Anali za istrske in mediteranske študije
Annali di Studi istriani e mediterranei
Annals for Istrian and Mediterranean Studies
Series Historia Naturalis, 35, 2025, 1
UDK 5                       Annales, Ser. hist. nat., 35, 2025, 1, pp. 1-170, Koper 2025  ISSN 1408-533X
KOPER 2025
Anali za istrske in mediteranske študije
Annali di Studi istriani e mediterranei
Annals for Istrian and Mediterranean Studies
Series Historia Naturalis, 35, 2025, 1
UDK 5                    ISSN 1408-533X 
                e-ISSN 2591-1783
ANNALES · Ser. hist. nat. · 35 · 2025 · 1
Anali za istrske in mediteranske študije - Annali di Studi istriani e mediterranei - Annals for Istrian and Mediterranean Studies
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e-ISSN 2591-1783
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ANNALES · Ser. hist. nat. · 35 · 2025 · 1
Anali za istrske in mediteranske študije - Annali di Studi istriani e mediterranei - Annals for Istrian and Mediterranean Studies
UDK 5                                                      Letnik 35, Koper 2025, številka 1                                      ISSN 1408-53 3X
e-ISSN 2591-1783 
VSEBINA / INDICE GENERALE / CONTENTS
BIOTSKA GLOBALIZACIJA
GLOBALIZZAZIONE BIOTICA
BIOTIC GLOBALIZATION
Okan AKYOL, Oğuzhan TAKICAK & 
Hasan TARUN
A Fugitive Lessepsian Fish in a Sea-Cage 
Farm in the Aegean Sea: Stephanolepis 
diaspros (Monacanthidae) ................................
Ubežni lesepski migrant iz ribogojnice 
v Egejskem morju: Stephanolepis 
diaspros (Monacanthidae)
Nicola BETTOSO, Lisa FARESI, Valentina 
TORBOLI & Jose A. CUESTA
Additional Record of the Pea Crab 
Pinnotheres bicristatus (Brachyura: 
Pinnotheridae) in the Adriatic Sea ....................
Dodatni zapis o pojavljanju stražne 
rakovice vrste Pinnotheres bicristatus 
(Brachyura: Pinnotheridae) 
v Jadranskem morju
Alan DEIDUN, Sarah BAUMANN, 
Bruno ZAVA & Maria CORSINI-FOKA
Confirming the Occurrence of the 
Non-Indigenous Pteragogus trispilus 
(Actinopterygii: Labridae) within 
Maltese Waters ................................................
Potrditev pojavljanja tujerodne ustnače 
vrste Pteragogus trispilus (Actinopterygii: 
Labridae) znotraj malteških voda
Deniz ERGÜDEN, Yusuf Kenan BAYHAN, 
Sibel ALAGÖZ ERGÜDEN & Deniz AYAS
A New Ichthyological Record and 
Distributional Update for Epigonus 
denticulatus Dieuzeide, 1950 in 
Turkish Mediterranean Waters ...........................
Nov ihtiološki zapis in podatki o 
razširjenosti rjavega veleokca, Epigonus 
denticulatus Dieuzeide, 1950 v turških 
sredozemskih vodah
Sara LADOUL, Farid HEMIDA, 
Christian REYNAUD & Christian CAPAPÉ
On the Occurrence of Cornish Blackfish 
Schedophilus medusophagus 
(Osteichthyes: Centrolophidae) 
from the Maghreb Shore 
(Southwestern Mediterranean Sea) ...................
Potrjena prisotnost meduzojeda 
Schedophilus medusophagus 
(Osteichthyes: Centrolophidae) 
z magrebske obale (jugozahodno 
Sredozemsko morje)
Christina MICHAIL & Francesco TIRALONGO
First Occurrence of Ariidae in 
Cypriot Waters – a Major 
Contribution to Biodiversity .............................
Prvo pojavljanje predstavnikov iz 
družine Ariidae v ciprskih vodah – 
velik prispevek k biodiverziteti
SREDOZEMSKE HRUSTANČNICE
SQUALI E RAZZE MEDITERRANEE
MEDITERRANEAN SHARKS AND RAYS
Lovrenc LIPEJ, Riccardo BATTISTELLA, 
Borut MAVRIČ & Danijel IVAJNŠIČ
An Insight into the Diet of the Bull Ray, 
Aetomylaeus bovinus (Geoffroy 
Saint-Hilaire, 1817) in the 
Northern Adriatic Sea ......................................
Vpogled v prehranjevalne navade 
kljunatega morskega goloba, 
Aetomylaeus bovinus (Geoffroy 
Saint-Hilaire, 1817) v severnem Jadranu
Cem ÇEVİK, Deniz ERGÜDEN & Deniz AYAS
A New Capture Record of Alopias 
superciliosus Lowe, 1841 from the 
Turkish Coast (Northeastern Mediterranean) ......
Nov ulov velikooke morske lisice 
Alopias superciliosus Lowe, 1841 
iz turške obale (severovzhodno Sredozemlje)
1
7
13
21
35
27
43
55
ANNALES · Ser. hist. nat. · 35 · 2025 · 1
Cem DALYAN, N. Bikem KESİCİ, Elif YÜCEDAĞ 
BAKIR, Yunus GÖNÜL & Hakan KABASAKAL
No Longer as Common as its Name: a Review 
of the Occurrence of Torpedo torpedo 
(Linnaeus, 1758) (Chondrichthyes: 
Elasmobranchii) in Turkish Waters, 
with Photographic Evidence .............................
Ni več tako pogost kot njegovo ime: pregled 
pojavljanja okatega električnega skata Torpedo 
torpedo (Linnaeus, 1758) (Chondrichthyes: 
Elasmobranchii) v turških vodah s 
fotografskimi dokazi
Deniz ERGÜDEN, Cemal TURAN, Servet Ahmet 
DOĞDU & Deniz AYAS 
Disc Deformity in a Juvenile Female Brown Ray, 
Raja miraletus (Family: Rajidae), from 
Northeastern Mediterranean (Türkiye) .................
Deformacija diska pri juvenilni samici modropege 
raže, Raja miraletus (družina: Rajidae), iz 
severovzhodnega Sredozemskega morja (Turčija)
Farid HEMIDA, Christian REYNAUD & 
Christian CAPAPÉ 
On an Old Record of the Smalltooth Sand Tiger 
Shark Odontaspis ferox (Chondrichthyes: 
Odontaspididae) from the Algerian Coast 
(Southwestern Mediterranean Sea) ........................
O starem zapisu o drobnozobem morskem biku 
Odontaspis ferox (Chondrichthyes: Odontaspididae) 
z alžirske obale (jugozahodno Sredozemsko morje)
Hakan KABASAKAL, Uğur UZER & 
F. Saadet KARAKULAK
Plastic Debris-Induced Fin Damage 
in the Smoothhound, Mustelus mustelus ..............
Poškodbe plavuti pri navadnem 
morskem psu, Mustelus mustelus, 
zaradi plastičnih odpadkov
Nicolas ZIANI, Florane TONDU, 
Rémi BRU, Chloé MOSNIER, 
Sarah FOXONET, Ruben Bao GALLIEN, 
Mathias POULY, Modan Lou TONIETTO, 
Lucille VERDON, Eloïse DEYSSON, 
Alessandro DE MADDALENA & 
Hakan KABASAKAL 
Bite Marks Observed on a Large Female 
White Shark Carcharodon carcharias 
Off Camargue, France Provide Potential 
Insights into the Reproduction of the 
Mediterranean Population ................................
Sledovi ugrizov na veliki samici 
belega morskega volka Carcharodon 
carcharias pri Camargu (Francija) 
kažejo na možno razmnoževanje 
sredozemske populacije
MORSKA FAVNA
FAUNA MARINA
MARINE FAUNA
Sihem RAFRAFI-NOUIRA, RIMEL 
BENMESSAOUD, Mourad CHÉRIF, 
Christian REYNAUD & Christian CAPAPÉ
Morphological Deformities in a 
Common Two-Banded Sea Bream, 
Diplodus vulgaris (Osteichthyes: Sparidae), 
from Northern Tunisian Waters 
(Central Mediterranean Sea) ............................
Morfološke deformacije pri fratru, 
Diplodus vulgaris (Osteichthyes: Sparidae), 
iz severnih tunizijskih vod 
(osrednje Sredozemsko morje)
Abdelkarim DERBALI, Aymen HADJ TAIEB & 
Wassim KAMMOUN
The Current Status of Polititapes aureus 
(Mollusca: Bivalvia) in the Coastal 
Zone of Sfax, Tunisia 
(Central Mediterranean) ....................................
Trenutno stanje vrste Polititapes aureus 
(Mollusca: Bivalvia) na obalnem 
območju Sfaxa v Tuniziji 
(osrednje Sredozemlje)
Neža LEBAN & Valentina PITACCO
Current Knowledge on the Distribution 
of the Poorly Known Echiurid Species 
Maxmuelleria gigas (M. Müller, 1852) 
in the Slovenian Sea .........................................
Trenutno poznavanje prostorske 
razporeditve manj poznane vrste 
zvezdaša Maxmuelleria gigas 
(M. Müller, 1852) v slovenskem morju
Jan MALEJ, Tjaša KOGOVŠEK, 
Martin VODOPIVEC, Janja FRANCÉ, 
Patricija MOZETIČ, Matevž MALEJ & 
Alenka MALEJ
Long-Term Study of Zooplankton 
Biomass in the Gulf of Trieste (Adriatic Sea) ......
Dolgoročna študija zooplanktonske 
biomase v Tržaškem zalivu 
(Jadransko morje)
Sihem RAFRAFI-NOUIRA, 
Rimel BENMESSAOUD, Mourad CHÉRIF, 
Christian REYNAUD & Christian CAPAPÉ
Occurrence of the Longjaw Snake Eel, 
Ophisurus serpens (Ophichthidae), in 
Tunisian Waters (Central Mediterranean Sea) .....
Pojavljanje zobate jegulje, Ophisurus 
serpens (Ophichthidae), iz tunizijskih 
voda (osrednje Sredozemsko morje)
83
73
91
65
125
117
109
133
145
97
ANNALES · Ser. hist. nat. · 35 · 2025 · 1
FLORA
FLORA
FLORA
Martina ORLANDO-BONACA, Artur BONACA, 
Diego BONACA & Ana ROTTER
Seagrasses: a Promising Source of 
Bioactive Compounds for Human 
Health Applications ..........................................
Morske cvetnice: obetaven vir 
bioaktivnih spojin za uporabo 
v zdravstvu
OCENE IN POROČILA
RECENSIONI E RELAZIONI
REVIEWS AND REPORTS
Shin-ichi Uye
Book review: Mirrors of the Sea: When 
Science and Art Meet. 30 Years of the 
Unesco Intergovernmental Oceanographic 
Commission in Slovenia ...................................
Kazalo k slikam na ovitku ...................................
Index to images on the cover ............................
153 167
169
169
ANNALES · Ser. hist. nat. · 35 · 2025 · 1
125
received: 2025-04-14                 DOI 10.19233/ASHN.2025.16
CURRENT KNOWLEDGE ON THE DISTRIBUTION OF THE POORLY 
KNOWN ECHIURID SPECIES MAXMUELLERIA GIGAS (M. MÜLLER, 1852) 
IN THE SLOVENIAN SEA
Neža LEBAN & Valentina PITACCO
Marine Biology Station Piran, National Institute of Biology, Fornače 41, 6330 Piran, Slovenia
e-mail: leban.neza@gmail.com
ABSTRACT
In September 2024, a specimen of Maxmuelleria gigas (M. Müller, 1852) was found during a monitoring 
campaign in the Bay of Koper. This record is the second one of this less known macrobenthic species in 
the Slovenian Sea and one among few up to date reported in the Adriatic Sea, as well. Sediment mounds 
observed with an underwater video sledge on muddy bottom in the southern part of the Gulf of Trieste have 
been related to this species. The species distribution and density (47 per 100 m2) were estimated based 
on the quantification of the observed sediment mounds. The potential underestimation of the density and 
distribution of this species in the Gulf of Trieste in the past studies is discussed in relation to sampling method. 
Key words: Echiura, sediment mounds, videotransects, Northern Adriatic
CONOSCENZA ATTUALE DELLA DISTRIBUZIONE DI MAXMUELLERIA GIGAS (M. 
MÜLLER, 1852), SPECIE DI ECHIURIDE POCO CONOSCIUTA, NEL MARE SLOVENO
SINTESI
La prima segnalazione di Maxmuelleria gigas (M. Müller, 1852) nelle acque slovene risale al 2020. In 
settembre 2024, è stato rinvenuto un secondo esemplare di questa specie durante una campagna di monitorag-
gio nella Baia di Capodistria. Durante alcuni campionamenti con l’uso di una videocamera subacquea sui 
fondali fangosi nella parte meridionale del golfo di Trieste, sono stati rilevati dei coni di sedimento che vengono 
attribuiti a questa specie. La distribuzione e la densità della specie (47 per 100m2) è stata stimata sulla base del 
conteggio dei cumuli di sedimento osservati. Viene discussa la potenziale sottostima della densità e della dis-
tribuzione di questa specie nel Golfo di Trieste nei lavori precedenti, in relazione al metodo di campionamento. 
Parole chiave: Echiura, cumuli di sedimento, videotransetti, Nord Adriatico
ANNALES · Ser. hist. nat. · 35 · 2025 · 1
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Neža LEBAN & Valentina PITACCO: CURRENT KNOWLEDGE ON THE DISTRIBUTION OF THE POORLY KNOWN ECHIURID SPECIES MAXMUELLERIA GIGAS ..., 125–132
INTRODUCTION
Named for their spoon-like proboscis, the Echiura 
or spoon worms, are present in soft-bottom marine 
environments from the intertidal to the deep sea (Bis-
eswar, 2009; Hughes et al., 1996a). The pelagic stage 
in their larval development, as well as their ability 
to withstand wide range of temperature and salinity, 
enables them to colonize vast areas from the Atlan-
tic to the Indo-West Pacific ocean (Biseswar, 2009, 
2012). Out of the six species known in the Mediter-
ranean (Murina, 1984) only two have been recorded 
in the Adriatic Sea: Bonellia viridis (Zavodnik, 2016) 
and Maxmuelleria gigas (Atkinson et al., 1998; Minelli 
et al., 2003; Simonini et al., 2007). While the first has 
been observed in the past (Lipej & Vrišer, 1999; Sket, 
2003), the latter was only recently recorded for the 
first time in the Slovenian Sea (Pitacco, 2020). 
The species of the genus Maxmuelleria inhabit-
ing soft sediments build U-shaped burrows, 42 cm 
deep (Nickell et al., 1995), with two openings on the 
surface that can be up to 100 cm apart (Hughes et 
al., 1996b). One of the openings is used primarily for 
feeding while the other serves as an excretory vent for 
the sediment discharge. Animals were observed to be 
located towards one side of the burrow, from where 
they extend their spoon-like proboscis to collect the 
surface sediments (Hughes et al., 1996a), carrying it 
towards the funnel-shaped opening, measuring 4 cm 
in diameter (Nickell et al., 1995). The expulsion of 
sediment in the form of a blow or fluidized slurry on 
the other side of the tunnel can result in a formation 
of a sediment mound around the opening, which can 
grow up to 60 cm wide and 30 cm high (Moore et 
al., 2013) in the shape of a dome or a sharp cone. 
While the active ejection of sediment can be observed 
throughout the day, the appearance of proboscis, 
retracting suddenly when shined on by a light, could 
only be recorded by night with an infrared-sensitive 
camera (Hughes et al., 1996a). All information on the 
burrow structure and feeding activity was derived from 
the observation of Maxmuelleria lankesteri (Herdman, 
1897) in the Northern Atlantic. However, besides 
some differences in the distribution of papillae on 
proboscis, M. lankesteri and M. gigas are believed to 
be closely related species, which some authors con-
sider the same (Stephen & Edmonds, 1972).
Active specimens of Maxmuelleria lankesteri 
were usually observed with an underwater television 
camera (Hughes et al., 1996a) or while SCUBA diving 
(Nickell et al., 1995). The shape of their burrows was 
described based on the shape of resin casts, where 
polyester or epoxy material was poured into the bur-
row to obtain its shape when hardened (Seike et al., 
2012). The few records reporting the species M. gigas 
in the Adriatic mostly rely on the observation of active 
proboscis (Atkinson et al., 1998) and the presence 
of sediment mounds (Zavodnik, 2016) for species 
identification. Recently, a live specimen was caught 
off Koper, Slovenia, which confirmed the presence of 
M. gigas in Slovenian waters (Pitacco, 2020). The 
present study introduces the second record of M. gigas 
in the Slovenian Sea, as well as the estimated distribu-
tion of the species, which was derived from integrated 
point sampling data obtained with Van Veen grab and 
visual data obtained with underwater video transects. 
MATERIAL AND METHODS
A specimen of M. gigas was captured on September 
23rd, 2024, during a monitoring project of soft-bottom 
macrofauna in the waters of Slovenia, North Adriatic 
(Fig. 1). Sediment samples were taken with the Van Veen 
grab (0.1 m2) at a depth of 22.3 m at the sampling loca-
tion (45.591667°N, 13.666667°E), 2.8 km west of the 
Punta Grossa, on a soft-bottom sediment floor; 53% silt, 
27% clay and 20% sand with 40-50% carbonate content 
(Ogorelec et al., 1991). The specimen was pinched with 
the grab scoop, which caused damage to the body wall 
and evisceration. The animal was released after being 
photographed. Van Veen grab is used for sampling of 
infaunal species, present in the upper layers of the sedi-
ment (Mackie et al., 2007).  
Linear video transects of the soft bottom were 
recorded by a video sledge (SKIKAM) during an 
observation of circalittoral benthic habitats in the 
Slovenian Sea. The study was carried out by the 
Marine Biology Station, Piran (National Institute 
of Biology, Slovenia) from 2021 to 2023 under the 
project "An upgrade on knowledge of biotic and 
abiotic characteristics and extent of benthic habitat 
types of circalittoral coarse sediments (MC3), circal-
ittoral mixed sediments (MC4) and circalittoral sands 
(MC5)" (Mavrič et al., 2023). The transects covered 
an area of 13046 m2, with a mean depth of 22.4 
m and pelite content ranging from 20% to 60%. In 
this study, cone-shaped structures associated with 
Maxmuelleria burrows were observed and counted. 
The sediment mounds surrounding a burrow opening 
were mostly observed individually; occasionally, 
two to three mounds were merged with the respec-
tive number of openings observed on top. The count-
ing criteria included the presence of an open burrow 
opening (not closed with sediment) surrounded by 
a sediment mound; in the case of merged mounds, 
one opening was counted as one mound. The sign 
of activity was marked in case of a light colored 
sediment (fluidized slurry) present on top of a mound 
around the opening as described by Hughes et al. 
(1996a) and Atkinson et al.(1998). Occasionally, 
blows of sediment were observed coming from the 
top of the mound. The mound density was calculated 
in relation to the surface area covered by the video 
transects, analyzed for this study (5166.6 m2). 
ANNALES · Ser. hist. nat. · 35 · 2025 · 1
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Neža LEBAN & Valentina PITACCO: CURRENT KNOWLEDGE ON THE DISTRIBUTION OF THE POORLY KNOWN ECHIURID SPECIES MAXMUELLERIA GIGAS ..., 125–132
RESULTS AND DISCUSSION
The specimen collected in 2024 represents the 
second record of Maxmuelleria gigas in the Slove-
nian Sea. It measured 11 cm in total length and was 
identified as M. gigas (M. Müller, 1852) based on a 
non-bifid proboscis and a green colored sausage-
like body (Fig. 1A). Green coloration of the echiurid 
is not related to chlorophyll, but instead comes 
from a chlorin pigment bonellin, which has proven 
to cause cytolysis and toxic effects on spermatozoa 
and echinoid egg development (Agius et al., 1979). 
The cytolysis and other effects turned out to be 
accelerated by light (photodynamic action), which 
could serve as a defense mechanism if released in 
the environment in the presence of predators (Agius 
et al., 1979).  
Sediment mounds (Fig. 1B), have been observed 
in high quantities (47 per 100 m2; overall surface 
area 5166 m2) during the sampling of the seafloor by 
a video-sledge (SKIKAM) in the northeastern part of 
the Gulf of Trieste (Fig. 2). They were similar to those 
associated with Maxmuelleria lankesteri in Scotland 
(Hughes et al., 1996b). The mounds were mostly 
observed individually (75%) and with clear openings 
(99.6%), where signs of activity were scarcely present 
(3%), mostly in the form of fluidized slurry around the 
opening. Most of the time, these mounds had other 
openings on the sides or in their vicinity, probably 
made by other burrowing species of crustaceans (e.g. 
Squilla mantis, Nephrops norvegicus) and fish. The 
black goby (Gobius niger) was observed dwelling near 
the burrow openings (0.9 per 100 m2), where it fled 
once the video-sledge approached; the brown comber 
(Serranus hepatus) was observed hiding behind the 
mounds (2 per 100 m2), carefully observing the ap-
proaching sledge before fleeing the field of view; one 
sighting of a fleeing shrimp included a tail disappear-
ing into one of the holes on the side of a sediment 
mound. 
The mounds were observed in higher density (81 
per 100 m2; surface area 2243.2 m2) on predominantly 
muddy seafloor with high proportions of silt (50–60%) 
in the inner parts of the Gulf of Trieste, on the southern 
opening of the Bay of Koper (Fig. 2, green). The density 
of mounds decreased (17 per 100 m2; surface area 3297 
m2) moving off-shore, where silt content in bottom sedi-
ments is lower (40–50%) (Fig. 2, blue). Silt content in 
sediments is known as a key factor influencing benthic 
communities in the studied area (Pitacco et al., 2023). 
Higher density of mounds in the areas with larger pro-
portion of silt can be related to the high detritus quantity 
in the surface sediment layers favoring the establishment 
of detritus-feeding macrobenthic communities (Rosen-
berg, 1995; Pan & Pratolongo, 2021). 
Similar structures to sediment mounds were de-
scribed in the area offshore Ancona, Italy (Atkinson et 
al., 1998) and related to M. gigas as the only sediment-
burrowing species of echiurids recorded in the Adriatic 
Sea (Zavodnik, 2016). These structures have been re-
lated to M. gigas due to the emergence of the proboscis, 
observed by underwater television recordings first by 
Atkinson et al. (1998) in Ancona and later recorded 
by divers in the area of Fiesa, Slovenia, in March 2023 
(C. Mlinar Cic & B. Mavrič, personal communication). 
In the latter, the proboscis was observed retracting into 
the inhalant burrow, carrying a load of sediment into 
the opening in an action resembling a conveyor belt. 
Fig. 1: Maxmuelleria gigas. A) Whole specimen, ventral view, B) sediment mounds, associated with M. gigas, found 
on the soft bottom in the Gulf of Trieste.
Sl. 1: Maxmuelleria gigas. A) Primerek s trebušne strani, B) sedimentni hribčki povezani z M. gigas, najdeni na 
sedimentnem dnu v Tržaškem zalivu.
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Neža LEBAN & Valentina PITACCO: CURRENT KNOWLEDGE ON THE DISTRIBUTION OF THE POORLY KNOWN ECHIURID SPECIES MAXMUELLERIA GIGAS ..., 125–132
However, no systematic sampling of these organisms 
has been done in the Northern Adriatic, which would 
provide direct association of each burrow and sediment 
mound to the presence of this species; therefore, we 
cannot assume the exclusivity of other burrowing fauna 
creating or inhabiting these kinds of sediment mounds. 
While the activity of the proboscis leaves little doubt in 
the identification, the mound structures of M. gigas can 
otherwise be recognized by a layer of ejected sediment 
of different color around the opening, with occasionally 
present faecal pellets 2-4 mm long and 0.7-1 mm wide 
(Hughes et al., 1996a).
Some species of burrowing shrimp (Necallianassa 
truncata, Gliyossius tyrrhenea, Jaxaea nocturna) create 
similar sediment mounds around one of the burrow 
openings, however, the size of the mound is usually 
smaller than the one of M. gigas (Pervesler & Dworschak, 
1985; Moore et al., 2013), while the other opening is 
usually in the shape of a funnel (Ziebis et al., 1996; 
Dworschak, 2001). Other species of sediment-dwelling 
shrimp usually build burrows with more than two 
openings (Upogebia pusilla, U. tipica, Squilla mantis, 
Nephrops norvegicus), which have a sediment excrete 
present around the opening, but never in the shape of 
a discrete mound (Rice & Chapman, 1971; Atkinson et 
al., 1997, 1998; Dworschak, 2004). Other burrowing 
species present on the soft muds of the Northern Adriatic 
(Solecurtus strigilatus, Brachynotus gemmellari, Gobius 
niger) were also observed on the same grounds as the 
mounds of M. gigas (Nickell et al., 1995; Moore et al., 
2013), however, their burrow structures do not resem-
ble the ones associated with the echiurid; S. strigilatus 
builds burrows swith openings flush with the surface, 
3 – 6 cm apart (Dworschak, 1987); the burrows of 
B. gemmellari are a shallow excavation, with only one 
opening (Atkinson et al., 1998); G. niger usually settles 
in abandoned shrimp burrows, where it modifies one of 
the openings to create a chamber close to the surface 
(Atkinson et al., 1998). 
Despite biannual samplings of sediment grabs along 
the Slovenian coast from 2007 onward (http://www.
arso.gov.si/vode/podatki/), this species was considered 
rare in the Northern Adriatic (Pitacco, 2020). Although 
grab sampling is used for collecting soft-bottom burrow-
ing fauna in the Northern Adriatic (Pitacco et al., 2023), 
grabs and corers are not suitable for deep-burrowing 
Fig. 2: A map of the study area in the Slovenian Sea. GPS positions of the video transects are marked in blue 
and green. The silt content in sediment (%) is marked by isoclines. The points in red present the GPS positions 
of the first (Pitacco, 2020; R1) and second record of this species (present work; R2). 
Sl. 2: Zemljevid obravnavanega območja slovenskega morja. Z zeleno in modro barvo so označene GPS lokacije 
video transektov. Vsebnost pelita v sedimentu (%) je označena z izoklinami. Z rdečo sta označeni GPS lokaciji 
prvega (Pitacco, 2020; R1) in drugega zapisa o pojavljanju vrste (to delo; R2). 
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organisms, which live below the penetration of most 
samplers with the average sediment penetration depth 
20 cm, the deepest 45 cm (Mackie et al., 2007); while 
a relative species Maxmuelleria lankesteri burrow can 
reach up to 80 cm deep (Hughes et al., 1996b). The 
previous lack of records in the Northern Adriatic may be 
due to the limitation of this point-sampling method. The 
method of resin casts made from the hardened material 
in the shape of the mold is widely used for describing 
the morphology of burrows, mostly made by burrowing 
crustaceans (Pervesler & Dworschak, 1985; Atkinson et 
al., 1997; Dworschak, 2001) and gobies (Rice & John-
stone, 1972; Atkinson et al., 1998). However, it is not 
optimal for discovering the true occupancy of the bur-
row, especially for the echiuran species, where only the 
slight green coloration of the resin cast can hint at the 
presence of the animal (Hughes et al., 1996b). Sampling 
with ship-borne equipment and in situ with SCUBA are 
also limited by the surface of the area studied, while 
underwater television is more suitable to cover large 
areas of soft-sediment floor. 
The underwater television observation technique has 
proven efficient in the stock assessment of the Norwe-
gian shrimp (N. norvegicus) (Naseer et al., 2022), how-
ever, there is still too little information of the burrowing 
structure of M. gigas to completely exclude the doubts 
surrounding burrow identification, burrow detection, 
counting strategies and most importantly occupancy as-
sessment (Marrs et al., 1996). While the strategy of "one 
burrow, one animal" has been adjusted for the Norwe-
gian shrimp, further studies on the echiuran abundance 
in the Northern Adriatic are needed, before implement-
ing similar density estimation strategies.
Although the ecology of the genus Maxmuelleria 
is poorly known, studies from the Irish Sea suggest 
their great importance in the role of bioturbation of 
soft sediments, overturning 13 g of dry sediment a day 
(Hughes et al., 1996b). The sediment mounds on the 
seafloor also increase the surface area, consequently 
enhancing the benthic flux (King, 2011). The density of 
120 sediment mounds per m2 created by a burrowing 
shrimp Necallianassa truncata increased the surface 
of the sediment-water interface by 400% (Ziebis et 
al., 1996). Furthermore, oxygenation of upper sedi-
ment layers was increased by a factor of 1.5 on the 
seafloor with a high density of sediment mounds (22 
mounds per m2), where oxygen penetrated deeper 
(40 mm) around a mound than on a smooth surface 
(4 mm) (Ziebis et al., 1996). Besides increasing the 
surface-water interface area, the mounds create a 
more structured seafloor providing habitat also for 
bottom dwelling fish such as the black goby, which 
is known for its opportunistic use of burrows, mostly 
reworking the upper parts of the burrows of Maxmuel-
leria and infaunal shrimps (Squilla mantis, Callianassa 
subterranea) (Atkinson et al., 1998).  
The high number of sediment structures observed in 
the present work on video-recordings indicated that the 
true density and distribution of M. gigas, together with 
its ecological role, have been underestimated so far. 
ACKNOWLEDGEMENTS
This work was possible thanks to the financial sup-
port of the Agency for Environment within national 
monitoring of the Ecological status of coastal waters 
within the Republic of Slovenia, and of the Slovenian 
Research Agency (research core funding No. P1-0237).
The authors thank Tihomir Makovec, Tristan Bartole, 
Simone Spinelli and Moira Buršić for their help during 
sampling and Milijan Šiško for the help with graphic 
material. Thanks also to dr. Borut Mavrič and Ciril Mlinar 
Cic for their input. Special thanks to Prof. dr. Lovrenc 
Lipej for his advice and encouragement. 
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TRENUTNO POZNAVANJE PROSTORSKE RAZPOREDITVE MANJ POZNANE VRSTE 
ZVEZDAŠA MAXMUELLERIA GIGAS (M. MÜLLER, 1852) V SLOVENSKEM MORJU
Neža LEBAN & Valentina PITACCO
Morska biološka postaja Piran, Nacionalni inštitut za biologijo, Fornače 41, 6330 Piran, Slovenia
e-mail: leban.neza@gmail.com
POVZETEK
Septembra 2024 je bil najden osebek vrste Maxmuelleria gigas (M. Müller, 1852) med vzorčenjem v Koprskem 
zalivu. Poleg redkih opažanj te vrste v Jadranskem morju, ta najdba predstavlja drugega in enega od novejših zapisov 
pojavljanja te vrste v slovenskem morju. Sedimentni hribčki, opaženi z video sanmi na muljastem sedimentnem 
dnu v Tržaškem zalivu, so bili povezani z dejavnostjo te vrste. Razporeditev in gostota osebkov (47 na 100 m2) sta 
bili ocenjeni na podlagi pojavljanja sedimentnih hribčkov. Avtorici obravnavata morebitno podcenjenost gostote 
pojavljanja te vrste v Tržaškem zalivu, v povezavi z vzorčevalno metodo. 
Ključne besede: Echiura, sedimentni hribčki, podvodni videozapisi, severni Jadran
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