Agonistic Behavior in the Squid Loligo plei (Loliginidae,Teuthoidea): Fighting Tactics and the Effects of Size and Resource Value

Observations of small schools of squids in captivity suggested that dominance relationships among males were based upon major differences in the frequency or duration of their agonistic behavior, but staged contests showed few differences. During staged contests, squids exhibited up to 21 separate behaviors. Some contests included a complex array of visual signals and side-by-side posturing (Lateral Display) followed by physical contact during Fin beating. There was behavioral variability and step-wise escalation during the contests: squids performed either 1. long sequences of visual signaling followed by Chasing and Fleeing; or 2. short sequences of visual signaling followed by physical Fin beating and ending with Chasing and Fleeing. Size influenced outcome in all contests; larger males were more likely to win the contest. Size had no effect on contest duration, but contest duration was shorter when resource value was high, especially when a male established temporary ownership of a female. We speculate that when the perceived resource value is high, male squids are more likely to engage in a shorter yet riskier fighting tactic.     

Characterization of the Bacterial Diversity in Indo-West Pacific Loliginid and Sepiolid Squid Light Organs

Loliginid and sepiolid squid light organs are known to host a variety of bacterial species from the family Vibrionaceae, yet little is known about the species diversity and characteristics among different host squids. Here we present a broad-ranging molecular and physiological analysis of the bacteria colonizing light organs in loliginid and sepiolid squids from various field locations of the Indo-West Pacific (Australia and Thailand). Our PCR-RFLP analysis, physiological characterization, carbon utilization profiling, and electron microscopy data indicate that loliginid squid in the Indo-West Pacific carry a consortium of bacterial species from the families Vibrionaceae and Photobacteriaceae. This research also confirms our previous report of the presence of Vibrio harveyi as a member of the bacterial population colonizing light organs in loliginid squid. pyrH sequence data were used to confirm isolate identity, and indicates that Vibrio and Photobacterium comprise most of the light organ colonizers of squids from Australia, confirming previous reports for Australian loliginid and sepiolid squids. In addition, combined phylogenetic analysis of PCR-RFLP and 16S rDNA data from Australian and Thai isolates associated both Photobacterium and Vibrio clades with both loliginid and sepiolid strains, providing support that geographical origin does not correlate with their relatedness. These results indicate that both loliginid and sepiolid squids demonstrate symbiont specificity (Vibrionaceae), but their distribution is more likely due to environmental factors that are present during the infection process. This study adds significantly to the growing evidence for complex and dynamic associations in nature and highlights the importance of exploring symbiotic relationships in which non-virulent strains of pathogenic Vibrio species could establish associations with marine invertebrates.     

The locomotory function of the fins in the squid Loligo pealei

Kinematic data of high spatial and temporal resolution, acquired from image sequences of adult long-finned squid, Loligo pealei, during steady swimming in a flume, were used to examine the role of fins and the coordination between fin and jet propulsion in squid locomotion. Fin shape and body outlines were digitized and used to calculate fin wave speed, amplitude, frequency, angle of attack, body deformation, speed, and acceleration. L. pealei were observed to have two fin gait patterns with a transition at 1.4-1.8 mantle lengths per second (Lm s-1) marked by alternation between the two patterns. Fin motion in L. pealei exhibited characteristics of both traveling waves and flapping wings. At low speeds, fin motion was more wave-like; at high speeds, fin motion was more flap-like and was marked by regular periods during which the fins were wrapped tightly against the mantle. Fin cycle frequencies were dependent on swimming speed and gait, and obvious coordination between the fins and jet were observed. Fin wave speed, angle of attack, and body acceleration confirmed the role of fins in thrust production and revealed a role of fins at all swimming speeds by a transition from drag-based to lift-based thrust when fin wave speed dropped below swimming speed. Estimates of peak fin thrust were as high as 0.44-0.96 times peak jet thrust in steady swimming over the range of swimming speeds observed. Fin downstrokes generally contributed more to thrust than did upstrokes, especially at high speeds.     

Ontogeny of squid mantle function: changes in the mechanics of escape-jet locomotion in the oval squid,Sepioteuthis lessoniana lesson, 1830

In Sepioteuthis lessoniana, the oval squid, ontogenetic changes in the kinematics of the mantle during escape-jet locomotion imply a decline in the relative mass flux of the escape jet and may affect the peak weight-specific thrust of the escape jet. To examine the relationship between ontogenetic changes in the kinematics of the mantle and the thrust generated during the escape jet, we simultaneously measured the peak thrust and the kinematics of the mantle of squid tethered to a force transducer. We tested an ontogenetic series of S. lessoniana that ranged in size from 5 to 40 mm dorsal mantle length (DML). In newly hatched squids, thrust peaked 40 ms after the start of the escape jet and reached a maximum of between 0.10 mN and 0.80 mN. In the largest animals, thrust peaked 70 ms after the start of the escape jet and reached a maximum of between 18 mN and 110 mN. Peak thrust was normalized by the wet weight of the squid and also by the cross-sectional area of the circumferential muscle that provides power for the escape jet. The weight-specific peak thrust of the escape jet averaged 0.36 in newly hatched squid and increased significantly to an average of 1.5 in the largest squids measured (P < 0.01). The thrust per unit area of circumferential muscle averaged 0.25 mN/mm(2) in hatchlings and increased significantly to an average of 1.4 mN/mm(2) in the largest animals tested (P < 0.01). The impulse of the escape jet was also lowest in newly hatched individuals (1.3 mN. s) and increased significantly to 1000 mN. s in the largest squids measured (P < 0.01). These ontogenetic changes in the mechanics of the escape jet suggest (1) that propulsion efficiency of the exhalant phase of the jet is highest in hatchlings, and (2) that the mechanics of the circumferential muscles of the mantle change during growth.     

Biodiversity among luminescent symbionts from squid of the genera Uroteuthis, Loliolus and Euprymna (Mollusca: Cephalopoda)

Luminescent bacteria in the family Vibrionaceae (Bacteria: γ-Proteobacteria) are commonly found in complex, bilobed light organs of sepiolid and loliginid squids. Although morphology of these organs in both families of squid is similar, the species of bacteria that inhabit each host has yet to be verified. We utilized sequences of 16S ribosomal RNA, luciferase α-subunit (luxA) and the glyceraldehyde-3-phosphate dehydrogenase (gapA) genes to determine phylogenetic relationships between 63 strains of Vibrio bacteria, which included representatives from different environments as well as unidentified luminescent isolates from loliginid and sepiolid squid from Thailand. A combined phylogenetic analysis was used including biochemical data such as carbon use, growth and luminescence. Results demonstrated that certain symbiotic Thai isolates found in the same geographic area were included in a clade containing bacterial species phenotypically suitable to colonize light organs. Moreover, multiple strains isolated from a single squid host were identified as more than one bacteria species in our phylogeny. This research presents evidence of species of luminescent bacteria that have not been previously described as symbiotic strains colonizing light organs of Indo-West Pacific loliginid and sepiolid squids, and supports the hypothesis of a non-species-specific association between certain sepiolid and loliginid squids and marine luminescent bacteria.     

Expression and tissue distribution of astacin-like squid metalloprotease (ALSM)

Astacin metalloprotease family members function in a wide variety of biologic events, including cell differentiation and morphogenesis during embryonic development and adult tissue differentiation. We previously isolated and characterized an astacin-like squid metalloprotease (ALSM). To elucidate the embryonic expression of ALSM, we performed immunohistochemical analysis with specific antibodies and examined the expression profiles of ALSM isoforms by in situ hybridization analysis. Tissue distribution and expression were also examined in adult spear squid. mRNA expression of ALSM isoforms I and III was first detected in newly hatched squid and was restricted to the liver. No mRNA signals were detected in other tissues even in adult squids. At the protein level, both isoforms were prominent in the liver of embryos and later in digestive organs of adult squid. Both isoforms were also detected in muscle tissues, including mantle and tentacle muscle. Staining for ALSM III was also identified in the iris and in tissues near the eye in squid embryos. However, no reactive bands were detected by immunoblotting of adult squid eyes. Thus, ALSM is initially expressed at the late stage of embryogenesis in spear squid, and expression is restricted to the liver. Thereafter, ALSM isoforms function in various tissues in an isoform-dependent manner.     

Plerocercoids of Nybelinia surmenicola (Cestoda: Tentacularidae) in Squids,Todarodes pacificus,from East Sea,the Republic of Korea

A visceral helminth of the squid, Todarodes pacificus, is reported from the East Sea, the Republic of Korea. Total 39 squid samples were purchased from a fish market in Jumunjin-eup, Gangneung-si (City) from August 2014 to July 2015 and were examined for helminth parasites with naked eyes and under a stereomicroscope after opening the abdominal cavity with a pair of scissors. Whitish larval worms were mainly found in the stomach and abdominal cavity of the squid. They were detected in 25 (64.1%) out of 39 squids examined, and the infection density was 7 larvae per infected squid. Spatula-shaped larvae were 8.2×2.0 mm in average size, round to slightly flattened anteriorly, with round hatching posteriorly, and had characteristic 4 tentacles with numerous hooklets in the scolex. The larvae were identified as the plerocercoid stage of Nybelinia surmenicola by their morphological features. This finding represents a new host record and the first report of N. surmenicola infection in T. pacificus squids from the east coast of Korea.     

The locomotory function of the fins in the squid Loligo pealei

Kinematic data of high spatial and temporal resolution, acquired from image sequences of adult long-finned squid, Loligo pealei, during steady swimming in a flume, were used to examine the role of fins and the coordination between fin and jet propulsion in squid locomotion. Fin shape and body outlines were digitized and used to calculate fin wave speed, amplitude, frequency, angle of attack, body deformation, speed, and acceleration. L. pealei were observed to have two fin gait patterns with a transition at 1.4-1.8 mantle lengths per second (L_m s^-1) marked by alternation between the two patterns. Fin motion in L. pealei exhibited characteristics of both traveling waves and flapping wings. At low speeds, fin motion was more wave-like; at high speeds, fin motion was more flap-like and was marked by regular periods during which the fins were wrapped tightly against the mantle. Fin cycle frequencies were dependent on swimming speed and gait, and obvious coordination between the fins and jet were observed. Fin wave speed, angle of attack, and body acceleration confirmed the role of fins in thrust production and revealed a role of fins at all swimming speeds by a transition from drag-based to lift-based thrust when fin wave speed dropped below swimming speed. Estimates of peak fin thrust were as high as 0.44-0.96 times peak jet thrust in steady swimming over the range of swimming speeds observed. Fin downstrokes generally contributed more to thrust than did upstrokes, especially at high speeds.     

An examination of the role of the digestive gland of two loliginid squids,with respect to lipid: storage or excretion?

The role of the digestive gland, with respect to non-structural lipid, was examined using proximal analysis, histochemistry and quantitative histological techniques in the tropical loliginid squids Sepioteuthis lessoniana (Lesson) and Photololigo sp. The digestive gland of both species was characterized by large and numerous lipid droplets in the apical portion of the digestive cells and very few in the basal portion. The apical lipid droplets were released into the lumen of the gland and subsequently rapidly removed. Despite the numerous large apical lipid droplets, the lipid concentration in the digestive glands of S. lessoniana and Photololigo sp. was lower than that reported for most squid species. There was no relationship between lipid concentration and stage of digestion, suggesting that lipid is not stored in the gland after a meal. There was also no relationship between lipid concentration and the sex of an individual or stage of reproductive maturity, suggesting that these squids are not storing lipid in the digestive gland for use in fuelling reproductive maturation or providing an energy source for oocytes. I believe this study is the first to combine proximal analysis and quantitative histological techniques to examine the role of the squid digestive gland with respect to non-structural lipids. The results indicate that the digestive gland of these tropical loliginid squids is excreting, not storing, excess dietary lipid.     

Temporal and ontogenetic variation in the diet of squid (<Emphasis Type="Italic">Loligo forbesii</Emphasis> Streenstrup) in Scottish waters

The squid Loligo forbesii is the only cephalopod species currently targeted by fisheries in the northern NE Atlantic. An active predator, it feeds primarily on fish, crustaceans and cephalopods. During 15 years since the only previous large-scale study of the diet of this species in Scottish waters, there have been substantial changes in marine fish abundances. The present study evaluates sources of variation (temporal, ontogenetic) in diet composition and prey size preferences of L. forbesii, including a comparison of contemporary (July 2006–June 2007) and historical (1990–1992) dietary datasets. Results revealed significant size-related and seasonal variation in diet composition and prey size. Teleost fish of the families Ammodytidae and Gobiidae were eaten by squid of all sampled sizes, although occurrence of gobies was generally more frequent in smaller squids, while Gadidae were eaten more frequently by larger squids. Cannibalism was also more frequent in larger squids. Compared to the 1990–1992 dataset, clupeid fish were less important in the diet of squid in 2006–2007, while the importance of gobies increased, and the size of gobies eaten also increased. The trend in gadoids differed according to the index used: their frequency of occurrence was considerably higher in 2006–2007 than in 1990–1992, but their numerical importance was slightly lower. In general, results provided little evidence that changes in the diet of L. forbesii correspond with changes in fish abundance, at least at the scales at which these are measured.     

Comprehensive Model of Jumbo Squid Dosidicus gigas Trophic Ecology in the Northern Humboldt Current System

The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and prey. We investigated the ontogenetic and spatiotemporal variability of the diet composition of jumbo squid in the northern Humboldt Current system. For that purpose we applied several statistical methods to an extensive dataset of 3,618 jumbo squid non empty stomachs collected off Peru from 2004 to 2011. A total of 55 prey taxa was identified that we aggregated into eleven groups. Our results evidenced a large variability in prey composition as already observed in other systems. However, our data do not support the hypothesis that jumbo squids select the most abundant or energetic taxon in a prey assemblage, neglecting the other available prey. Indeed, multinomial model predictions showed that stomach fullness increased with the number of prey taxa, while most stomachs with low contents contained one or two prey taxa only. Our results therefore question the common hypothesis that predators seek locally dense aggregations of monospecific prey. In addition D. gigas consumes very few anchovy Engraulis ringens in Peru, whereas a tremendous biomass of anchovy is potentially available. It seems that D. gigas cannot reach the oxygen unsaturated waters very close to the coast, where the bulk of anchovy occurs. Indeed, even if jumbo squid can forage in hypoxic deep waters during the day, surface normoxic waters are then required to recover its maintenance respiration (or energy?). Oxygen concentration could thus limit the co-occurrence of both species and then preclude predator-prey interactions. Finally we propose a conceptual model illustrating the opportunistic foraging behaviour of jumbo squid impacted by ontogenetic migration and potentially constrained by oxygen saturation in surface waters.     

Catalytical properties of liver monoamine oxidases of the Commander squid <Emphasis Type="Italic">Berryteuthis magister</Emphasis> from various habitation zones

There has been performed kinetic analysis of enzymatic reactions of deamination of tyramine, tryptamine, serotonin, benzylamine, β-phenylethylamine, and histamine under action of liver monoamine oxidase (MAO) of the Commander squid Berryteuthis magister from various habitation zones in the Bering and Japan Seas. A substrate inhibition by high concentrations of all studied substrates has been revealed, which seems to indicate mutual effect of various MAO forms present in liver of the studied squids. Analysis of kinetic parameters of enzymatic reactions of deamination of six studied substrates and the substrate-inhibitory analysis with use of two derivatives of acridine and deprenyl indicate the enzyme heterogeneity, the presence of at least two MAO-A forms, and the absence of intraspecies differences in MAO of the Commander squids from various habitation zones. The most active was the MAO form responsible for serotonin deamination. There were obtained quantitative difference in substrate specificity and reaction ability with respect to inhibitor of proflavin for the liver MAO of the Commander and Pacific squids.     

STOMACH CONTENTS OF FALSE KILLER WHALES (PSEUDORCA CRASSIDENS) STRANDED ON THE COASTS OF THE STRAIT OF MAGELLAN,TIERRA DEL FUEGO

We examined the stomachs of 25 false killer whales collected from a mass stranding of 181 animals along both coasts of the Strait of Magellan, Chile, in March 1989. The 21 stomachs (nine males and 12 females), with food remains contained 11 prey species (nine cephalopods and two fishes) with a total of 442 individuals. Except for one case, food remains were meager, indicating that the animals had not eaten for some time or through stress had vomited on the beach. Eleven of the 21 animals had mud (often with squid beaks) in the esophagus and first stomach. The prey were identified employing squid beaks, fish otoliths and bones, and their wet weights were estimated using regressions between hard parts and known weights of species. The most important prey were the oceanic and neritic-oceanic squids, Martialia byadesi and Illex argentinus, followed by the neritic fish, Macruronus magellanicus. Of less importance were the oceanic squid, Todaroes fillipovae, the oceanic and epipelagic octopus, Ocytboe sp., and the oceanic squid, Moroteuthis ingens. The rest of the prey were poorly represented and included four oceanic squids and one neritic fish. The prey species of these animals were subantarctic, with two antarctic species, abundant over the Patagonian shelf and adjacent oceanic waters around Tierra del Fuego.     

Insight into the short-finned squid Illex coindetii (Cephalopoda: Ommastrephidae) feeding ecology: is there a link between helminth parasites and food composition?

Squids are especially frequent as paratenic hosts of helminth parasites, particularly to those that have elasmobranchs and mammals as final hosts. Among those parasite species, anisakid nematode larvae and cestode plerocercoids are most effectively transferred through the trophic chain by oegopsid squids. A total of 439 short-finned squids, Illex coindetii (245 males, 190 females and 4 unsexed) were sampled in the central part of the eastern Adriatic Sea in order to assess their helminth component community and parasite dynamics with respect to host sex, maturity, seasonality, and feeding behavior. Two larval helminths were isolated, i.e., larvae of Anisakis pegreffii, characterized by molecular tools at the species level, and plerocercoids of Phyllobothrium sp., with prevalences of 30.5% and 2.3%, respectively. Highly significant seasonal variation in diet consumption, congruent with seasonal variation in anisakid intensity, was observed, underlining the tight role of squid prey in the trophic transmission of parasite. Likewise, the highest helminth prevalence and intensity of infection was recorded in autumn, when the fish prey, mostly Maurolicus muelleri, comprised the greatest proportion of diet. This helped to assign the Adriatic broadtail shortfin squid not as a first, but as a second, paratenic host for the anisakid, unlike as suggested previously. The presence of larval A. pegreffii confirms its previously reported zoogeographical distribution in the Mediterranean and Adriatic Seas. The presence of 2 helminths in I. coindetii describes the feeding patterns of the squid, as well as clearly defined and coevolved predator-prey relationships.     

Reproduction of the Atlantic bobtail squid Sepiola atlantica (Cephalopoda: Sepiolidae) in northwest Spain

Atlantic bobtail squid (Sepiola atlantica) in northwest Spain show seasonal variation in population structure, with juvenile abundance peaking during summer and autumn. However, whether similar patterns exist for reproduction is unknown. Therefore, we describe the reproductive biology of 505 specimens of S. atlantica collected monthly during two consecutive years at two different sites off of Areamilla beach in the Ría de Vigo. Mature males displayed a type of sexual dimorphism previously unknown in members of this species, developing a muscular nodule in the base of each of the ventral arms over ontogeny. Reproductive output of both sexes was similar to that of other bobtail squids. Relative oocyte size (~10% mantle length) appeared to be similar to those of other bobtail squids. Females did not show evidence of having mated before complete maturity. Females of S. atlantica have group‐synchronous ovary maturation, with a positive correlation between female mantle length and ripe oocyte mass, suggesting a terminal investment strategy. Atlantic bobtail squids displayed the same seasonal patterns of reproductive traits at both sampling sites, with significant differences in reproductive activity between males and females. We consider reproductive traits in these small animals as adaptations to the coastal shelf lifestyle.     

An ethogram of body patterning behavior in the biomedically and commercially valuable squid Loligo pealei off Cape Cod, Massachusetts.

Squids have a wide repertoire of body patterns; these patterns contain visual signals assembled from a highly diverse inventory of chromatic, postural, and locomotor components. The chromatic components reflect the activity of dermal chromatophore organs that, like the postural and locomotor muscles, are controlled directly from the central nervous system. Because a thorough knowledge of body patterns is fundamental to an understanding of squid behavior, we have compiled and described an ethogram (a catalog of body patterns and associated behaviors) for Loligo pealei. Observations of this species were made over a period of three years (> or = 440 h) and under a variety of behavioral circumstances. The natural behavior of the squid was filmed on spawning grounds off Cape Cod (northwestern Atlantic), and behavioral trials in the laboratory were run in large tanks. The body pattern components--34 chromatic (including 4 polarization components), 5 postural, and 12 locomotor--are each described in detail. Eleven of the most common body patterns are also described. Four of them are chronic, or long-lasting, patterns for crypsis; an example is Banded Bottom Sitting, which produces disruptive coloration against the substrate. The remaining seven patterns are acute; they are mostly used in intraspecific communication among spawning squids. Two of these acute patterns--Lateral Display and Mate Guarding Pattern--are used during agonistic bouts and mate guarding; they are visually bright and conspicuous, which may subject the squids to predation; but we hypothesize that schooling and diurnal activity may offset the disadvantage presented by increased visibility to predators. The rapid changeability and the diversity of body patterns used for crypsis and communication are discussed in the context of the behavioral ecology of this species.     

An encounter between a pelagic shark and giant cephalopod

An oceanic whitetip shark (Carcharhinus longimanus) was observed off the coast of Kona, Hawaii, with scars caused by the tentacles of a large cephalopod. While the exact species could not be confirmed, candidate species include the giant squid (Architeuthis dux) or species from the genera Thysanoteuthis (flying squids) and Megalocranchia (glass squids). Telemetry shows C. longimanus will dive within the mesopelagic zone and may interact with or even forage for large cephalopods.     

Seafloor mapping and landscape ecology analyses used to monitor variations in spawning site preference and benthic egg mop abundance for the California market squid (Doryteuthis opalescens)

The California squid fishery is concentrated largely on nearshore squid spawning aggregations. Because of this practice a central concern for sustainable squid fisheries in California is to determine whether reproductive activities and subsequent egg laying occur at rates that are sufficient to support harvestable populations of this sub-annual species. Using high-resolution data collected via acoustic mapping methodology, we estimated a 99% decrease in egg mops abundance from 2005 to 2007. Sidescan sonar images from detailed benthic mapping suggest that although squids prefer a sandy substrate as their primary egg mop habitat, the depths across which egg mops were distributed differed significantly between surveys and spatial distribution of egg mops varied across years on this large spawning ground. Our results suggest that sidescan sonar surveys could serve as an important tool used to aid sustainable management of the California market squid fishery through the monitoring, designation and adaptive management of seasonally variable no-take spawning zones and can help in developing stock assessments of this commercially important species.     

The diet of strap-toothed whales (Mesoplodon layardii)

The food habits of strap-toothed whales ( Mesoplodon layardii ) were examined in detail using stomach contents from 14 stranded whales found on South African and New Zealand coasts. Although a few unidentified fish otoliths and crustacean remains were found in two of these stomachs, 24 species of oceanic squids (some of which occur at a great depth) accounted for 94.8% of counted prey items ( n = 232). Histioteuthis sp. and Taonius pavo were the predominant prey species (25.0 and 17.2% by number, 21.4 and 19.9% by mass, respectively). The presence of sub-Antarctic squid species suggested a northward migration to South African waters in late summer/autumn. Prey sizes were compared between males with fully grown strap-teeth and females/immature males without erupted teeth, using dorsal mantle lengths (DML) and weights of squids estimated from beak measurements. Although females/immature males ate longer squids than males, there was no significant difference in the estimated weights of squids eaten by the two groups. The presence of fully-erupted teeth in adult males, therefore, did not seem to influence the size of prey ingested, even though an adult male could only open its jaws about half as wide as a female. In general, the sizes of cephalopods eaten by strap-toothed whales were not significantly different from those eaten by smaller odontocetes, such as spotted dolphins and dwarf sperm whales, but were significantly smaller than those eaten by larger odontocetes, such as false killer, long-finned pilot, Cuvier's beaked, and southern bottlenose whales.     

Host-symbiont recognition in the environmentally transmitted sepiolid squid-Vibrio mutualism

Associations between environmentally transmitted symbionts and their hosts provide a unique opportunity to study the evolution of specificity and subsequent radiation of tightly coupled host-symbiont assemblages [3, 8, 24]. The evidence provided here from the environmentally transmitted bacterial symbiont Vibrio fischeri and its sepiolid squid host (Sepiolidae: Euprymna) demonstrates how host-symbiont specificity can still evolve without vertical transmission of the symbiont [1]. Infection by intraspecific V. fischeri symbionts exhibited preferential colonization over interspecific V. fischeri symbionts, indicating a high degree of specificity for the native symbiotic strains. Inoculation with symbiotic bacteria from other taxa (monocentrid fish and loliginid squids) produced little or no colonization in two species of Euprymna, despite their presence in the same or similar habitats as these squids. These findings of host specificity between native Vibrios and sepiolid squids provides evidence that the presence of multiple strains of symbionts does not dictate the composition of bacterial symbionts in the host.