Immergentia zelandica patagonica López-Gappa, 1981 , p. 24

Johnson, Mildred J., Saadi, Ahmed J., Kuklinski, Piotr, Smith, Abigail M., López-Gappa, Juan & Schwaha, Thomas, 2024, Digging into boring bryozoans: new characters and new species of Immergentiidae, Organisms Diversity & Evolution 24 (2), pp. 217-256 : 233-235

Immergentia zelandica patagonica López-Gappa, 1981, p. 24 , pl.1, figs. 1–3; new synonym

Material examined. SOUTH-WEST ATLANTIC • dense colonies, heavily bored in gastropods, Savatiera chordata Castellanos, Rolán & Bartolotta, 1987; Burdwood Bank, near Argentina; 54º25.144’S 59º12.892’W; depth: 120; 30 March 2016; ‘ R / V Puerto Deseado’ cruise; ARG–E28–L51 • dense colonies, heavily bored in gastropods, Argeneuthria cerealis de Rochebrune & Mabille, 1885 ; Burdwood Bank; 54º00.240’S 61º04.762’W; depth: 139; 08 May 2017; ‘ R / V Puerto Deseado’ cruise; ARG–E28–L290 • dense colonies, heavily bored in gastropods, Trophon ohlini Strebel, 1904 ; Burdwood Bank; 54º30.390’S 59º48.654’W; depth: 105; 10 April 2016; ‘ R / V Puerto Deseado’ cruise; ARG–E28–L198 • dense colonies, heavily bored in gastropods, Pareuthria atrata E. A. Smith, 1881 ; Burdwood Bank; 54º31.679’S 61º27.979’W; depth: 137; 31 March 2016; ‘ R / V Puerto Deseado’ cruise; ARG–E28–L88 (gastropods 1 & 2).

Description: Colony dense with zooids irregularly spaced (Fig. 9a), average interval between neighbouring zooids 268 ± 63 µm. Borehole apertures elongated, resembling a bulged ‘S’ shape and strongly enantiomorphic (Fig. 9a) with average width of 36 ± 8 µm. Typical vase shaped autozooids, length 333 ± 26 µm and width of 124 ± 32 µm, with tapered basal tip (Figs. 7a and 8a–c), acutely positioned in the substrate. Some zooids may curve at acute angle toward primary cystid appendage (Fig. 8a). Short narrow projection present in basal end of some zooids. Polypide with 9 tentacles (Fig. 10a, b) and low-positioned lophophoral anus (Fig. 7b). Opposite branching from the primary cystid appendage can occur (Fig. 9a). Tubulets on the primary cystid appendage may be present or not. Up to three secondary cystid appendages in mid-region of the zooids. Intercalary kenozooids may connect primary or secondary cystid appendages. Sac zooids bulb shaped with distal flat end and 1/3 to 2/3 of autozooid size (Fig. 8g). Basal end of sac zooids typically rounded.

Remarks: Pohowsky (1978) described the species based on d’Orbigny’s material collected from Patagonia, Argentina, between 1826 and 1833. Though only micrographs of borehole apertures of the species were presented by Pohowsky (1978), he described deep depressions of the apertures, the strong enantiomorphic borehole aperture, and the strong curvature of some zooids. Consequently, we consider that the present material corresponds to the same species. Therefore, the soft body morphology for I. patagoniana is presented here for the first time. The acute curvature of zooids has also been observed in I. angulata (Soule & Soule, 1969) , which differs in size and tentacle numbers. López-Gappa (1981) described I. zelandica patagonica from the same area including additional characteristics such as zooid size (from resin casts), colony structure, tentacle number, position, and size of cystid appendages. All characters mentioned above fit those of samples collected and investigated in this study from the same region in the southwest Atlantic. The curvature and two pairs of secondary cystid appendages are visible in micrographs of casts by López-Gappa (1981, figs. 1 and 2). Furthermore, he also indicates a proximal projection in the tip of a zooid ( López-Gappa, 1981; fig. 3). Hence, we suggest that I. zelandica patagonica be considered a junior synonym of I. patagoniana on the bases that the distribution and collection sites, morphology, and gastropod hosts are similar to those described here and by Pohowsky (1978).

Immergentia pohowskii Johnson & Schwaha sp. nov. Figures 3b , 9d, 10e and 11a–e

Material examined. Holotype: SOUTH-WEST PACIFIC OCEAN • small colony in molluscan shell fragment; New Zealand, South Island, Taiaroa Head; 45º45.36’S 170º47.36’E; depth: 23 m; 05 November 2021; ‘PB Otago Shelf’ cruise; Taiaroa Head sediment characterized by coarse shells; ZooBank : urn:lsid:zoobank.org:act:B50F54B2-0A06-4AE8-96C3-D38B2AB4F3E7 ; GenBank : SAMN38786231 ; NIWA-161223.

◂ Fig. 8 Autozooids and heterozooids in Immergentia from whole mounts after shell decalcification. a Autozooids of Immergentia patagoniana , from Burdwood Bank, south-western Atlantic Ocean, with two zooids distinct curvature in the mid-zooidal region (indicated by arrow). b Close up of autozooid from the same colony as in a. Vestibulum and parieto-vestibular muscles with bulge caused by caecum in Immergentia patagoniana . c. Large caecum in the proximal region of Immergentia patagoniana . d Autozooid of Immergentia cf. suecica from Roscoff, France. Tapered basal tip and slanted zooid. e Autozooids of Immergentia cf. zelandica from Inner Otago shelf, New Zealand, with primary and secondary cystid appendages. Bulge caused by digestive tract (arrow). f A reproductive zooid of Immergentia cf. zelandica with primary and secondary cystid appendages and an intercalary kenozooid. Arrow points to bulge of cystid wall. g Bulb shaped sac zooid Immergentia patagoniana with cystid appandages and interzooidal septa. Birefringent spherules fill the zooid. h Vase-shaped sac zooid Immergentia cf. zelandica . i Degenerating zooid of Immergentia stephanieae sp. nov with a proximal cyctid appendage from Roscoff, France. Abbreviations: az – autozooid, bsp – birefringent spherules, cae – caecum, dz – degenerated zooid, ikz – intercalary kenozooid, izs – interzooidal septum, pca – proximal cystid appendage, pcy – primary cystid appendage, pm – parietal muscles, pvm – parieto-vestibular muscles, rm – retractor muscle, scy – secondary cystid appendage, sz – sac zooid, t – tentacles, ts – tentacle sheath, v – vestibulum

Paratype: SOUTH-WEST PACIFIC OCEAN • slides, serial sections; same collection data as for holotype; NIWA-161224.

Etymology: The species is named in honour of Robert A. Pohowsky for his invaluable contributions to the nomenclature and characterization of boring bryozoans.

Diagnosis: Endolithic bryozoan with regularly spaced borehole apertures and 8 tentacles.

Description: Borehole apertures oval or spindle shaped, enantiomorphic (Fig. 9d) with average width of 35 ± 9 µm. Average distance between adjacent zooids is 943 ± 118 µm. Autozooid shape cylindrical, length 299 ± SD 30 µm and width of 76 ± 8 µm, slightly narrowed at mid-zooidal region and elongated rounded basal tip ( Fig. 3b ). Some zooids have tapered basal tip slightly curved toward primary cystid appendage ( Figs. 3b and 11a). Polypide with 8 tentacles (Fig. 10e) and low to mid-positioned lophophoral anus (Figs. 11c, e). Opposite branching from the primary cystid appendage observed (Fig. 9d). Tubulets on the primary cystid appendage may be present or not. Up to three secondary cystid appendages form in the middle to frontal sections of zooids. A proximal cystid appendage may also occur. Intercalary kenozooids may connect primary or secondary cystid appendages. Sac zooids typically vase or bulb shaped and overall 1/3 or 2/3 the size of autozooid.

Remarks: Two conspicuous differences in the species from New Zealand are that I. pohowskii sp. nov. has 8 tentacles and oval to spindle-shaped apertures while I. cf. zelandica has 9 tentacles and circular to oval shaped apertures. In the shell fragments the borehole apertures of I. pohowskii sp. nov. were regularly spaced but dense in others where the interzooidal intervals could not be determined. The zooid size range of I. pohowskii sp. nov. sometimes exceeded 100 µm. A proximal cystid appendage may also occur as that observed in I. stephanieae sp. nov., albeit rare. Lophophoral anus terminates distal of the lophophoral base, in the mid region of the lophophore, different from that of I. patagoniana , I. stephanieae sp. nov. and I. cf. suecica . However, in sectioned individuals, the lophophore and digestive system are relatively smaller, not occupying the larger part of the body cavity. Prior to this study, I. angulata from the Hawaiian Islands was the only other species known to have 8 tentacles (see Soule & Soule, 1969) but differs from I. pohowskii sp. nov. in size, and their zooids are acutely bent in the substrate, similar to those of I. patagoniana . In addition, genetic distances based on cox1 support the notion that I. pohowskii sp. nov. and I. cf. zelandica are distinct (see Phylogenetic analysis).

Figures

Fig. 3 Zooidal plasticity of Immergentia. a–d Zooids of immergentiids after decalcification of substrate. a Autozooids and sac zooid of Immergentia cf. zelandica (Locality: Inner Otago shelf, New Zealand). Zooid with slightly narrowed mid-zooidal region and elongated rounded basal end (arrow). b Autozooids and sac zooid of Immergentia pohowskii sp. nov. (Locality: Taiaroa Head, New Zealand). Several zooids with slightly narrowed mid- region (arrow). c Autozooids of Immergentia cf. suecica from France. d Zooidal plasticity of