Ultrastructure of the spermatozoon of Macvicaria obovata (Digenea, Opecoelidae), a parasite of Sparus aurata (Pisces, Teleostei) from the Gulf of Gabès, Mediterranean Sea

The ultrastructural organization of the spermatozoon of the digenean Macvicaria obovata (Opecoelidae) is described by transmission electron microscopy. Alive digeneans were collected from the digestive tract of Sparus aurata (Teleostei, Sparidae), caught from the Gulf of Gabès in Chebba, Tunisia (Eastern Mediterranean Sea). The male gamete of M. obovata is a filiform cell, tapered at both extremities and exhibits typical characters such as two axonemes of different lengths showing the 9+'1' trepaxonematan pattern, a nucleus, mitochondria, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies and granules of glycogen. Cortical microtubules are absent in the anterior spermatozoon extremity and appear after the disappearance of the electron-dense material. The first mitochondrion is of moniliform type and it is associated with the external ornamentation of the plasma membrane and spine-like bodies. The second mitochondrion is more posteriorly located, reaching the nuclear region. The present study provides new data on the mature male gamete of M. obovata that may be useful for the understanding of digenean relationships and phylogenetic studies

Lessepsian migration and parasitism: richness, prevalence and intensity of parasites in the invasive fish Sphyraena chrysotaenia compared to its native congener Sphyraena sphyraena in Tunisian coastal waters

Background Parasites can play various roles in the invasion of non-native species, but these are still understudied in marine ecosystems. This also applies to invasions from the Red Sea to the Mediterranean Sea via the Suez Canal, the so-called Lessepsian migration. In this study, we investigated the role of parasites in the invasion of the Lessepsian migrant Sphyraena chrysotaenia in the Tunisian Mediterranean Sea. Methods We compared metazoan parasite richness, prevalence and intensity of S. chrysotaenia (Perciformes: Sphyraenidae) with infections in its native congener Sphyraena sphyraena by sampling these fish species at seven locations along the Tunisian coast. Additionally, we reviewed the literature to identify native and invasive parasite species recorded in these two hosts. Results Our results suggest the loss of at least two parasite species of the invasive fish. At the same time, the Lessepsian migrant has co-introduced three parasite species during the initial migration to the Mediterranean Sea, that are assumed to originate from the Red Sea of which only one parasite species has been reported during the spread to Tunisian waters. In addition, we found that the invasive fish has acquired six parasite species that are native in the Mediterranean Sea. However, parasite richness, prevalence and intensity were overall much lower in the invasive compared to the native fish host in the Mediterranean Sea. Discussion These results suggest that the Lessepsian migrant may affect native fish hosts by potentially altering the dynamics of native and invasive parasite-host interactions via parasite release, parasite co-introduction and parasite acquisition. They further suggest that the lower infection levels in the invasive fish may result in a competitive advantage over native fish hosts (enemy release hypothesis). This study demonstrates that cross-species comparisons of parasite infection levels are a valuable tool to identify the different roles of parasites in the course of Lessepsian migrations

Total mercury and selenium concentrations in Sarpa salpa and Balistes capriscus and in their respective Digenean endoparasites Robphildollfusium fractum and Neoapocreadium chabaudi from Tunisia

The present study reports the levels of mercury and selenium in Sarpa salpa and Balistes capriscus collected along the coast of Mahdia and Sfax (Tunisia). The systems constituted by S. salpa and Robphildollfusium fractum and by B. capriscus and Neoapocreadium chabaudi were tested as potential bioindicators to monitor environmental Hg pollution in marine ecosystems. Mercury and selenium concentrations were assessed in kidney, liver and muscle of 51 S. salpa and of 45 B. capriscus as well as in their respective endoparasites R. fractum and N. chabaudi. The Se:Hg molar ratios were evaluated for both species across the study areas. Surprisingly, the Se:Hg molar ratio in B. capriscus muscle from Mahdia is significantly lower than in Sfax. Our results indicate that some parasites may also be implicated in the amount of Se and Hg available in tissues and therefore contribute to oscillations of the Se:Hg molar ratios. In the model involving the carnivorous species (B. capriscus), the 5.1-times higher levels of mercury in N. chabaudi than in B. capriscus muscle in Sfax enable this fluke to be a sensitive biomonitoring tool for Hg pollution. The present results confirm that the habitual consumption of S. salpa should not suppose any potential health risk for Tunisian people. On the other hand, the consumption of B. capriscus may be of concern and further monitoring is advisable, since the Hg average concentration in Mahdia was above the maximum allowed Hg concentration in the edible portion of fish fixed by the European Union

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Triloculotrema euzeti n. sp. (Monogenea, Monocotylidae) from the nasal tissues of the blackspotted smooth-hound Mustelus punctulatus (Carcharhiniformes, Triakidae) from off Tunisia

Triloculotrema euzeti n. sp. (Monogenea, Monocotylidae, Merizocotylinae) is described from the nasal tissues of the blackspotted smooth-hound Mustelus punctulatus collected from the coastal marine waters off Tunisia. The new parasite species is distinguished from the other two species of the genus, T. japanicae Kearn, 1993 and T. chisholmae Justine, 2009, by the morphology of the sclerotised male copulatory organ which has longitudinal ridges. The species is also characterised by its oötype with short descending and ascending limbs (long and more convoluted in the other two species). The presence of three peripheral loculi, which is the main characteristic of the genus Triloculotrema Kearn, 1993, is unconfirmed. This is the first description of a species of this genus in the Mediterranean Sea and the first record from a coastal shark

Redescription de <i>Rhipidocotyle galeata</i> (Rudolphi, 1819) (Digenea, Bucephalidae), l’espèce type de<i> Rhipidocotyle</i> Diesing, 1907

Rhipidocotyle galeata (Rudolphi, 1819), l’espèce type du genre est redécrite en utilisant du matériel de Lichia amia (Linnaeus, 1758) (Actinopterygii, Perciformes) collecté dans le golfe de Gabès, sur les côtes tunisiennes de la Méditerranée. Rhipidocotyle galeata est comparée avec d’autres espèces du genre, incluant R. genovi, R. minima, R. triglae et R. viperae. Cette redescription fournit d’autres informations sur la position et la distribution des follicules vitellins qui forment un arc ne dépassant pas antérieurement le niveau de l’ovaire, sur l’étendue de l’utérus jusqu’au rhynchus et sur la position de l’ovaire à coté du testicule antérieur. Une clé des huit espèces du genre Rhipidocotyle de la Méditerranée est présentée.Rhipidocotyle galeata (Rudolphi, 1819), the type species of the genus, is redescribed using material from Lichia amia (Linnaeus, 1758) (Actinopterygii, Perciformes) collected from the Gulf of Gabès in the Mediterranean Sea off Tunisia. Rhipidocotyle galeata is compared with other nominal species of the genus, including R. genovi, R. minima, R. triglae and R. viperae. This redescription provides additional information about the position and the distribution of the vitelline follicles, which form an arc that does not extend anteriorly past the level of the ovary, an uterus that extends almost to the posterior margin of the rhynchus and an ovary that is positioned adjacent to the anterior testis. A key to the eight Rhipidocotyle species from the Mediterranean Sea is presented.</p

&lt;i&gt;Oesophagotrema mediterranea &lt;/i&gt;n. gen., n. sp. (Platyhelminthes, Digenea, Zoogonidae), parasite de la grande aiguille &lt;i&gt;Tylosurus acus imperialis&lt;/i&gt; (Beloniformes, Belonidae) en Tunisie

Oesophagotrema mediterranea n. gen., n. sp. (Digenea, Zoogonidae) est décrit chez la grande aiguille Tylosurus acus imperialis (Beloniformes, Belonidae) des côtes tunisiennes. Oesophagotrema n. gen. se distingue de tous les autres genres de Lepidophyllinae par une combinaison de caractères : ventouse ventrale arrondie et saillante, caeca intestinaux atteignant l’extrémité antérieure du testicule postérieur, des testicules arrangés en tandem dans le tiers moyen de l’espace post-acétabulaire et des vitellogènes latérales, symétriques, disposées en grappe entre l’ovaire et le testicule antérieur. Cette espèce montre une spécificité typique vis-à-vis du site d’infection, l’œsophage et les dents vomériennes. La position de ce Digène Zoogonidae dans l’œsophage est discutée.Oesophagotrema mediterranea n. gen., n. sp. (Digenea, Zoogonidae) is described from the needlefish Tylosurus acus imperialis (Beloniformes, Belonidae) off the Tunisian coast. Oesophagotrema n. gen. is distinguished from all other Lepidophyllinae genera by the combination of a prominent rounded ventral sucker, caeca reaching to the anterior edge of the posterior testis, testes arranged in tandem in the middle third of the hindbody and the vitellarium in symmetrical lateral bunches located between the ovary and anterior testis. This species shows a typical specific site of infection within the digestive tract, i.e., the oesophagus and vomer teeth. The position of this zoogonid digenean on the oesophagus is discussed.</p

Gonadal maturation and histological observations of the grey triggerfish Balistes capriscus Gmelin, 1789 (Teleostei: Balistidae) in the Gulf of Gabès, Tunisia

Objective: To determine the spawning activity using gonadosomatic index (GSI) and gonad histology the Balistes capriscus (Teleostei: Balistidae) of the Gulf of Gabès (Southern Tunisia, Central Mediterranean Sea). Methods: The reproductive biology of the species, based on 756 (480 females and 276 males), collected from commercial catches at several fishing ports including Chebba, Kerkennah and Zarzis at respective GPS coordinates (34°14' N, 11°06' E), (34°45' N, 11°17' E), (33°41' N, 11°48' E) was studied over 28 months (January 2008-April 2010) using GSI and gonad histology. Sizes used in this study ranged from 11.30 to 45.60 cm in fork length. Results: Both GSI and gonad histology suggest that spawning activity occurred mainly between July and mid-September with a peak in July, coinciding with summer time. The first maturation occurred at 20.26 cm fork length for females and 21.30 cm fork length for males. The monthly values of hepatosomatic index and condition factor (K) indicated that the liver is the main organ responsible for the mobilization process of the energizing reserves during the sexual cycle. Conclusions: It is the first inventory of gonadal maturation and histological observations of the grey triggerfish Balistes capriscus Gmelin, 1789 (Teleostei: Balistidae) in the Gulf of Gabès, (Southern Tunisia, Central Mediterranean Sea)