Hippopodina similis Souto & Reverter Gil, 2024 Cryptogenic

Ruiz-Velasco, Sofía, Ros, Macarena, Guerra-García, José M. & López-Fé, Carlos M., 2025, Fouling bryozoans in recreational marinas of the Canary Islands (North-Eastern Atlantic) with new records of non-indigenous and cryptogenic species, Zootaxa 5656 (1), pp. 1-63 : 33

Hippopodina similis Souto & Reverter Gil, 2024 Cryptogenic

( Fig. 16 ; Table 16)

Hippopodina similis Souto & Reverter-Gil, 2024: 10 , fig. 7.

Hippopodina sp. A : Ulman et al. 2017, figs SM 2B, C.

Figured material. Pasito Blanco (26/06/23) (2C on buoy) ( MNCN 25.03/4464).

Other material examined. Taliarte (26/06/23) (5C on buoy).

Description. Colony encrusting, pale orange, multiserial and unilaminar. Autozooids rectangular, with the slightly convex frontal wall filled with evenly distributed small circular pores ( Fig. 16A ), except in the area surrounding the primary orifice ( Fig 16B ). Primary orifice bell-shaped, poster and anter with the same width, including a pronounced lateral indentation near the proximal edge bearing a conical condyle, proximal edge slightly concave. Single adventitious avicularium, with an elongated triangle shape, directed medially ( Figs. 16C, D ). Ovicells not observed.

Remarks. This species has often been confused with Hippopodina feegeensis ( Busk, 1884) due to its general morphology (rectangular autozooids, frontal wall filled with small pores, bell-shaped orifice, triangular avicularia). To compound the confusion, it seems that previous records of H. feegeensis include three additional species ( Tilbrook 1999). Tilbrook (1999) described three different species from material that had been previously assigned to H. feegensis : Hippopodina pulcherrima ( Canu & Bassler, 1928) , that differs from our material in the proximo-medial orientation of the avicularia; Hippopodina iririkiensis Tilbrook, 1999 , with the orifice very rounded distally; and he also described Hippopodina viriosa Tilbrook, 1999 , now a synonym of Hippopodina tahitiensis ( Leca & d’Hondt, 1993) ( Tilbrook & Cook 2004) characterized by the shorter and distally oriented avicularia, among other characters. Hippopodina similis can be distinguished from H. feegensis and other similar species by (1) the lack of pores in the frontal wall surrounding the primary orifice, (2) primary orifice with poster and anter of the same width, (3) distolateral avicularia generally single or absent, directed medially ( Ulman et al. 2017; Souto & Reverter-Gil 2024). It must be noted that zooid length in our material was shorter in comparison to that of Souto & Reverter-Gil (2024) ( Table 16). Arístegui (1984b, 1987) recorded H. feegeensis in the Canary Islands, material that shows characters that match the description of H. similis .

Distribution and status. The geographical distribution of this species is probably underestimated due to its misidentification as H. feegeensis . For now, H. similis has been detected in Greece ( Corsini-Foka et al. 2015) and Turkey ( Ulman et al. 2017), the Mediterranean Sea, and in the Bay of Cádiz ( Spain) ( Sempere-Valverde et al. 2024; Souto & Reverter-Gil 2024) and the Canary Islands (present study) in the Atlantic Ocean. Although records of this species in the Canary Islands might go back to the 80’s ( Arístegui 1984b, 1987), considering that we were not able to examine this material identified as H. feegeensis , it is still an uncertain record. Therefore, the present study constitutes the first formal record of H. similis in the Canary Islands. Souto & Reverter-Gil (2024) suggested that this species was probably introduced in its known native range based on the affinity of Recent Hippopodina species with tropical and warm waters, and the morphological similarity with material identified as H. feegeensis by Levinsen (1909), which shows an imperforate area surrounding the primary orifice. Additional support for its potential introduction in Macaronesia is the fact that in the Canary Islands our specimens and the material from Arístegui (1984b, 1987) have only been recorded in port environments. Considering the uncertainty regarding its native range, we consider this species cryptogenic in the Canary Islands.

Figures

FIGURE 16. Hippopodina similis Souto &Reverter Gil, 2024 (MNCN25.03/4464).A.View of colony through stereomicroscope and B. through SEM. C. D. Slight differences in morphology of autozooids. Scale bars: A = 500 µm; B = 400 µm; C = 40 µm; D = 100 µm.