Synapseudes marinae Bâlcu, 2025

Synapseudes marinae Bâlcu sp. nov.

Figs 1 View Figure 1 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10 , Tables 1 View Table 1 , 2 View Table 2 , 3 View Table 3

Material examined.

Holotype • 1 ovigerous female with four eggs in marsupium, length about 1.6 mm (No. 250671) GoogleMaps . Paratypes • 1 female with oostegites, length about 1.8 mm (No. 250672); 1 female with empty marsupium, destroyed for DNA sequencing; 1 non-ovigerous female, dissected (permanent slide); from Greece, Sea of Crete, north of Crete Island, Bay of Malia, Milatos Beach , 35°19.22'N, 25°34.37'E, depth 0.4–0.5 m; from algae on rocks, rocky bottom; 23 October 2023; leg. Dr. Oana Paula Popa and Dr. Andrei Ștefan GoogleMaps .

Topotypes • 7 females (3 females with oostegites, 2 ovigerous females, 1 non-ovigerous female, 1 female with empty marsupium) and 2 manca I (No. 250673): 3 females destroyed (1 with oostegites, dissected, temporary slide; 1 with oostegites; 1 ovigerous for DNA sequencing); same collection data as holotype and paratypes; 18 June 2024; leg. Maxim-Jean Bâlcu, Dr. Oana Paula Popa and Dr. Andrei Ștefan GoogleMaps .

Other material.

• 5 females (2 females with oostegites, 2 females with empty marsupium, 1 ovigerous) and 12 manca I (No. 250674): 1 manca I and 1 female with oostegites dissected for SEM analyses; 2 females with empty marsupium destroyed for DNA sequencing; from Greece, Sea of Crete, north of Crete Island, Bay of Malia , 35°19.54'N, 25°34.94'E, depth 0.5 m; from algae on rocks, rocky bottom; 18 June 2024; leg. Maxim-Jean Bâlcu GoogleMaps • 2 females (1 female with oostegites, 1 female with empty marsupium) and 2 manca I (No. 250675): 1 female with empty marsupium used for SEM analyses; from Greece, Sea of Crete, north of Crete Island, near Xepapadeas Beach , 35°20.22'N, 25°44.96'E, depth 0.3–0.5 m; from algae on rocks, rocky bottom; 18 June 2024; leg. Maxim-Jean Bâlcu GoogleMaps • 3 females (1 ovigerous female, 1 female with oostegites, 1 female with empty marsupium) and 11 manca I (No. 250676): 1 female with oostegites dissected for SEM analyses; 1 manca I destroyed for DNA sequencing; from Greece, Sea of Crete, north of Crete Island, near Xepapadeas Beach , 35°20.27'N, 25°44.94'E, depth 0.3–0.5 m; from algae on rocks, rocky bottom; 18 June 2024; leg. Maxim-Jean Bâlcu GoogleMaps • 2 ovigerous females and 9 manca I (No. 250677): 1 manca I destroyed for DNA sequencing; from Greece, Mediterranean Sea, south of Crete Island , 35°1.2'N, 26°4.63'E, depth 0.5 m; from algae on rocks, sandy-rocky bottom; 19 June 2024; leg. Maxim-Jean Bâlcu GoogleMaps • 1 ovigerous female and 3 manca I (No. 250678): 1 manca I destroyed for DNA sequencing; from Greece, Sea of Crete, Kalydon Island , 35°15.56'N, 25°45.27'E, depth 0.5 m; from algae on rocks, rocky bottom; 20 June 2024; leg. Maxim-Jean Bâlcu GoogleMaps .

Type locality.

Greece, Sea of Crete, north of Crete Island, Bay of Malia, Milatos Beach, 35°19.22'N, 25°34.37'E.

Diagnosis.

Adult females body length 1.4–2.3 mm. Rostrum long and wide at base; anterior margin concave and rugose; with rows of scales. Pereonites 1–6 with one seta (apparently plumose) on each anterolateral corner. Pereonites 1–3 with one very small simple seta on each posterolateral corner. Pereonites 4–6 with three, two, and one setae, respectively, on each posterolateral corner. Pereonite 3 longest. Each pereonite much wider than long; rounded laterally. Pleonite 1 longer and wider than second. Pleotelson with mid row of 10 long apparently plumose setae and two small simple setae dorsally; one long apparently plumose and one small simple seta posterolaterally; two apparently plumose setae on apex caudo-dorsally. Antennule peduncle with four articles; articles 2 and 4 wider than long; first article longer than remaining articles combined; inner margin with two sharp thick and four rounded denticles. Inner flagellum with two articles; second article with three simple setae and one penicillate seta terminally. Outer flagellum with three articles; last article with four long simple setae and one penicillate seta terminally. Antenna peduncle with four articles; flagellum biarticulate, small, with four long thick setulate setae terminally. Maxilliped first palp article with one simple seta on inner side and one long thick bipinnate spine in outer distal corner. Article 2 largest; with six simple and four setulate setae on inner margin; one long thick bipinnate setiform spine on outer distal corner. Pereopod 1 basis with three or four dorsal apophyses; pereopods 2, 3 basis with one to three dorsal apophyses. Pereopod 1 propodus with three (rarely four) spines and one simple seta ventrally. Pereopods 2, 3 propodus with three (rarely four) spines. Pereopods 4–6 carpus with six, two, and one ventral spines, respectively. Pereopods 4–6 propodus with two small ventral spines.

Description of non-ovigerous female (dissected paratype).

Body (Figs 5 A View Figure 5 , 7 A, B View Figure 7 ) short, relatively cylindrical, 4.8 times as long as wide; length about 1.5 mm.

Cephalothorax (Figs 5 A View Figure 5 , 7 A, B View Figure 7 ) (including rostrum) approximately 25 % of body length, about 1.3 times as long as wide. Rostrum (Figs 5 B View Figure 5 , 8 D View Figure 8 ) long and wide at base, with anterior margin concave and rugose, and with rows of scales. Ocular lobes undefined; visual elements with dark pigment; one very small simple seta present under eyes. Carapace with two pairs of mid-dorsal simple setae, one medial simple seta on lateral sides, and two very small posterodorsal simple setae.

Pereon (Figs 5 A View Figure 5 , 7 A, B View Figure 7 ) approximately 61 % of body length, about 2.4 times as long as carapace length; each pereonite much wider than long and rounded laterally. Pereonite 3 longest, about 0.6 times as long as wide. All pereonites with one seta (apparently plumose) on each anterolateral corner. Pereonites 1–3 with three pairs of dorsal setae, the longest ones apparently plumose, and one very small simple seta on each posterolateral corner. Pereonite 4 with four pairs of dorsal setae, the longest ones apparently plumose; one apparently plumose seta and two very small simple setae on each posterolateral corner. Pereonites 5 and 6 with five pairs of dorsal setae, the longest ones apparently plumose; two simple setae and one simple seta, respectively, on each posterolateral corner.

Pleon (Figs 5 A View Figure 5 , 7 A, B View Figure 7 ) approximately 14 % of body length, consisting of two free pleonites and pleotelson. Pleonite 1 longer and wider than second, with one apparently plumose seta laterally and a row of nine apparently plumose setae dorsally. Pleonite 2 with a row of eight apparently plumose setae dorsally. Each pleonite expanded posterolaterally into a small spiniform process.

Pleotelson (Figs 5 A View Figure 5 , 7 A, B View Figure 7 ) about 1.6 times as long as combined length of pleonites, somewhat triangular; with acute apex in dorsal view, and crest-like in lateral view (Fig. 5 C View Figure 5 ), with a row of 10 long apparently plumose setae and two small simple setae dorsally; one long apparently plumose seta and one small simple seta posterolaterally; two apparently plumose setae on apex, caudo-dorsally.

Antennule (Figs 5 D View Figure 5 , 8 A, B View Figure 8 ). Peduncle with four articles; first article longest, about 1.6 times as long as wide; inner margin with six denticles (two mid-sharp thick and four rounded), two simple setae and some scales distally; outer margin with two penicillate, two long simple setae, and one setulate seta; four penicillate setae on ventral surface, subterminally; two penicillate and about three small setae on dorsal surface. Articles 2 and 4 wider than long. Article 2 about 0.4 times as long as article 1, with inner and outer distal dentiform prolongations; two small simple setae on inner margin, and three setulate setae and one simple seta on outer margin distally; five penicillate setae on ventral surface, terminally. Article 3 much narrower and about 0.9 times as long as article 2, with one simple and one setulate seta on inner margin and one simple seta on outer margin distally. Article 4 (common) 0.5 times as long as article 3, with two simple setae inner distally and a small notch for insertion of outer flagellum with one penicillate seta. Inner flagellum with two articles; first article with one simple and one penicillate seta inner distally; second article with two long thick simple setae, one small simple seta, and one penicillate seta terminally. Outer flagellum slightly longer than inner one, with three articles; first article with one aesthetasc and two simple setae on inner distal corner, two simple setae on outer corner; article 2 with two long simple setae and one aesthetasc; article 3 with four long simple setae and one penicillate seta terminally.

In ventral view, common article 4 appears to consist of two parts and the peduncle of only three articles; outer flagellum with four articles; inner flagellum with three articles (Fig. 8 B View Figure 8 ).

Antenna (Figs 5 E View Figure 5 , 8 C View Figure 8 ) (without terminal setae) smaller than first peduncular article of antennule. Peduncle with four articles. First article wider than long, with an inner dentiform expansion bearing many hairs and some rows of scales. Articles 2 and 3 wider than long. Article 2 about 0.5 times as long as article 1, with rows of scales, two sharp denticles, and one small simple seta on inner margin, and one small simple seta on outer distal corner. Article 3 shortest, about 0.7 times as long as article 2; outer and inner margins slightly denticled, with one small simple seta on inner distal corner. Article 4 longer than articles 2 or 3, with inner and outer distal dentiform prolongations; one mid-inner and five terminal penicillate setae; one long setulate seta, subterminally. Flagellum biarticulate, small; first article naked; second article minute, with four long thick setulate setae, terminally. Squama absent.

Labrum (Figs 5 F View Figure 5 , 8 G View Figure 8 ) with many long setulae and with a conical projection, anteriorly directed.

Mandibles (Figs 5 G, H View Figure 5 , 8 H – K View Figure 8 ) with three-articled palp; article 1 about 2.7 times as long as wide, naked; article 2 about 2.5 times as long as wide, naked; article 3 smallest, with two unequal setulate setae, terminally. Pars molaris without distinctive features. Pars incisiva of left mandible (Figs 5 G View Figure 5 , 8 H, I View Figure 8 ) wide, without conspicuous denticles; lacinia mobilis with four rounded denticles; setiferous lobe with three finely serrated setae. Pars incisiva of right mandible (Figs 5 H View Figure 5 , 8 J, K View Figure 8 ) wide, without conspicuous denticles; setiferous lobe with three finely serrated setae and one stout furcate seta.

Labium (Figs 5 I View Figure 5 , 8 L View Figure 8 ) with numerous setulae along outer margin of basal lobe and rostral area, on anterior part. Palp narrow, ovate, with numerous setulae on outer margin and two small fine spines, terminally.

Maxillule (Figs 5 J View Figure 5 , 8 M, N View Figure 8 ) with biarticled palp ending in two long unequal setulate setae. Outer endite with 10 narrow spines (two denticled), terminally; one small simple seta, subterminally; and numerous setulae on outer margin (Fig. 5 J View Figure 5 ). Inner margin with small sharp denticles; inner endite with four terminal setulate setae and numerous setulae on outer margin (Fig. 5 J View Figure 5 ).

Maxilla (Fig. 5 K View Figure 5 ) with outer lobe of movable endite bearing six long simple setae distally; outer margin with setulae. Inner lobe of movable endite with about six setae. Outer lobe of fixed endite with three simple setae, two stout furcate setae, and three serrated setae. Inner lobe of fixed endite with a row of eight setae (thicker at base), followed distally by two robust bipinnate setae; inner margin with small denticles.

Maxilliped (Figs 5 L View Figure 5 , 8 E View Figure 8 ) with basis 1.1 times as long as wide, naked. First palp article short and broad, with one simple seta on inner side and one long, thick bipinnate spine on outer distal corner. Article 2 largest, narrower proximally, with six simple and four setulate setae on inner margin; one long, thick bipinnate setiform spine on outer distal corner. Article 3 smaller than article 2, with four stout serrated setae and five finely serrated setae on inner margin. Article 4 smaller than previous articles, with three serrated setae subterminally; seven unequal serrated setae and one small simple seta on inner side. Endite (Figs 5 M View Figure 5 , 8 F View Figure 8 ) with one long simple seta and seven setulate truncate setae, and many hairs on rostral side; one curved simple seta subterminally. Inner margin with five circumplumose setae and two coupling hooks; outer margin with hairs.

Epignath (Fig. 5 N View Figure 5 ) narrow, curved; margins with many hairs; one long distal spine, longer than half the length of epignath.

Cheliped (Figs 6 A View Figure 6 , 9 A View Figure 9 ). Basis about 1.4 times as long as wide, broad, oval ventrally, with one mid and one distal simple seta, ventrally; dorsal margin with some scales. Exopod absent. Merus subtriangular, 3.7 times as long as wide, extended ventrally about half length of carpal margin; two very small proximal and two distal simple setae, ventrally. Carpus two times as long as wide, with two distal simple setae, ventrally; one distal simple seta, dorsally. Propodus as long as carpus; palm with one long and one small simple seta on outer face; one long simple seta and two small serrated setae near dactylus joint on inner face. Fixed finger thick, with two ventral simple setae, four submarginal simple setae in distal third of fixed finger, and two inner simple setae near claw; cutting edge with about 10 rounded denticles; claw small, orange-brown. Dactylus as wide as fixed finger; cutting edge proximally with two or three rounded denticles; three simple setae near claw on inner face; claw stout, orange-brown, stronger than fixed finger and with bidentate tip.

Pereopod 1 (Figs 6 B View Figure 6 , 9 B, C View Figure 9 ) largest. Exopod absent. Basis 3.2 times as long as wide; ventral margin with three small simple setae; four apophyses interspersed by four small simple setae dorsally; two penicillate setae on outer face. Ischium very short, 0.3 times as long as wide, with one long ventral simple seta. Merus 1.6 times as long as wide; ventral margin with one small and three long simple setae and one spine; one small simple seta and one robust spine dorsally. Carpus shorter than merus, about as long as wide; two spines and two simple setae ventrally; two outer subdistal spines; one robust spine and two long simple setae dorsally. Propodus 1.8 times as long as wide, with three (Fig. 9 B View Figure 9 ), rarely four (Figs 6 B View Figure 6 , 9 C View Figure 9 ) spines and one simple seta ventrally; two outer subdistal spines; one penicillate seta, one robust spine and one long simple seta dorsally; one subdistal small inner serrated seta near dactylus articulation, ventrally. Dactylus with two small ventral setae; unguis short and curved.

Pereopod 2 (Figs 6 C View Figure 6 , 9 D View Figure 9 ). Basis 3.4 times as long as wide; ventral margin with two small distal simple setae; three mid-apophyses, one small simple seta and two penicillate setae, dorsally. Ischium very short, 0.3 times as long as wide, with one ventral simple seta. Merus 1.6 times as long as wide; ventral margin with two small and two long simple setae; one small simple seta and one robust spine, dorsally. Carpus shorter than merus, about as long as wide; one simple seta and four spines, ventrally; two outer subdistal spines; one long simple seta and one slender spine, dorsally. Propodus about 2.3 times as long as wide; three ventral spines (increasing in size distally); two outer subdistal spines; one penicillate seta, one robust spine and one long simple seta, dorsally; one subdistal small inner serrated seta near dactylus articulation, ventrally. Dactylus and unguis similar to that of pereopod 1, but smaller.

Pereopod 3 (Figs 6 D View Figure 6 , 9 E View Figure 9 ) smaller than pereopod 2. Basis 4.1 times as long as wide; ventral margin with three small simple setae and one proximal penicillate seta; two mid-apophyses, two small simple and two penicillate setae, dorsally. Ischium short, 0.4 times as long as wide, with one long ventral simple seta. Merus 1.7 times as long as wide; ventral margin with four simple setae; one slender spine and one simple seta, dorsally. Carpus shorter than merus, 1.3 times as long as wide; three spines and one simple seta, ventrally; two outer subdistal spines; one distal simple seta, dorsally. Propodus 1.7 times as long as wide; three ventral spines (increasing in size distally); two outer subdistal spines; one penicillate seta, one very long simple seta and one robust spine, dorsally; one subdistal small inner serrated seta near dactylus articulation, ventrally. Dactylus and unguis similar to that of pereopod 2, but smaller.

Pereopod 4 (Figs 6 E View Figure 6 , 9 F View Figure 9 ). Basis 4.6 times as long as wide; three small simple setae, ventrally; two penicillate setae, dorsally. Ischium very short, 0.2 times as long as wide, with one long simple seta, ventrally. Merus 1.2 times as long as wide; four simple setae and one subdistal small spine, ventrally; one slender spine, dorsally. Carpus slightly shorter than merus, 1.5 times as long as wide; six spines (in three pairs) and one simple seta, ventrally; one subdistal small seta; one robust spine and one simple seta, dorsally. Propodus slightly longer than merus or carpus, about two times as long as wide; two small (one mid and one subdistal) spines, ventrally; one penicillate seta and three inner and three outer serrated setae, dorsally. Dactylus slightly curved, with two small ventral setae; unguis short and curved.

Pereopod 5 (Figs 6 F View Figure 6 , 9 G View Figure 9 ). Basis 3.2 times as long as wide; three small simple setae, ventrally; two penicillate and two small simple setae on the outer face; two penicillate setae, dorsally. Ischium short, 0.4 times as long as wide, with two simple setae, ventrally. Merus 1.6 times as long as wide; four simple setae, ventrally; one distal robust spine, dorsally. Carpus shorter than merus, about as long as wide; two spines and two simple setae, ventrally; one spine and two simple setae, dorsally. Propodus 2.6 times as long as wide; two small (one mid, one subdistal) spines and one simple seta, ventrally; one outer simple seta; one penicillate and one serrated seta, dorsally. Dactylus and unguis as in pereopod 4.

Pereopod 6 (Figs 6 G View Figure 6 , 9 H View Figure 9 ). Basis 3.7 times as long as wide; four small simple setae, ventrally; one small simple seta on the outer face; two penicillate setae, dorsally. Ischium short, 0.5 times as long as wide, with two simple setae, ventrally. Merus 1.5 times as long as wide; three simple setae, ventrally; one distal spine, dorsally. Carpus shorter than merus, 1.1 times as long as wide; two simple setae and one small spine, ventrally; one slender spine and one long simple seta, dorsally. Propodus 2.8 times as long as wide; two small (one mid, one subdistal) spines, ventrally; one outer simple seta; one penicillate and one serrated seta, dorsally. Dactylus thick, with two small ventral setae; unguis robust and curved.

Pleopods absent.

Uropod (Fig. 6 H View Figure 6 ) short, peduncle 2.1 times as long as wide, with an inner apophysis and two unequal simple setae outer distally. Exopod with two articles; first article 2.5 times longer than second, with one simple seta; second article with two long unequal simple setae, terminally. Endopod with three articles; first article largest, with one distal simple seta; second article with one distal small simple seta; third article with three long simple setae and one penicillate seta, terminally.

Male. Unknown.

Some remarks about manca I.

Body (Fig. 7 C View Figure 7 ) length 0.7–1.0 mm. Pereopods 1–3 propodus always with two ventral spines (n = 39).

Etymology.

Dedicated to Marina Hărățu, the mother of the first author, in gratitude for her unwavering efforts, patience, and support in all aspects of his life.

Intraspecific variation.

S. marinae sp. nov. displays some degree of variation among the 23 females examined in this study: (1) number of dorsal apophyses of pereopod 1 basis varies between three-four; (2) number of dorsal apophyses of pereopods 2, 3 basis varies between one-three; (3) out of 23 adult females, 17 adult females (74 %) have the left and right pereopods 1–3 propodus with three spines and one simple seta, ventrally, and six adult females (26 %) have the left and right pereopods 1–3 propodus with three-four spines and one simple seta, ventrally.

Size-distribution.

Manca I body length ranged from 0.7 to 1.0 mm (n = 39). Non-ovigerous females body length ranged from 1.5 to 2.1 mm (n = 2). Females with oostegites body length ranged from 1.6 to 2.2 mm (n = 7). Ovigerous females body length ranged from 1.4 to 1.78 mm (n = 6). Females with empty marsupium body length ranged from 1.7 to 2.3 mm (n = 4).

Distribution and habitat.

Crete Island (Sea of Crete and Mediterranean Sea), Greece; from algae on the rocks ( Jania sp. , Liagora sp. , Cladophora sp. , Corallina sp. ), rocky bottom (Fig. 1 View Figure 1 ).

Remarks.

The new species distinguished from the other Mediterranean Synapseudes species by the following characters: (1) the length and shape of the rostrum: long and wide at the base, with anterior margin concave and rugose, and with rows of scales; (2) a much higher number and disposition of dorsal setae on the cephalothorax, pereon, pleon and pleotelson; (3) the number and the disposition of anterior and posterior lateral setae on the pereon, pleon and pleotelson; (4) pereonite 3 longest; (5) the length of the pleonites: pleonite 1 longer and wider than the second one; (6) length and width of the articles of the antennule peduncle: articles 2, 4 are wider than long; (7) the number and shape of the denticles on the inner margin of antennule article 1: two sharp thick and four rounded denticles; (8) antenna flagellum: biarticulate; (9) number of dorsal apophyses of pereopods 1–3 basis: three-four, one-three and one-three, respectively; (10) outer subdistal spines of pereopods 1–3 propodus: two spines; (11) ventral spines of pereopods 1–3 propodus: three-four; and (12) ventral spines of pereopods 4–6 carpus: six, two and one, respectively.

Some of the new species diagnostic characters, listed above, are presented in a structured form in Table 2 View Table 2 .

Twenty-six percent of analyzed specimens (six adult females out of 23 adult individuals) show variation of three or four ventral spines between left and right pereopods 1–3 propodus of the same individual, but never four ventral spines simultaneously on both left and right pereopods 1–3 propodus, as observed in all adult specimens of S. mediterraneus .

Genetic information.

A 610 bp fragment of the cytochrome c oxidase subunit I (COI) gene obtained from a specimen of Synapseudes sp. nov. (PV 748674), representing the first publicly available sequence record for a Synapseudes species in GenBank and BOLD Systems.

The sequence contained 235 polymorphic sites, of which 203 were parsimony-informative and 32 singleton variable sites. The best-fitting nucleotide substitution model for the COI dataset: HKY with gamma-distributed rate variation among sites.

To assess genetic divergence, pairwise genetic distances calculated between species within the same genus, providing a comparative framework with other tanaid genera. For example, genetic distances among Leptochelia species ranged from 25 % to 28 %. Intraspecific distances also estimated for well-represented species in BOLD and GenBank (Table 3 View Table 3 ). Genetic distance observed for Synapseudes sp. nov.: 28 %.

The Bayesian inference phylogenetic tree (Fig. 10 View Figure 10 ) confirmed that Synapseudes marinae sp. nov. belongs to Metapseudidae , clustering with another Synapseudes species. However, Metapseudidae , represented by the three genera Synapseudes , Calozodion , and Pseudoapseudomorpha , recovered as polyphyletic.

Our analysis further revealed that Tanaidomorpha is not monophyletic, with Tanaidacea and Leptocheliidae nested within some Apseudomorpha taxa ( Apseudidae , Metapseudidae , Parapseudidae ), consistent with Drumm (2010). In contrast, monophyly of Kalliapseudidae strongly supported in this phylogeny and previous studies ( Drumm and Heard 2011). Broader taxon sampling and inclusion of additional molecular markers needed to further test this hypothesis and generate a more robust phylogeny.