm) containing various stages of development up to ready-to-hatch juveniles 2.5 mm in length. Based on their morphology and development in egg masses maintained in the laboratory, the embryonic period for B. hodgsoni is estimated to be up to 10 years, and for D. kerguelenensis 13 months. Thus, B. hodgsoni has the largest egg capsules and probably the largest hatchlings of any mollusc. Chemical analyses of D. kerguelenensis egg masses showed no trace of terpenoid acylglycerols, although these compounds were present in field-collected juveniles and adults. None of four sponges that likely serve as food for D. kerguelenensis had the glycerides, or their precursors, found in the nudibranch.

Nuevo registro batimétrico para el pez carbonero cabezón Laemonema verecundum (Gadiformes: Moridae) en el Golfo de California, México

Background. The presence of Laemonema verecundum (Jordan & Cramer, 1897) had not been previously reported at depths less than 666 m. Goals. The objective of the research was to study the bathymetric distribution of L. verecundum. Methods. In the eastern continental shelf of the Gulf of California, 648 specimens of L. verecundum were collected during two experimental research cruises in September 2004 and February 2005. Results. Specimens were collected at depths between 165 and 483 m, where temperatures ranged between 9.5 and 19.9° C, and average oxygen concentration was 1.7 mg/l. Conclusions. This new record expands the known bathymetric distribution range of this species inhabiting shallow waters in the gulf.

Error cascade in taxonomy: The case of Cardiomya perrostrata (Mollusca: Bivalvia: Cuspidariidae) in Brazilian waters.

Successions of erroneous taxonomic identifications in biodiversity studies are an undesirable but not rare phenomenon. Such cascades of errors frequently involve taxa with few, polymorphic diagnostic characters, such as representatives of the cuspidariid genus Cardiomya. Four species of the genus are believed to live in Brazilian waters: C. cleryana (d'Orbigny, 1842), C. ornatissima (d'Orbigny, 1853), C. striata (Jeffreys, 1876) and C. perrostrata (Dall, 1881). Many reported occurrences of these species are based on misidentifications, but the error cascade of incorrect records of C. perrostrata is by far the most extensive. Although the species has been reported to live in Brazilian waters for about half a century, all previous records seem to be based on a succession of mistaken identifications. This paper redescribes C. perrostrata based on an analysis of the type series, several lots of museum vouchers and new material collected in the Campos Basis (Rio de Janeiro, Brazil). Ontogenetic changes in shell outline and ultrastructural details of the hinge plate, periostracal surface and larval shell are described and illustrated for the first time. Based on a critical appraisal of the literature, we present an updated geographic and bathymetric distribution of the species. Cardiomya perrostrata displays a gradual increase in the relative length of the rostrum during its ontogeny and in larger specimens the rostrum is more prominently curved upwards. The larval shell is of type 2D, measuring about 215-235 μm in length. The periostracum is minutely pitted and a lithodesma is present. Its distribution is Western Atlantic, ranging from 42°N to 30°S, in depths of 18 to 1646-1829 m. Cardiomya knudseni (Allen & Morgan, 1981), a possibly related amphi-Atlantic species whose type material has been lost, is regarded herein as a nomen dubium.

Sexual dimorphism and associated population characteristics in the benthopelagic shrimp &lt;em&gt;Pasiphaea sivado&lt;/em&gt; (Crustacea: Caridea: Pasiphaeidae)

Morphological and size dimorphism between genders of the benthopelagic shrimp Pasiphaea sivado are reported for the first time in the present work. All five pleopod protopods of females are thinner and more elongated than the male pleopod protopods, which in turn are anteriorly rounded and have robust shapes. The shape variability of the second pleopod protopods was also analysed using geometric morphometrics techniques which clearly differentiated between the thinner, elongated shape of the females and the robust shape of males. An important application of the observations of sexual dimorphism in pleopod shape in adult P. sivado is, from now on, the ability to quickly assess the gender of individuals when fisheries and population biology studies are carried out in the field unaided by a magnifying. A critical size from which the population sex ratio biases changed from female to male dominance was found in all studied western Mediterranean populations of P. sivado. This critical size different and became progressively smaller from populations in the Alboran Sea to populations in the Catalan Sea. Concerning sex ratio, no significant tendency of gender segregation was found across the bathymetric distribution range of the species, suggesting that this species does not perform differential depth distribution by gender.

Black corals (Anthozoa: Antipatharia) of the Clarion-Clipperton Fracture Zone

The antipatharian fauna of the Clarion-Clipperton Fracture Zone is discussed. Five species of black corals from three genera were identified in collections from this area, including one new species. A list is provided of the 15 species of antipatharians that have been collected at depths greater than 3000 m, and a figure is included that shows the bathymetric distribution of all genera in the order. A new genus, Alternatipathes, in the family Schizopathidae is also described herein.

Molecular phylogenies confirm the presence of two cryptic Hemimycale species in the Mediterranean and reveal the polyphyly of the genera Crella and Hemimycale (Demospongiae: Poecilosclerida).

BackgroundSponges are particularly prone to hiding cryptic species as their paradigmatic plasticity often favors species phenotypic convergence as a result of adaptation to similar habitat conditions. Hemimycale is a sponge genus (Family Hymedesmiidae, Order Poecilosclerida) with four formally described species, from which only Hemimycale columella has been recorded in the Atlanto-Mediterranean basin, on shallow to 80 m deep bottoms. Contrasting biological features between shallow and deep individuals of Hemimycale columella suggested larger genetic differences than those expected between sponge populations. To assess whether shallow and deep populations indeed belong to different species, we performed a phylogenetic study of Hemimycale columella across the Mediterranean. We also included other Hemimycale and Crella species from the Red Sea, with the additional aim of clarifying the relationships of the genus Hemimycale.MethodsHemimycale columella was sampled across the Mediterranean, and Adriatic Seas. Hemimycale arabica and Crella cyathophora were collected from the Red Sea and Pacific. From two to three specimens per species and locality were extracted, amplified for Cytochrome C Oxidase I (COI) (M1–M6 partition), 18S rRNA, and 28S (D3–D5 partition) and sequenced. Sequences were aligned using Clustal W v.1.81. Phylogenetic trees were constructed under neighbor joining (NJ), Bayesian inference (BI), and maximum likelihood (ML) criteria as implemented in Geneious software 9.01. Moreover, spicules of the target species were observed through a Scanning Electron microscope.ResultsThe several phylogenetic reconstructions retrieved both Crella and Hemimycale polyphyletic. Strong differences in COI sequences indicated that C. cyathophora from the Red Sea might belong in a different genus, closer to Hemimycale arabica than to the Atlanto-Mediterranean Crella spp. Molecular and external morphological differences between Hemimycale arabica and the Atlanto-Mediterranean Hemimycale also suggest that Hemimycale arabica fit in a separate genus. On the other hand, the Atlanto-Mediterranean Crellidae appeared in 18S and 28S phylogenies as a sister group of the Atlanto-Mediterranean Hemimycale. Moreover, what was known up to now as Hemimycale columella, is formed by two cryptic species with contrasting bathymetric distributions. Some small but consistent morphological differences allow species distinction.ConclusionsA new family (Hemimycalidae) including the genus Hemimycale and the two purported new genera receiving C. cyathophora and Hemimycale arabica might be proposed according to our phylogenetic results. However, the inclusion of additional Operational Taxonomic Unit (OTUs) appears convenient before taking definite taxonomical decisions. A new cryptic species (Hemimycale mediterranea sp. nov.) is described. Morphologically undifferentiated species with contrasting biological traits, as those here reported, confirm that unidentified cryptic species may confound ecological studies.

Temporal and bathymetric distribution of juveniles and adults of the speckled swimming crab Arenaeus cribrarius from coastal waters of southern Brazil

AbstractThis study evaluated the temporal and bathymetric distribution of the speckled swimming crab

Endemic Lake Baikal sponges from deep water. 2: Taxonomy and Bathymetric Distribution.

Unique samples of deep-water sponges of Lake Baikal were collected between 120 and 1450 m depth and their taxonomy and bathymetric distribution were studied. Based on morphological studies with scanning electron microscopy (SEM) and molecular analyses (CO1, ITS) we describe a new species, Baikalospongia abyssalis sp. nov. Spicule morphology of this new species is similar to Palaeoephydatia sp., a species previously known only from fossils in Late Pliocene (3.2-2.8 mya) sediments. Other sponge samples collected were identified as Baikalospongia intermedia intermedia, B. intermedia profundalis, B. bacillifera, B. fungiformis, B. martinsoni and Swartschewskia papyracea, all from the family Lubomirskiidae. Sponge specimens with giant spicules, identified as B. fungiformis, were found at great depths. B.i. intermedia and B. i. profundalis are dominating species at great depth. Light is a limiting factor for distribution of Lubomirskia baicalensis, possibly due to its symbiosis with photosynthetic protists. The current study extends our knowledge on the distribution boundaries of Lubomirskiidae at great depths.

Polychaeta Orbiniidae from Antarctica, the Southern Ocean, the Abyssal Pacific Ocean, and off South America

The orbiniid polychaetes chiefly from Antarctic and subantarctic seas and off South America are described based on collections of the National Museum of Natural History and new material from surveys conducted by the United States Antarctic Program and other federal and privately funded sources as well as participation in international programs. A total of 44 species of Orbiniidae distributed in 10 genera are reported from the Pacific Ocean and waters off South America and Antarctica. Twenty-one species are new to science; one species is renamed. Berkeleyia heroae n. sp., B. abyssala n. sp., B. weddellia n. sp.; B. hadala n. sp., Leitoscoloplos simplex n. sp., L. plataensis n. sp., L. nasus n. sp., L. eltaninae n. sp., L. phyllobranchus n. sp., L. rankini n. sp., Scoloplos bathytatus n. sp., S. suroestense n. sp., Leodamas hyphalos n. sp., L. maciolekae n. sp., L. perissobranchiatus n. sp., Califia bilamellata n. sp., Orbinia orensanzi n. sp., Naineris antarctica n. sp., N. argentiniensis n. sp., Orbiniella spinosa n. sp., and O. landrumae n. sp. are new to science. A new name, Naineris furcillata, replaces N. chilensis Carrasco, 1977, a junior homonym of N. dendtritica chilensis Hartmann‑Schröder, 1965, which is raised to full species status. Leodamas cochleatus (Ehlers, 1900) is removed from synonymy and redescribed. A neotype is established for Leodamas verax Kinberg, 1966, the type species. A general overview of Leodamas species is provided. The Leitoscoloplos kerguelensis (McIntosh, 1885) complex is reviewed and partially revised. Definitions of the genera of the Orbiniidae are updated to conform to recently described taxa. Several new synonymies are proposed following a reexamination of previously described type specimens. The morphological characters used to identify and classify orbiniids are reviewed. The biogeographic and bathymetric distributions of the South American and Southern Ocean orbiniid fauna are reviewed.

Distribution, abundance and population structure of Hexaplex trunculus and Bolinus brandaris (Gastropoda: Muricidae) in offshore areas of the Gulf of Gabès, southern Tunisia

The banded murex Hexaplex trunculus and purple dye murex Bolinus brandaris are frequently caught as bycatch by bottom trawlers operating in the Gulf of Gabès, southern Tunisia. Although these muricid gastropods might importantly constitute an additional source of income for fishermen as well as help to diversify local shellfish production, information on their catches is relatively scarce. Hence, the present study aimed to assess the status of local populations of H. trunculus and B. brandaris, including data on their spatial and depth distributions, abundance, biomass, population structure and mortality. Fishing surveys using bottom trawls were performed between May 2006 and June 2007 in offshore areas of the Gulf of Gabès. In total, 198 fishing hauls were analysed, corresponding to a total fishing duration of 333.3 hours and a total prospecting area of 1 534 ha at depths of 20–86 m. Altogether, 3 026 H. trunculus and 3 599 B. brandaris of a broad size range (22.9−91.1 and 22.4−97.0 mm shell length, respectively) were sampled during the study period. GIS-produced maps were employed to determine the species’ spatial and bathymetric distributions by extrapolating their estimated fishing yield (bycatch per unit effort), abundance, biomass and mortality in relation to the total area surveyed in the gulf. The results provide valuable baseline information that may be applied to management proposals for regulating this untargeted resource, ultimately assisting sustainable exploitation and long-term preservation of this alternative fishing resource in the offshore areas of the Gulf of Gabès.

New records and bathymetric distribution of deep-sea shrimps of the family Glyphocrangonidae (Decapoda: Caridea) from the Potiguar Basin, northeastern Brazil

Abstract The caridean family Glyphocrangonidae Smith, 1884 is monotypic, including only the genus Glyphocrangon A. Milne-Edwards, 1881. The species of this genus are exclusively inhabitants of deep sea. The current contribution aims to enrich the knowledge of Glyphocrangon in the southwestern Atlantic, by reporting its occurrence and bathymetric distribution in the Potiguar Basin, northeastern Brazil. The samples were collected by R/V Luke Thomas and R/V Seward Johnson, with bottom trawling at isobaths of 400, 1,000 and 2,000 m, using an otter trawl semi-balloon. The specimens were identified and stored in the carcinological collection of the Museu de Oceanografia Prof. Petronio Alves Coelho, in Recife, Brazil. A total of 810 specimens were examined from five species: Glyphocrangon aculeata A. Milne-Edwards, 1881, G. alispina Chace, 1939, G. longirostris (Smith, 1882), G. sculpta (Smith, 1882) and G. spinicauda A. Milne-Edwards, 1881. Glyphocrangon spinicauda was the most abundant with 334 individuals, and G. sculpta was the rarest, with only one individual. All species were recorded in the study area for the first time.

The sexual segregation of the European eel, Conger conger (Linnaeus,1758) (Anguilliformes, Congridae) and female semelparity in the northwest Mediterranean.

The objective of this study is to evaluate the bathymetric distribution, sex ratio, stages of gonad maturation and reproductive strategy of the European eel (Conger conger) in coastal inshore waters of the Costa Brava (north-west Mediterranean) and to answer many questions about its biology. The observations confirm the absence of both males and mature or spent females in the area. The only males obtained were caught at greater depths (between 600 and 800 m) than females (100 to 400 m). Ten morphometric characters were used to calculate morphometric indices and compare anatomical differences between males and females. To describe the different stages of maturity, gonads were sectioned, stained and observed under a microscope. Gonadosomatic and hepatosomatic indices were also calculated. Results confirm that males show various morphometric differences from females of the same size, which may be related to the different depths at which they live. A histological examination of ovaries demonstrated that C. conger has synchronous ovaries. Although some females were in the early vitellogenic stages of gonad development, the great majority were still in the pre-vitellogenic stages, characterized by a large amount of adipose tissue between the germ cells, which decreases progressively with maturation. When females are fully mature, their ovaries have grown enormously; the germinal tissue has grown and consumed the adipose tissue, a process that is believed to take place during pre-reproductive migration to deeper spawning grounds. Males’ mature gonads show an increase in weight, but never of the magnitude of females. Some males in our sample were completely mature and full of sperm. In conclusion, our observations are clearly consistent with a semelparous strategy for females. However, males seem to be capable of recovering after spawning and no signs of degeneration have been detected. The difficulty in obtaining a larger sample of males means our results should be taken as approaches, pending further studies to corroborate them.

Dragonets (Callionymidae) of soft bottoms from the coastal zone of southern Central Vietnam

A review of dragonets (Gallionymidae) from the coastal waters of Khanh Hoa (Nha Trang and Van Phong bays) and Binh Thuan (Phu Quy Island) provinces, Vietnam, was conducted based on the samples of the author. In total, nine species were recorded, including three species indicated in the fauna of the country for the first time. In addition, geographic and bathymetric distribution of C. altipinnis, as well as morphological variation of several other species, was specified.

The current status of demersal fish resources in the Russian waters of the Sea of Japan

A bottom trawl survey was conducted over all of the shelf and continental slope in the Russian waters of the Sea of Japan, from Peter the Great Bay to the La Perouse Strait, from March 31 to July 8, 2015. The species composition and biomass of demersal fish were determined for Peter the Great Bay, waters of southern and northern Primorye, and the West Sakhalin subzone. The bulk of the biomass (over 90% of the estimated biomass in the study areas) was formed by four families: Gadidae, Pleuronectidae, Cottidae, and Clupeidae. The highest biomass, 218000 t, was recorded from the West Sakhalin subzone; the lowest, 77400 t, was found from Peter the Great Bay. The proportions of biomasses of the considered species varied substantially between areas: walleye pollock and plain sculpin dominated by biomass in Peter the Great Bay; walleye pollock and scale-eye plaice dominated off southern Primorye; herring dominated off northern Primorye; and scale-eye plaice and speckled founder were dominant in the West Sakhalin subzone. The density of the fish concentration was determined for several bathymetric ranges in the considered areas. In the period of studies, the pattern of distribution of fish in Peter the Great Bay was still of the winter type, which is characterized by high concentrations over the continental slope. There was some shift towards shallower depths in Primorye waters; however, taking the great latitudinal span of the area of the research and the early spring into account, these migrations were not so clearly pronounced, as would be observed in later periods. The most distinct differences in the bathymetric distribution were found in the West Sakhalin subzone, where the distribution pattern corresponded mostly to the summer type with its high concentrations in shallow waters and low ones over the continental slope. According to the estimates in 2015, the biomass of demersal fish slightly increased as compared to the values of the 1980s–1990s.

New depth record of the dappled flounder Paralichthys woolmani (Pleuronectiformes: Paralichthyidae) in the Gulf of California, México

Ten specimens of the dappled flounder Paralichthys woolmani were captured at a depths from 109 to 248.1 m in the central Gulf of California in an exploration cruise on board the research ship BIP XII in February 2005. The average temperature and dissolved oxygen concentration were 14.5°C and 1.01 mg O2 L-1, respectively. P. woolmani had not been reported at greater depth than 100 m. This new record represents an increase of 148.1 m in its bathymetric distribution in the Gulf of California.

On a new marine podocopid genus and species (Ostracoda: Hemicytheridae) from Brazil.

Bulbocythere calida gen. et sp. nov., a benthic marine ostracode, is herein described and illustrated. The geographic and bathymetric distributions of this new taxon are based on the analysis of 923 bottom samples collected along the entire Brazilian continental shelf in a depth range of about 11 to 280 m, plus sediments of 176 samples from the Sepetiba Bay and 37 samples from the Tamandaré Bay. In the study material, this ostracode was rare, and restricted to the warm waters of the E and NE shelves and to the substrates around the reefs of the Tamandaré Bay.

A census of deep-water sipunculans (Sipuncula)

The Sipuncula, or peanut worms, are a small taxon of lophotrochozoan worms that live mostly in warm shallow waters, but little is known about the diversity and distribution of this group in the deeper parts of the ocean (>2000 m). To address this point, all existing information from the scientific literature on deep-water sipunculans was retrieved, and a census was organised in several data matrices by species and by geographic and bathymetric distribution. From this data, deep-water sipunculan fauna were found to include representatives of 4 families, 10 genera, 51 species and 3 subspecies. Geographical range maps for all the censused species were created. The most ubiquitous species are Nephasoma diaphanes (Gerould, 1913); Phascolion lutense Selenka, 1885; Golfingia muricaudata (Southern, 1913); Apionsoma murinae (Cutler, 1969), G. margaritacea (Sars, 1851) and Onchnesoma magnibathum Cutler, 1969. By contrast, 18 species of various genera in the dataset are considered to be extremely rare, with only one previous record. No endemic species have been detected on the sea bottoms investigated to date. With regard to vertical distribution, most deep-water sipunculans were collected at depths ranging from 2500 to 3000 m, whereas there were fewer ultra-abyssal and hadal records (>6500 m). This also applies to the deepest depths investigated (>7000 m), where only three isolated records of three different species (N. diaphanes, P. lutense and P. pacificum Murina, 1957) were found. By relating species richness to depth, a significant linear regression was found, with lower richness values at greater depths. Finally, attempts to relate the species richness values to latitudinal or longitudinal gradients have as yet proved unsuccessful. The conclusion drawn from this census is that sipunculan fauna down to a depth of 2000 m is characterised as remarkably sensitive to bathymetry, with the lowest species richness values recorded in the deeper bottoms.

Early Cretaceous sea level fluctuations in the eastern part of the East European Platform

The quantitative sea-level curve in the eastern part of the East European Platform during the Early Cretaceous first compiled for this region is based on the results of analysis of the corresponding deposits and the bathymetric distribution of benthic foraminifers in their sections. This quantitative curve is correlated with the sea-level curve constructed for central areas of the East European Platform [9]. According to [9], the basin in the central part of the platform was as deep as 110 m, while in its eastern areas the depth amounted to 350 m. It is revealed that tectono-eustatic cycles defined previously in the central part of the platform and cycles (megasequences) in its eastern areas are asynchronous and are characterized by different orders. Such asynchrony is determined by the different tectonic trends in these regions during the Early Cretaceous.

Distribution of the deep-sea genus Bathypterois (Pisces: Ipnopidae) in the Eastern Central Pacific.

The genus Bathypterois (tripod fish) comprises 19 species of deep-sea fishes distributed worldwide. The biology and distribution of the species of this genus are relatively poorly known throughout the Eastern Central Pacific (ECP). This work aims to update the geographic and bathymetric distribution of species of Bathypterois throughout the ECP. To describe the influence of depth, temperature and dissolved oxygen concentrations (DO) on latitudinal and depth distribution of members of the genus throughout the Mexican Pacific, 51 specimens of B. atricolor (12 trawls) and 112 of B. ventralis (18 trawls), collected during TALUD project, were analyzed. Bathypterois atricolor had broader environmental niches (depth: 0.47, temperature: 0.46, DO: 0.39), and inhabits deeper and colder sites (Electivity positives: > 1 000 m, < 3.2 °C, 1.0-1.62 mL/L) than B. ventralis, which had narrow environmental niches (depth: 0.34, temperature: 0.32, DO: 0.28), with high affinity to warmer sites and lower DO concentrations (Electivity positives: 778-1 400 m, 3.3-5.8 °C, < 1.0 mL/L). Both species used different environmental strata (niche overlap; depth: 0.34, temperature: 0.32, DO: 0.28). The adaptation of B. atricolor to live in a broad range of DO concentrations explains its almost circumglobal distribution, while B. ventralis lives almost permanently in the Oxygen Minimum Zone (< 0.05 mL/L), so the DO could be a limiting factor, reducing its potential geographic and bathymetric distributions. None of these species had been previously recorded in the central Gulf of California, and B. ventralis had not been recorded along the West coast of Baja California. This study confirms that both species have a continuous distribution within the ECP, our new records extended the known northernmost range for B. atricolor by 886 km (from 22°46' N to 30°45’ N) and for B. ventralis by 645 km (from 21°18’ N to 27°07’ N).