Coralliozetus clausus, Hastings, 2021

Hastings, Philip A., 2021, The Pandemic Blenny, Coralliozetus clausus, a new species of tube blenny endemic to Isla del Coco, Costa Rica (Teleostei: Chaenopsidae), Zootaxa 4926 (2), pp. 296-300 : 296-299

Coralliozetus clausus sp. nov. ( Figure 1 )

"Pandemic Blenny; Tubícola Pandémica"

Synonymy

Coralliozetus boehlkei (in part): Stephens et al. 1966; Hastings 2000; Cortés 2012; Robertson & Allen 2015; Fourriére et al. 2017.

Coralliozetus springeri (in part): Stephens et al. 1966; Hastings 2000; Cortés 2012; Robertson & Allen 2015; Fourriére et al. 2017.

Holotype. USNM 451460 , 13.2 mm SL, Chatham Bay , Isla del Coco, 5°33' N, 87°02' W, 7-9 November 1990, collected by D. R. Robertson.

Paratypes: LACM 54458.004 (1 specimen, 10.7 mm SL), Chatham Bay , Isla del Coco , R / V Velero III, station 104- 33, 28 February 1933 ; SIO 11-336 (formerly UAZ 89-1 ), (5, 10.8-11.8), Isla Munuelita, Isla del Coco, Costa Rica, 5°33.7' N, 87°2.9' W, 19-21 November 1989, collected by Alex Kerstich ( AK 891119 -21); UCR 859012 (1, 15.0), Bahia Wafer , south side of Peninsula Presidio , Isla del Coco , Costa Rica; UCR 863020 (1, 10.5), Isla del Coco , Costa Rica, 19 April 1975; UCR 1154029 (2, 11.3-11.7), Bahia Iglesias between Isla Rafael and the coast, Isla del Coco, Costa Rica; UCR 2118004 (2, 10.3-10.9), Isla del Coco, Costa Rica ; USNM 451461 , (8, 12.6-14.0), collected with the holotype .

Diagnosis. A small, short-bodied species of Coralliozetus with a single very short supraorbital cirrus (10-12% of orbital diameter), dorsal fin modally with XVIII spines, 10 or 11 segmented rays, and modally 29 total elements, anal fin modally with 19 rays. Operculum and branchiostegal rays covered with dark dots; anterior dorsal fin white in breeding males. Smallest species in the genus, not exceeding 15 mm SL.

Description. A small species, not exceeding 15 mm SL. Head length 3.7 times in SL, body depth seven to eight times in SL. Jaw extends past posterior orbital margin in males, to mid-orbit in females ( Fig 1D ). A single, very small supraorbital cirrus above each eye, length eight to ten times in bony orbital diameter. Nasal cirrus unbranched, twice as long as supraorbital cirrus. Anterior dorsal fin even; males with a thin fleshy flap anterior of first spine and a shallow notch between spinous and segmented-ray portions. Pectoral fins large, length five times in SL; rounded in males, more pointed in females. Pelvic-fin length (second ray) 60% of pectoral fin length. Caudal fin somewhat rounded.

Dorsal fin with XVII (1 specimen), XVIII (15*; * includes holotype) or XIX (4) spines, 10 (9) or 11 (10*) segmented rays, 28 (7), 29 (12*) or 30 (1) total elements; anal fin with two spines and 18 (4), 19 (15*) or 20 (1) segmented rays; pectoral fin with 13 (34*) segmented rays; pelvic fin with a small spine and three rays.

Cephalic sensory pore counts of mature males are as follows (number reported is for each side; number of counts in parentheses; * = holotype): mandibular: 4 (n = 14*); common: 1 (14*); preopercular: 4 (1) or 5 (13*); posttemporal: 3 (8*) or 4 (6); lateral supratemporal: 1 (13*) or 3 (1); median supratemporal: 0 (6*) or 1 (1); anterior infraorbital: 3 (14*); posterior infraorbital: 3 (14*); supraorbital: 1 (14*); frontal: 0 (14*); commissural: 0 (6*) or 1 (1); anterofrontal: 1 (14*); nasal: 1 (14*). As reported for Coralliozetus angelicus and the other species in the genus ( Hastings 1991, 2002), the number of pores is high in juveniles and decreases in number in males at sexual maturity but not in females. The small size and delicate nature of specimens precluded accurate counts of head pores in juveniles and most females. One female (USNM 451461; 12.7 mm SL) differed from average males in having five lateral supratemporal pores (vs. one or three), one median supratemporal pore (vs. none), two supraorbital pores (vs. one), four frontal pores (vs. none), two commissural pores (vs. none), and two anterofrontal pores (vs. one).

Measurements (mm) of a male paratype (USNM 451461): standard length 13.2; maximum head length 3.57; snout to opercular membrane insertion 3.32; snout length 0.84; upper jaw length 2.0; bony orbital diameter 1.0; iris diameter 0.91; interorbital width 0.48; predorsal length 2.57; preanal length 5.89; caudal peduncle depth 0.96; maximum body depth 1.72; body depth at anal-fin origin 1.72; supraorbital cirrus length 0.12; nasal cirrus length 0.28; pectoral-fin length 2.60; longest (second) pelvic-fin ray length 1.60.

Color of holotype in preservative ( Fig. 1A ) faded to an unknown extent; head dark with a few dark dots on branchiostegal membranes; no pigment evident on body; anterior dorsal fin mostly dark especially along distal margin; anterior dorsal-fin flap white. Color of male paratypes (USNM 451461) in preservative mostly faded but several males with dark heads, dark dots on operculum and branchiostegal membranes ( Fig. 1B,C ); dorsal fin varies from faded with dark distal margin to white on membranes between first two spines and anterior dorsal-fin flap and a dark distal margin posterior to second spine. Female in preservative ( Fig. 1D ) with no pigment on head and body and a few melanophores on mid-dorsal fin and anal fin.

Color of male from a photograph of freshly caught specimen is shown in Fig. 1E . Head black, covered with melanophores, grading to specks of white posteriorly on operculum and branchiostegal rays, and continuing onto anterior base of pectoral fin that grades to white. Dark dots surrounded by white evident on operculum and branchiostegal rays. Iris red with posteroventral patch of white and an inner ring of white. Supraorbital cirrus dark. Body hyaline, with a series of paired black saddles along dorsum: anterior three paired inverted triangles, posterior five joined into increasingly narrow dashes. A series of 12 black marks along anal-fin base, with intervening white flecks along lower body margin. Melanophores evident internally along most neural and hemal spines and vertebral centra, with three or four intervening lighter areas, especially prominent along anterior vertebral column; irregular yellowish patches present in these light areas. Peritoneum with scattered melanophores and an irregular yellowish patch posteroventrally; a white blotch between posterior peritoneum and vertebral column. Posterior margin of hypural plate with a vertical black mark and dark marks on upper and lower caudal peduncle. Anterior dorsal fin bright white from base to distal tip of spines I to II, followed posteriorly by a black mark from base to distal tip of spines II to III. More posteriorly, dorsal fin with melanophores along spines and rays with intervening clear membranes except for a series of black markings near distal tips of most rays and white flecks on spinous dorsal fin in vertical rows above light areas between dorsal saddles. Anal fin with melanophores proximally and white along distal margin. Pectoral fin clear above with lower rays white. Pelvic-fin rays white. Caudal fin with scattered melanophores and whitish areas on membranes posteriorly.

Distribution. Restricted to Isla del Coco, Costa Rica, approximately 550 km southwest of mainland Costa Rica.

Etymology. clausus from the Latin meaning "enclosed" or "having been shut off," in reference to the restricted distribution of this species, known only from Isla del Coco, Costa Rica. The name also refers to the isolation imposed on the author by the Covid-19 pandemic, providing an opportunity to complete the description of this species whose distinctiveness had been known for some time. The common name of "Pandemic Blenny" ("Tubícola Pandémica" in Spanish) is suggested in light of these difficult times.

Comparisons and Comments. The Pandemic Blenny is most similar to Coralliozetus springeri found along the mainland coast from Costa Rica southward to Isla La Plata, Ecuador and C. cardonae from the Caribbean ( Stephens 1963; Stephens et al. 1966; Lasso-Alcalá, et al. 2012). They, along with C. angelicus are similar in body form (i.e., ro-bust) compared to the more elongate body form of C. boehlkei , C. micropes , and C. rosenblatti . Coralliozetus clausus and C. springeri have similar meristics but differ in that C. clausus has a single very short supraorbital cirrus over each eye that is easily overlooked; C. springeri has a pair of cirri over each eye and in males the anterior one is over one half to greater than the orbital diameter, while the second is tiny and easily overlooked. In breeding males of C. springeri the larger cirrus is iridescent blue, but the color of the cirrus of breeding male C. clausus is unknown. Color and shape of the supraorbital cirri are often distinguishing features of species of the genus Coralliozetus : in addition to the blue cirrus of C. springeri , the simple straight cirrus of breeding males is black in C. micropes and C. cardonae , white in C. boehlkei , bright yellow in C. angelicus and mottled and flap-like in C. rosenblatti . Breeding males of C. clausus have a dark head with dense melanophores and a profusion of dark dots on the operculum and branchiostegal rays that are often outlined in white ( Fig. 1B,C,E ); these dots are not present in C. springeri . The anterior dorsal fin of male C. clausus has a white reflective area on the anterior dorsal fin flap and between spines I and II ( Fig. 1E ) while this area appears to be dark in C. springeri . Finally C. clausus is even smaller than the diminutive C. springeri , with a maximum recorded size of 15.0 mm SL versus 20.8 for C. springeri . Sexually mature males of the Pandemic Blenny, based on the presence of dark coloration and an obvious conical genital papilla, are as small as 12.6 mm SL.

Despite reports to the contrary (e.g., Stephens et al. 1966; Hastings 2000; Cortés 2012; Robertson & Allen 2015; Fourriére et al. 2017), C. clausus appears to be the only species of this genus confirmed for Isla del Coco. It has been confused with the similar C. springeri (see above and synonymy) as well as C. boehlkei . Coralliozetus clausus could easily be confused with faded specimens of C. boehlkei . However, males of the latter species have a more elongate body, distinctive stripes on the cheek and a single, supraorbital cirrus that although less than one half the eye diameter ( Stephens 1963), is longer than that of C. clausus . Stephens et al. (1966) reported that five specimens of C. boehlkei were taken at Cocos Island by Walker and Hobson (UCLA 64-45 and UCLA 64-46). I was unable to locate these specimens, but assume they represent C. clausus .

The ichthyofauna of Isla del Coco includes twelve endemic species of reef-associated cryptobenthic fishes. These include two species of chaenopsids, C. clausus and Acanthemblemaria atrata ( Hastings & Robertson 1999) , one species of sand stargazer, Gillellus chathamensis Dawson 1977 ), one triplefin blenny, Axoclinus cocoensis Bussing 1991 , two species of clingfishes, Gobiesox woodsi ( Schultz 1944) and Tomicodon vermiculatus Briggs 1955 , five species of gobies, Chriolepis atrimelum Bussing 1997 , Chriolepis dialepta Bussing 1990 , Lythrypnus alphigena Bussing 1990 , Lythrypnus cobalus Bussing 1990 , Lythrypnus lavenbergi Bussing, 1990 , and one species of bythitid Ogilbia cocoensis Møller, Schwarzhans & Nielsen 2005 . Other endemic cryptobenthic fishes collected along with C. clausus (SIO 11-336) include Axoclinus cocoensis and Lythrypnus cobalus .

Comparative material examined. Coralliozetus angelicus: SIO 01-182 (15 specimens), Puerto Vallarta , Jalisco, Mexico; UAZ 77-20 (144), Isla San Ignacio de Farallon , Gulf of California, Mexico . Coralliozetus boehlkei: SIO 01-182 (4), Puerto Vallarta , Jalisco, Mexico ; UAZ 69-48 (74), Mazatlán , Sinaloa, Mexico . Coralliozetus cardonae: SIO 01-5 (33), Soufriere, Saint Lucia; SIO 03-141 (11), Bahia Azul , Bocas del Toro, Panama . Coralliozetus micropes: SIO 61-274 (91), Isla Partida, Gulf of California , Mexico ; UAZ 74-36 (69), El Bajo, Baja California Sur, Gulf of California , Mexico . Coralliozetus rosenblatti: LACM 32086 (18), Bahia Magdalena , Baja California Sur, Mexico ; SIO 61-256 (48), Isla Cerralvo, Gulf of California , Mexico . Coralliozetus springeri: ANSP 102332 (1), Isla La Plata, Ecuador ; SIO 01-164 (132), Isla Taboquilla, Panama ; SIO 03-142 (13), Isla Taboga, Panama ; SIO 67-34 (55), Isla Taboquilla, Panama ; SIO 67-35 (5), Isla del Rey, Islas Perlas , Panama ; SIO 67-36 (2) Isla del Rey, Islas Perlas , Panama ; SIO 67-37 (20), Isla San Jose, Islas Perlas , Panama ; SIO 67-40 (4), Isla Saboga, Islas Perlas, Panama ; SIO 70-356 (1), Isla Jicaron, Islas Perlas, Panama ; UAZ 85-17 (8), Isla Taboga, Panama ; UCR 423033 (200), Punta Arenas , Costa Rica ; UCR 6780066 (8), Isla del Caño, Costa Rica ; UCR 693004 (10), Costa Rica ; USNM 317699 (1), Isla Tabogilla, Panama ; USNM 317688 (8), Isla Saboga, Isla Perlas, Panama ; USNM 317707 (2), Punta Mariata , Panama ; USNM 317684 (1), Isla del Rey, Islas Perlas , Panama .

Figures

FIGURE 1. Coralliozetus clausus. A) Holotype (USNM 451460), 13.2 mm SL male after preservation; B) Right side of head of paratype (USNM 451461), 13.5 mm SL male showing dots on operculum; C) Left side of head of same specimen as B) showing dots on branchiostegal rays; D) 12.7 mm SL female (USNM 451461); E) Photo of freshly caught male specimen from Isla del Coco.