Argulus floridensis Meehean, 1940

Poly, William J., 2018, Redescription of the Holotype of Argulus floridensis Meehean, 1940, Proceedings of the California Academy of Sciences 65 (4), pp. 133-138 : 134-137

Argulus floridensis Meehean, 1940

Florida fishlouse Figures 1–6.

MATERIAL EXAMINED.— Holotype (unique), adult male, 5.46 mm total length [ Meehean 1940: 5.85 mm], USNM 77810 [see note], Key West, Florida, 1884, collector: A.E. Verrill [= Addison Emery Verrill]. Note: Meehean (1940, p. 467) listed the catalog number as “77810 (old number 60589);” mentioned here in case of relevant information in historical records under the old number. DIAGNOSIS.— Two respiratory areas with smaller oblong “area” anterior to slightly larger oblong posterior “area;” single postantennal spines very broad; male with 77 support rods in suction cup; 14–19 sclerites per rod in male; mouth tube with at least 19 scales on basal half; basal plate of second maxilla with 3 stout spines, scales covering nearly entire raised pad, one stout, naked seta on posterior margin of pad; accessory spines on thorax large, very broad base on raised pad with many scales, tapering to rounded tips; first 2 pairs of legs lacking flagella; posteroventral surface of coxae of second legs of male expanded into a broadly-rounded lobe that is covered with many small and closely-arranged scales; third legs of male with two pegs issuing from cleft on dorsal side of legs and two fingerlike papillae; small fleshy lobe at posterior of thorax; male abdomen bilobate with testes extending to the level of the anal sinus base; caudal rami long, slen- der, basal in anal sinus. DESCRIPTION.— Total length 5.46 mm [ Meehean 1940: 5.85 mm]. Carapace shape is “ovate, sinuses shallow, cephalic areas broad...; alae reaching abdomen [ Meehean 1940].” Carapace length [ Meehean 1940: 4.88 mm]. Maximum carapace width [ Meehean 1940: 4.28 mm]. Pair of compound eyes anteriorly with diameters 250 (left) and 220 (right) µm. Transverse distance between eyes 0.83 mm (830 µm). Nauplius eye with one anterior and two posterior ocelli. Sclerotized dorsal ridges not forked anterior of eyes. Ventrally, carapace with small, posteriorly-projecting spines along outer margin [due to the deteriorated condition of the carapace alae, additional details cannot be included here]. Respiratory areas consist of two oblong-shaped areas, anterior one slightly smaller than posterior [from Meehean 1940] (Fig. 1). No pigmentation present (but probably lost in preservative and/or due to clearing). Thorax compressed dorsoventrally, 4-segmented, with 2 pairs of posteriorly-projecting spines ventrally. Spines digitate with broad base, anterior pair (accessory spines) larger than posterior pair (postmaxillary spines), both pairs angled mesially. Accessory spines between basal segments of second maxillae; very broad base on a raised pad covered with many scales; spines tapering to round- ed tips ( Fig. 2 ). Male with ovoid fleshy lobe at posterior of fourth thoracic segment between natatory lobes (Figs. 3A, 4). Thorax with FIGURE 1. Argulus floridensis :

shape of anterior and posterior scales scattered on ventral surface; thoracic segment at base of third respiratory areas (redrawn from leg produced laterally into expanded anterolateral lobe with scales Meehean 1940). with secondary sexual structures (Figs. FIGURE 3. Argulus floridensis : A) ventral view of legs 2, 3, and 4 3A, B). (precoxa, coxa, and basis only); exopods, endopods, setae, and sensil-

First legs lack secondary modifica- lae omitted. B) dorsal view of leg 3 (precoxa, coxa, and basis only). tions. Second legs, the posterior ventral Scale bar = 500 µm.

margin of coxae expanded into broadly-rounded lobe with many small, closely-arranged scales. Third legs, dorsal anterior coxae with broadly-rounded hump armed with many scales directed proximally; distal to this hump are two smaller, unarmed protuberances; at anterior distal margin of coxae an anteriorly-directed, fleshy projection (“upright fingerlike papilla” of Meehean 1940) (Fig. 3A).

Third legs with two sclerotized pegs in cleft on dorsal side at distal margins of coxae (or fused coxae+bases); pegs with a single, large horn and orifice distally; sclerotized ridge at anterior dorsal of coxa/basis junction; one fleshy papilla extends proximally (mesially) from sclerotized ridge anterior of two pegs and overhanging cleft (“saddle-shaped depression” of Meehean 1940). Posterior to pegs and cleft a triangular-shaped lobe covered with scales (Fig. 3B). Posterior margins of both precoxae+coxae and bases of fourth legs with natatory lobes bearing plumose setae. Anterior of bases a sclerotized ridge lies on basal half, opposed by recurved, finger-like appendage covered with fine scales distally; tiny spines or scales on its tip (Fig. 3A).

Abdomen bilobate. Abdomen length 1.72 mm [ Meehean 1940: 1.58 mm]; maximum width 1.44 mm [ Meehean 1940: 1.35 mm]. Anal sinus length 0.72 mm (720 µm) [ Meehean 1940: 0.98 mm]. Caudal rami paired, long, slender, near base of anal sinus (could not see the setae clearly, usually there are 5 simple setae at the tip of each). Tips of abdominal lobes narrowly rounded, not pointy. Testes extending to level of anal sinus base ( Fig. 4 ). Scales absent on ventral surface of abdomen; spines or scales absent along margins of abdominal lobes.

Mouth tube long, slender, with at least 19 scales on basal half.

First antennae 4-segmented. First segment (basal segment) sclerotized, large with stout posteriorly-projecting posterior spine, narrowly rounded at tip; second segment sclerotized with small recurved spine anteriorly with narrow, blunt tip, posteriorly-projecting medial spine with rounded tip, and large recurved terminal spine; third and fourth fleshy segments missing or obscured on the holotype (Fig. 5). Width of first antennae (mean of both antennae, µm) 530–540 (535) in male. Second antennae 5-segmented, fleshy. First two segments larger; remaining three thin, cylindrical; basal segment bears posteriorly-projecting posterior spine with narrowly-rounded tip. Postantennal spines single (as opposed to double in some taxa), very wide at base, tapering to narrowly-rounded tip (Fig. 5).

First maxillae modified into suction cups in adult. In male, first maxillae inner diameter 680 µm and outer diameter 1,050 µm (n = 1). Number of sclerites per support rod in male 14–19 (n = 25 support rods) [excludes abnormal rods with missing sclerites]. Basal (proximal) sclerite usually subquadrangular, shape variable; distal sclerites imbricate bowls, plates (Fig. 6). Suction cup with 29 sensilla on inside circumference.

Second maxillae 5-segmented with broad basal plate bearing three stout spines with the mesial spine broader than the other two ( Fig. 2 ). Basal plate with elevated pad bearing 43 scales and one stout FIGURE 6. Argulus floridensis :

Two support rods from suction seta posteriorly. Bi-dentate to multidentate scales on ventral surfaces cup (right first maxilla), Scale bar of segments 2 and 3; segment 4 lacking armature. Distal segment with = 100 µm,

2 sharp claws (1 broken/missing) and one blunt, elongate lobe positioned above claws (did not see a small sensillum at tip of lobe).

HOST.— Unknown.

ETYMOLOGY.— The specific name, floridensis , is derived from the state, Florida, in which the type locality is located and has an adjectival suffix, ensis, meaning “of or from Florida.”

Figures

FIGURE 2. Argulus floridensis: Second maxil- la, raised pad with scales (adjacent on thorax), accessory spine, and postmaxillary spine. Scale bar = 200 µm.

FIGURE 4. Argulus floridensis: abdomen; fleshy lobe at FIGURE 5. Argulus floridensis: first and second antennae. posterior of thorax is shown as a dashed outline at anterior of The fleshy segments of the first antennae were obscured or abdomen. Setae not shown on caudal rami. Scale bar = 500 missing on this structure but are included as dashed outlines. µm. Scale bar = 200 µm.