Prionospio multisetosa, Delgado-Blas & Peraza, 2024

Delgado-Blas, Víctor Hugo & Peraza, Russell Giovanni Uc, 2024, Two new species of Prionospio (Annelida: Spionidae) from the Northwest and Northeast Atlantic, Zootaxa 5432 (1), pp. 69-82 : 75-79

Prionospio multisetosa sp. nov.

Figures 4A–T ; 5A–B

Prionospio (Prionospio) dubia .— Maciolek, 1985: 336-339, figs. 2, 3 (in part, Sweden).

Prionospio dubia .— Sigvaldadóttir and Mackie, 1993: 211-215, figs. 6-8 (in part, Sweden, Scotland).

Material examined: NORTH ATLANTIC, North Sea, Sweden, Västra Götaland County, Skagerrak, Kosterfjord Kilesand , Sydkoster , East Sneholmer , 58.892ºN, 11.064ºE, 80–120 m, Warenslade , R/V NEREUS, coll. Andens Waren, 12 February 1995, holotype ( LACM-AHF POLY 14389 ) and 3 paratypes ( LACM-AHF POLY 4433 ) . Sweden, North Sea, Västra Götaland County, Skagerrak, Kosterfjord , South of Yttria Vatternholm Island, 58.871ºN, 11.105ºE to 58.869ºN, 11.109ºE, 110–113 m, silt and clay, biological dredge with fine mesh end, R/V NEREUS sta. LH-Tjarno 9, coll. Arne Nygren, Leslie H. Harris, 10 April 2002, LH02-250, non-type LACM-AHF Poly 4859 , 7 specimens. Sweden, Västra Götaland County, Skagerrak, Kosterfjord , Southwest of Yttre Vattenholmen island, 58.879ºN, 11.1ºE, 20–150 m, biological dredge with fine mesh end, R/V Nereus, 11 February 1995, coll. Arne Nygren, non-type LACM-AHF POLY 4432 , 4 specimens.

Description: Holotype complete: 37 mm long with 98 chaetigers, 0.7 mm wide; paratype complete: 11 mm long, 60 chaetigers, 0.2 mm wide; incomplete paratypes: 6–13 mm, 26–37 chaetigers, 0.4–0.6 mm wide. Color in alcohol, light brown. The numbers in parentheses refers to the variation in the largest and smallest paratypes. Some specimens reproductive, with oocytes present on chaetigers 20–78 (holotype, 22–81). Prostomium skittle-shaped, anteriorly rounded, with short, blunt caruncle reaching to posterior edge of chaetiger 1, with large nuchal organs on either side ( Figs 4A , 5A ). Eyes absent. Palps lost, except in one specimen with the right palp inserted anterior to the nuchal organs; palp with a short basal sheath, and with a frontal longitudinal groove lined with fine cilia ( Figs 4B , 5B ). Peristomium long, collar-like surrounding the prostomium, fusing dorsally with the large, wide, erect, rounded notopodial lamellae of chaetiger 1 ( Figs 4A, C , 5A ). Neuropodial postchaetal lamellae on chaetiger 1 large, tongue-shaped with rounded edges, slightly smaller than the notopodial lamellae ( Figs 4A, C , 5A ).

Four pairs of branchiae present on chaetigers 2–5 ( Figs 4A, C , 5A ). First pair robust and fourth pair slender, both pairs with long digitiform pinnules and very short naked distal tips ( Figs 4A, C , 5A, B ). First pair of branchiae two to three times the length of the other pairs, with dense posterior pinnules ( Figs 4A, C , 5A, B ), extending up to chaetiger 5; fourth pair short with dense pinnules arranged along the outer lateral margin, not covering posterior faces ( Figs 4A, C , 5A ), slightly longer than the notopodial lamellae ( Figs 4A, C , 5A ). Central stem of branchial pairs 1 and 4 pinnate, elongate; pair 1 with articulations ( Fig. 5A, B ), pair 4 smoother (less articulated). Pairs 2 and 3 apinnate, subtriangular, thick ( Figs 4A, C , 5A ), with dense lateral ciliation and sharply pointed short tips ( Figs 4D , 5A ), subequal in length, slightly smaller than notopodial lamellae ( Figs 4A, C , 5A ).

Notopodial postchaetal lamellae of chaetigers 2–5 triangular, slender with pointed short tips, and with narrow, rounded bases ( Figs 4F–H , 5A ), except the lamella on chaetiger 2 which has a small subtriangular ventral edge ( Fig. 4C, E ); lamellae largest on chaetigers 3–5 ( Figs 4A, C , 5A ), then gradually decreasing in size and becoming rounded on chaetigers 14–15 (holotype, 14) ( Figs 4A , 5A ); lamellae thereafter rounded, wide, extending slightly onto dorsum from chaetigers 19–25 (holotype, 25) ( Fig. 4J ), but never connected along the dorsal ridge or crest; lamellae on following chaetigers similarly broadly rounded ( Fig. 4L ) and with the chaetal row located in the ventral region of the noto-lamella, decreasing in size in posteriormost segments. Anterior notopodial prechaetal lamellae very low ( Figs 4C , 5B ), lamellae becoming rounded, moderate in size on chaetigers 13–33 (holotype, 18–33) ( Fig. 4A ), then rudimentary throughout. No dorsolateral skin folds.

Neuropodial postchaetal lamellae of chaetiger 2 oval ( Fig. 4C, E ), lamellae of chaetiger 3 subtriangular with blunt dorsal edge to oval ( Fig. 4F ) (left or right parapodial lamellae sometimes rectangular) ( Fig. 5B ), lamellae of chaetiger 4 rounded ( Figs 4C , 5B ), and subsequent neuropodial lamellae also rounded ( Figs 4 J-L, 5B), smallest on far posterior chaetigers. Neuropodial prechaetal lamellae very low ( Fig. 4 E-H), rudimentary throughout. Interparapodial pouches lacking.

Anterior chaetigers with numerous thick ( Fig. 5B ) and very long chaetae with the appearance of brushes, later decreasing in number, becoming thin and even longer ( Fig. 4L ), easily broken on middle chaetigers. Notopodial and neuropodial capillaries smooth, alimbate, arranged in one row on chaetiger 1; from chaetiger 2 onwards all notochaetae long, heavily granulated, unilimbate ( Fig. 4M ), arranged in four rows ( Fig. 4N ); around chaetiger 14, granulation of capillaries diminishes, capillaries arranged in two rows. Middle and posterior capillaries smooth, long, and slender. Neuropodial chaetae on chaetigers 2–5 with smooth, unilimbate capillaries ( Fig. 4O ), arranged in two rows; from chaetiger 6 onwards neuropodial capillaries moderately granulated, alimbate and with long tips ( Fig. 4P ) on both rows. Neuropodial hooded hooks ( Fig. 4Q ) from chaetigers 19–22 (holotype, 22) (smaller specimen, 16), up to nine per fascicle, accompanied by slender capillaries. Notopodial hooded hooks ( Fig. 4R ) from chaetigers 50–55 (holotype, 55) (smaller specimen, 46), up to six per fascicle, accompanied by four or five capillaries; hooks with three pairs of teeth above the main tooth, secondary hood absent ( Fig. 4Q, R ). Sabre chaetae from chaetigers 19–24 (holotype, 21) (smaller specimen, 14), up to two per neuropodium, each chaeta heavily granulated, basally radial and alimbate ( Fig. 4S ).

Pygidium with very short slender mid-dorsal cirrus and two small lateral lobes ( Fig. 4T ).

Methyl green staining pattern. Dorsal and ventral surfaces of the anterior region of the prostomium and the tips of the anterior notopodial postchaetal lamellae stained, but staining quickly lost; rest of the body unstained.

Remarks. Prionospio multisetosa sp. nov. is very similar to P. dubia Day, 1961 , P. jonatani Delgado-Blas, 2015 , and Prionospio gayheadia sp. nov. Prionospio multisetosa sp. nov. is similar to P. dubia Day, 1961 , as regards the first pair of branchiae with pinnules 4–5 times as long as notopodial lamellae, the first and fourth pairs pinnate branchiae with short naked distal tips. However, Prionospio multisetosa sp. nov. can be distinguished from the original description of P. dubia Day, 1961 and the redescriptions of P. dubia given by Wilson (1990), in that the former has no eyes, independent of the size of the animal; the first pair of branchiae are shorter, only extending up to chaetiger 5; whereas in P. dubia the first pair of branchiae extend up to chaetiger 7; in P. multisetosa sp. nov. the fourth pair of branchiae are slightly longer than, or equal to the notopodial lamellae; whereas in P. dubia the fourth pair of branchiae are 2/3 longer. In P. multisetosa sp. nov. the fourth pair of branchiae only have pinnules on the outer lateral margin of the branchial axis; the notopodial lamellae extend slightly onto the dorsum of chaetigers 14– 37; whereas in P. dubia the fourth pair of branchiae have many pinnules on posterior surfaces, and the notopodial lamellae do not extend onto the dorsum. In P. multisetosa sp. nov. the notopodial prechaetal lamellae are well-developed on or around chaetigers 13–33, whereas in P. dubia the lamellae are very low; in P. multisetosa sp. nov. the neuropodial postchaetal lamellae on chaetiger 3 are subtriangular with blunt dorsal edges, to oval, whereas in P. dubia are ovoid. In addition, the structure of the anterior chaetae show morphological differences, thus Prionospio multisetosa sp. nov. has neuropodial chaetae on chaetigers 2–5 that are smooth capillaries, whereas in P. dubia are granulated capillaries. The structure of the notopodial and neuropodial hooded hooks, and sabre chaetae also differs, as does when they first appear, and the range of chaetigers where they are present. Thus, in Prionospio multisetosa sp. nov. the notopodial and neuropodial hooded hooks have three accessory teeth and are present from chaetigers 50–55 (smaller specimen, 46) and 19–22 (smaller specimen, 16), respectively, whereas P. dubia has notopodial and neuropodial hooded hooks with three to four accessory teeth that are present from chaetigers 46–50, and 18– 19, respectively. The sabre chaetae of P. multisetosa sp. nov. are heavily granulated, basally radial, alimbate and present from chaetigers 19–24 (smaller specimen, 14), whereas in P. dubia , the sabre chaetae are granulated, slightly unilimbate, and present from chaetigers 17–20.

Prionospio multisetosa sp. nov. is morphologically similar to P. jonatani Delgado-Blas (2015) due to the shape of the prostomium, and that neither species have any eyes, the first pair of branchiae is 4–5 times as long as notopodial lamellae, the fourth branchial pair is pinnate and longer than the apinnate pairs 2–3, and the sabre chaetae are alimbate. However, Prionospio multisetosa sp. nov. can be distinguished from P. jonatani sp. nov. in that the former is larger in size; the first branchial pair is shorter; the first and fourth branchial pairs have many digitiform pinnules with short, naked distal tips; the notopodial prechaetal lamellae are not basally fused with the notopodial postchaetal lamellae in the branchial region. In P. multisetosa sp. nov. the notopodial prechaetal lamellae are well developed on chaetigers 13–33, whereas in P. jonatani the lamellae are very low; in P. multisetosa sp. nov. the neuropodial postchaetal lamellae of chaetiger 1 are large, tongue-shaped, whereas in P. jonatani the lamellae are very short, rounded. In addition, the shapes of the neuropodial postchaetal lamellae differ between the species: in P. multisetosa sp. nov., the lamellae are oval on chaetigers 2, and subtriangular on chaetiger 3, whereas in P. jonatani the lamellae are square. The number of rows of capillaries, and capillary texture on the anterior notopodial chaetigers is also different: in P. multisetosa sp. nov. the chaetae are arranged in four rows of capillaries, whereas in P. jonatani they are arranged in three rows; both rows of neuropodial chaetae on chaetigers 1–5 are smooth in P. multisetosa sp. nov., while in P. jonatani they are heavily granulated. Differences between the species as regards when the sabre chaetae, notopodial and neuropodial hooded hooks first appear, the range over which they are present, and the number of accessory teeth on the hooded hooks were also recorded: in P. multisetosa sp. nov. the sabre chaetae are present from chaetigers 19–24 (smaller specimen, 14), and the notopodial and neuropodial hooded hooks from chaetigers 50–55 (smaller specimen, 46) and 19–22 (smaller specimen, 16), respectively, the hooks have three pairs of accessory teeth, while in P. jonatani the sabre chaetae are present from chaetigers 14–18, the notopodial and neuropodial hooded hooks from chaetigers 35–77 and 16–28, respectively, and the hooks have four pairs of accessory teeth.

The differences in the morphology of P. multisetosa sp. nov. and P. gayheadia sp. nov. are given in the remarks of P. gayheadia sp. nov. The differences between these new species and other morphologically similar species are provided in the key and in Table 1 .

Etymology. The specific epithet multisetosa is composed of the prefix of Latin origin multi, meaning many, much or multiple, and the Latin adjective setosa, which refers to the large number of rows of chaetae the species possesses in the anterior notopodial chaetigers.

Type locality. Sweden, Skagerrak, Sydkoster, 20–150 m.

Figures

FIGURE 4. Prionospio multisetosa sp. nov., paratype (LACM-AHF-POLY 4433): (A) anterior region, dorsal view; (B) left palp removed; (C) anterior region, lateral view; (D) Branchia, chaetiger 3; (E) parapodium, chaetiger 2; (F) parapodium, chaetiger 3; (G) parapodium, chaetiger 4; (H) notopodium, chaetiger 5; (I) parapodium, chaetiger 13; (J) parapodium, chaetiger 31; (K) parapodium, middle chaetiger; (L) parapodium, posterior chaetiger; (M) capillary notochaeta, chaetiger 2; (N) shows the arrangement of the rows of the chaetae of the anterior chaetiger illustrated in Fig. 4A; (O) capillary neurochaeta, chaetiger 3; (P) capillary neurochaeta, chaetiger 14; (Q) neuropodial hooded hook; (R) notopodial hooded hook; (S) sabre chaeta; (T) pygidium, lateral view. Abbreviation: Nuchal organ (No). Scale bars: A–C, T 10 µm; D–M, O–S 5 µm; N 2 µm.

FIGURE 5. Prionospio multisetosa sp. nov., paratype (LACM-AHF-POLY 4859): (A) anterior region, dorsal view; (B) anterior region, lateral view. Scale bars: A 0.5 mm; B 0.5 mm.