Can muscle fatty acid signature be used to distinguish diets during the marine trophic phase of sea lamprey (Petromyzon marinus, L.)?

Characterization of muscle and liver fatty acid profiles, determination of liver lipogenic and lipolytic activities and estimation of liver fatty elongases and desaturases activities of sea lamprey were realized at the beginning of the spawning migration. The muscle fatty acid profile was consistent with the location of capture, and revealed that animals captured far upstream from the river mouth presented the lowest C18:1ω9 levels and the highest relative proportions of C20:4ω6, C20:5ω3 (EPA), C22:5ω3 (DPA) and C22:6ω3 (DHA). These results suggest: (i) the vital importance of the conservation of C20:4ω6 as a precursor of eicosanoids; (ii) the retention of EPA, DPA and DHA for metabolic energy for reproduction; and (iii) the utilization of C18:1ω9 for metabolic fuel use in the beginning of the spawning period. Hepatic lipolysis and lipogenesis revealed significant differences which could, eventually, result from the diet during the parasitic phase of sea lamprey life cycle. Present results revealed that the muscle act as a fat depot site which explains the few significant correlations observed for fatty acids between muscle and liver. Muscle neutral lipids fatty acid signature at the beginning of the spawning migration can be used to distinguish differences in the diet of sea lampreys during the marine trophic phase of their life cycle.     

First records of the North American catfish Ameiurus melas in Portugal

The North American catfish Ameiurus melas is recorded for the first time in Portugal. Its presence in the Tagus River Basin is probably due to natural spread of individuals from Spanish populations, while episodic translocation could explain its occurence in the previously non-invaded Guadiana and Sado River basins.     

The use of PIT telemetry to study movements of ammocoetes and metamorphosing sea lampreys in river beds

Passive integrated transponder (PIT) tags were surgically implanted in 118 sea lamprey Petromyzon marinus ammocoetes which were left to recover in the laboratory for 2 months. During this period 55 individuals started to metamorphose. In the late summer of 2002 the tagged animals were released in a small tributary of the River Mondego, Portugal, and were regularly monitored for a period of 2 months using a portable PIT tag reader. The distribution of the released animals changed from an initial uniform pattern to a random distribution, and then to an aggregated pattern. At the end of the first week 60% of the tagged sea lampreys had already left the study area, indicating their dynamic behaviour. Ammocoetes were more active than metamorphosing sea lampreys, and downstream movements were more frequent when compared to the upstream ones, which were usually a short distance. In order to determine the influence of the dark‐light cycle in the diel activity rhythms, 10 tagged sea lamprey ammocoetes were released in a tank (2000 l capacity) and their position monitored twice a day, for a period of 1 month. Ammocoetes locomotor activity appeared to be conditioned by circadian rhythms, and they were particularly active during darkness.     

HPLC and ELISA analyses of larval bile acids from Pacific and western brook lampreys

Comparative studies were performed on two native lamprey species, Pacific lamprey (Lampetra tridentata) and western brook lamprey (Lampetra richardsoni) from the Pacific coast along with sea lamprey (Petromyzon marinus) from the Great Lakes, to investigate their bile acid production and release. HPLC and ELISA analyses of the gall bladders and liver extract revealed that the major bile acid compound from Pacific and western brook larval lampreys was petromyzonol sulfate (PZS), previously identified as a migratory pheromone in larval sea lamprey. An ELISA for PZS has been developed in a working range of 20 pg-10 ng per well. The tissue concentrations of PZS in gall bladder were 127.40, 145.86, and 276.96 micro g/g body mass in sea lamprey, Pacific lamprey, and western brook lamprey, respectively. Releasing rates for PZS in the three species were measured using ELISA to find that western brook and sea lamprey released PZS 20 times higher than Pacific lamprey did. Further studies are required to determine whether PZS is a chemical cue in Pacific and western brook lampreys.     

Population ecology of the sea lamprey (<Emphasis Type="Italic">Petromyzon marinus</Emphasis>) as an invasive species in the Laurentian Great Lakes and an imperiled species in Europe

The sea lamprey Petromyzon marinus (Linnaeus) is both an invasive non-native species in the Laurentian Great Lakes of North America and an imperiled species in much of its native range in North America and Europe. To compare and contrast how understanding of population ecology is useful for control programs in the Great Lakes and restoration programs in Europe, we review current understanding of the population ecology of the sea lamprey in its native and introduced range. Some attributes of sea lamprey population ecology are particularly useful for both control programs in the Great Lakes and restoration programs in the native range. First, traps within fish ladders are beneficial for removing sea lampreys in Great Lakes streams and passing sea lampreys in the native range. Second, attractants and repellants are suitable for luring sea lampreys into traps for control in the Great Lakes and guiding sea lamprey passage for conservation in the native range. Third, assessment methods used for targeting sea lamprey control in the Great Lakes are useful for targeting habitat protection in the native range. Last, assessment methods used to quantify numbers of all life stages of sea lampreys would be appropriate for measuring success of control in the Great Lakes and success of conservation in the native range.     

In vitro and in vivo effects of GABA, muscimol, and bicuculline on lamprey GnRH concentration in the brain of the sea lamprey (Petromyzon marinus)

gamma-Aminobutyric acid (GABA) is a neurotransmitter with a demonstrated neuroregulatory role in reproduction in most representative species of vertebrate classes via the hypothalamus. The role of GABA on the hypothalamus-pituitary axis in lampreys has not been fully elucidated. Recent immunocytochemical and in situ hybridization studies suggest that there may be a neuroregulatory role of GABA on the gonadotropin-releasing hormone (GnRH) system in lampreys. To assess possible GABA-GnRH interactions, the effects of GABA and its analogs on lamprey GnRH in vitro and in vivo were studied in adult female sea lampreys (Petromyzon marinus). In vitro perfusion of GABA and its analogs at increasing concentrations (0.1-100 microM) was performed over a 3-h time course. There was a substantial increase of GnRH-I and GnRH-III following treatment of muscimol at 100 microM. In in vivo studies, GABA or muscimol injected at 200 microg/kg significantly increased lamprey GnRH concentration in the brain 0.5 h after treatment compared to controls in female sea lampreys. No significant change in lamprey GnRH-I or GnRH-III was observed following treatment with bicuculline. These data provide novel physiological data supporting the hypothesis that GABA may influence GnRH in the brain of sea lamprey.     

Efficacy of animal anti-fertility compounds against sea lamprey (Petromyzon marinus) spermatozoa

Sterile-male-release technique is currently used to control the sea lamprey (Petromyzon marinus) population in the Great Lakes. The chemosterilant (bisazir) used in this program is extremely hazardous; special safety measures are necessary when handling this chemical. Therefore, replacement of bisazir with safer agents is desirable. In this study, we examined the effects of low-toxicity compounds with previously described spermicidal activity (mainly against mammalian sperm) on motility and fertilizing ability of sea lamprey spermatozoa. Nonoxynol-9, benzalkonium chloride, zinc acetate, cupric chloride, cysteamine, tannic acid and propranolol were able to inhibit both sperm motility and fertilizing ability. Effective concentrations of these spermicides ranged from 0.15 to 1%. Therefore, they can be potentially used in further study directed at in vivo sterilization of male sea lampreys.     

15Alpha-hydroxyprogesterone in male sea lampreys, Petromyzon marinus L

There is growing evidence that sea lampreys, Petromyzon marinus L., produce gonadal steroids differing from those of other vertebrates by possessing an additional hydroxyl group at the C15 position. Here we demonstrate that sea lamprey testes produce 15alpha-hydroxyprogesterone (15alpha-P) in vitro when incubated with tritiated progesterone, that 15alpha-P is present in the plasma of sea lampreys, and that plasma concentrations of immunoreactive (ir) 15alpha-P rise dramatically in response to injections of gonadotropin-releasing hormone (GnRH). The identity of the tritiated 15alpha-P produced in vitro was confirmed by co-elution with standard 15alpha-P on high performance liquid chromatography, co-elution with standard and acetylated 15alpha-P on thin layer chromatography, and specific binding to antibodies raised against standard 15alpha-P. The in vitro conversion was used to produce tritiated 15alpha-P label for a radioimmunoassay (RIA), which is able to detect 15alpha-P in amounts as low as 2 pg per tube. The RIA has been used to measure the plasma concentrations of 15alpha-P in males given two serial injections, 24 h apart, of either lamprey GnRH I or GnRH III (50, 100, or 200 microg/kg) or saline control, with plasma being sampled 8 and 24 h after the second injection. Plasma concentrations of ir-15alpha-P rose from < 1 to 36 ng/ml (mean of all treatments) 8 h after injection and declined within 24 h. This is the first time that an RIA has detected such high steroid concentrations in lampreys. This finding is suggestive of a role for 15alpha-P in control of reproduction in the sea lamprey.     

Shifting patterns of nitrogen excretion and amino acid catabolism capacity during the life cycle of the sea lamprey (Petromyzon marinus)

The jawless fish, the sea lamprey (Petromyzon marinus), spends part of its life as a burrow-dwelling, suspension-feeding larva (ammocoete) before undergoing a metamorphosis into a free swimming, parasitic juvenile that feeds on the blood of fishes. We predicted that animals in this juvenile, parasitic stage have a great capacity for catabolizing amino acids when large quantities of protein-rich blood are ingested. The sixfold to 20-fold greater ammonia excretion rates (J(Amm)) in postmetamorphic (nonfeeding) and parasitic lampreys compared with ammocoetes suggested that basal rates of amino acid catabolism increased following metamorphosis. This was likely due to a greater basal amino acid catabolizing capacity in which there was a sixfold higher hepatic glutamate dehydrogenase (GDH) activity in parasitic lampreys compared with ammocoetes. Immunoblotting also revealed that GDH quantity was 10-fold and threefold greater in parasitic lampreys than in ammocoetes and upstream migrant lampreys, respectively. Higher hepatic alanine and aspartate aminotransferase activities in the parasitic lampreys also suggested an enhanced amino acid catabolizing capacity in this life stage. In contrast to parasitic lampreys, the twofold larger free amino acid pool in the muscle of upstream migrant lampreys confirmed that this period of natural starvation is accompanied by a prominent proteolysis. Carbamoyl phosphate synthetase III was detected at low levels in the liver of parasitic and upstream migrant lampreys, but there was no evidence of extrahepatic (muscle, intestine) urea production via the ornithine urea cycle. However, detection of arginase activity and high concentrations of arginine in the liver at all life stages examined infers that arginine hydrolysis is an important source of urea. We conclude that metamorphosis is accompanied by a metabolic reorganization that increases the capacity of parasitic sea lampreys to catabolize intermittently large amino acid loads arising from the ingestion of protein rich blood from their prey/hosts. The subsequent generation of energy-rich carbon skeletons can then be oxidized or retained for glycogen and fatty acid synthesis, which are essential fuels for the upstream migratory and spawning phases of the sea lamprey's life cycle.     

The presence of teleost-type angiotensin components in lamprey buccal gland suggests a role in endocrine mimicry

Previous characterization of a native lamprey angiotensin II (LpAng II) that possesses a different sequence and function than teleost-type angiotensin II (Ang II) has raised a question as to the role of teleost-type angiotensin peptides in lampreys. In this study, teleost-type angiotensin like-peptides were identified in the buccal gland of lampreys by immunoassays and immunohistochemistry. The possible sources of angiotensin like-peptides were investigated in lampreys by manipulating their choice of host and food. Ang II immunoreactivity (irAng II) was detected in the buccal gland and plasma of feeding phase sea lampreys exposed to Atlantic cod, but was mostly absent in fasting lamprey. Qualitatively, the HPLC profiles of irAng II observed in the plasma, when present, were highly similar to those in buccal gland, implying that the buccal gland could be a source of plasma Ang II. Japanese lampreys force-fed with dogfish blood had significantly elevated concentrations of irAng II in their buccal glands when compared to unfed individuals, suggesting that feeding stimuli may have enhanced buccal gland activity. Teleost-type Ang II-containing proteins, other than angiotensinogen, are present in the buccal gland as trypsinization generated Ang II in vitro, and the HPLC profile of these irAng II was highly comparable to those naturally present in the buccal gland. [Asn¹, Val⁵, Thr⁹]-Ang I that was identified in the buccal gland of Japanese lampreys has the same amino acid sequence to those previously isolated from the incubation of plasma and kidney extract, providing an alternative explanation for the previous isolation of teleost-type Ang I in lampreys. irAng I and irAng II were localized in the granule-like structures in the apical region of the secretory epithelia, suggesting that these peptides may be active components of lamphredin. The teleost-type angiotensin peptides in the buccal gland secretion suggested that these host-specific peptides could be part of the endocrine mimicry strategy used by lampreys to evade host immune responses and reduce immune-rejection.     

Variations in the presence of chloride cells in the gills of lampreys (Petromyzontiformes) and their evolutionary implications

Although confined to fresh water, non‐parasitic species of lampreys and the landlocked parasitic sea lamprey, all of which were derived relatively recently from anadromous ancestors, still develop chloride cells, whose function in their ancestors was for osmoregulation in marine waters during the adult parasitic phase. In contrast, such cells are not developed by the non‐parasitic least brook lamprey Lampetra aepyptera, which has been separated from its ancestor for >2 million years, nor by the freshwater parasitic species of the genus Ichthyomyzon. The length of time that a non‐parasitic species or landlocked parasitic form or species has spent in fresh water is thus considered the overriding factor determining whether chloride cells are developed by those lampreys.     

Downstream migration and hematophagous feeding of newly metamorphosed sea lampreys (Petromyzon marinus Linnaeus, 1758)

The metamorphosis of sea lamprey (Petromyzon marinus Linnaeus, 1758) allows young postmetamorphic individuals to migrate to the sea and start the hematophagous feeding. However, the information about this phase is very limited, especially for European populations. Herein, we provide for the first time a comprehensive study on the phenology of downstream migration, the timing and location of first feeding and the prey species in the River Ulla and its estuary (NW Spain). Results show that downstream migration occurs between October and May with a peak in March. At least for a part of the postmetamorphic lampreys this migration stops for several months when they reach the estuary, where lampreys find shelter and abundant food, before moving to coastal waters. Hematophagous feeding in the estuary allows postmetamorphics to increase their total length and weight exponentially. Our results also suggest that part of the postmetamorphics (10–30%) start the hematophagous feeding in the river, with a special affinity for anadromous species, probably because of their larger size.     

Icelandic lampreys (<Emphasis Type="Italic">Petromyzon marinus</Emphasis>): where do they come from?

The recent discovery of sea lamprey wounds on salmonids in Icelandic rivers prompted an investigation on the origin of sea lampreys in Icelandic waters. Using a mitochondrial DNA fragment, the origin of the lampreys examined was assigned to the European stock and not to the North American one.     

Not so much a sea bass: Divergent European sea bass (Dicentrarchus labrax L.) freshwater incursions

European sea bass (Dicentrarchus labrax [Linnaeus, 1758]) is a euryhaline marine migrant fish highly valuable for fisheries and aquaculture. Although juveniles are known to use estuaries and occasionally move to freshwater environments, these freshwater incursions had not been reported for adults. Recently, this behavior was observed in the Tagus River (Portugal) for adults occurring up to 150 km from the river mouth, about 80 km upstream from the tidal influence, suggesting the existence of a freshwater contingent. Fisheries management of sea bass should consider the putative existence of a freshwater contingent.     

Morphological analysis of geographic variation of sea lamprey ammocoetes in Portuguese river basins

The main objective of this study was to compare the morphological variability of sea lamprey (Petromyzon marinus L.) larvae from the main Portuguese river basins. Samples were collected in rivers Minho, Lima, Cávado, Vouga, Mondego, Tejo and Guadiana. Specimens were analysed in terms of morphometric (linear body measures) and meristic (number of myomeres) characters to investigate the hypothesis of population fragmentation between river basins caused by some degree of homing behaviour. The discriminant analysis showed a morphological segregation of the studied populations based on the characters head, tail and branchial length. The discriminatory power of the meristic characters was comparatively weaker, with the number of trunk myomeres, and to some extent the head myomeres, being responsible for the reduced separation between groups. Both analyses were consistent in identifying the cephalic region as the most important morphological feature to discriminate populations of sea lamprey larvae in the Portuguese territory. The largest cephalic region of the ammocoetes sampled in the northern river basins may be responsible for a better feeding efficiency and, consequently, higher values of condition factor. Guest editors: S. Dufour, E. Prévost, E. Rochard & P. Williot Fish and diadromy in Europe (ecology, management, conservation)     

Peculiarities of Ultraviolet Absorption Spectra of Lamprey and Rat Brain Lipid Extracts and Their Correlation with Fatty Acid Composition

The ultraviolet (UV) absorption spectra of rat and lamprey brain lipid extracts have been studied. It was found that in both species the absorption of UV light took place, the shift of the absorption spectra to the more long-wave region being observed in the lamprey brain lipid extract. The established fact indicate the presence of oxidation products of lipids and their diene conjugates in the studied extracts, i.e., the appearance of the conjugated system of unsaturated bonds in the phospholipid molecules. The shift of the spectra to the more long-wave region in lampreys indicates a possible difference in the amount of polyenoic fatty acids in lamprey phospholipids. It was found that in lampreys it is predominantly the products of oxidation of phosphotidylcholine fatty acids, which shift the absorption spectrum to the more long-wave region. These are docosahexaenoic (C22:6 3), docosapentaenoic (C22:5 3), and eicosapentaenoic acids (C20:5 3). It is suggested that the membrane construction itself provides the basis for the energy accumulation.     

Neuroendocrine and behavioral responses to weak electric fields in adult sea lampreys (Petromyzon marinus)

We characterized the behavioral and neuroendocrine responses of adult sea lampreys (Petromyzon marinus) to weak electric fields. Adult sea lampreys, captured during upstream spawning migration, exhibited limited active behaviors during exposure to weak electric fields and spent the most time attached to the wall of the testing arena near the cathode (−). For adult male sea lampreys, exposure to weak electric fields resulted in increased lamprey (l) GnRH-I mRNA expression but decreased lGnRH-I immunoreactivities in the forebrain, and decreased Jun (a neuronal activation marker) mRNA levels in the brain stem. Similar effects were not observed in the brains of female sea lampreys after weak electric field stimulation. The influence of electroreception on forebrain lGnRH suggests that electroreception may modulate the reproductive systems in adult male sea lampreys. The changes in Jun expression may be associated with swimming inhibition during weak electric field stimulation. The results for adult sea lampreys are the opposite of those obtained using parasitic-stage sea lampreys, which displayed increased activity during and after cathodal stimulation. Our results demonstrate that adult sea lampreys are sensitive to weak electric fields, which may play a role in reproduction. They also suggest that electrical stimuli mediate different behaviors in feeding-stage and spawning-stage sea lampreys.     

The haematophagous feeding stage of anadromous populations of sea lamprey Petromyzon marinus: low host selectivity and wide range of habitats

Limited information is available regarding habitat use and host species of the haematophagous feeding stage of the anadromous sea lamprey Petromyzon marinus Linnaeus, 1758, due to the difficulties in capturing feeding lampreys and wounded hosts. The aim of this study is to provide new records of P. marinus feeding on host species and to review the available information in this regard to better know the ecology and distribution of sea lamprey during this stage. Thus, new records of P. marinus individuals or wounds on 23 species of fishes and cetaceans are provided. Nineteen of these species were described for the first time as hosts of P. marinus. As a result, an updated list of 54 host species is provided. They belong to diverse taxonomic groups and exhibit different morphological, physiological and ecological patterns. The attacks were located from fresh and brackish waters to open sea. The results suggest that the marine distribution of P. marinus is mainly related to coastal areas with part of the population widely dispersed in offshore areas. This remarkable capacity of inhabiting a broad range of aquatic ecosystems and exploiting different host species could have favoured the dispersal ability and evolutionary success of sea lamprey.